mariadb/storage/rocksdb/rdb_datadic.cc

/*
   Copyright (c) 2012,2013 Monty Program Ab
   Copyright (c) 2020, MariaDB Corporation.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1301 USA */

#ifdef USE_PRAGMA_IMPLEMENTATION
#pragma implementation  // gcc: Class implementation
#endif

/* For use of 'PRIu64': */
#define __STDC_FORMAT_MACROS

#include <my_global.h>
/* This C++ file's header file */
#include "./rdb_datadic.h"

#include <inttypes.h>
/* C++ standard header files */
#include <algorithm>
#include <array>
#include <limits>
#include <map>
#include <set>
#include <string>
#include <utility>
#include <vector>

/* MySQL header files */
#include "./field.h"
#include "./key.h"
#include "./m_ctype.h"
#include "./my_bit.h"
#include "./my_bitmap.h"
#include "./sql_table.h"

/* MyRocks header files */
#include "./ha_rocksdb.h"
#include "./ha_rocksdb_proto.h"
#include "./my_stacktrace.h"
#include "./rdb_cf_manager.h"
#include "./rdb_psi.h"
#include "./rdb_utils.h"

namespace myrocks {

void get_mem_comparable_space(const CHARSET_INFO *cs,
                              const std::vector<uchar> **xfrm, size_t *xfrm_len,
                              size_t *mb_len);

/*
  MariaDB's replacement for FB/MySQL Field::check_field_name_match :
*/
inline bool field_check_field_name_match(Field *field, const char *name)
{
  return (0 == my_strcasecmp(system_charset_info,
                             field->field_name.str,
                             name));
}


/*
  Decode  current key field
  @param  fpi               IN      data structure contains field metadata
  @param  field             IN      current field
  @param  reader            IN      key slice reader
  @param  unp_reader        IN      unpack information reader
  @return
    HA_EXIT_SUCCESS    OK
    other              HA_ERR error code
*/
int Rdb_convert_to_record_key_decoder::decode_field(
    Rdb_field_packing *fpi, Field *field, Rdb_string_reader *reader,
    const uchar *const default_value, Rdb_string_reader *unpack_reader) {
  if (fpi->m_maybe_null) {
    const char *nullp;
    if (!(nullp = reader->read(1))) {
      return HA_EXIT_FAILURE;
    }

    if (*nullp == 0) {
      /* Set the NULL-bit of this field */
      field->set_null();
      /* Also set the field to its default value */
      memcpy(field->ptr, default_value, field->pack_length());
      return HA_EXIT_SUCCESS;
    } else if (*nullp == 1) {
      field->set_notnull();
    } else {
      return HA_EXIT_FAILURE;
    }
  }

  return (fpi->m_unpack_func)(fpi, field, field->ptr, reader, unpack_reader);
}

/*
  Decode  current key field

  @param  buf               OUT     the buf starting address
  @param  offset            OUT     the bytes offset when data is written
  @param  fpi               IN      data structure contains field metadata
  @param  table             IN      current table
  @param  field             IN      current field
  @param  has_unpack_inf    IN      whether contains unpack inf
  @param  reader            IN      key slice reader
  @param  unp_reader        IN      unpack information reader
  @return
    HA_EXIT_SUCCESS    OK
    other              HA_ERR error code
*/
int Rdb_convert_to_record_key_decoder::decode(
    uchar *const buf, uint *offset, Rdb_field_packing *fpi, TABLE *table,
    Field *field, bool has_unpack_info, Rdb_string_reader *reader,
    Rdb_string_reader *unpack_reader) {
  DBUG_ASSERT(buf != nullptr);
  DBUG_ASSERT(offset != nullptr);

  uint field_offset = field->ptr - table->record[0];
  *offset = field_offset;
  uint null_offset = field->null_offset();
  bool maybe_null = field->real_maybe_null();

  field->move_field(buf + field_offset,
                    maybe_null ? buf + null_offset : nullptr, field->null_bit);

  // If we need unpack info, but there is none, tell the unpack function
  // this by passing unp_reader as nullptr. If we never read unpack_info
  // during unpacking anyway, then there won't an error.
  bool maybe_missing_unpack = !has_unpack_info && fpi->uses_unpack_info();

  int res =
      decode_field(fpi, field, reader, table->s->default_values + field_offset,
                   maybe_missing_unpack ? nullptr : unpack_reader);

  // Restore field->ptr and field->null_ptr
  field->move_field(table->record[0] + field_offset,
                    maybe_null ? table->record[0] + null_offset : nullptr,
                    field->null_bit);
  if (res != UNPACK_SUCCESS) {
    return HA_ERR_ROCKSDB_CORRUPT_DATA;
  }
  return HA_EXIT_SUCCESS;
}

/*
  Skip current key field

  @param  fpi          IN    data structure contains field metadata
  @param  field        IN    current field
  @param  reader       IN    key slice reader
  @param  unp_reader   IN    unpack information reader
  @return
    HA_EXIT_SUCCESS    OK
    other              HA_ERR error code
*/
int Rdb_convert_to_record_key_decoder::skip(const Rdb_field_packing *fpi,
                                            const Field *field,
                                            Rdb_string_reader *reader,
                                            Rdb_string_reader *unp_reader) {
  /* It is impossible to unpack the column. Skip it. */
  if (fpi->m_maybe_null) {
    const char *nullp;
    if (!(nullp = reader->read(1))) {
      return HA_ERR_ROCKSDB_CORRUPT_DATA;
    }
    if (*nullp == 0) {
      /* This is a NULL value */
      return HA_EXIT_SUCCESS;
    }
    /* If NULL marker is not '0', it can be only '1'  */
    if (*nullp != 1) {
      return HA_ERR_ROCKSDB_CORRUPT_DATA;
    }
  }
  if ((fpi->m_skip_func)(fpi, field, reader)) {
    return HA_ERR_ROCKSDB_CORRUPT_DATA;
  }
  // If this is a space padded varchar, we need to skip the indicator
  // bytes for trailing bytes. They're useless since we can't restore the
  // field anyway.
  //
  // There is a special case for prefixed varchars where we do not
  // generate unpack info, because we know prefixed varchars cannot be
  // unpacked. In this case, it is not necessary to skip.
  if (fpi->m_skip_func == &Rdb_key_def::skip_variable_space_pad &&
      !fpi->m_unpack_info_stores_value) {
    unp_reader->read(fpi->m_unpack_info_uses_two_bytes ? 2 : 1);
  }
  return HA_EXIT_SUCCESS;
}

Rdb_key_field_iterator::Rdb_key_field_iterator(
    const Rdb_key_def *key_def, Rdb_field_packing *pack_info,
    Rdb_string_reader *reader, Rdb_string_reader *unp_reader, TABLE *table,
    bool has_unpack_info, const MY_BITMAP *covered_bitmap, uchar *const buf) {
  m_key_def = key_def;
  m_pack_info = pack_info;
  m_iter_index = 0;
  m_iter_end = key_def->get_key_parts();
  m_reader = reader;
  m_unp_reader = unp_reader;
  m_table = table;
  m_has_unpack_info = has_unpack_info;
  m_covered_bitmap = covered_bitmap;
  m_buf = buf;
  m_secondary_key =
      (key_def->m_index_type == Rdb_key_def::INDEX_TYPE_SECONDARY);
  m_hidden_pk_exists = Rdb_key_def::table_has_hidden_pk(table);
  m_is_hidden_pk =
      (key_def->m_index_type == Rdb_key_def::INDEX_TYPE_HIDDEN_PRIMARY);
  m_curr_bitmap_pos = 0;
  m_offset = 0;
}

void *Rdb_key_field_iterator::get_dst() const { return m_buf + m_offset; }

int Rdb_key_field_iterator::get_field_index() const {
  DBUG_ASSERT(m_field != nullptr);
  return m_field->field_index;
}

bool Rdb_key_field_iterator::get_is_null() const { return m_is_null; }
Field *Rdb_key_field_iterator::get_field() const {
  DBUG_ASSERT(m_field != nullptr);
  return m_field;
}

bool Rdb_key_field_iterator::has_next() { return m_iter_index < m_iter_end; }

/**
 Iterate each field in the key and decode/skip one by one
*/
int Rdb_key_field_iterator::next() {
  int status = HA_EXIT_SUCCESS;
  while (m_iter_index < m_iter_end) {
    int curr_index = m_iter_index++;

    m_fpi = &m_pack_info[curr_index];
    /*
      Hidden pk field is packed at the end of the secondary keys, but the SQL
      layer does not know about it. Skip retrieving field if hidden pk.
    */
    if ((m_secondary_key && m_hidden_pk_exists &&
         curr_index + 1 == m_iter_end) ||
        m_is_hidden_pk) {
      DBUG_ASSERT(m_fpi->m_unpack_func);
      if ((m_fpi->m_skip_func)(m_fpi, nullptr, m_reader)) {
        return HA_ERR_ROCKSDB_CORRUPT_DATA;
      }
      return HA_EXIT_SUCCESS;
    }

    m_field = m_fpi->get_field_in_table(m_table);

    bool covered_column = true;
    if (m_covered_bitmap != nullptr &&
        m_field->real_type() == MYSQL_TYPE_VARCHAR && !m_fpi->m_covered) {
      uint tmp= m_curr_bitmap_pos++;
      covered_column = m_curr_bitmap_pos < MAX_REF_PARTS &&
                       bitmap_is_set(m_covered_bitmap, tmp);
    }

    if (m_fpi->m_unpack_func && covered_column) {
      /* It is possible to unpack this column. Do it. */
      status = Rdb_convert_to_record_key_decoder::decode(
          m_buf, &m_offset, m_fpi, m_table, m_field, m_has_unpack_info,
          m_reader, m_unp_reader);
      if (status) {
        return status;
      }
      break;
    } else {
      status = Rdb_convert_to_record_key_decoder::skip(m_fpi, m_field, m_reader,
                                                       m_unp_reader);
      if (status) {
        return status;
      }
    }
  }
  return HA_EXIT_SUCCESS;
}

/*
  Rdb_key_def class implementation
*/
Rdb_key_def::Rdb_key_def(uint indexnr_arg, uint keyno_arg,
                         rocksdb::ColumnFamilyHandle *cf_handle_arg,
                         uint16_t index_dict_version_arg, uchar index_type_arg,
                         uint16_t kv_format_version_arg, bool is_reverse_cf_arg,
                         bool is_per_partition_cf_arg, const char *_name,
                         Rdb_index_stats _stats, uint32 index_flags_bitmap,
                         uint32 ttl_rec_offset, uint64 ttl_duration)
    : m_index_number(indexnr_arg),
      m_cf_handle(cf_handle_arg),
      m_index_dict_version(index_dict_version_arg),
      m_index_type(index_type_arg),
      m_kv_format_version(kv_format_version_arg),
      m_is_reverse_cf(is_reverse_cf_arg),
      m_is_per_partition_cf(is_per_partition_cf_arg),
      m_name(_name),
      m_stats(_stats),
      m_index_flags_bitmap(index_flags_bitmap),
      m_ttl_rec_offset(ttl_rec_offset),
      m_ttl_duration(ttl_duration),
      m_ttl_column(""),
      m_pk_part_no(nullptr),
      m_pack_info(nullptr),
      m_keyno(keyno_arg),
      m_key_parts(0),
      m_ttl_pk_key_part_offset(UINT_MAX),
      m_ttl_field_index(UINT_MAX),
      m_prefix_extractor(nullptr),
      m_maxlength(0)  // means 'not intialized'
{
  mysql_mutex_init(0, &m_mutex, MY_MUTEX_INIT_FAST);
  rdb_netbuf_store_index(m_index_number_storage_form, m_index_number);
  m_total_index_flags_length =
      calculate_index_flag_offset(m_index_flags_bitmap, MAX_FLAG);
  DBUG_ASSERT_IMP(m_index_type == INDEX_TYPE_SECONDARY &&
                      m_kv_format_version <= SECONDARY_FORMAT_VERSION_UPDATE2,
                  m_total_index_flags_length == 0);
  DBUG_ASSERT_IMP(m_index_type == INDEX_TYPE_PRIMARY &&
                      m_kv_format_version <= PRIMARY_FORMAT_VERSION_UPDATE2,
                  m_total_index_flags_length == 0);
  DBUG_ASSERT(m_cf_handle != nullptr);
}

Rdb_key_def::Rdb_key_def(const Rdb_key_def &k)
    : m_index_number(k.m_index_number),
      m_cf_handle(k.m_cf_handle),
      m_is_reverse_cf(k.m_is_reverse_cf),
      m_is_per_partition_cf(k.m_is_per_partition_cf),
      m_name(k.m_name),
      m_stats(k.m_stats),
      m_index_flags_bitmap(k.m_index_flags_bitmap),
      m_ttl_rec_offset(k.m_ttl_rec_offset),
      m_ttl_duration(k.m_ttl_duration),
      m_ttl_column(k.m_ttl_column),
      m_pk_part_no(k.m_pk_part_no),
      m_pack_info(k.m_pack_info),
      m_keyno(k.m_keyno),
      m_key_parts(k.m_key_parts),
      m_ttl_pk_key_part_offset(k.m_ttl_pk_key_part_offset),
      m_ttl_field_index(UINT_MAX),
      m_prefix_extractor(k.m_prefix_extractor),
      m_maxlength(k.m_maxlength) {
  mysql_mutex_init(0, &m_mutex, MY_MUTEX_INIT_FAST);
  rdb_netbuf_store_index(m_index_number_storage_form, m_index_number);
  m_total_index_flags_length =
      calculate_index_flag_offset(m_index_flags_bitmap, MAX_FLAG);
  DBUG_ASSERT_IMP(m_index_type == INDEX_TYPE_SECONDARY &&
                      m_kv_format_version <= SECONDARY_FORMAT_VERSION_UPDATE2,
                  m_total_index_flags_length == 0);
  DBUG_ASSERT_IMP(m_index_type == INDEX_TYPE_PRIMARY &&
                      m_kv_format_version <= PRIMARY_FORMAT_VERSION_UPDATE2,
                  m_total_index_flags_length == 0);
  if (k.m_pack_info) {
    const size_t size = sizeof(Rdb_field_packing) * k.m_key_parts;
    void *pack_info= my_malloc(PSI_INSTRUMENT_ME, size, MYF(0));
    memcpy(pack_info, k.m_pack_info, size);
    m_pack_info = reinterpret_cast<Rdb_field_packing *>(pack_info);
  }

  if (k.m_pk_part_no) {
    const size_t size = sizeof(uint) * m_key_parts;
    m_pk_part_no = reinterpret_cast<uint *>(my_malloc(PSI_INSTRUMENT_ME, size, MYF(0)));
    memcpy(m_pk_part_no, k.m_pk_part_no, size);
  }
}

Rdb_key_def::~Rdb_key_def() {
  mysql_mutex_destroy(&m_mutex);

  my_free(m_pk_part_no);
  m_pk_part_no = nullptr;

  my_free(m_pack_info);
  m_pack_info = nullptr;
}

void Rdb_key_def::setup(const TABLE *const tbl,
                        const Rdb_tbl_def *const tbl_def) {
  DBUG_ASSERT(tbl != nullptr);
  DBUG_ASSERT(tbl_def != nullptr);

  /*
    Set max_length based on the table.  This can be called concurrently from
    multiple threads, so there is a mutex to protect this code.
  */
  const bool is_hidden_pk = (m_index_type == INDEX_TYPE_HIDDEN_PRIMARY);
  const bool hidden_pk_exists = table_has_hidden_pk(tbl);
  const bool secondary_key = (m_index_type == INDEX_TYPE_SECONDARY);
  if (!m_maxlength) {
    RDB_MUTEX_LOCK_CHECK(m_mutex);
    if (m_maxlength != 0) {
      RDB_MUTEX_UNLOCK_CHECK(m_mutex);
      return;
    }

    KEY *key_info = nullptr;
    KEY *pk_info = nullptr;
    if (!is_hidden_pk) {
      key_info = &tbl->key_info[m_keyno];
      if (!hidden_pk_exists) pk_info = &tbl->key_info[tbl->s->primary_key];
      m_name = std::string(key_info->name.str);
    } else {
      m_name = HIDDEN_PK_NAME;
    }

    if (secondary_key) {
      m_pk_key_parts= hidden_pk_exists ? 1 : pk_info->ext_key_parts;
    } else {
      pk_info = nullptr;
      m_pk_key_parts = 0;
    }

    // "unique" secondary keys support:
    m_key_parts= is_hidden_pk ? 1 : key_info->ext_key_parts;

    if (secondary_key) {
      /*
        In most cases, SQL layer puts PK columns as invisible suffix at the
        end of secondary key. There are cases where this doesn't happen:
        - unique secondary indexes.
        - partitioned tables.

        Internally, we always need PK columns as suffix (and InnoDB does,
        too, if you were wondering).

        The loop below will attempt to put all PK columns at the end of key
        definition.  Columns that are already included in the index (either
        by the user or by "extended keys" feature) are not included for the
        second time.
      */
      m_key_parts += m_pk_key_parts;
    }

    if (secondary_key) {
      m_pk_part_no = reinterpret_cast<uint *>(
          my_malloc(PSI_INSTRUMENT_ME, sizeof(uint) * m_key_parts, MYF(0)));
    } else {
      m_pk_part_no = nullptr;
    }

    const size_t size = sizeof(Rdb_field_packing) * m_key_parts;
    m_pack_info =
        reinterpret_cast<Rdb_field_packing *>(my_malloc(PSI_INSTRUMENT_ME, size, MYF(0)));

    /*
      Guaranteed not to error here as checks have been made already during
      table creation.
    */
    Rdb_key_def::extract_ttl_col(tbl, tbl_def, &m_ttl_column,
                                 &m_ttl_field_index, true);

    size_t max_len = INDEX_NUMBER_SIZE;
    int unpack_len = 0;
    int max_part_len = 0;
    bool simulating_extkey = false;
    uint dst_i = 0;

    uint keyno_to_set = m_keyno;
    uint keypart_to_set = 0;

    if (is_hidden_pk) {
      Field *field = nullptr;
      m_pack_info[dst_i].setup(this, field, keyno_to_set, 0, 0);
      m_pack_info[dst_i].m_unpack_data_offset = unpack_len;
      max_len += m_pack_info[dst_i].m_max_image_len;
      max_part_len = std::max(max_part_len, m_pack_info[dst_i].m_max_image_len);
      dst_i++;
    } else {
      KEY_PART_INFO *key_part = key_info->key_part;

      /* this loop also loops over the 'extended key' tail */
      for (uint src_i = 0; src_i < m_key_parts; src_i++, keypart_to_set++) {
        Field *const field = key_part ? key_part->field : nullptr;

        if (simulating_extkey && !hidden_pk_exists) {
          DBUG_ASSERT(secondary_key);
          /* Check if this field is already present in the key definition */
          bool found = false;
          for (uint j= 0; j < key_info->ext_key_parts; j++) {
            if (field->field_index ==
                    key_info->key_part[j].field->field_index &&
                key_part->length == key_info->key_part[j].length) {
              found = true;
              break;
            }
          }

          if (found) {
            key_part++;
            continue;
          }
        }

        if (field && field->real_maybe_null()) max_len += 1;  // NULL-byte

        m_pack_info[dst_i].setup(this, field, keyno_to_set, keypart_to_set,
                                 key_part ? key_part->length : 0);
        m_pack_info[dst_i].m_unpack_data_offset = unpack_len;

        if (pk_info) {
          m_pk_part_no[dst_i] = -1;
          for (uint j = 0; j < m_pk_key_parts; j++) {
            if (field->field_index == pk_info->key_part[j].field->field_index) {
              m_pk_part_no[dst_i] = j;
              break;
            }
          }
        } else if (secondary_key && hidden_pk_exists) {
          /*
            The hidden pk can never be part of the sk.  So it is always
            appended to the end of the sk.
          */
          m_pk_part_no[dst_i] = -1;
          if (simulating_extkey) m_pk_part_no[dst_i] = 0;
        }

        max_len += m_pack_info[dst_i].m_max_image_len;

        max_part_len =
            std::max(max_part_len, m_pack_info[dst_i].m_max_image_len);

        /*
          Check key part name here, if it matches the TTL column then we store
          the offset of the TTL key part here.
        */
        if (!m_ttl_column.empty() &&
            field_check_field_name_match(field, m_ttl_column.c_str())) {
          DBUG_ASSERT(field->real_type() == MYSQL_TYPE_LONGLONG);
          DBUG_ASSERT(field->key_type() == HA_KEYTYPE_ULONGLONG);
          DBUG_ASSERT(!field->real_maybe_null());
          m_ttl_pk_key_part_offset = dst_i;
        }

        key_part++;
        /*
          For "unique" secondary indexes, pretend they have
          "index extensions".

          MariaDB also has this property: if an index has a partially-covered
          column like KEY(varchar_col(N)), then the SQL layer will think it is
          not "extended" with PK columns. The code below handles this case,
          also.
         */
        if (secondary_key && src_i+1 == key_info->ext_key_parts) {
          simulating_extkey = true;
          if (!hidden_pk_exists) {
            keyno_to_set = tbl->s->primary_key;
            key_part = pk_info->key_part;
            keypart_to_set = (uint)-1;
          } else {
            keyno_to_set = tbl_def->m_key_count - 1;
            key_part = nullptr;
            keypart_to_set = 0;
          }
        }

        dst_i++;
      }
    }

    m_key_parts = dst_i;

    /* Initialize the memory needed by the stats structure */
    m_stats.m_distinct_keys_per_prefix.resize(get_key_parts());

    /* Cache prefix extractor for bloom filter usage later */
    rocksdb::Options opt = rdb_get_rocksdb_db()->GetOptions(get_cf());
    m_prefix_extractor = opt.prefix_extractor;

    /*
      This should be the last member variable set before releasing the mutex
      so that other threads can't see the object partially set up.
     */
    m_maxlength = max_len;

    RDB_MUTEX_UNLOCK_CHECK(m_mutex);
  }
}

/*
  Determine if the table has TTL enabled by parsing the table comment.

  @param[IN]  table_arg
  @param[IN]  tbl_def_arg
  @param[OUT] ttl_duration        Default TTL value parsed from table comment
*/
uint Rdb_key_def::extract_ttl_duration(const TABLE *const table_arg,
                                       const Rdb_tbl_def *const tbl_def_arg,
                                       uint64 *ttl_duration) {
  DBUG_ASSERT(table_arg != nullptr);
  DBUG_ASSERT(tbl_def_arg != nullptr);
  DBUG_ASSERT(ttl_duration != nullptr);
  std::string table_comment(table_arg->s->comment.str,
                            table_arg->s->comment.length);

  bool ttl_duration_per_part_match_found = false;
  std::string ttl_duration_str = Rdb_key_def::parse_comment_for_qualifier(
      table_comment, table_arg, tbl_def_arg, &ttl_duration_per_part_match_found,
      RDB_TTL_DURATION_QUALIFIER);

  /* If we don't have a ttl duration, nothing to do here. */
  if (ttl_duration_str.empty()) {
    return HA_EXIT_SUCCESS;
  }

  /*
    Catch errors where a non-integral value was used as ttl duration, strtoull
    will return 0.
  */
  *ttl_duration = std::strtoull(ttl_duration_str.c_str(), nullptr, 0);
  if (!*ttl_duration) {
    my_error(ER_RDB_TTL_DURATION_FORMAT, MYF(0), ttl_duration_str.c_str());
    return HA_EXIT_FAILURE;
  }

  return HA_EXIT_SUCCESS;
}

/*
  Determine if the table has TTL enabled by parsing the table comment.

  @param[IN]  table_arg
  @param[IN]  tbl_def_arg
  @param[OUT] ttl_column          TTL column in the table
  @param[IN]  skip_checks         Skip validation checks (when called in
                                  setup())
*/
uint Rdb_key_def::extract_ttl_col(const TABLE *const table_arg,
                                  const Rdb_tbl_def *const tbl_def_arg,
                                  std::string *ttl_column,
                                  uint *ttl_field_index, bool skip_checks) {
  std::string table_comment(table_arg->s->comment.str,
                            table_arg->s->comment.length);
  /*
    Check if there is a TTL column specified. Note that this is not required
    and if omitted, an 8-byte ttl field will be prepended to each record
    implicitly.
  */
  bool ttl_col_per_part_match_found = false;
  std::string ttl_col_str = Rdb_key_def::parse_comment_for_qualifier(
      table_comment, table_arg, tbl_def_arg, &ttl_col_per_part_match_found,
      RDB_TTL_COL_QUALIFIER);

  if (skip_checks) {
    for (uint i = 0; i < table_arg->s->fields; i++) {
      Field *const field = table_arg->field[i];
      if (field_check_field_name_match(field, ttl_col_str.c_str())) {
        *ttl_column = ttl_col_str;
        *ttl_field_index = i;
      }
    }
    return HA_EXIT_SUCCESS;
  }

  /* Check if TTL column exists in table */
  if (!ttl_col_str.empty()) {
    bool found = false;
    for (uint i = 0; i < table_arg->s->fields; i++) {
      Field *const field = table_arg->field[i];
      if (field_check_field_name_match(field, ttl_col_str.c_str()) &&
          field->real_type() == MYSQL_TYPE_LONGLONG &&
          field->key_type() == HA_KEYTYPE_ULONGLONG &&
          !field->real_maybe_null()) {
        *ttl_column = ttl_col_str;
        *ttl_field_index = i;
        found = true;
        break;
      }
    }

    if (!found) {
      my_error(ER_RDB_TTL_COL_FORMAT, MYF(0), ttl_col_str.c_str());
      return HA_EXIT_FAILURE;
    }
  }

  return HA_EXIT_SUCCESS;
}

const std::string Rdb_key_def::gen_qualifier_for_table(
    const char *const qualifier, const std::string &partition_name) {
  bool has_partition = !partition_name.empty();
  std::string qualifier_str = "";

  if (!strcmp(qualifier, RDB_CF_NAME_QUALIFIER)) {
    return has_partition ? gen_cf_name_qualifier_for_partition(partition_name)
                         : qualifier_str + RDB_CF_NAME_QUALIFIER +
                               RDB_QUALIFIER_VALUE_SEP;
  } else if (!strcmp(qualifier, RDB_TTL_DURATION_QUALIFIER)) {
    return has_partition
               ? gen_ttl_duration_qualifier_for_partition(partition_name)
               : qualifier_str + RDB_TTL_DURATION_QUALIFIER +
                     RDB_QUALIFIER_VALUE_SEP;
  } else if (!strcmp(qualifier, RDB_TTL_COL_QUALIFIER)) {
    return has_partition ? gen_ttl_col_qualifier_for_partition(partition_name)
                         : qualifier_str + RDB_TTL_COL_QUALIFIER +
                               RDB_QUALIFIER_VALUE_SEP;
  } else {
    DBUG_ASSERT(0);
  }

  return qualifier_str;
}

/*
  Formats the string and returns the column family name assignment part for a
  specific partition.
*/
const std::string Rdb_key_def::gen_cf_name_qualifier_for_partition(
    const std::string &prefix) {
  DBUG_ASSERT(!prefix.empty());

  return prefix + RDB_PER_PARTITION_QUALIFIER_NAME_SEP + RDB_CF_NAME_QUALIFIER +
         RDB_QUALIFIER_VALUE_SEP;
}

const std::string Rdb_key_def::gen_ttl_duration_qualifier_for_partition(
    const std::string &prefix) {
  DBUG_ASSERT(!prefix.empty());

  return prefix + RDB_PER_PARTITION_QUALIFIER_NAME_SEP +
         RDB_TTL_DURATION_QUALIFIER + RDB_QUALIFIER_VALUE_SEP;
}

const std::string Rdb_key_def::gen_ttl_col_qualifier_for_partition(
    const std::string &prefix) {
  DBUG_ASSERT(!prefix.empty());

  return prefix + RDB_PER_PARTITION_QUALIFIER_NAME_SEP + RDB_TTL_COL_QUALIFIER +
         RDB_QUALIFIER_VALUE_SEP;
}

const std::string Rdb_key_def::parse_comment_for_qualifier(
    const std::string &comment, const TABLE *const table_arg,
    const Rdb_tbl_def *const tbl_def_arg, bool *per_part_match_found,
    const char *const qualifier) {
  DBUG_ASSERT(table_arg != nullptr);
  DBUG_ASSERT(tbl_def_arg != nullptr);
  DBUG_ASSERT(per_part_match_found != nullptr);
  DBUG_ASSERT(qualifier != nullptr);

  std::string empty_result;

  // Flag which marks if partition specific options were found.
  *per_part_match_found = false;

  if (comment.empty()) {
    return empty_result;
  }

  // Let's fetch the comment for a index and check if there's a custom key
  // name specified for a partition we are handling.
  std::vector<std::string> v =
      myrocks::parse_into_tokens(comment, RDB_QUALIFIER_SEP);

  std::string search_str = gen_qualifier_for_table(qualifier);

  // If table has partitions then we need to check if user has requested
  // qualifiers on a per partition basis.
  //
  // NOTE: this means if you specify a qualifier for a specific partition it
  // will take precedence the 'table level' qualifier if one exists.
  std::string search_str_part;
  if (IF_PARTITIONING(table_arg->part_info,nullptr) != nullptr) {
    std::string partition_name = tbl_def_arg->base_partition();
    DBUG_ASSERT(!partition_name.empty());
    search_str_part = gen_qualifier_for_table(qualifier, partition_name);
  }

  DBUG_ASSERT(!search_str.empty());

  // Basic O(N) search for a matching assignment. At most we expect maybe
  // ten or so elements here.
  if (!search_str_part.empty()) {
    for (const auto &it : v) {
      if (it.substr(0, search_str_part.length()) == search_str_part) {
        // We found a prefix match. Try to parse it as an assignment.
        std::vector<std::string> tokens =
            myrocks::parse_into_tokens(it, RDB_QUALIFIER_VALUE_SEP);

        // We found a custom qualifier, it was in the form we expected it to be.
        // Return that instead of whatever we initially wanted to return. In
        // a case below the `foo` part will be returned to the caller.
        //
        // p3_cfname=foo
        //
        // If no value was specified then we'll return an empty string which
        // later gets translated into using a default CF.
        if (tokens.size() == 2) {
          *per_part_match_found = true;
          return tokens[1];
        } else {
          return empty_result;
        }
      }
    }
  }

  // Do this loop again, this time searching for 'table level' qualifiers if we
  // didn't find any partition level qualifiers above.
  for (const auto &it : v) {
    if (it.substr(0, search_str.length()) == search_str) {
      std::vector<std::string> tokens =
          myrocks::parse_into_tokens(it, RDB_QUALIFIER_VALUE_SEP);
      if (tokens.size() == 2) {
        return tokens[1];
      } else {
        return empty_result;
      }
    }
  }

  // If we didn't find any partitioned/non-partitioned qualifiers, return an
  // empty string.
  return empty_result;
}

/**
  Read a memcmp key part from a slice using the passed in reader.

  Returns -1 if field was null, 1 if error, 0 otherwise.
*/
int Rdb_key_def::read_memcmp_key_part(const TABLE *table_arg,
                                      Rdb_string_reader *reader,
                                      const uint part_num) const {
  /* It is impossible to unpack the column. Skip it. */
  if (m_pack_info[part_num].m_maybe_null) {
    const char *nullp;
    if (!(nullp = reader->read(1))) return 1;
    if (*nullp == 0) {
      /* This is a NULL value */
      return -1;
    } else {
      /* If NULL marker is not '0', it can be only '1'  */
      if (*nullp != 1) return 1;
    }
  }

  Rdb_field_packing *fpi = &m_pack_info[part_num];
  DBUG_ASSERT(table_arg->s != nullptr);

  bool is_hidden_pk_part = (part_num + 1 == m_key_parts) &&
                           (table_arg->s->primary_key == MAX_INDEXES);
  Field *field = nullptr;
  if (!is_hidden_pk_part) {
    field = fpi->get_field_in_table(table_arg);
  }
  if ((fpi->m_skip_func)(fpi, field, reader)) {
    return 1;
  }
  return 0;
}

/**
  Get a mem-comparable form of Primary Key from mem-comparable form of this key

  @param
    pk_descr        Primary Key descriptor
    key             Index tuple from this key in mem-comparable form
    pk_buffer  OUT  Put here mem-comparable form of the Primary Key.

  @note
    It may or may not be possible to restore primary key columns to their
    mem-comparable form.  To handle all cases, this function copies mem-
    comparable forms directly.

    RocksDB SE supports "Extended keys". This means that PK columns are present
    at the end of every key.  If the key already includes PK columns, then
    these columns are not present at the end of the key.

    Because of the above, we copy each primary key column.

  @todo
    If we checked crc32 checksums in this function, we would catch some CRC
    violations that we currently don't. On the other hand, there is a broader
    set of queries for which we would check the checksum twice.
*/

uint Rdb_key_def::get_primary_key_tuple(const TABLE *const table,
                                        const Rdb_key_def &pk_descr,
                                        const rocksdb::Slice *const key,
                                        uchar *const pk_buffer) const {
  DBUG_ASSERT(table != nullptr);
  DBUG_ASSERT(key != nullptr);
  DBUG_ASSERT(m_index_type == Rdb_key_def::INDEX_TYPE_SECONDARY);
  DBUG_ASSERT(pk_buffer);

  uint size = 0;
  uchar *buf = pk_buffer;
  DBUG_ASSERT(m_pk_key_parts);

  /* Put the PK number */
  rdb_netbuf_store_index(buf, pk_descr.m_index_number);
  buf += INDEX_NUMBER_SIZE;
  size += INDEX_NUMBER_SIZE;

  const char *start_offs[MAX_REF_PARTS];
  const char *end_offs[MAX_REF_PARTS];
  int pk_key_part;
  uint i;
  Rdb_string_reader reader(key);

  // Skip the index number
  if ((!reader.read(INDEX_NUMBER_SIZE))) return RDB_INVALID_KEY_LEN;

  for (i = 0; i < m_key_parts; i++) {
    if ((pk_key_part = m_pk_part_no[i]) != -1) {
      start_offs[pk_key_part] = reader.get_current_ptr();
    }

    if (read_memcmp_key_part(table, &reader, i) > 0) {
      return RDB_INVALID_KEY_LEN;
    }

    if (pk_key_part != -1) {
      end_offs[pk_key_part] = reader.get_current_ptr();
    }
  }

  for (i = 0; i < m_pk_key_parts; i++) {
    const uint part_size = end_offs[i] - start_offs[i];
    memcpy(buf, start_offs[i], end_offs[i] - start_offs[i]);
    buf += part_size;
    size += part_size;
  }

  return size;
}

/**
  Get a mem-comparable form of Secondary Key from mem-comparable form of this
  key, without the extended primary key tail.

  @param
    key                Index tuple from this key in mem-comparable form
    sk_buffer     OUT  Put here mem-comparable form of the Secondary Key.
    n_null_fields OUT  Put number of null fields contained within sk entry
*/
uint Rdb_key_def::get_memcmp_sk_parts(const TABLE *table,
                                      const rocksdb::Slice &key,
                                      uchar *sk_buffer,
                                      uint *n_null_fields) const {
  DBUG_ASSERT(table != nullptr);
  DBUG_ASSERT(sk_buffer != nullptr);
  DBUG_ASSERT(n_null_fields != nullptr);
  DBUG_ASSERT(m_keyno != table->s->primary_key && !table_has_hidden_pk(table));

  uchar *buf = sk_buffer;

  int res;
  Rdb_string_reader reader(&key);
  const char *start = reader.get_current_ptr();

  // Skip the index number
  if ((!reader.read(INDEX_NUMBER_SIZE))) return RDB_INVALID_KEY_LEN;

  for (uint i = 0; i < table->key_info[m_keyno].user_defined_key_parts; i++) {
    if ((res = read_memcmp_key_part(table, &reader, i)) > 0) {
      return RDB_INVALID_KEY_LEN;
    } else if (res == -1) {
      (*n_null_fields)++;
    }
  }

  uint sk_memcmp_len = reader.get_current_ptr() - start;
  memcpy(buf, start, sk_memcmp_len);
  return sk_memcmp_len;
}

/**
  Convert index tuple into storage (i.e. mem-comparable) format

  @detail
    Currently this is done by unpacking into record_buffer and then
    packing index columns into storage format.

  @param pack_buffer Temporary area for packing varchar columns. Its
                     size is at least max_storage_fmt_length() bytes.
*/

uint Rdb_key_def::pack_index_tuple(TABLE *const tbl, uchar *const pack_buffer,
                                   uchar *const packed_tuple,
                                   uchar *const record_buffer,
                                   const uchar *const key_tuple,
                                   const key_part_map &keypart_map) const {
  DBUG_ASSERT(tbl != nullptr);
  DBUG_ASSERT(pack_buffer != nullptr);
  DBUG_ASSERT(packed_tuple != nullptr);
  DBUG_ASSERT(key_tuple != nullptr);

  /* We were given a record in KeyTupleFormat. First, save it to record */
  const uint key_len = calculate_key_len(tbl, m_keyno, key_tuple, keypart_map);
  key_restore(record_buffer, key_tuple, &tbl->key_info[m_keyno], key_len);

  uint n_used_parts = my_count_bits(keypart_map);
  if (keypart_map == HA_WHOLE_KEY) n_used_parts = 0;  // Full key is used

  /* Then, convert the record into a mem-comparable form */
  return pack_record(tbl, pack_buffer, record_buffer, packed_tuple, nullptr,
                     false, 0, n_used_parts);
}

/**
  @brief
    Check if "unpack info" data includes checksum.

  @detail
    This is used only by CHECK TABLE to count the number of rows that have
    checksums.
*/

bool Rdb_key_def::unpack_info_has_checksum(const rocksdb::Slice &unpack_info) {
  size_t size = unpack_info.size();
  if (size == 0) {
    return false;
  }
  const uchar *ptr = (const uchar *)unpack_info.data();

  // Skip unpack info if present.
  if (is_unpack_data_tag(ptr[0]) && size >= get_unpack_header_size(ptr[0])) {
    const uint16 skip_len = rdb_netbuf_to_uint16(ptr + 1);
    SHIP_ASSERT(size >= skip_len);

    size -= skip_len;
    ptr += skip_len;
  }

  return (size == RDB_CHECKSUM_CHUNK_SIZE && ptr[0] == RDB_CHECKSUM_DATA_TAG);
}

/*
  @return Number of bytes that were changed
*/
int Rdb_key_def::successor(uchar *const packed_tuple, const uint len) {
  DBUG_ASSERT(packed_tuple != nullptr);

  int changed = 0;
  uchar *p = packed_tuple + len - 1;
  for (; p > packed_tuple; p--) {
    changed++;
    if (*p != uchar(0xFF)) {
      *p = *p + 1;
      break;
    }
    *p = '\0';
  }
  return changed;
}

/*
  @return Number of bytes that were changed
*/
int Rdb_key_def::predecessor(uchar *const packed_tuple, const uint len) {
  DBUG_ASSERT(packed_tuple != nullptr);

  int changed = 0;
  uchar *p = packed_tuple + len - 1;
  for (; p > packed_tuple; p--) {
    changed++;
    if (*p != uchar(0x00)) {
      *p = *p - 1;
      break;
    }
    *p = 0xFF;
  }
  return changed;
}

static const std::map<char, size_t> UNPACK_HEADER_SIZES = {
    {RDB_UNPACK_DATA_TAG, RDB_UNPACK_HEADER_SIZE},
    {RDB_UNPACK_COVERED_DATA_TAG, RDB_UNPACK_COVERED_HEADER_SIZE}};

/*
  @return The length in bytes of the header specified by the given tag
*/
size_t Rdb_key_def::get_unpack_header_size(char tag) {
  DBUG_ASSERT(is_unpack_data_tag(tag));
  return UNPACK_HEADER_SIZES.at(tag);
}

/*
  Get a bitmap indicating which varchar columns must be covered for this
  lookup to be covered. If the bitmap is a subset of the covered bitmap, then
  the lookup is covered. If it can already be determined that the lookup is
  not covered, map->bitmap will be set to null.
 */
void Rdb_key_def::get_lookup_bitmap(const TABLE *table, MY_BITMAP *map) const {
  DBUG_ASSERT(map->bitmap == nullptr);
  bitmap_init(map, nullptr, MAX_REF_PARTS, false);
  uint curr_bitmap_pos = 0;

  // Indicates which columns in the read set might be covered.
  MY_BITMAP maybe_covered_bitmap;
  bitmap_init(&maybe_covered_bitmap, nullptr, table->read_set->n_bits, false);

  for (uint i = 0; i < m_key_parts; i++) {
    if (table_has_hidden_pk(table) && i + 1 == m_key_parts) {
      continue;
    }

    Field *const field = m_pack_info[i].get_field_in_table(table);

    // Columns which are always covered are not stored in the covered bitmap so
    // we can ignore them here too.
    if (m_pack_info[i].m_covered &&
        bitmap_is_set(table->read_set, field->field_index)) {
      bitmap_set_bit(&maybe_covered_bitmap, field->field_index);
      continue;
    }

    switch (field->real_type()) {
      // This type may be covered depending on the record. If it was requested,
      // we require the covered bitmap to have this bit set.
      case MYSQL_TYPE_VARCHAR:
        if (curr_bitmap_pos < MAX_REF_PARTS) {
          if (bitmap_is_set(table->read_set, field->field_index)) {
            bitmap_set_bit(map, curr_bitmap_pos);
            bitmap_set_bit(&maybe_covered_bitmap, field->field_index);
          }
          curr_bitmap_pos++;
        } else {
          bitmap_free(&maybe_covered_bitmap);
          bitmap_free(map);
          return;
        }
        break;
      // This column is a type which is never covered. If it was requested, we
      // know this lookup will never be covered.
      default:
        if (bitmap_is_set(table->read_set, field->field_index)) {
          bitmap_free(&maybe_covered_bitmap);
          bitmap_free(map);
          return;
        }
        break;
    }
  }

  // If there are columns which are not covered in the read set, the lookup
  // can't be covered.
  if (!bitmap_cmp(table->read_set, &maybe_covered_bitmap)) {
    bitmap_free(map);
  }
  bitmap_free(&maybe_covered_bitmap);
}

/*
  Return true if for this secondary index
  - All of the requested columns are in the index
  - All values for columns that are prefix-only indexes are shorter or equal
    in length to the prefix
 */
bool Rdb_key_def::covers_lookup(const rocksdb::Slice *const unpack_info,
                                const MY_BITMAP *const lookup_bitmap) const {
  DBUG_ASSERT(lookup_bitmap != nullptr);
  if (!use_covered_bitmap_format() || lookup_bitmap->bitmap == nullptr) {
    return false;
  }

  Rdb_string_reader unp_reader = Rdb_string_reader::read_or_empty(unpack_info);

  // Check if this unpack_info has a covered_bitmap
  const char *unpack_header = unp_reader.get_current_ptr();
  const bool has_covered_unpack_info =
      unp_reader.remaining_bytes() &&
      unpack_header[0] == RDB_UNPACK_COVERED_DATA_TAG;
  if (!has_covered_unpack_info ||
      !unp_reader.read(RDB_UNPACK_COVERED_HEADER_SIZE)) {
    return false;
  }

  MY_BITMAP covered_bitmap;
  my_bitmap_map covered_bits;
  bitmap_init(&covered_bitmap, &covered_bits, MAX_REF_PARTS, false);
  covered_bits = rdb_netbuf_to_uint16((const uchar *)unpack_header +
                                      sizeof(RDB_UNPACK_COVERED_DATA_TAG) +
                                      RDB_UNPACK_COVERED_DATA_LEN_SIZE);

  return bitmap_is_subset(lookup_bitmap, &covered_bitmap);
}

/* Indicates that all key parts can be unpacked to cover a secondary lookup */
bool Rdb_key_def::can_cover_lookup() const {
  for (uint i = 0; i < m_key_parts; i++) {
    if (!m_pack_info[i].m_covered) return false;
  }
  return true;
}

uchar *Rdb_key_def::pack_field(Field *const field, Rdb_field_packing *pack_info,
                               uchar *tuple, uchar *const packed_tuple,
                               uchar *const pack_buffer,
                               Rdb_string_writer *const unpack_info,
                               uint *const n_null_fields) const {
  if (field->real_maybe_null()) {
    DBUG_ASSERT(is_storage_available(tuple - packed_tuple, 1));
    if (field->is_real_null()) {
      /* NULL value. store '\0' so that it sorts before non-NULL values */
      *tuple++ = 0;
      /* That's it, don't store anything else */
      if (n_null_fields) (*n_null_fields)++;
      return tuple;
    } else {
      /* Not a NULL value. Store '1' */
      *tuple++ = 1;
    }
  }

  const bool create_unpack_info =
      (unpack_info &&  // we were requested to generate unpack_info
       pack_info->uses_unpack_info());  // and this keypart uses it
  Rdb_pack_field_context pack_ctx(unpack_info);

  // Set the offset for methods which do not take an offset as an argument
  DBUG_ASSERT(
      is_storage_available(tuple - packed_tuple, pack_info->m_max_image_len));

  (pack_info->m_pack_func)(pack_info, field, pack_buffer, &tuple, &pack_ctx);

  /* Make "unpack info" to be stored in the value */
  if (create_unpack_info) {
    (pack_info->m_make_unpack_info_func)(pack_info->m_charset_codec, field,
                                         &pack_ctx);
  }

  return tuple;
}

/**
  Get index columns from the record and pack them into mem-comparable form.

  @param
    tbl                   Table we're working on
    record           IN   Record buffer with fields in table->record format
    pack_buffer      IN   Temporary area for packing varchars. The size is
                          at least max_storage_fmt_length() bytes.
    packed_tuple     OUT  Key in the mem-comparable form
    unpack_info      OUT  Unpack data
    unpack_info_len  OUT  Unpack data length
    n_key_parts           Number of keyparts to process. 0 means all of them.
    n_null_fields    OUT  Number of key fields with NULL value.
    ttl_bytes        IN   Previous ttl bytes from old record for update case or
                          current ttl bytes from just packed primary key/value
  @detail
    Some callers do not need the unpack information, they can pass
    unpack_info=nullptr, unpack_info_len=nullptr.

  @return
    Length of the packed tuple
*/

uint Rdb_key_def::pack_record(const TABLE *const tbl, uchar *const pack_buffer,
                              const uchar *const record,
                              uchar *const packed_tuple,
                              Rdb_string_writer *const unpack_info,
                              const bool should_store_row_debug_checksums,
                              const longlong hidden_pk_id, uint n_key_parts,
                              uint *const n_null_fields,
                              const char *const ttl_bytes) const {
  DBUG_ASSERT(tbl != nullptr);
  DBUG_ASSERT(pack_buffer != nullptr);
  DBUG_ASSERT(record != nullptr);
  DBUG_ASSERT(packed_tuple != nullptr);
  // Checksums for PKs are made when record is packed.
  // We should never attempt to make checksum just from PK values
  DBUG_ASSERT_IMP(should_store_row_debug_checksums,
                  (m_index_type == INDEX_TYPE_SECONDARY));

  uchar *tuple = packed_tuple;
  size_t unpack_start_pos = size_t(-1);
  size_t unpack_len_pos = size_t(-1);
  size_t covered_bitmap_pos = size_t(-1);
  const bool hidden_pk_exists = table_has_hidden_pk(tbl);

  rdb_netbuf_store_index(tuple, m_index_number);
  tuple += INDEX_NUMBER_SIZE;

  // If n_key_parts is 0, it means all columns.
  // The following includes the 'extended key' tail.
  // The 'extended key' includes primary key. This is done to 'uniqify'
  // non-unique indexes
  const bool use_all_columns = n_key_parts == 0 || n_key_parts == MAX_REF_PARTS;

  // If hidden pk exists, but hidden pk wasnt passed in, we can't pack the
  // hidden key part.  So we skip it (its always 1 part).
  if (hidden_pk_exists && !hidden_pk_id && use_all_columns) {
    n_key_parts = m_key_parts - 1;
  } else if (use_all_columns) {
    n_key_parts = m_key_parts;
  }

  if (n_null_fields) *n_null_fields = 0;

  // Check if we need a covered bitmap. If it is certain that all key parts are
  // covering, we don't need one.
  bool store_covered_bitmap = false;
  if (unpack_info && use_covered_bitmap_format()) {
    for (uint i = 0; i < n_key_parts; i++) {
      if (!m_pack_info[i].m_covered) {
        store_covered_bitmap = true;
        break;
      }
    }
  }

  const char tag =
      store_covered_bitmap ? RDB_UNPACK_COVERED_DATA_TAG : RDB_UNPACK_DATA_TAG;

  if (unpack_info) {
    unpack_info->clear();

    if (m_index_type == INDEX_TYPE_SECONDARY &&
        m_total_index_flags_length > 0) {
      // Reserve space for index flag fields
      unpack_info->allocate(m_total_index_flags_length);

      // Insert TTL timestamp
      if (has_ttl() && ttl_bytes) {
        write_index_flag_field(unpack_info,
                               reinterpret_cast<const uchar *>(ttl_bytes),
                               Rdb_key_def::TTL_FLAG);
      }
    }

    unpack_start_pos = unpack_info->get_current_pos();
    unpack_info->write_uint8(tag);
    unpack_len_pos = unpack_info->get_current_pos();
    // we don't know the total length yet, so write a zero
    unpack_info->write_uint16(0);

    if (store_covered_bitmap) {
      // Reserve two bytes for the covered bitmap. This will store, for key
      // parts which are not always covering, whether or not it is covering
      // for this record.
      covered_bitmap_pos = unpack_info->get_current_pos();
      unpack_info->write_uint16(0);
    }
  }

  MY_BITMAP covered_bitmap;
  my_bitmap_map covered_bits;
  uint curr_bitmap_pos = 0;
  bitmap_init(&covered_bitmap, &covered_bits, MAX_REF_PARTS, false);

  for (uint i = 0; i < n_key_parts; i++) {
    // Fill hidden pk id into the last key part for secondary keys for tables
    // with no pk
    if (hidden_pk_exists && hidden_pk_id && i + 1 == n_key_parts) {
      m_pack_info[i].fill_hidden_pk_val(&tuple, hidden_pk_id);
      break;
    }

    Field *const field = m_pack_info[i].get_field_in_table(tbl);
    DBUG_ASSERT(field != nullptr);

    uint field_offset = field->ptr - tbl->record[0];
    uint null_offset = field->null_offset(tbl->record[0]);
    bool maybe_null = field->real_maybe_null();

    field->move_field(
        const_cast<uchar *>(record) + field_offset,
        maybe_null ? const_cast<uchar *>(record) + null_offset : nullptr,
        field->null_bit);
    // WARNING! Don't return without restoring field->ptr and field->null_ptr

    tuple = pack_field(field, &m_pack_info[i], tuple, packed_tuple, pack_buffer,
                       unpack_info, n_null_fields);

    // If this key part is a prefix of a VARCHAR field, check if it's covered.
    if (store_covered_bitmap && field->real_type() == MYSQL_TYPE_VARCHAR &&
        !m_pack_info[i].m_covered && curr_bitmap_pos < MAX_REF_PARTS) {
      size_t data_length = field->data_length();
      uint16 key_length;
      if (m_pk_part_no[i] == (uint)-1) {
        key_length = tbl->key_info[get_keyno()].key_part[i].length;
      } else {
        key_length =
            tbl->key_info[tbl->s->primary_key].key_part[m_pk_part_no[i]].length;
      }

      if (m_pack_info[i].m_unpack_func != nullptr &&
          data_length <= key_length) {
        bitmap_set_bit(&covered_bitmap, curr_bitmap_pos);
      }
      curr_bitmap_pos++;
    }

    // Restore field->ptr and field->null_ptr
    field->move_field(tbl->record[0] + field_offset,
                      maybe_null ? tbl->record[0] + null_offset : nullptr,
                      field->null_bit);
  }

  if (unpack_info) {
    const size_t len = unpack_info->get_current_pos() - unpack_start_pos;
    DBUG_ASSERT(len <= std::numeric_limits<uint16_t>::max());

    // Don't store the unpack_info if it has only the header (that is, there's
    // no meaningful content).
    // Primary Keys are special: for them, store the unpack_info even if it's
    // empty (provided m_maybe_unpack_info==true, see
    // ha_rocksdb::convert_record_to_storage_format)
    if (m_index_type == Rdb_key_def::INDEX_TYPE_SECONDARY) {
      if (len == get_unpack_header_size(tag) && !covered_bits) {
        unpack_info->truncate(unpack_start_pos);
      } else if (store_covered_bitmap) {
        unpack_info->write_uint16_at(covered_bitmap_pos, covered_bits);
      }
    } else {
      unpack_info->write_uint16_at(unpack_len_pos, len);
    }

    //
    // Secondary keys have key and value checksums in the value part
    // Primary key is a special case (the value part has non-indexed columns),
    // so the checksums are computed and stored by
    // ha_rocksdb::convert_record_to_storage_format
    //
    if (should_store_row_debug_checksums) {
      const uint32_t key_crc32 =
          my_checksum(0, packed_tuple, tuple - packed_tuple);
      const uint32_t val_crc32 =
          my_checksum(0, unpack_info->ptr(), unpack_info->get_current_pos());

      unpack_info->write_uint8(RDB_CHECKSUM_DATA_TAG);
      unpack_info->write_uint32(key_crc32);
      unpack_info->write_uint32(val_crc32);
    }
  }

  DBUG_ASSERT(is_storage_available(tuple - packed_tuple, 0));

  return tuple - packed_tuple;
}

/**
  Pack the hidden primary key into mem-comparable form.

  @param
    tbl                   Table we're working on
    hidden_pk_id     IN   New value to be packed into key
    packed_tuple     OUT  Key in the mem-comparable form

  @return
    Length of the packed tuple
*/

uint Rdb_key_def::pack_hidden_pk(const longlong hidden_pk_id,
                                 uchar *const packed_tuple) const {
  DBUG_ASSERT(packed_tuple != nullptr);

  uchar *tuple = packed_tuple;
  rdb_netbuf_store_index(tuple, m_index_number);
  tuple += INDEX_NUMBER_SIZE;
  DBUG_ASSERT(m_key_parts == 1);
  DBUG_ASSERT(is_storage_available(tuple - packed_tuple,
                                   m_pack_info[0].m_max_image_len));

  m_pack_info[0].fill_hidden_pk_val(&tuple, hidden_pk_id);

  DBUG_ASSERT(is_storage_available(tuple - packed_tuple, 0));
  return tuple - packed_tuple;
}

/*
  Function of type rdb_index_field_pack_t
*/

void Rdb_key_def::pack_with_make_sort_key(
    Rdb_field_packing *const fpi, Field *const field,
    uchar *const buf MY_ATTRIBUTE((__unused__)), uchar **dst,
    Rdb_pack_field_context *const pack_ctx MY_ATTRIBUTE((__unused__))) {
  DBUG_ASSERT(fpi != nullptr);
  DBUG_ASSERT(field != nullptr);
  DBUG_ASSERT(dst != nullptr);
  DBUG_ASSERT(*dst != nullptr);

  const int max_len = fpi->m_max_image_len;
  MY_BITMAP*old_map;

  old_map= dbug_tmp_use_all_columns(field->table,
                                    &field->table->read_set);
  field->sort_string(*dst, max_len);
  dbug_tmp_restore_column_map(&field->table->read_set, old_map);
  *dst += max_len;
}

/*
  Compares two keys without unpacking

  @detail
  @return
    0 - Ok. column_index is the index of the first column which is different.
          -1 if two kes are equal
    1 - Data format error.
*/
int Rdb_key_def::compare_keys(const rocksdb::Slice *key1,
                              const rocksdb::Slice *key2,
                              std::size_t *const column_index) const {
  DBUG_ASSERT(key1 != nullptr);
  DBUG_ASSERT(key2 != nullptr);
  DBUG_ASSERT(column_index != nullptr);

  // the caller should check the return value and
  // not rely on column_index being valid
  *column_index = 0xbadf00d;

  Rdb_string_reader reader1(key1);
  Rdb_string_reader reader2(key2);

  // Skip the index number
  if ((!reader1.read(INDEX_NUMBER_SIZE))) return HA_EXIT_FAILURE;

  if ((!reader2.read(INDEX_NUMBER_SIZE))) return HA_EXIT_FAILURE;

  for (uint i = 0; i < m_key_parts; i++) {
    const Rdb_field_packing *const fpi = &m_pack_info[i];
    if (fpi->m_maybe_null) {
      const auto nullp1 = reader1.read(1);
      const auto nullp2 = reader2.read(1);

      if (nullp1 == nullptr || nullp2 == nullptr) {
        return HA_EXIT_FAILURE;
      }

      if (*nullp1 != *nullp2) {
        *column_index = i;
        return HA_EXIT_SUCCESS;
      }

      if (*nullp1 == 0) {
        /* This is a NULL value */
        continue;
      }
    }

    const auto before_skip1 = reader1.get_current_ptr();
    const auto before_skip2 = reader2.get_current_ptr();
    DBUG_ASSERT(fpi->m_skip_func);
    if ((fpi->m_skip_func)(fpi, nullptr, &reader1)) {
      return HA_EXIT_FAILURE;
    }
    if ((fpi->m_skip_func)(fpi, nullptr, &reader2)) {
      return HA_EXIT_FAILURE;
    }
    const auto size1 = reader1.get_current_ptr() - before_skip1;
    const auto size2 = reader2.get_current_ptr() - before_skip2;
    if (size1 != size2) {
      *column_index = i;
      return HA_EXIT_SUCCESS;
    }

    if (memcmp(before_skip1, before_skip2, size1) != 0) {
      *column_index = i;
      return HA_EXIT_SUCCESS;
    }
  }

  *column_index = m_key_parts;
  return HA_EXIT_SUCCESS;
}

/*
  @brief
    Given a zero-padded key, determine its real key length

  @detail
    Fixed-size skip functions just read.
*/

size_t Rdb_key_def::key_length(const TABLE *const table,
                               const rocksdb::Slice &key) const {
  DBUG_ASSERT(table != nullptr);

  Rdb_string_reader reader(&key);

  if ((!reader.read(INDEX_NUMBER_SIZE))) {
    return size_t(-1);
  }
  for (uint i = 0; i < m_key_parts; i++) {
    const Rdb_field_packing *fpi = &m_pack_info[i];
    const Field *field = nullptr;
    if (m_index_type != INDEX_TYPE_HIDDEN_PRIMARY) {
      field = fpi->get_field_in_table(table);
    }
    if ((fpi->m_skip_func)(fpi, field, &reader)) {
      return size_t(-1);
    }
  }
  return key.size() - reader.remaining_bytes();
}

/*
  Take mem-comparable form and unpack_info and unpack it to Table->record

  @detail
    not all indexes support this

  @return
    HA_EXIT_SUCCESS    OK
    other              HA_ERR error code
*/

int Rdb_key_def::unpack_record(TABLE *const table, uchar *const buf,
                               const rocksdb::Slice *const packed_key,
                               const rocksdb::Slice *const unpack_info,
                               const bool verify_row_debug_checksums) const {
  Rdb_string_reader reader(packed_key);
  Rdb_string_reader unp_reader = Rdb_string_reader::read_or_empty(unpack_info);

  // There is no checksuming data after unpack_info for primary keys, because
  // the layout there is different. The checksum is verified in
  // ha_rocksdb::convert_record_from_storage_format instead.
  DBUG_ASSERT_IMP(!(m_index_type == INDEX_TYPE_SECONDARY),
                  !verify_row_debug_checksums);

  // Skip the index number
  if ((!reader.read(INDEX_NUMBER_SIZE))) {
    return HA_ERR_ROCKSDB_CORRUPT_DATA;
  }

  // For secondary keys, we expect the value field to contain index flags,
  // unpack data, and checksum data in that order. One or all can be missing,
  // but they cannot be reordered.
  if (unp_reader.remaining_bytes()) {
    if (m_index_type == INDEX_TYPE_SECONDARY &&
        m_total_index_flags_length > 0 &&
        !unp_reader.read(m_total_index_flags_length)) {
      return HA_ERR_ROCKSDB_CORRUPT_DATA;
    }
  }

  const char *unpack_header = unp_reader.get_current_ptr();
  bool has_unpack_info =
      unp_reader.remaining_bytes() && is_unpack_data_tag(unpack_header[0]);
  if (has_unpack_info) {
    if (!unp_reader.read(get_unpack_header_size(unpack_header[0]))) {
      return HA_ERR_ROCKSDB_CORRUPT_DATA;
    }
  }

  // Read the covered bitmap
  MY_BITMAP covered_bitmap;
  my_bitmap_map covered_bits;
  bool has_covered_bitmap =
      has_unpack_info && (unpack_header[0] == RDB_UNPACK_COVERED_DATA_TAG);
  if (has_covered_bitmap) {
    bitmap_init(&covered_bitmap, &covered_bits, MAX_REF_PARTS, false);
    covered_bits = rdb_netbuf_to_uint16((const uchar *)unpack_header +
                                        sizeof(RDB_UNPACK_COVERED_DATA_TAG) +
                                        RDB_UNPACK_COVERED_DATA_LEN_SIZE);
  }

  int err = HA_EXIT_SUCCESS;


  Rdb_key_field_iterator iter(
      this, m_pack_info, &reader, &unp_reader, table, has_unpack_info,
      has_covered_bitmap ? &covered_bitmap : nullptr, buf);
  while (iter.has_next()) {
    err = iter.next();
    if (err) {
      return err;
    }
  }

  /*
    Check checksum values if present
  */
  const char *ptr;
  if ((ptr = unp_reader.read(1)) && *ptr == RDB_CHECKSUM_DATA_TAG) {
    if (verify_row_debug_checksums) {
      uint32_t stored_key_chksum = rdb_netbuf_to_uint32(
          (const uchar *)unp_reader.read(RDB_CHECKSUM_SIZE));
      const uint32_t stored_val_chksum = rdb_netbuf_to_uint32(
          (const uchar *)unp_reader.read(RDB_CHECKSUM_SIZE));

      const uint32_t computed_key_chksum =
          my_checksum(0, packed_key->data(), packed_key->size());
      const uint32_t computed_val_chksum =
          my_checksum(0, unpack_info->data(),
                unpack_info->size() - RDB_CHECKSUM_CHUNK_SIZE);

      DBUG_EXECUTE_IF("myrocks_simulate_bad_key_checksum1",
                      stored_key_chksum++;);

      if (stored_key_chksum != computed_key_chksum) {
        report_checksum_mismatch(true, packed_key->data(), packed_key->size());
        return HA_ERR_ROCKSDB_CHECKSUM_MISMATCH;
      }

      if (stored_val_chksum != computed_val_chksum) {
        report_checksum_mismatch(false, unpack_info->data(),
                                 unpack_info->size() - RDB_CHECKSUM_CHUNK_SIZE);
        return HA_ERR_ROCKSDB_CHECKSUM_MISMATCH;
      }
    } else {
      /* The checksums are present but we are not checking checksums */
    }
  }

  if (reader.remaining_bytes()) return HA_ERR_ROCKSDB_CORRUPT_DATA;

  return HA_EXIT_SUCCESS;
}

bool Rdb_key_def::table_has_hidden_pk(const TABLE *const table) {
  return table->s->primary_key == MAX_INDEXES;
}

void Rdb_key_def::report_checksum_mismatch(const bool is_key,
                                           const char *const data,
                                           const size_t data_size) const {
  // NO_LINT_DEBUG
  sql_print_error("Checksum mismatch in %s of key-value pair for index 0x%x",
                  is_key ? "key" : "value", get_index_number());

  const std::string buf = rdb_hexdump(data, data_size, RDB_MAX_HEXDUMP_LEN);
  // NO_LINT_DEBUG
  sql_print_error("Data with incorrect checksum (%" PRIu64 " bytes): %s",
                  (uint64_t)data_size, buf.c_str());

  my_error(ER_INTERNAL_ERROR, MYF(0), "Record checksum mismatch");
}

bool Rdb_key_def::index_format_min_check(const int pk_min,
                                         const int sk_min) const {
  switch (m_index_type) {
    case INDEX_TYPE_PRIMARY:
    case INDEX_TYPE_HIDDEN_PRIMARY:
      return (m_kv_format_version >= pk_min);
    case INDEX_TYPE_SECONDARY:
      return (m_kv_format_version >= sk_min);
    default:
      DBUG_ASSERT(0);
      return false;
  }
}

///////////////////////////////////////////////////////////////////////////////////////////
// Rdb_field_packing
///////////////////////////////////////////////////////////////////////////////////////////

/*
  Function of type rdb_index_field_skip_t
*/

int Rdb_key_def::skip_max_length(const Rdb_field_packing *const fpi,
                                 const Field *const field
                                     MY_ATTRIBUTE((__unused__)),
                                 Rdb_string_reader *const reader) {
  if (!reader->read(fpi->m_max_image_len)) return HA_EXIT_FAILURE;
  return HA_EXIT_SUCCESS;
}

/*
  (RDB_ESCAPE_LENGTH-1) must be an even number so that pieces of lines are not
  split in the middle of an UTF-8 character. See the implementation of
  unpack_binary_or_utf8_varchar.
*/
#define RDB_ESCAPE_LENGTH 9
#define RDB_LEGACY_ESCAPE_LENGTH RDB_ESCAPE_LENGTH
static_assert((RDB_ESCAPE_LENGTH - 1) % 2 == 0,
              "RDB_ESCAPE_LENGTH-1 must be even.");

#define RDB_ENCODED_SIZE(len)                                   \
  ((len + (RDB_ESCAPE_LENGTH - 2)) / (RDB_ESCAPE_LENGTH - 1)) * \
      RDB_ESCAPE_LENGTH

#define RDB_LEGACY_ENCODED_SIZE(len)                                          \
  ((len + (RDB_LEGACY_ESCAPE_LENGTH - 1)) / (RDB_LEGACY_ESCAPE_LENGTH - 1)) * \
      RDB_LEGACY_ESCAPE_LENGTH

/*
  Function of type rdb_index_field_skip_t
*/

int Rdb_key_def::skip_variable_length(const Rdb_field_packing *const fpi,
                                      const Field *const field,
                                      Rdb_string_reader *const reader) {
  const uchar *ptr;
  bool finished = false;

  size_t dst_len; /* How much data can be there */
  if (field) {
    const Field_varstring *const field_var =
        static_cast<const Field_varstring *>(field);
    dst_len = field_var->pack_length() - field_var->length_bytes;
  } else {
    dst_len = UINT_MAX;
  }

  bool use_legacy_format = fpi->m_use_legacy_varbinary_format;

  /* Decode the length-emitted encoding here */
  while ((ptr = (const uchar *)reader->read(RDB_ESCAPE_LENGTH))) {
    uint used_bytes;

    /* See pack_with_varchar_encoding. */
    if (use_legacy_format) {
      used_bytes = calc_unpack_legacy_variable_format(
          ptr[RDB_ESCAPE_LENGTH - 1], &finished);
    } else {
      used_bytes =
          calc_unpack_variable_format(ptr[RDB_ESCAPE_LENGTH - 1], &finished);
    }

    if (used_bytes == (uint)-1 || dst_len < used_bytes) {
      return HA_EXIT_FAILURE;  // Corruption in the data
    }

    if (finished) {
      break;
    }

    dst_len -= used_bytes;
  }

  if (!finished) {
    return HA_EXIT_FAILURE;
  }

  return HA_EXIT_SUCCESS;
}

const int VARCHAR_CMP_LESS_THAN_SPACES = 1;
const int VARCHAR_CMP_EQUAL_TO_SPACES = 2;
const int VARCHAR_CMP_GREATER_THAN_SPACES = 3;

/*
  Skip a keypart that uses Variable-Length Space-Padded encoding
*/

int Rdb_key_def::skip_variable_space_pad(const Rdb_field_packing *const fpi,
                                         const Field *const field,
                                         Rdb_string_reader *const reader) {
  const uchar *ptr;
  bool finished = false;

  size_t dst_len = UINT_MAX; /* How much data can be there */

  if (field) {
    const Field_varstring *const field_var =
        static_cast<const Field_varstring *>(field);
    dst_len = field_var->pack_length() - field_var->length_bytes;
  }

  /* Decode the length-emitted encoding here */
  while ((ptr = (const uchar *)reader->read(fpi->m_segment_size))) {
    // See pack_with_varchar_space_pad
    const uchar c = ptr[fpi->m_segment_size - 1];
    if (c == VARCHAR_CMP_EQUAL_TO_SPACES) {
      // This is the last segment
      finished = true;
      break;
    } else if (c == VARCHAR_CMP_LESS_THAN_SPACES ||
               c == VARCHAR_CMP_GREATER_THAN_SPACES) {
      // This is not the last segment
      if ((fpi->m_segment_size - 1) > dst_len) {
        // The segment is full of data but the table field can't hold that
        // much! This must be data corruption.
        return HA_EXIT_FAILURE;
      }
      dst_len -= (fpi->m_segment_size - 1);
    } else {
      // Encountered a value that's none of the VARCHAR_CMP* constants
      // It's data corruption.
      return HA_EXIT_FAILURE;
    }
  }
  return finished ? HA_EXIT_SUCCESS : HA_EXIT_FAILURE;
}

/*
  Function of type rdb_index_field_unpack_t
*/

int Rdb_key_def::unpack_integer(
    Rdb_field_packing *const fpi, Field *const field, uchar *const to,
    Rdb_string_reader *const reader,
    Rdb_string_reader *const unp_reader MY_ATTRIBUTE((__unused__))) {
  const int length = fpi->m_max_image_len;

  const uchar *from;
  if (!(from = (const uchar *)reader->read(length))) {
    return UNPACK_FAILURE; /* Mem-comparable image doesn't have enough bytes */
  }

#ifdef WORDS_BIGENDIAN
  {
    if (static_cast<Field_num *>(field)->unsigned_flag) {
      to[0] = from[0];
    } else {
      to[0] = static_cast<char>(from[0] ^ 128);  // Reverse the sign bit.
    }
    memcpy(to + 1, from + 1, length - 1);
  }
#else
  {
    const int sign_byte = from[0];
    if (static_cast<Field_num *>(field)->unsigned_flag) {
      to[length - 1] = sign_byte;
    } else {
      to[length - 1] =
          static_cast<char>(sign_byte ^ 128);  // Reverse the sign bit.
    }
    for (int i = 0, j = length - 1; i < length - 1; ++i, --j) to[i] = from[j];
  }
#endif
  return UNPACK_SUCCESS;
}

#if !defined(WORDS_BIGENDIAN)
static void rdb_swap_double_bytes(uchar *const dst, const uchar *const src) {
#if defined(__FLOAT_WORD_ORDER) && (__FLOAT_WORD_ORDER == __BIG_ENDIAN)
  // A few systems store the most-significant _word_ first on little-endian
  dst[0] = src[3];
  dst[1] = src[2];
  dst[2] = src[1];
  dst[3] = src[0];
  dst[4] = src[7];
  dst[5] = src[6];
  dst[6] = src[5];
  dst[7] = src[4];
#else
  dst[0] = src[7];
  dst[1] = src[6];
  dst[2] = src[5];
  dst[3] = src[4];
  dst[4] = src[3];
  dst[5] = src[2];
  dst[6] = src[1];
  dst[7] = src[0];
#endif
}

static void rdb_swap_float_bytes(uchar *const dst, const uchar *const src) {
  dst[0] = src[3];
  dst[1] = src[2];
  dst[2] = src[1];
  dst[3] = src[0];
}
#else
#define rdb_swap_double_bytes nullptr
#define rdb_swap_float_bytes nullptr
#endif

int Rdb_key_def::unpack_floating_point(
    uchar *const dst, Rdb_string_reader *const reader, const size_t size,
    const int exp_digit, const uchar *const zero_pattern,
    const uchar *const zero_val, void (*swap_func)(uchar *, const uchar *)) {
  const uchar *const from = (const uchar *)reader->read(size);
  if (from == nullptr) {
    /* Mem-comparable image doesn't have enough bytes */
    return UNPACK_FAILURE;
  }

  /* Check to see if the value is zero */
  if (memcmp(from, zero_pattern, size) == 0) {
    memcpy(dst, zero_val, size);
    return UNPACK_SUCCESS;
  }

#if defined(WORDS_BIGENDIAN)
  // On big-endian, output can go directly into result
  uchar *const tmp = dst;
#else
  // Otherwise use a temporary buffer to make byte-swapping easier later
  uchar tmp[8];
#endif

  memcpy(tmp, from, size);

  if (tmp[0] & 0x80) {
    // If the high bit is set the original value was positive so
    // remove the high bit and subtract one from the exponent.
    ushort exp_part = ((ushort)tmp[0] << 8) | (ushort)tmp[1];
    exp_part &= 0x7FFF;                             // clear high bit;
    exp_part -= (ushort)1 << (16 - 1 - exp_digit);  // subtract from exponent
    tmp[0] = (uchar)(exp_part >> 8);
    tmp[1] = (uchar)exp_part;
  } else {
    // Otherwise the original value was negative and all bytes have been
    // negated.
    for (size_t ii = 0; ii < size; ii++) tmp[ii] ^= 0xFF;
  }

#if !defined(WORDS_BIGENDIAN)
  // On little-endian, swap the bytes around
  swap_func(dst, tmp);
#else
  DBUG_ASSERT(swap_func == nullptr);
#endif

  return UNPACK_SUCCESS;
}

#if !defined(DBL_EXP_DIG)
#define DBL_EXP_DIG (sizeof(double) * 8 - DBL_MANT_DIG)
#endif

/*
  Function of type rdb_index_field_unpack_t

  Unpack a double by doing the reverse action of change_double_for_sort
  (sql/filesort.cc).  Note that this only works on IEEE values.
  Note also that this code assumes that NaN and +/-Infinity are never
  allowed in the database.
*/
int Rdb_key_def::unpack_double(
    Rdb_field_packing *const fpi MY_ATTRIBUTE((__unused__)),
    Field *const field MY_ATTRIBUTE((__unused__)), uchar *const field_ptr,
    Rdb_string_reader *const reader,
    Rdb_string_reader *const unp_reader MY_ATTRIBUTE((__unused__))) {
  static double zero_val = 0.0;
  static const uchar zero_pattern[8] = {128, 0, 0, 0, 0, 0, 0, 0};

  return unpack_floating_point(field_ptr, reader, sizeof(double), DBL_EXP_DIG,
                               zero_pattern, (const uchar *)&zero_val,
                               rdb_swap_double_bytes);
}

#if !defined(FLT_EXP_DIG)
#define FLT_EXP_DIG (sizeof(float) * 8 - FLT_MANT_DIG)
#endif

/*
  Function of type rdb_index_field_unpack_t

  Unpack a float by doing the reverse action of Field_float::make_sort_key
  (sql/field.cc).  Note that this only works on IEEE values.
  Note also that this code assumes that NaN and +/-Infinity are never
  allowed in the database.
*/
int Rdb_key_def::unpack_float(
    Rdb_field_packing *const fpi, Field *const field MY_ATTRIBUTE((__unused__)),
    uchar *const field_ptr, Rdb_string_reader *const reader,
    Rdb_string_reader *const unp_reader MY_ATTRIBUTE((__unused__))) {
  static float zero_val = 0.0;
  static const uchar zero_pattern[4] = {128, 0, 0, 0};

  return unpack_floating_point(field_ptr, reader, sizeof(float), FLT_EXP_DIG,
                               zero_pattern, (const uchar *)&zero_val,
                               rdb_swap_float_bytes);
}

/*
  Function of type rdb_index_field_unpack_t used to
  Unpack by doing the reverse action to Field_newdate::make_sort_key.
*/

int Rdb_key_def::unpack_newdate(
    Rdb_field_packing *const fpi, Field *const field MY_ATTRIBUTE((__unused__)),
    uchar *const field_ptr, Rdb_string_reader *const reader,
    Rdb_string_reader *const unp_reader MY_ATTRIBUTE((__unused__))) {
  const char *from;
  DBUG_ASSERT(fpi->m_max_image_len == 3);

  if (!(from = reader->read(3))) {
    /* Mem-comparable image doesn't have enough bytes */
    return UNPACK_FAILURE;
  }

  field_ptr[0] = from[2];
  field_ptr[1] = from[1];
  field_ptr[2] = from[0];
  return UNPACK_SUCCESS;
}

/*
  Function of type rdb_index_field_unpack_t, used to
  Unpack the string by copying it over.
  This is for BINARY(n) where the value occupies the whole length.
*/

int Rdb_key_def::unpack_binary_str(
    Rdb_field_packing *const fpi, Field *const field, uchar *const to,
    Rdb_string_reader *const reader,
    Rdb_string_reader *const unp_reader MY_ATTRIBUTE((__unused__))) {
  const char *from;
  if (!(from = reader->read(fpi->m_max_image_len))) {
    /* Mem-comparable image doesn't have enough bytes */
    return UNPACK_FAILURE;
  }

  memcpy(to, from, fpi->m_max_image_len);
  return UNPACK_SUCCESS;
}

/*
  Function of type rdb_index_field_unpack_t.
  For UTF-8, we need to convert 2-byte wide-character entities back into
  UTF8 sequences.
*/

int Rdb_key_def::unpack_utf8_str(
    Rdb_field_packing *const fpi, Field *const field, uchar *dst,
    Rdb_string_reader *const reader,
    Rdb_string_reader *const unp_reader MY_ATTRIBUTE((__unused__))) {
  my_core::CHARSET_INFO *const cset = (my_core::CHARSET_INFO *)field->charset();
  const uchar *src;
  if (!(src = (const uchar *)reader->read(fpi->m_max_image_len))) {
    /* Mem-comparable image doesn't have enough bytes */
    return UNPACK_FAILURE;
  }

  const uchar *const src_end = src + fpi->m_max_image_len;
  uchar *const dst_end = dst + field->pack_length();

  while (src < src_end) {
    my_wc_t wc = (src[0] << 8) | src[1];
    src += 2;
    int res = cset->wc_mb(wc, dst, dst_end);
    DBUG_ASSERT(res > 0 && res <= 3);
    if (res < 0) return UNPACK_FAILURE;
    dst += res;
  }

  cset->fill(reinterpret_cast<char *>(dst), dst_end - dst,
             cset->pad_char);
  return UNPACK_SUCCESS;
}

/*
  This is the original algorithm to encode a variable binary field.  It
  sets a flag byte every Nth byte.  The flag value is (255 - #pad) where
  #pad is the number of padding bytes that were needed (0 if all N-1
  bytes were used).

  If N=8 and the field is:
  * 3 bytes (1, 2, 3) this is encoded as: 1, 2, 3, 0, 0, 0, 0, 251
  * 4 bytes (1, 2, 3, 0) this is encoded as: 1, 2, 3, 0, 0, 0, 0, 252
  And the 4 byte string compares as greater than the 3 byte string

  Unfortunately the algorithm has a flaw.  If the input is exactly a
  multiple of N-1, an extra N bytes are written.  Since we usually use
  N=9, an 8 byte input will generate 18 bytes of output instead of the
  9 bytes of output that is optimal.

  See pack_variable_format for the newer algorithm.
*/
void Rdb_key_def::pack_legacy_variable_format(
    const uchar *src,  // The data to encode
    size_t src_len,    // The length of the data to encode
    uchar **dst)       // The location to encode the data
{
  size_t copy_len;
  size_t padding_bytes;
  uchar *ptr = *dst;

  do {
    copy_len = std::min((size_t)RDB_LEGACY_ESCAPE_LENGTH - 1, src_len);
    padding_bytes = RDB_LEGACY_ESCAPE_LENGTH - 1 - copy_len;
    memcpy(ptr, src, copy_len);
    ptr += copy_len;
    src += copy_len;
    // pad with zeros if necessary
    if (padding_bytes > 0) {
      memset(ptr, 0, padding_bytes);
      ptr += padding_bytes;
    }

    *(ptr++) = 255 - padding_bytes;

    src_len -= copy_len;
  } while (padding_bytes == 0);

  *dst = ptr;
}

/*
  This is the new algorithm.  Similarly to the legacy format the input
  is split up into N-1 bytes and a flag byte is used as the Nth byte
  in the output.

  - If the previous segment needed any padding the flag is set to the
    number of bytes used (0..N-2).  0 is possible in the first segment
    if the input is 0 bytes long.
  - If no padding was used and there is no more data left in the input
    the flag is set to N-1
  - If no padding was used and there is still data left in the input the
    flag is set to N.

  For N=9, the following input values encode to the specified
  outout (where 'X' indicates a byte of the original input):
  - 0 bytes  is encoded as 0 0 0 0 0 0 0 0 0
  - 1 byte   is encoded as X 0 0 0 0 0 0 0 1
  - 2 bytes  is encoded as X X 0 0 0 0 0 0 2
  - 7 bytes  is encoded as X X X X X X X 0 7
  - 8 bytes  is encoded as X X X X X X X X 8
  - 9 bytes  is encoded as X X X X X X X X 9 X 0 0 0 0 0 0 0 1
  - 10 bytes is encoded as X X X X X X X X 9 X X 0 0 0 0 0 0 2
*/
void Rdb_key_def::pack_variable_format(
    const uchar *src,  // The data to encode
    size_t src_len,    // The length of the data to encode
    uchar **dst)       // The location to encode the data
{
  uchar *ptr = *dst;

  for (;;) {
    // Figure out how many bytes to copy, copy them and adjust pointers
    const size_t copy_len = std::min((size_t)RDB_ESCAPE_LENGTH - 1, src_len);
    memcpy(ptr, src, copy_len);
    ptr += copy_len;
    src += copy_len;
    src_len -= copy_len;

    // Are we at the end of the input?
    if (src_len == 0) {
      // pad with zeros if necessary;
      const size_t padding_bytes = RDB_ESCAPE_LENGTH - 1 - copy_len;
      if (padding_bytes > 0) {
        memset(ptr, 0, padding_bytes);
        ptr += padding_bytes;
      }

      // Put the flag byte (0 - N-1) in the output
      *(ptr++) = (uchar)copy_len;
      break;
    }

    // We have more data - put the flag byte (N) in and continue
    *(ptr++) = RDB_ESCAPE_LENGTH;
  }

  *dst = ptr;
}

/*
  Function of type rdb_index_field_pack_t
*/

void Rdb_key_def::pack_with_varchar_encoding(
    Rdb_field_packing *const fpi, Field *const field, uchar *buf, uchar **dst,
    Rdb_pack_field_context *const pack_ctx MY_ATTRIBUTE((__unused__))) {
  const CHARSET_INFO *const charset = field->charset();
  Field_varstring *const field_var = (Field_varstring *)field;

  const size_t value_length = (field_var->length_bytes == 1)
                                  ? (uint)*field->ptr
                                  : uint2korr(field->ptr);
  size_t xfrm_len = charset->strnxfrm(
      buf, fpi->m_max_image_len, field_var->char_length(),
      field_var->ptr + field_var->length_bytes, value_length, 0);

  /* Got a mem-comparable image in 'buf'. Now, produce varlength encoding */
  if (fpi->m_use_legacy_varbinary_format) {
    pack_legacy_variable_format(buf, xfrm_len, dst);
  } else {
    pack_variable_format(buf, xfrm_len, dst);
  }
}

/*
  Compare the string in [buf..buf_end) with a string that is an infinite
  sequence of strings in space_xfrm
*/

static int rdb_compare_string_with_spaces(
    const uchar *buf, const uchar *const buf_end,
    const std::vector<uchar> *const space_xfrm) {
  int cmp = 0;
  while (buf < buf_end) {
    size_t bytes = std::min((size_t)(buf_end - buf), space_xfrm->size());
    if ((cmp = memcmp(buf, space_xfrm->data(), bytes)) != 0) break;
    buf += bytes;
  }
  return cmp;
}

static const int RDB_TRIMMED_CHARS_OFFSET = 8;
/*
  Pack the data with Variable-Length Space-Padded Encoding.

  The encoding is there to meet two goals:

  Goal#1. Comparison. The SQL standard says

    " If the collation for the comparison has the PAD SPACE characteristic,
    for the purposes of the comparison, the shorter value is effectively
    extended to the length of the longer by concatenation of <space>s on the
    right.

  At the moment, all MySQL collations except one have the PAD SPACE
  characteristic.  The exception is the "binary" collation that is used by
  [VAR]BINARY columns. (Note that binary collations for specific charsets,
  like utf8_bin or latin1_bin are not the same as "binary" collation, they have
  the PAD SPACE characteristic).

  Goal#2 is to preserve the number of trailing spaces in the original value.

  This is achieved by using the following encoding:
  The key part:
  - Stores mem-comparable image of the column
  - It is stored in chunks of fpi->m_segment_size bytes (*)
    = If the remainder of the chunk is not occupied, it is padded with mem-
      comparable image of the space character (cs->pad_char to be precise).
  - The last byte of the chunk shows how the rest of column's mem-comparable
    image would compare to mem-comparable image of the column extended with
    spaces. There are three possible values.
     - VARCHAR_CMP_LESS_THAN_SPACES,
     - VARCHAR_CMP_EQUAL_TO_SPACES
     - VARCHAR_CMP_GREATER_THAN_SPACES

  VARCHAR_CMP_EQUAL_TO_SPACES means that this chunk is the last one (the rest
  is spaces, or something that sorts as spaces, so there is no reason to store
  it).

  Example: if fpi->m_segment_size=5, and the collation is latin1_bin:

   'abcd\0'   => [ 'abcd' <VARCHAR_CMP_LESS> ]['\0    ' <VARCHAR_CMP_EQUAL> ]
   'abcd'     => [ 'abcd' <VARCHAR_CMP_EQUAL>]
   'abcd   '  => [ 'abcd' <VARCHAR_CMP_EQUAL>]
   'abcdZZZZ' => [ 'abcd' <VARCHAR_CMP_GREATER>][ 'ZZZZ' <VARCHAR_CMP_EQUAL>]

  As mentioned above, the last chunk is padded with mem-comparable images of
  cs->pad_char. It can be 1-byte long (latin1), 2 (utf8_bin), 3 (utf8mb4), etc.

  fpi->m_segment_size depends on the used collation. It is chosen to be such
  that no mem-comparable image of space will ever stretch across the segments
  (see get_segment_size_from_collation).

  == The value part (aka unpack_info) ==
  The value part stores the number of space characters that one needs to add
  when unpacking the string.
  - If the number is positive, it means add this many spaces at the end
  - If the number is negative, it means padding has added extra spaces which
    must be removed.

  Storage considerations
  - depending on column's max size, the number may occupy 1 or 2 bytes
  - the number of spaces that need to be removed is not more than
    RDB_TRIMMED_CHARS_OFFSET=8, so we offset the number by that value and
    then store it as unsigned.

  @seealso
    unpack_binary_or_utf8_varchar_space_pad
    unpack_simple_varchar_space_pad
    dummy_make_unpack_info
    skip_variable_space_pad
*/

void Rdb_key_def::pack_with_varchar_space_pad(
    Rdb_field_packing *const fpi, Field *const field, uchar *buf, uchar **dst,
    Rdb_pack_field_context *const pack_ctx) {
  Rdb_string_writer *const unpack_info = pack_ctx->writer;
  const CHARSET_INFO *const charset = field->charset();
  const auto field_var = static_cast<Field_varstring *>(field);

  const size_t value_length = (field_var->length_bytes == 1)
                                  ? (uint)*field->ptr
                                  : uint2korr(field->ptr);

  const size_t trimmed_len = charset->lengthsp(
      (const char *)field_var->ptr + field_var->length_bytes,
      value_length);
  const size_t xfrm_len = charset->strnxfrm(
      buf, fpi->m_max_image_len, field_var->char_length(),
      field_var->ptr + field_var->length_bytes, trimmed_len, 0);

  /* Got a mem-comparable image in 'buf'. Now, produce varlength encoding */
  uchar *const buf_end = buf + xfrm_len;

  size_t encoded_size = 0;
  uchar *ptr = *dst;
  size_t padding_bytes;
  while (true) {
    const size_t copy_len =
        std::min<size_t>(fpi->m_segment_size - 1, buf_end - buf);
    padding_bytes = fpi->m_segment_size - 1 - copy_len;
    memcpy(ptr, buf, copy_len);
    ptr += copy_len;
    buf += copy_len;

    if (padding_bytes) {
      memcpy(ptr, fpi->space_xfrm->data(), padding_bytes);
      ptr += padding_bytes;
      *ptr = VARCHAR_CMP_EQUAL_TO_SPACES;  // last segment
    } else {
      // Compare the string suffix with a hypothetical infinite string of
      // spaces. It could be that the first difference is beyond the end of
      // current chunk.
      const int cmp =
          rdb_compare_string_with_spaces(buf, buf_end, fpi->space_xfrm);

      if (cmp < 0) {
        *ptr = VARCHAR_CMP_LESS_THAN_SPACES;
      } else if (cmp > 0) {
        *ptr = VARCHAR_CMP_GREATER_THAN_SPACES;
      } else {
        // It turns out all the rest are spaces.
        *ptr = VARCHAR_CMP_EQUAL_TO_SPACES;
      }
    }
    encoded_size += fpi->m_segment_size;

    if (*(ptr++) == VARCHAR_CMP_EQUAL_TO_SPACES) break;
  }

  // m_unpack_info_stores_value means unpack_info stores the whole original
  // value. There is no need to store the number of trimmed/padded endspaces
  // in that case.
  if (unpack_info && !fpi->m_unpack_info_stores_value) {
    // (value_length - trimmed_len) is the number of trimmed space *characters*
    // then, padding_bytes is the number of *bytes* added as padding
    // then, we add 8, because we don't store negative values.
    DBUG_ASSERT(padding_bytes % fpi->space_xfrm_len == 0);
    DBUG_ASSERT((value_length - trimmed_len) % fpi->space_mb_len == 0);
    const size_t removed_chars =
        RDB_TRIMMED_CHARS_OFFSET +
        (value_length - trimmed_len) / fpi->space_mb_len -
        padding_bytes / fpi->space_xfrm_len;

    if (fpi->m_unpack_info_uses_two_bytes) {
      unpack_info->write_uint16(removed_chars);
    } else {
      DBUG_ASSERT(removed_chars < 0x100);
      unpack_info->write_uint8(removed_chars);
    }
  }

  *dst += encoded_size;
}

/*
  Calculate the number of used bytes in the chunk and whether this is the
  last chunk in the input.  This is based on the old legacy format - see
  pack_legacy_variable_format.
 */
uint Rdb_key_def::calc_unpack_legacy_variable_format(uchar flag, bool *done) {
  uint pad = 255 - flag;
  uint used_bytes = RDB_LEGACY_ESCAPE_LENGTH - 1 - pad;
  if (used_bytes > RDB_LEGACY_ESCAPE_LENGTH - 1) {
    return (uint)-1;
  }

  *done = used_bytes < RDB_LEGACY_ESCAPE_LENGTH - 1;
  return used_bytes;
}

/*
  Calculate the number of used bytes in the chunk and whether this is the
  last chunk in the input.  This is based on the new format - see
  pack_variable_format.
 */
uint Rdb_key_def::calc_unpack_variable_format(uchar flag, bool *done) {
  // Check for invalid flag values
  if (flag > RDB_ESCAPE_LENGTH) {
    return (uint)-1;
  }

  // Values from 1 to N-1 indicate this is the last chunk and that is how
  // many bytes were used
  if (flag < RDB_ESCAPE_LENGTH) {
    *done = true;
    return flag;
  }

  // A value of N means we used N-1 bytes and had more to go
  *done = false;
  return RDB_ESCAPE_LENGTH - 1;
}

/*
  Unpack data that has charset information.  Each two bytes of the input is
  treated as a wide-character and converted to its multibyte equivalent in
  the output.
 */
static int unpack_charset(
    const CHARSET_INFO *cset,  // character set information
    const uchar *src,          // source data to unpack
    uint src_len,              // length of source data
    uchar *dst,                // destination of unpacked data
    uint dst_len,              // length of destination data
    uint *used_bytes)          // output number of bytes used
{
  if (src_len & 1) {
    /*
      UTF-8 characters are encoded into two-byte entities. There is no way
      we can have an odd number of bytes after encoding.
    */
    return UNPACK_FAILURE;
  }

  uchar *dst_end = dst + dst_len;
  uint used = 0;

  for (uint ii = 0; ii < src_len; ii += 2) {
    my_wc_t wc = (src[ii] << 8) | src[ii + 1];
    int res = cset->wc_mb(wc, dst + used, dst_end);
    DBUG_ASSERT(res > 0 && res <= 3);
    if (res < 0) {
      return UNPACK_FAILURE;
    }

    used += res;
  }

  *used_bytes = used;
  return UNPACK_SUCCESS;
}

/*
  Function of type rdb_index_field_unpack_t
*/

int Rdb_key_def::unpack_binary_or_utf8_varchar(
    Rdb_field_packing *const fpi, Field *const field, uchar *dst,
    Rdb_string_reader *const reader,
    Rdb_string_reader *const unp_reader MY_ATTRIBUTE((__unused__))) {
  const uchar *ptr;
  size_t len = 0;
  bool finished = false;
  uchar *d0 = dst;
  Field_varstring *const field_var = (Field_varstring *)field;
  dst += field_var->length_bytes;
  // How much we can unpack
  size_t dst_len = field_var->pack_length() - field_var->length_bytes;

  bool use_legacy_format = fpi->m_use_legacy_varbinary_format;

  /* Decode the length-emitted encoding here */
  while ((ptr = (const uchar *)reader->read(RDB_ESCAPE_LENGTH))) {
    uint used_bytes;

    /* See pack_with_varchar_encoding. */
    if (use_legacy_format) {
      used_bytes = calc_unpack_legacy_variable_format(
          ptr[RDB_ESCAPE_LENGTH - 1], &finished);
    } else {
      used_bytes =
          calc_unpack_variable_format(ptr[RDB_ESCAPE_LENGTH - 1], &finished);
    }

    if (used_bytes == (uint)-1 || dst_len < used_bytes) {
      return UNPACK_FAILURE;  // Corruption in the data
    }

    /*
      Now, we need to decode used_bytes of data and append them to the value.
    */
    if (fpi->m_varchar_charset->number == COLLATION_UTF8_BIN) {
      int err = unpack_charset(fpi->m_varchar_charset, ptr, used_bytes, dst,
                               dst_len, &used_bytes);
      if (err != UNPACK_SUCCESS) {
        return err;
      }
    } else {
      memcpy(dst, ptr, used_bytes);
    }

    dst += used_bytes;
    dst_len -= used_bytes;
    len += used_bytes;

    if (finished) {
      break;
    }
  }

  if (!finished) {
    return UNPACK_FAILURE;
  }

  /* Save the length */
  if (field_var->length_bytes == 1) {
    d0[0] = (uchar)len;
  } else {
    DBUG_ASSERT(field_var->length_bytes == 2);
    int2store(d0, len);
  }
  return UNPACK_SUCCESS;
}

/*
  @seealso
    pack_with_varchar_space_pad - packing function
    unpack_simple_varchar_space_pad - unpacking function for 'simple'
    charsets.
    skip_variable_space_pad - skip function
*/
int Rdb_key_def::unpack_binary_or_utf8_varchar_space_pad(
    Rdb_field_packing *const fpi, Field *const field, uchar *dst,
    Rdb_string_reader *const reader, Rdb_string_reader *const unp_reader) {
  const uchar *ptr;
  size_t len = 0;
  bool finished = false;
  Field_varstring *const field_var = static_cast<Field_varstring *>(field);
  uchar *d0 = dst;
  uchar *dst_end = dst + field_var->pack_length();
  dst += field_var->length_bytes;

  uint space_padding_bytes = 0;
  uint extra_spaces;
  if ((fpi->m_unpack_info_uses_two_bytes
           ? unp_reader->read_uint16(&extra_spaces)
           : unp_reader->read_uint8(&extra_spaces))) {
    return UNPACK_FAILURE;
  }

  if (extra_spaces <= RDB_TRIMMED_CHARS_OFFSET) {
    space_padding_bytes =
        -(static_cast<int>(extra_spaces) - RDB_TRIMMED_CHARS_OFFSET);
    extra_spaces = 0;
  } else {
    extra_spaces -= RDB_TRIMMED_CHARS_OFFSET;
  }

  space_padding_bytes *= fpi->space_xfrm_len;

  /* Decode the length-emitted encoding here */
  while ((ptr = (const uchar *)reader->read(fpi->m_segment_size))) {
    const char last_byte = ptr[fpi->m_segment_size - 1];
    size_t used_bytes;
    if (last_byte == VARCHAR_CMP_EQUAL_TO_SPACES)  // this is the last segment
    {
      if (space_padding_bytes > (fpi->m_segment_size - 1)) {
        return UNPACK_FAILURE;  // Cannot happen, corrupted data
      }
      used_bytes = (fpi->m_segment_size - 1) - space_padding_bytes;
      finished = true;
    } else {
      if (last_byte != VARCHAR_CMP_LESS_THAN_SPACES &&
          last_byte != VARCHAR_CMP_GREATER_THAN_SPACES) {
        return UNPACK_FAILURE;  // Invalid value
      }
      used_bytes = fpi->m_segment_size - 1;
    }

    // Now, need to decode used_bytes of data and append them to the value.
    if (fpi->m_varchar_charset->number == COLLATION_UTF8_BIN) {
      if (used_bytes & 1) {
        /*
          UTF-8 characters are encoded into two-byte entities. There is no way
          we can have an odd number of bytes after encoding.
        */
        return UNPACK_FAILURE;
      }

      const uchar *src = ptr;
      const uchar *const src_end = ptr + used_bytes;
      while (src < src_end) {
        my_wc_t wc = (src[0] << 8) | src[1];
        src += 2;
        const CHARSET_INFO *cset = fpi->m_varchar_charset;
        int res = cset->wc_mb(wc, dst, dst_end);
        DBUG_ASSERT(res <= 3);
        if (res <= 0) return UNPACK_FAILURE;
        dst += res;
        len += res;
      }
    } else {
      if (dst + used_bytes > dst_end) return UNPACK_FAILURE;
      memcpy(dst, ptr, used_bytes);
      dst += used_bytes;
      len += used_bytes;
    }

    if (finished) {
      if (extra_spaces) {
        // Both binary and UTF-8 charset store space as ' ',
        // so the following is ok:
        if (dst + extra_spaces > dst_end) return UNPACK_FAILURE;
        memset(dst, fpi->m_varchar_charset->pad_char, extra_spaces);
        len += extra_spaces;
      }
      break;
    }
  }

  if (!finished) return UNPACK_FAILURE;

  /* Save the length */
  if (field_var->length_bytes == 1) {
    d0[0] = (uchar)len;
  } else {
    DBUG_ASSERT(field_var->length_bytes == 2);
    int2store(d0, len);
  }
  return UNPACK_SUCCESS;
}

/////////////////////////////////////////////////////////////////////////

/*
  Function of type rdb_make_unpack_info_t
*/

void Rdb_key_def::make_unpack_unknown(
    const Rdb_collation_codec *codec MY_ATTRIBUTE((__unused__)),
    const Field *const field, Rdb_pack_field_context *const pack_ctx) {
  pack_ctx->writer->write(field->ptr, field->pack_length());
}

/*
  This point of this function is only to indicate that unpack_info is
  available.

  The actual unpack_info data is produced by the function that packs the key,
  that is, pack_with_varchar_space_pad.
*/

void Rdb_key_def::dummy_make_unpack_info(
    const Rdb_collation_codec *codec MY_ATTRIBUTE((__unused__)),
    const Field *field MY_ATTRIBUTE((__unused__)),
    Rdb_pack_field_context *pack_ctx MY_ATTRIBUTE((__unused__))) {
  // Do nothing
}

/*
  Function of type rdb_index_field_unpack_t
*/

int Rdb_key_def::unpack_unknown(Rdb_field_packing *const fpi,
                                Field *const field, uchar *const dst,
                                Rdb_string_reader *const reader,
                                Rdb_string_reader *const unp_reader) {
  const uchar *ptr;
  const uint len = fpi->m_unpack_data_len;
  // We don't use anything from the key, so skip over it.
  if (skip_max_length(fpi, field, reader)) {
    return UNPACK_FAILURE;
  }

  DBUG_ASSERT_IMP(len > 0, unp_reader != nullptr);

  if ((ptr = (const uchar *)unp_reader->read(len))) {
    memcpy(dst, ptr, len);
    return UNPACK_SUCCESS;
  }
  return UNPACK_FAILURE;
}

/*
  Function of type rdb_make_unpack_info_t
*/

void Rdb_key_def::make_unpack_unknown_varchar(
    const Rdb_collation_codec *const codec MY_ATTRIBUTE((__unused__)),
    const Field *const field, Rdb_pack_field_context *const pack_ctx) {
  const auto f = static_cast<const Field_varstring *>(field);
  uint len = f->length_bytes == 1 ? (uint)*f->ptr : uint2korr(f->ptr);
  len += f->length_bytes;
  pack_ctx->writer->write(field->ptr, len);
}

/*
  Function of type rdb_index_field_unpack_t

  @detail
  Unpack a key part in an "unknown" collation from its
  (mem_comparable_form, unpack_info) form.

  "Unknown" means we have no clue about how mem_comparable_form is made from
  the original string, so we keep the whole original string in the unpack_info.

  @seealso
    make_unpack_unknown, unpack_unknown
*/

int Rdb_key_def::unpack_unknown_varchar(Rdb_field_packing *const fpi,
                                        Field *const field, uchar *dst,
                                        Rdb_string_reader *const reader,
                                        Rdb_string_reader *const unp_reader) {
  const uchar *ptr;
  uchar *const d0 = dst;
  const auto f = static_cast<Field_varstring *>(field);
  dst += f->length_bytes;
  const uint len_bytes = f->length_bytes;
  // We don't use anything from the key, so skip over it.
  if ((fpi->m_skip_func)(fpi, field, reader)) {
    return UNPACK_FAILURE;
  }

  DBUG_ASSERT(len_bytes > 0);
  DBUG_ASSERT(unp_reader != nullptr);

  if ((ptr = (const uchar *)unp_reader->read(len_bytes))) {
    memcpy(d0, ptr, len_bytes);
    const uint len = len_bytes == 1 ? (uint)*ptr : uint2korr(ptr);
    if ((ptr = (const uchar *)unp_reader->read(len))) {
      memcpy(dst, ptr, len);
      return UNPACK_SUCCESS;
    }
  }
  return UNPACK_FAILURE;
}

/*
  Write unpack_data for a "simple" collation
*/
static void rdb_write_unpack_simple(Rdb_bit_writer *const writer,
                                    const Rdb_collation_codec *const codec,
                                    const uchar *const src,
                                    const size_t src_len) {
  for (uint i = 0; i < src_len; i++) {
    writer->write(codec->m_enc_size[src[i]], codec->m_enc_idx[src[i]]);
  }
}

static uint rdb_read_unpack_simple(Rdb_bit_reader *const reader,
                                   const Rdb_collation_codec *const codec,
                                   const uchar *const src, const size_t src_len,
                                   uchar *const dst) {
  for (uint i = 0; i < src_len; i++) {
    if (codec->m_dec_size[src[i]] > 0) {
      uint *ret;
      DBUG_ASSERT(reader != nullptr);

      if ((ret = reader->read(codec->m_dec_size[src[i]])) == nullptr) {
        return UNPACK_FAILURE;
      }
      dst[i] = codec->m_dec_idx[*ret][src[i]];
    } else {
      dst[i] = codec->m_dec_idx[0][src[i]];
    }
  }

  return UNPACK_SUCCESS;
}

/*
  Function of type rdb_make_unpack_info_t

  @detail
    Make unpack_data for VARCHAR(n) in a "simple" charset.
*/

void Rdb_key_def::make_unpack_simple_varchar(
    const Rdb_collation_codec *const codec, const Field *const field,
    Rdb_pack_field_context *const pack_ctx) {
  const auto f = static_cast<const Field_varstring *>(field);
  uchar *const src = f->ptr + f->length_bytes;
  const size_t src_len =
      f->length_bytes == 1 ? (uint)*f->ptr : uint2korr(f->ptr);
  Rdb_bit_writer bit_writer(pack_ctx->writer);
  // The std::min compares characters with bytes, but for simple collations,
  // mbmaxlen = 1.
  rdb_write_unpack_simple(&bit_writer, codec, src,
                          std::min((size_t)f->char_length(), src_len));
}

/*
  Function of type rdb_index_field_unpack_t

  @seealso
    pack_with_varchar_space_pad - packing function
    unpack_binary_or_utf8_varchar_space_pad - a similar unpacking function
*/

int Rdb_key_def::unpack_simple_varchar_space_pad(
    Rdb_field_packing *const fpi, Field *const field, uchar *dst,
    Rdb_string_reader *const reader, Rdb_string_reader *const unp_reader) {
  const uchar *ptr;
  size_t len = 0;
  bool finished = false;
  uchar *d0 = dst;
  const Field_varstring *const field_var =
      static_cast<Field_varstring *>(field);
  // For simple collations, char_length is also number of bytes.
  DBUG_ASSERT((size_t)fpi->m_max_image_len >= field_var->char_length());
  uchar *dst_end = dst + field_var->pack_length();
  dst += field_var->length_bytes;
  Rdb_bit_reader bit_reader(unp_reader);

  uint space_padding_bytes = 0;
  uint extra_spaces;
  DBUG_ASSERT(unp_reader != nullptr);

  if ((fpi->m_unpack_info_uses_two_bytes
           ? unp_reader->read_uint16(&extra_spaces)
           : unp_reader->read_uint8(&extra_spaces))) {
    return UNPACK_FAILURE;
  }

  if (extra_spaces <= 8) {
    space_padding_bytes = -(static_cast<int>(extra_spaces) - 8);
    extra_spaces = 0;
  } else {
    extra_spaces -= 8;
  }

  space_padding_bytes *= fpi->space_xfrm_len;

  /* Decode the length-emitted encoding here */
  while ((ptr = (const uchar *)reader->read(fpi->m_segment_size))) {
    const char last_byte =
        ptr[fpi->m_segment_size - 1];  // number of padding bytes
    size_t used_bytes;
    if (last_byte == VARCHAR_CMP_EQUAL_TO_SPACES) {
      // this is the last one
      if (space_padding_bytes > (fpi->m_segment_size - 1)) {
        return UNPACK_FAILURE;  // Cannot happen, corrupted data
      }
      used_bytes = (fpi->m_segment_size - 1) - space_padding_bytes;
      finished = true;
    } else {
      if (last_byte != VARCHAR_CMP_LESS_THAN_SPACES &&
          last_byte != VARCHAR_CMP_GREATER_THAN_SPACES) {
        return UNPACK_FAILURE;
      }
      used_bytes = fpi->m_segment_size - 1;
    }

    if (dst + used_bytes > dst_end) {
      // The value on disk is longer than the field definition allows?
      return UNPACK_FAILURE;
    }

    uint ret;
    if ((ret = rdb_read_unpack_simple(&bit_reader, fpi->m_charset_codec, ptr,
                                      used_bytes, dst)) != UNPACK_SUCCESS) {
      return ret;
    }

    dst += used_bytes;
    len += used_bytes;

    if (finished) {
      if (extra_spaces) {
        if (dst + extra_spaces > dst_end) return UNPACK_FAILURE;
        // pad_char has a 1-byte form in all charsets that
        // are handled by rdb_init_collation_mapping.
        memset(dst, field_var->charset()->pad_char, extra_spaces);
        len += extra_spaces;
      }
      break;
    }
  }

  if (!finished) return UNPACK_FAILURE;

  /* Save the length */
  if (field_var->length_bytes == 1) {
    d0[0] = (uchar)len;
  } else {
    DBUG_ASSERT(field_var->length_bytes == 2);
    int2store(d0, len);
  }
  return UNPACK_SUCCESS;
}

/*
  Function of type rdb_make_unpack_info_t

  @detail
    Make unpack_data for CHAR(n) value in a "simple" charset.
    It is CHAR(N), so SQL layer has padded the value with spaces up to N chars.

  @seealso
    The VARCHAR variant is in make_unpack_simple_varchar
*/

void Rdb_key_def::make_unpack_simple(const Rdb_collation_codec *const codec,
                                     const Field *const field,
                                     Rdb_pack_field_context *const pack_ctx) {
  const uchar *const src = field->ptr;
  Rdb_bit_writer bit_writer(pack_ctx->writer);
  rdb_write_unpack_simple(&bit_writer, codec, src, field->pack_length());
}

/*
  Function of type rdb_index_field_unpack_t
*/

int Rdb_key_def::unpack_simple(Rdb_field_packing *const fpi,
                               Field *const field MY_ATTRIBUTE((__unused__)),
                               uchar *const dst,
                               Rdb_string_reader *const reader,
                               Rdb_string_reader *const unp_reader) {
  const uchar *ptr;
  const uint len = fpi->m_max_image_len;
  Rdb_bit_reader bit_reader(unp_reader);

  if (!(ptr = (const uchar *)reader->read(len))) {
    return UNPACK_FAILURE;
  }

  return rdb_read_unpack_simple(unp_reader ? &bit_reader : nullptr,
                                fpi->m_charset_codec, ptr, len, dst);
}

// See Rdb_charset_space_info::spaces_xfrm
const int RDB_SPACE_XFRM_SIZE = 32;

// A class holding information about how space character is represented in a
// charset.
class Rdb_charset_space_info {
 public:
  Rdb_charset_space_info(const Rdb_charset_space_info &) = delete;
  Rdb_charset_space_info &operator=(const Rdb_charset_space_info &) = delete;
  Rdb_charset_space_info() = default;

  // A few strxfrm'ed space characters, at least RDB_SPACE_XFRM_SIZE bytes
  std::vector<uchar> spaces_xfrm;

  // length(strxfrm(' '))
  size_t space_xfrm_len;

  // length of the space character itself
  // Typically space is just 0x20 (length=1) but in ucs2 it is 0x00 0x20
  // (length=2)
  size_t space_mb_len;
};

static std::array<std::unique_ptr<Rdb_charset_space_info>, MY_ALL_CHARSETS_SIZE>
    rdb_mem_comparable_space;

/*
  @brief
  For a given charset, get
   - strxfrm('    '), a sample that is at least RDB_SPACE_XFRM_SIZE bytes long.
   - length of strxfrm(charset, ' ')
   - length of the space character in the charset

  @param cs  IN    Charset to get the space for
  @param ptr OUT   A few space characters
  @param len OUT   Return length of the space (in bytes)

  @detail
    It is tempting to pre-generate mem-comparable form of space character for
    every charset on server startup.
    One can't do that: some charsets are not initialized until somebody
    attempts to use them (e.g. create or open a table that has a field that
    uses the charset).
*/

static void rdb_get_mem_comparable_space(const CHARSET_INFO *const cs,
                                         const std::vector<uchar> **xfrm,
                                         size_t *const xfrm_len,
                                         size_t *const mb_len) {
  DBUG_ASSERT(cs->number < MY_ALL_CHARSETS_SIZE);
  if (!rdb_mem_comparable_space[cs->number].get()) {
    RDB_MUTEX_LOCK_CHECK(rdb_mem_cmp_space_mutex);
    if (!rdb_mem_comparable_space[cs->number].get()) {
      // Upper bound of how many bytes can be occupied by multi-byte form of a
      // character in any charset.
      const int MAX_MULTI_BYTE_CHAR_SIZE = 4;
      DBUG_ASSERT(cs->mbmaxlen <= MAX_MULTI_BYTE_CHAR_SIZE);

      // multi-byte form of the ' ' (space) character
      uchar space_mb[MAX_MULTI_BYTE_CHAR_SIZE];

      const size_t space_mb_len = cs->wc_mb(
          (my_wc_t)cs->pad_char, space_mb, space_mb + sizeof(space_mb));

      // mem-comparable image of the space character
      std::array<uchar, 20> space;

      const size_t space_len = cs->strnxfrm(
          space.data(), sizeof(space), 1, space_mb, space_mb_len, 0);
      Rdb_charset_space_info *const info = new Rdb_charset_space_info;
      info->space_xfrm_len = space_len;
      info->space_mb_len = space_mb_len;
      while (info->spaces_xfrm.size() < RDB_SPACE_XFRM_SIZE) {
        info->spaces_xfrm.insert(info->spaces_xfrm.end(), space.data(),
                                 space.data() + space_len);
      }
      rdb_mem_comparable_space[cs->number].reset(info);
    }
    RDB_MUTEX_UNLOCK_CHECK(rdb_mem_cmp_space_mutex);
  }

  *xfrm = &rdb_mem_comparable_space[cs->number]->spaces_xfrm;
  *xfrm_len = rdb_mem_comparable_space[cs->number]->space_xfrm_len;
  *mb_len = rdb_mem_comparable_space[cs->number]->space_mb_len;
}

mysql_mutex_t rdb_mem_cmp_space_mutex;

std::array<const Rdb_collation_codec *, MY_ALL_CHARSETS_SIZE>
    rdb_collation_data;
mysql_mutex_t rdb_collation_data_mutex;

bool rdb_is_collation_supported(const my_core::CHARSET_INFO *const cs) {
  return cs->strxfrm_multiply==1 && cs->mbmaxlen == 1 &&
         !(cs->state & (MY_CS_BINSORT | MY_CS_NOPAD));
}

static const Rdb_collation_codec *rdb_init_collation_mapping(
    const my_core::CHARSET_INFO *const cs) {
  DBUG_ASSERT(cs && cs->state & MY_CS_AVAILABLE);
  const Rdb_collation_codec *codec = rdb_collation_data[cs->number];

  if (codec == nullptr && rdb_is_collation_supported(cs)) {
    RDB_MUTEX_LOCK_CHECK(rdb_collation_data_mutex);

    codec = rdb_collation_data[cs->number];
    if (codec == nullptr) {
      Rdb_collation_codec *cur = nullptr;

      // Compute reverse mapping for simple collations.
      if (rdb_is_collation_supported(cs)) {
        cur = new Rdb_collation_codec;
        std::map<uchar, std::vector<uchar>> rev_map;
        size_t max_conflict_size = 0;
        for (int src = 0; src < 256; src++) {
          uchar dst = cs->sort_order[src];
          rev_map[dst].push_back(src);
          max_conflict_size = std::max(max_conflict_size, rev_map[dst].size());
        }
        cur->m_dec_idx.resize(max_conflict_size);

        for (auto const &p : rev_map) {
          uchar dst = p.first;
          for (uint idx = 0; idx < p.second.size(); idx++) {
            uchar src = p.second[idx];
            uchar bits =
                my_bit_log2_uint32(my_round_up_to_next_power(p.second.size()));
            cur->m_enc_idx[src] = idx;
            cur->m_enc_size[src] = bits;
            cur->m_dec_size[dst] = bits;
            cur->m_dec_idx[idx][dst] = src;
          }
        }

        cur->m_make_unpack_info_func = {Rdb_key_def::make_unpack_simple_varchar,
                                        Rdb_key_def::make_unpack_simple};
        cur->m_unpack_func = {Rdb_key_def::unpack_simple_varchar_space_pad,
                              Rdb_key_def::unpack_simple};
      } else {
        // Out of luck for now.
      }

      if (cur != nullptr) {
        codec = cur;
        cur->m_cs = cs;
        rdb_collation_data[cs->number] = cur;
      }
    }

    RDB_MUTEX_UNLOCK_CHECK(rdb_collation_data_mutex);
  }

  return codec;
}

static int get_segment_size_from_collation(const CHARSET_INFO *const cs) {
  int ret;
  if (cs->number == COLLATION_UTF8MB4_BIN || cs->number == COLLATION_UTF16_BIN ||
      cs->number == COLLATION_UTF16LE_BIN || cs->number == COLLATION_UTF32_BIN) {
    /*
      In these collations, a character produces one weight, which is 3 bytes.
      Segment has 3 characters, add one byte for VARCHAR_CMP_* marker, and we
      get 3*3+1=10
    */
    ret = 10;
  } else {
    /*
      All other collations. There are two classes:
      - Unicode-based, except for collations mentioned in the if-condition.
        For these all weights are 2 bytes long, a character may produce 0..8
        weights.
        in any case, 8 bytes of payload in the segment guarantee that the last
        space character won't span across segments.

      - Collations not based on unicode. These have length(strxfrm(' '))=1,
        there nothing to worry about.

      In both cases, take 8 bytes payload + 1 byte for VARCHAR_CMP* marker.
    */
    ret = 9;
  }
  DBUG_ASSERT(ret < RDB_SPACE_XFRM_SIZE);
  return ret;
}

/*
  @brief
    Setup packing of index field into its mem-comparable form

  @detail
    - It is possible produce mem-comparable form for any datatype.
    - Some datatypes also allow to unpack the original value from its
      mem-comparable form.
      = Some of these require extra information to be stored in "unpack_info".
        unpack_info is not a part of mem-comparable form, it is only used to
        restore the original value

  @param
    field  IN  field to be packed/un-packed

  @return
    TRUE  -  Field can be read with index-only reads
    FALSE -  Otherwise
*/

bool Rdb_field_packing::setup(const Rdb_key_def *const key_descr,
                              const Field *const field, const uint keynr_arg,
                              const uint key_part_arg,
                              const uint16 key_length) {
  int res = false;
  enum_field_types type = field ? field->real_type() : MYSQL_TYPE_LONGLONG;

  m_keynr = keynr_arg;
  m_key_part = key_part_arg;

  m_maybe_null = field ? field->real_maybe_null() : false;
  m_unpack_func = nullptr;
  m_make_unpack_info_func = nullptr;
  m_unpack_data_len = 0;
  space_xfrm = nullptr;  // safety
  // whether to use legacy format for varchar
  m_use_legacy_varbinary_format = false;
  // ha_rocksdb::index_flags() will pass key_descr == null to
  // see whether field(column) can be read-only reads through return value,
  // but the legacy vs. new varchar format doesn't affect return value.
  // Just change m_use_legacy_varbinary_format to true if key_descr isn't given.
  if (!key_descr || key_descr->use_legacy_varbinary_format()) {
    m_use_legacy_varbinary_format = true;
  }
  /* Calculate image length. By default, is is pack_length() */
  m_max_image_len =
      field ? field->pack_length() : ROCKSDB_SIZEOF_HIDDEN_PK_COLUMN;
  m_skip_func = Rdb_key_def::skip_max_length;
  m_pack_func = Rdb_key_def::pack_with_make_sort_key;

  m_covered = false;

  switch (type) {
    case MYSQL_TYPE_LONGLONG:
    case MYSQL_TYPE_LONG:
    case MYSQL_TYPE_INT24:
    case MYSQL_TYPE_SHORT:
    case MYSQL_TYPE_TINY:
      m_unpack_func = Rdb_key_def::unpack_integer;
      m_covered = true;
      return true;

    case MYSQL_TYPE_DOUBLE:
      m_unpack_func = Rdb_key_def::unpack_double;
      m_covered = true;
      return true;

    case MYSQL_TYPE_FLOAT:
      m_unpack_func = Rdb_key_def::unpack_float;
      m_covered = true;
      return true;

    case MYSQL_TYPE_NEWDECIMAL:
    /*
      Decimal is packed with Field_new_decimal::make_sort_key, which just
      does memcpy.
      Unpacking decimal values was supported only after fix for issue#253,
      because of that ha_rocksdb::get_storage_type() handles decimal values
      in a special way.
    */
    case MYSQL_TYPE_DATETIME2:
    case MYSQL_TYPE_TIMESTAMP2:
    /* These are packed with Field_temporal_with_date_and_timef::make_sort_key
     */
    case MYSQL_TYPE_TIME2: /* TIME is packed with Field_timef::make_sort_key */
    case MYSQL_TYPE_YEAR:  /* YEAR is packed with  Field_tiny::make_sort_key */
      /* Everything that comes here is packed with just a memcpy(). */
      m_unpack_func = Rdb_key_def::unpack_binary_str;
      m_covered = true;
      return true;

    case MYSQL_TYPE_NEWDATE:
      /*
        This is packed by Field_newdate::make_sort_key. It assumes the data is
        3 bytes, and packing is done by swapping the byte order (for both big-
        and little-endian)
      */
      m_unpack_func = Rdb_key_def::unpack_newdate;
      m_covered = true;
      return true;
    case MYSQL_TYPE_TINY_BLOB:
    case MYSQL_TYPE_MEDIUM_BLOB:
    case MYSQL_TYPE_LONG_BLOB:
    case MYSQL_TYPE_BLOB: {
      if (key_descr) {
        // The my_charset_bin collation is special in that it will consider
        // shorter strings sorting as less than longer strings.
        //
        // See Field_blob::make_sort_key for details.
        m_max_image_len =
          key_length + (field->charset()->number == COLLATION_BINARY
                              ? reinterpret_cast<const Field_blob *>(field)
                                    ->pack_length_no_ptr()
                              : 0);
        // Return false because indexes on text/blob will always require
        // a prefix. With a prefix, the optimizer will not be able to do an
        // index-only scan since there may be content occuring after the prefix
        // length.
        return false;
      }
      break;
    }
    default:
      break;
  }

  m_unpack_info_stores_value = false;
  /* Handle [VAR](CHAR|BINARY) */

  if (type == MYSQL_TYPE_VARCHAR || type == MYSQL_TYPE_STRING) {
    /*
      For CHAR-based columns, check how strxfrm image will take.
      field->field_length = field->char_length() * cs->mbmaxlen.
    */
    const CHARSET_INFO *cs = field->charset();
    m_max_image_len = cs->strnxfrmlen(type == MYSQL_TYPE_STRING ?
                                      field->pack_length() :
                                      field->field_length);
  }
  const bool is_varchar = (type == MYSQL_TYPE_VARCHAR);
  const CHARSET_INFO *cs = field->charset();
  // max_image_len before chunking is taken into account
  const int max_image_len_before_chunks = m_max_image_len;

  if (is_varchar) {
    // The default for varchar is variable-length, without space-padding for
    // comparisons
    m_varchar_charset = cs;
    m_skip_func = Rdb_key_def::skip_variable_length;
    m_pack_func = Rdb_key_def::pack_with_varchar_encoding;
    if (!key_descr || key_descr->use_legacy_varbinary_format()) {
      m_max_image_len = RDB_LEGACY_ENCODED_SIZE(m_max_image_len);
    } else {
      // Calculate the maximum size of the short section plus the
      // maximum size of the long section
      m_max_image_len = RDB_ENCODED_SIZE(m_max_image_len);
    }

    const auto field_var = static_cast<const Field_varstring *>(field);
    m_unpack_info_uses_two_bytes = (field_var->field_length + 8 >= 0x100);
  }

  if (type == MYSQL_TYPE_VARCHAR || type == MYSQL_TYPE_STRING) {
    // See http://dev.mysql.com/doc/refman/5.7/en/string-types.html for
    // information about character-based datatypes are compared.
    bool use_unknown_collation = false;
    DBUG_EXECUTE_IF("myrocks_enable_unknown_collation_index_only_scans",
                    use_unknown_collation = true;);

    if (cs->number == COLLATION_BINARY) {
      // - SQL layer pads BINARY(N) so that it always is N bytes long.
      // - For VARBINARY(N), values may have different lengths, so we're using
      //   variable-length encoding. This is also the only charset where the
      //   values are not space-padded for comparison.
      m_unpack_func = is_varchar ? Rdb_key_def::unpack_binary_or_utf8_varchar
                                 : Rdb_key_def::unpack_binary_str;
      res = true;
    } else if (cs->number == COLLATION_LATIN1_BIN || cs->number == COLLATION_UTF8_BIN) {
      // For _bin collations, mem-comparable form of the string is the string
      // itself.

      if (is_varchar) {
        // VARCHARs - are compared as if they were space-padded - but are
        // not actually space-padded (reading the value back produces the
        // original value, without the padding)
        m_unpack_func = Rdb_key_def::unpack_binary_or_utf8_varchar_space_pad;
        m_skip_func = Rdb_key_def::skip_variable_space_pad;
        m_pack_func = Rdb_key_def::pack_with_varchar_space_pad;
        m_make_unpack_info_func = Rdb_key_def::dummy_make_unpack_info;
        m_segment_size = get_segment_size_from_collation(cs);
        m_max_image_len =
            (max_image_len_before_chunks / (m_segment_size - 1) + 1) *
            m_segment_size;
        rdb_get_mem_comparable_space(cs, &space_xfrm, &space_xfrm_len,
                                     &space_mb_len);
      } else {
        // SQL layer pads CHAR(N) values to their maximum length.
        // We just store that and restore it back.
        m_unpack_func = (cs->number == COLLATION_LATIN1_BIN)
                            ? Rdb_key_def::unpack_binary_str
                            : Rdb_key_def::unpack_utf8_str;
      }
      res = true;
    } else {
      // This is [VAR]CHAR(n) and the collation is not $(charset_name)_bin

      res = true;  // index-only scans are possible
      m_unpack_data_len = is_varchar ? 0 : field->field_length;
      const uint idx = is_varchar ? 0 : 1;
      const Rdb_collation_codec *codec = nullptr;

      if (is_varchar) {
        // VARCHAR requires space-padding for doing comparisons
        //
        // The check for cs->levels_for_order is to catch
        // latin2_czech_cs and cp1250_czech_cs - multi-level collations
        // that Variable-Length Space Padded Encoding can't handle.
        // It is not expected to work for any other multi-level collations,
        // either.
        // Currently we handle these collations as NO_PAD, even if they have
        // PAD_SPACE attribute.
        if (cs->levels_for_order == 1) {
          m_pack_func = Rdb_key_def::pack_with_varchar_space_pad;
          m_skip_func = Rdb_key_def::skip_variable_space_pad;
          m_segment_size = get_segment_size_from_collation(cs);
          m_max_image_len =
              (max_image_len_before_chunks / (m_segment_size - 1) + 1) *
              m_segment_size;
          rdb_get_mem_comparable_space(cs, &space_xfrm, &space_xfrm_len,
                                       &space_mb_len);
        } else {
          //  NO_LINT_DEBUG
          sql_print_warning(
              "RocksDB: you're trying to create an index "
              "with a multi-level collation %s",
              cs->name);
          //  NO_LINT_DEBUG
          sql_print_warning(
              "MyRocks will handle this collation internally "
              " as if it had a NO_PAD attribute.");
          m_pack_func = Rdb_key_def::pack_with_varchar_encoding;
          m_skip_func = Rdb_key_def::skip_variable_length;
        }
      }

      if ((codec = rdb_init_collation_mapping(cs)) != nullptr) {
        // The collation allows to store extra information in the unpack_info
        // which can be used to restore the original value from the
        // mem-comparable form.
        m_make_unpack_info_func = codec->m_make_unpack_info_func[idx];
        m_unpack_func = codec->m_unpack_func[idx];
        m_charset_codec = codec;
      } else if (use_unknown_collation) {
        // We have no clue about how this collation produces mem-comparable
        // form. Our way of restoring the original value is to keep a copy of
        // the original value in unpack_info.
        m_unpack_info_stores_value = true;
        m_make_unpack_info_func = is_varchar
                                      ? Rdb_key_def::make_unpack_unknown_varchar
                                      : Rdb_key_def::make_unpack_unknown;
        m_unpack_func = is_varchar ? Rdb_key_def::unpack_unknown_varchar
                                   : Rdb_key_def::unpack_unknown;
      } else {
        // Same as above: we don't know how to restore the value from its
        // mem-comparable form.
        // Here, we just indicate to the SQL layer we can't do it.
        DBUG_ASSERT(m_unpack_func == nullptr);
        m_unpack_info_stores_value = false;
        res = false;  // Indicate that index-only reads are not possible
      }
    }

    // Make an adjustment: if this column is partially covered, tell the SQL
    // layer we can't do index-only scans. Later when we perform an index read,
    // we'll check on a record-by-record basis if we can do an index-only scan
    // or not.
    uint field_length;
    if (field->table) {
      field_length = field->table->field[field->field_index]->field_length;
    } else {
      field_length = field->field_length;
    }

    if (field_length != key_length) {
      res = false;
      // If this index doesn't support covered bitmaps, then we won't know
      // during a read if the column is actually covered or not. If so, we need
      // to assume the column isn't covered and skip it during unpacking.
      //
      // If key_descr == NULL, then this is a dummy field and we probably don't
      // need to perform this step. However, to preserve the behavior before
      // this change, we'll only skip this step if we have an index which
      // supports covered bitmaps.
      if (!key_descr || !key_descr->use_covered_bitmap_format()) {
        m_unpack_func = nullptr;
        m_make_unpack_info_func = nullptr;
        m_unpack_info_stores_value = true;
      }
    }
  }

  m_covered = res;
  return res;
}

Field *Rdb_field_packing::get_field_in_table(const TABLE *const tbl) const {
  return tbl->key_info[m_keynr].key_part[m_key_part].field;
}

void Rdb_field_packing::fill_hidden_pk_val(uchar **dst,
                                           const longlong hidden_pk_id) const {
  DBUG_ASSERT(m_max_image_len == 8);

  String to;
  rdb_netstr_append_uint64(&to, hidden_pk_id);
  memcpy(*dst, to.ptr(), m_max_image_len);

  *dst += m_max_image_len;
}

///////////////////////////////////////////////////////////////////////////////////////////
// Rdb_ddl_manager
///////////////////////////////////////////////////////////////////////////////////////////

Rdb_tbl_def::~Rdb_tbl_def() {
  auto ddl_manager = rdb_get_ddl_manager();
  /* Don't free key definitions */
  if (m_key_descr_arr) {
    for (uint i = 0; i < m_key_count; i++) {
      if (ddl_manager && m_key_descr_arr[i]) {
        ddl_manager->erase_index_num(m_key_descr_arr[i]->get_gl_index_id());
      }

      m_key_descr_arr[i] = nullptr;
    }

    delete[] m_key_descr_arr;
    m_key_descr_arr = nullptr;
  }
}

/*
  Put table definition DDL entry. Actual write is done at
  Rdb_dict_manager::commit.

  We write
    dbname.tablename -> version + {key_entry, key_entry, key_entry, ... }

  Where key entries are a tuple of
    ( cf_id, index_nr )
*/

bool Rdb_tbl_def::put_dict(Rdb_dict_manager *const dict,
                           rocksdb::WriteBatch *const batch,
                           const rocksdb::Slice &key) {
  StringBuffer<8 * Rdb_key_def::PACKED_SIZE> indexes;
  indexes.alloc(Rdb_key_def::VERSION_SIZE +
                m_key_count * Rdb_key_def::PACKED_SIZE * 2);
  rdb_netstr_append_uint16(&indexes, Rdb_key_def::DDL_ENTRY_INDEX_VERSION);

  for (uint i = 0; i < m_key_count; i++) {
    const Rdb_key_def &kd = *m_key_descr_arr[i];

    uchar flags =
        (kd.m_is_reverse_cf ? Rdb_key_def::REVERSE_CF_FLAG : 0) |
        (kd.m_is_per_partition_cf ? Rdb_key_def::PER_PARTITION_CF_FLAG : 0);

    const uint cf_id = kd.get_cf()->GetID();
    /*
      If cf_id already exists, cf_flags must be the same.
      To prevent race condition, reading/modifying/committing CF flags
      need to be protected by mutex (dict_manager->lock()).
      When RocksDB supports transaction with pessimistic concurrency
      control, we can switch to use it and removing mutex.
    */
    uint existing_cf_flags;
    const std::string cf_name = kd.get_cf()->GetName();

    if (dict->get_cf_flags(cf_id, &existing_cf_flags)) {
      // For the purposes of comparison we'll clear the partitioning bit. The
      // intent here is to make sure that both partitioned and non-partitioned
      // tables can refer to the same CF.
      existing_cf_flags &= ~Rdb_key_def::CF_FLAGS_TO_IGNORE;
      flags &= ~Rdb_key_def::CF_FLAGS_TO_IGNORE;

      if (existing_cf_flags != flags) {
        my_error(ER_CF_DIFFERENT, MYF(0), cf_name.c_str(), flags,
                 existing_cf_flags);
        return true;
      }
    } else {
      dict->add_cf_flags(batch, cf_id, flags);
    }

    rdb_netstr_append_uint32(&indexes, cf_id);

    uint32 index_number = kd.get_index_number();
    rdb_netstr_append_uint32(&indexes, index_number);

    struct Rdb_index_info index_info;
    index_info.m_gl_index_id = {cf_id, index_number};
    index_info.m_index_dict_version = Rdb_key_def::INDEX_INFO_VERSION_LATEST;
    index_info.m_index_type = kd.m_index_type;
    index_info.m_kv_version = kd.m_kv_format_version;
    index_info.m_index_flags = kd.m_index_flags_bitmap;
    index_info.m_ttl_duration = kd.m_ttl_duration;

    dict->add_or_update_index_cf_mapping(batch, &index_info);
  }

  const rocksdb::Slice svalue(indexes.c_ptr(), indexes.length());

  dict->put_key(batch, key, svalue);
  return false;
}

time_t Rdb_tbl_def::get_create_time() {
  time_t create_time = m_create_time;

  if (create_time == CREATE_TIME_UNKNOWN) {
    // Read it from the .frm file. It's not a problem if several threads do this
    // concurrently
    char path[FN_REFLEN];
    snprintf(path, sizeof(path), "%s/%s/%s%s", mysql_data_home,
             m_dbname.c_str(), m_tablename.c_str(), reg_ext);
    unpack_filename(path,path);
    MY_STAT f_stat;
    if (my_stat(path, &f_stat, MYF(0)))
      create_time = f_stat.st_ctime;
    else
      create_time = 0; // will be shown as SQL NULL
    m_create_time = create_time;
  }
  return create_time;
}

// Length that each index flag takes inside the record.
// Each index in the array maps to the enum INDEX_FLAG
static const std::array<uint, 1> index_flag_lengths = {
    {ROCKSDB_SIZEOF_TTL_RECORD}};

bool Rdb_key_def::has_index_flag(uint32 index_flags, enum INDEX_FLAG flag) {
  return flag & index_flags;
}

uint32 Rdb_key_def::calculate_index_flag_offset(uint32 index_flags,
                                                enum INDEX_FLAG flag,
                                                uint *const length) {
  DBUG_ASSERT_IMP(flag != MAX_FLAG,
                  Rdb_key_def::has_index_flag(index_flags, flag));

  uint offset = 0;
  for (size_t bit = 0; bit < sizeof(index_flags) * CHAR_BIT; ++bit) {
    int mask = 1 << bit;

    /* Exit once we've reached the proper flag */
    if (flag & mask) {
      if (length != nullptr) {
        *length = index_flag_lengths[bit];
      }
      break;
    }

    if (index_flags & mask) {
      offset += index_flag_lengths[bit];
    }
  }

  return offset;
}

void Rdb_key_def::write_index_flag_field(Rdb_string_writer *const buf,
                                         const uchar *const val,
                                         enum INDEX_FLAG flag) const {
  uint len;
  uint offset = calculate_index_flag_offset(m_index_flags_bitmap, flag, &len);
  DBUG_ASSERT(offset + len <= buf->get_current_pos());
  memcpy(buf->ptr() + offset, val, len);
}

void Rdb_tbl_def::check_if_is_mysql_system_table() {
  static const char *const system_dbs[] = {
      "mysql",
      "performance_schema",
      "information_schema",
  };

  m_is_mysql_system_table = false;
  for (uint ii = 0; ii < array_elements(system_dbs); ii++) {
    if (strcmp(m_dbname.c_str(), system_dbs[ii]) == 0) {
      m_is_mysql_system_table = true;
      break;
    }
  }
}

void Rdb_tbl_def::check_and_set_read_free_rpl_table() {
  m_is_read_free_rpl_table =
#if 0 // MARIAROCKS_NOT_YET : read-free replication is not supported
      rdb_read_free_regex_handler.matches(base_tablename());
#else
      false;
#endif
}

void Rdb_tbl_def::set_name(const std::string &name) {
  int err MY_ATTRIBUTE((__unused__));

  m_dbname_tablename = name;
  err = rdb_split_normalized_tablename(name, &m_dbname, &m_tablename,
                                       &m_partition);
  DBUG_ASSERT(err == 0);

  check_if_is_mysql_system_table();
}

GL_INDEX_ID Rdb_tbl_def::get_autoincr_gl_index_id() {
  for (uint i = 0; i < m_key_count; i++) {
    auto &k = m_key_descr_arr[i];
    if (k->m_index_type == Rdb_key_def::INDEX_TYPE_PRIMARY ||
        k->m_index_type == Rdb_key_def::INDEX_TYPE_HIDDEN_PRIMARY) {
      return k->get_gl_index_id();
    }
  }

  // Every table must have a primary key, even if it's hidden.
  abort();
  return GL_INDEX_ID();
}

void Rdb_ddl_manager::erase_index_num(const GL_INDEX_ID &gl_index_id) {
  m_index_num_to_keydef.erase(gl_index_id);
}

void Rdb_ddl_manager::add_uncommitted_keydefs(
    const std::unordered_set<std::shared_ptr<Rdb_key_def>> &indexes) {
  mysql_rwlock_wrlock(&m_rwlock);
  for (const auto &index : indexes) {
    m_index_num_to_uncommitted_keydef[index->get_gl_index_id()] = index;
  }
  mysql_rwlock_unlock(&m_rwlock);
}

void Rdb_ddl_manager::remove_uncommitted_keydefs(
    const std::unordered_set<std::shared_ptr<Rdb_key_def>> &indexes) {
  mysql_rwlock_wrlock(&m_rwlock);
  for (const auto &index : indexes) {
    m_index_num_to_uncommitted_keydef.erase(index->get_gl_index_id());
  }
  mysql_rwlock_unlock(&m_rwlock);
}

namespace  // anonymous namespace = not visible outside this source file
{
struct Rdb_validate_tbls : public Rdb_tables_scanner {
  using tbl_info_t = std::pair<std::string, bool>;
  using tbl_list_t = std::map<std::string, std::set<tbl_info_t>>;

  tbl_list_t m_list;

  int add_table(Rdb_tbl_def *tdef) override;

  bool compare_to_actual_tables(const std::string &datadir, bool *has_errors);

  bool scan_for_frms(const std::string &datadir, const std::string &dbname,
                     bool *has_errors);

  bool check_frm_file(const std::string &fullpath, const std::string &dbname,
                      const std::string &tablename, bool *has_errors);
};
}  // anonymous namespace

/*
  Get a list of tables that we expect to have .frm files for.  This will use the
  information just read from the RocksDB data dictionary.
*/
int Rdb_validate_tbls::add_table(Rdb_tbl_def *tdef) {
  DBUG_ASSERT(tdef != nullptr);

  /* Add the database/table into the list that are not temp table */
  if (tdef->base_tablename().find(tmp_file_prefix) == std::string::npos) {
    bool is_partition = tdef->base_partition().size() != 0;
    m_list[tdef->base_dbname()].insert(
        tbl_info_t(tdef->base_tablename(), is_partition));
  }

  return HA_EXIT_SUCCESS;
}

/*
  Access the .frm file for this dbname/tablename and see if it is a RocksDB
  table (or partition table).
*/
bool Rdb_validate_tbls::check_frm_file(const std::string &fullpath,
                                       const std::string &dbname,
                                       const std::string &tablename,
                                       bool *has_errors) {
  /* Check this .frm file to see what engine it uses */
  String fullfilename(fullpath.c_str(), &my_charset_bin);
  fullfilename.append(FN_DIRSEP);
  fullfilename.append(tablename.c_str());
  fullfilename.append(".frm");

  /*
    This function will return the legacy_db_type of the table.  Currently
    it does not reference the first parameter (THD* thd), but if it ever
    did in the future we would need to make a version that does it without
    the connection handle as we don't have one here.
  */
  char eng_type_buf[NAME_CHAR_LEN+1];
  LEX_CSTRING eng_type_str = {eng_type_buf, 0}; 
  enum Table_type type = dd_frm_type(nullptr, fullfilename.c_ptr(), &eng_type_str);
  if (type == TABLE_TYPE_UNKNOWN) {
    // NO_LINT_DEBUG
    sql_print_warning("RocksDB: Failed to open/read .from file: %s",
                      fullfilename.ptr());
    return false;
  }

  if (type == TABLE_TYPE_NORMAL) {
    /* For a RocksDB table do we have a reference in the data dictionary? */
    if (!strncmp(eng_type_str.str, "ROCKSDB", eng_type_str.length)) {
      /*
        Attempt to remove the table entry from the list of tables.  If this
        fails then we know we had a .frm file that wasn't registered in RocksDB.
      */
      tbl_info_t element(tablename, false);
      if (m_list.count(dbname) == 0 || m_list[dbname].erase(element) == 0) {
        // NO_LINT_DEBUG
        sql_print_warning(
            "RocksDB: Schema mismatch - "
            "A .frm file exists for table %s.%s, "
            "but that table is not registered in RocksDB",
            dbname.c_str(), tablename.c_str());
        *has_errors = true;
      }
    } else if (!strncmp(eng_type_str.str, "partition", eng_type_str.length)) {
      /*
        For partition tables, see if it is in the m_list as a partition,
        but don't generate an error if it isn't there - we don't know that the
        .frm is for RocksDB.
      */
      if (m_list.count(dbname) > 0) {
        m_list[dbname].erase(tbl_info_t(tablename, true));
      }
    }
  }

  return true;
}

/* Scan the database subdirectory for .frm files */
bool Rdb_validate_tbls::scan_for_frms(const std::string &datadir,
                                      const std::string &dbname,
                                      bool *has_errors) {
  bool result = true;
  std::string fullpath = datadir + dbname;
  struct st_my_dir *dir_info = my_dir(fullpath.c_str(), MYF(MY_DONT_SORT));

  /* Access the directory */
  if (dir_info == nullptr) {
    // NO_LINT_DEBUG
    sql_print_warning("RocksDB: Could not open database directory: %s",
                      fullpath.c_str());
    return false;
  }

  /* Scan through the files in the directory */
  struct fileinfo *file_info = dir_info->dir_entry;
  for (uint ii = 0; ii < dir_info->number_of_files; ii++, file_info++) {
    /* Find .frm files that are not temp files (those that contain '#sql') */
    const char *ext = strrchr(file_info->name, '.');
    if (ext != nullptr && strstr(file_info->name, tmp_file_prefix) == nullptr &&
        strcmp(ext, ".frm") == 0) {
      std::string tablename =
          std::string(file_info->name, ext - file_info->name);

      /* Check to see if the .frm file is from RocksDB */
      if (!check_frm_file(fullpath, dbname, tablename, has_errors)) {
        result = false;
        break;
      }
    }
  }

  /* Remove any databases who have no more tables listed */
  if (m_list.count(dbname) == 1 && m_list[dbname].size() == 0) {
    m_list.erase(dbname);
  }

  /* Release the directory entry */
  my_dirend(dir_info);

  return result;
}

/*
  Scan the datadir for all databases (subdirectories) and get a list of .frm
  files they contain
*/
bool Rdb_validate_tbls::compare_to_actual_tables(const std::string &datadir,
                                                 bool *has_errors) {
  bool result = true;
  struct st_my_dir *dir_info;
  struct fileinfo *file_info;

  dir_info = my_dir(datadir.c_str(), MYF(MY_DONT_SORT | MY_WANT_STAT));
  if (dir_info == nullptr) {
    // NO_LINT_DEBUG
    sql_print_warning("RocksDB: could not open datadir: %s", datadir.c_str());
    return false;
  }

  file_info = dir_info->dir_entry;
  for (uint ii = 0; ii < dir_info->number_of_files; ii++, file_info++) {
    /* Ignore files/dirs starting with '.' */
    if (file_info->name[0] == '.') continue;

    /* Ignore all non-directory files */
    if (!MY_S_ISDIR(file_info->mystat->st_mode)) continue;

    /* Scan all the .frm files in the directory */
    if (!scan_for_frms(datadir, file_info->name, has_errors)) {
      result = false;
      break;
    }
  }

  /* Release the directory info */
  my_dirend(dir_info);

  return result;
}

/*
  Validate that all auto increment values in the data dictionary are on a
  supported version.
*/
bool Rdb_ddl_manager::validate_auto_incr() {
  std::unique_ptr<rocksdb::Iterator> it(m_dict->new_iterator());

  uchar auto_incr_entry[Rdb_key_def::INDEX_NUMBER_SIZE];
  rdb_netbuf_store_index(auto_incr_entry, Rdb_key_def::AUTO_INC);
  const rocksdb::Slice auto_incr_entry_slice(
      reinterpret_cast<char *>(auto_incr_entry),
      Rdb_key_def::INDEX_NUMBER_SIZE);
  for (it->Seek(auto_incr_entry_slice); it->Valid(); it->Next()) {
    const rocksdb::Slice key = it->key();
    const rocksdb::Slice val = it->value();
    GL_INDEX_ID gl_index_id;

    if (key.size() >= Rdb_key_def::INDEX_NUMBER_SIZE &&
        memcmp(key.data(), auto_incr_entry, Rdb_key_def::INDEX_NUMBER_SIZE)) {
      break;
    }

    if (key.size() != Rdb_key_def::INDEX_NUMBER_SIZE * 3) {
      return false;
    }

    if (val.size() <= Rdb_key_def::VERSION_SIZE) {
      return false;
    }

    // Check if we have orphaned entries for whatever reason by cross
    // referencing ddl entries.
    auto ptr = reinterpret_cast<const uchar *>(key.data());
    ptr += Rdb_key_def::INDEX_NUMBER_SIZE;
    rdb_netbuf_read_gl_index(&ptr, &gl_index_id);
    if (!m_dict->get_index_info(gl_index_id, nullptr)) {
      // NO_LINT_DEBUG
      sql_print_warning(
          "RocksDB: AUTOINC mismatch - "
          "Index number (%u, %u) found in AUTOINC "
          "but does not exist as a DDL entry",
          gl_index_id.cf_id, gl_index_id.index_id);
      return false;
    }

    ptr = reinterpret_cast<const uchar *>(val.data());
    const int version = rdb_netbuf_read_uint16(&ptr);
    if (version > Rdb_key_def::AUTO_INCREMENT_VERSION) {
      // NO_LINT_DEBUG
      sql_print_warning(
          "RocksDB: AUTOINC mismatch - "
          "Index number (%u, %u) found in AUTOINC "
          "is on unsupported version %d",
          gl_index_id.cf_id, gl_index_id.index_id, version);
      return false;
    }
  }

  if (!it->status().ok()) {
    return false;
  }

  return true;
}

/*
  Validate that all the tables in the RocksDB database dictionary match the .frm
  files in the datadir
*/
bool Rdb_ddl_manager::validate_schemas(void) {
  bool has_errors = false;
  const std::string datadir = std::string(mysql_real_data_home);
  Rdb_validate_tbls table_list;

  /* Get the list of tables from the database dictionary */
  if (scan_for_tables(&table_list) != 0) {
    return false;
  }

  /* Compare that to the list of actual .frm files */
  if (!table_list.compare_to_actual_tables(datadir, &has_errors)) {
    return false;
  }

  /*
    Any tables left in the tables list are ones that are registered in RocksDB
    but don't have .frm files.
  */
  for (const auto &db : table_list.m_list) {
    for (const auto &table : db.second) {
      // NO_LINT_DEBUG
      sql_print_warning(
          "RocksDB: Schema mismatch - "
          "Table %s.%s is registered in RocksDB "
          "but does not have a .frm file",
          db.first.c_str(), table.first.c_str());
      has_errors = true;
    }
  }

  return !has_errors;
}

bool Rdb_ddl_manager::init(Rdb_dict_manager *const dict_arg,
                           Rdb_cf_manager *const cf_manager,
                           const uint32_t validate_tables) {
  m_dict = dict_arg;
  mysql_rwlock_init(0, &m_rwlock);

  /* Read the data dictionary and populate the hash */
  uchar ddl_entry[Rdb_key_def::INDEX_NUMBER_SIZE];
  rdb_netbuf_store_index(ddl_entry, Rdb_key_def::DDL_ENTRY_INDEX_START_NUMBER);
  const rocksdb::Slice ddl_entry_slice((char *)ddl_entry,
                                       Rdb_key_def::INDEX_NUMBER_SIZE);

  /* Reading data dictionary should always skip bloom filter */
  rocksdb::Iterator *it = m_dict->new_iterator();
  int i = 0;

  uint max_index_id_in_dict = 0;
  m_dict->get_max_index_id(&max_index_id_in_dict);

  for (it->Seek(ddl_entry_slice); it->Valid(); it->Next()) {
    const uchar *ptr;
    const uchar *ptr_end;
    const rocksdb::Slice key = it->key();
    const rocksdb::Slice val = it->value();

    if (key.size() >= Rdb_key_def::INDEX_NUMBER_SIZE &&
        memcmp(key.data(), ddl_entry, Rdb_key_def::INDEX_NUMBER_SIZE)) {
      break;
    }

    if (key.size() <= Rdb_key_def::INDEX_NUMBER_SIZE) {
      // NO_LINT_DEBUG
      sql_print_error("RocksDB: Table_store: key has length %d (corruption?)",
                      (int)key.size());
      return true;
    }

    Rdb_tbl_def *const tdef =
        new Rdb_tbl_def(key, Rdb_key_def::INDEX_NUMBER_SIZE);

    // Now, read the DDLs.
    const int real_val_size = val.size() - Rdb_key_def::VERSION_SIZE;
    if (real_val_size % Rdb_key_def::PACKED_SIZE * 2 > 0) {
      // NO_LINT_DEBUG
      sql_print_error("RocksDB: Table_store: invalid keylist for table %s",
                      tdef->full_tablename().c_str());
      return true;
    }
    tdef->m_key_count = real_val_size / (Rdb_key_def::PACKED_SIZE * 2);
    tdef->m_key_descr_arr = new std::shared_ptr<Rdb_key_def>[tdef->m_key_count];

    ptr = reinterpret_cast<const uchar *>(val.data());
    const int version = rdb_netbuf_read_uint16(&ptr);
    if (version != Rdb_key_def::DDL_ENTRY_INDEX_VERSION) {
      // NO_LINT_DEBUG
      sql_print_error(
          "RocksDB: DDL ENTRY Version was not expected."
          "Expected: %d, Actual: %d",
          Rdb_key_def::DDL_ENTRY_INDEX_VERSION, version);
      return true;
    }
    ptr_end = ptr + real_val_size;
    for (uint keyno = 0; ptr < ptr_end; keyno++) {
      GL_INDEX_ID gl_index_id;
      rdb_netbuf_read_gl_index(&ptr, &gl_index_id);
      uint flags = 0;
      struct Rdb_index_info index_info;
      if (!m_dict->get_index_info(gl_index_id, &index_info)) {
        // NO_LINT_DEBUG
        sql_print_error(
            "RocksDB: Could not get index information "
            "for Index Number (%u,%u), table %s",
            gl_index_id.cf_id, gl_index_id.index_id,
            tdef->full_tablename().c_str());
        return true;
      }
      if (max_index_id_in_dict < gl_index_id.index_id) {
        // NO_LINT_DEBUG
        sql_print_error(
            "RocksDB: Found max index id %u from data dictionary "
            "but also found larger index id %u from dictionary. "
            "This should never happen and possibly a bug.",
            max_index_id_in_dict, gl_index_id.index_id);
        return true;
      }
      if (!m_dict->get_cf_flags(gl_index_id.cf_id, &flags)) {
        // NO_LINT_DEBUG
        sql_print_error(
            "RocksDB: Could not get Column Family Flags "
            "for CF Number %d, table %s",
            gl_index_id.cf_id, tdef->full_tablename().c_str());
        return true;
      }

      if ((flags & Rdb_key_def::AUTO_CF_FLAG) != 0) {
        // The per-index cf option is deprecated.  Make sure we don't have the
        // flag set in any existing database.   NO_LINT_DEBUG
        // NO_LINT_DEBUG
        sql_print_error(
            "RocksDB: The defunct AUTO_CF_FLAG is enabled for CF "
            "number %d, table %s",
            gl_index_id.cf_id, tdef->full_tablename().c_str());
      }

      rocksdb::ColumnFamilyHandle *const cfh =
          cf_manager->get_cf(gl_index_id.cf_id);
      DBUG_ASSERT(cfh != nullptr);

      uint32 ttl_rec_offset =
          Rdb_key_def::has_index_flag(index_info.m_index_flags,
                                      Rdb_key_def::TTL_FLAG)
              ? Rdb_key_def::calculate_index_flag_offset(
                    index_info.m_index_flags, Rdb_key_def::TTL_FLAG)
              : UINT_MAX;

      /*
        We can't fully initialize Rdb_key_def object here, because full
        initialization requires that there is an open TABLE* where we could
        look at Field* objects and set max_length and other attributes
      */
      tdef->m_key_descr_arr[keyno] = std::make_shared<Rdb_key_def>(
          gl_index_id.index_id, keyno, cfh, index_info.m_index_dict_version,
          index_info.m_index_type, index_info.m_kv_version,
          flags & Rdb_key_def::REVERSE_CF_FLAG,
          flags & Rdb_key_def::PER_PARTITION_CF_FLAG, "",
          m_dict->get_stats(gl_index_id), index_info.m_index_flags,
          ttl_rec_offset, index_info.m_ttl_duration);
    }
    put(tdef);
    i++;
  }

  /*
    If validate_tables is greater than 0 run the validation.  Only fail the
    initialzation if the setting is 1.  If the setting is 2 we continue.
  */
  if (validate_tables > 0) {
    std::string msg;
    if (!validate_schemas()) {
      msg =
          "RocksDB: Problems validating data dictionary "
          "against .frm files, exiting";
    } else if (!validate_auto_incr()) {
      msg =
          "RocksDB: Problems validating auto increment values in "
          "data dictionary, exiting";
    }
    if (validate_tables == 1 && !msg.empty()) {
      // NO_LINT_DEBUG
      sql_print_error("%s", msg.c_str());
      return true;
    }
  }

  // index ids used by applications should not conflict with
  // data dictionary index ids
  if (max_index_id_in_dict < Rdb_key_def::END_DICT_INDEX_ID) {
    max_index_id_in_dict = Rdb_key_def::END_DICT_INDEX_ID;
  }

  m_sequence.init(max_index_id_in_dict + 1);

  if (!it->status().ok()) {
    rdb_log_status_error(it->status(), "Table_store load error");
    return true;
  }
  delete it;
  // NO_LINT_DEBUG
  sql_print_information("RocksDB: Table_store: loaded DDL data for %d tables",
                        i);
  return false;
}

Rdb_tbl_def *Rdb_ddl_manager::find(const std::string &table_name,
                                   const bool lock) {
  if (lock) {
    mysql_rwlock_rdlock(&m_rwlock);
  }

  Rdb_tbl_def *rec = nullptr;
  const auto it = m_ddl_map.find(table_name);
  if (it != m_ddl_map.end()) {
    rec = it->second;
  }

  if (lock) {
    mysql_rwlock_unlock(&m_rwlock);
  }

  return rec;
}

// this is a safe version of the find() function below.  It acquires a read
// lock on m_rwlock to make sure the Rdb_key_def is not discarded while we
// are finding it.  Copying it into 'ret' increments the count making sure
// that the object will not be discarded until we are finished with it.
std::shared_ptr<const Rdb_key_def> Rdb_ddl_manager::safe_find(
    GL_INDEX_ID gl_index_id) {
  std::shared_ptr<const Rdb_key_def> ret(nullptr);

  mysql_rwlock_rdlock(&m_rwlock);

  auto it = m_index_num_to_keydef.find(gl_index_id);
  if (it != m_index_num_to_keydef.end()) {
    const auto table_def = find(it->second.first, false);
    if (table_def && it->second.second < table_def->m_key_count) {
      const auto &kd = table_def->m_key_descr_arr[it->second.second];
      if (kd->max_storage_fmt_length() != 0) {
        ret = kd;
      }
    }
  } else {
    auto it = m_index_num_to_uncommitted_keydef.find(gl_index_id);
    if (it != m_index_num_to_uncommitted_keydef.end()) {
      const auto &kd = it->second;
      if (kd->max_storage_fmt_length() != 0) {
        ret = kd;
      }
    }
  }

  mysql_rwlock_unlock(&m_rwlock);

  return ret;
}

// this method assumes at least read-only lock on m_rwlock
const std::shared_ptr<Rdb_key_def> &Rdb_ddl_manager::find(
    GL_INDEX_ID gl_index_id) {
  auto it = m_index_num_to_keydef.find(gl_index_id);
  if (it != m_index_num_to_keydef.end()) {
    auto table_def = find(it->second.first, false);
    if (table_def) {
      if (it->second.second < table_def->m_key_count) {
        return table_def->m_key_descr_arr[it->second.second];
      }
    }
  } else {
    auto it = m_index_num_to_uncommitted_keydef.find(gl_index_id);
    if (it != m_index_num_to_uncommitted_keydef.end()) {
      return it->second;
    }
  }

  static std::shared_ptr<Rdb_key_def> empty = nullptr;

  return empty;
}

// this method returns the name of the table based on an index id. It acquires
// a read lock on m_rwlock.
const std::string Rdb_ddl_manager::safe_get_table_name(
    const GL_INDEX_ID &gl_index_id) {
  std::string ret;
  mysql_rwlock_rdlock(&m_rwlock);
  auto it = m_index_num_to_keydef.find(gl_index_id);
  if (it != m_index_num_to_keydef.end()) {
    ret = it->second.first;
  }
  mysql_rwlock_unlock(&m_rwlock);
  return ret;
}

void Rdb_ddl_manager::set_stats(
    const std::unordered_map<GL_INDEX_ID, Rdb_index_stats> &stats) {
  mysql_rwlock_wrlock(&m_rwlock);
  for (auto src : stats) {
    const auto &keydef = find(src.second.m_gl_index_id);
    if (keydef) {
      keydef->m_stats = src.second;
      m_stats2store[keydef->m_stats.m_gl_index_id] = keydef->m_stats;
    }
  }
  mysql_rwlock_unlock(&m_rwlock);
}

void Rdb_ddl_manager::adjust_stats(
    const std::vector<Rdb_index_stats> &new_data,
    const std::vector<Rdb_index_stats> &deleted_data) {
  mysql_rwlock_wrlock(&m_rwlock);
  int i = 0;
  for (const auto &data : {new_data, deleted_data}) {
    for (const auto &src : data) {
      const auto &keydef = find(src.m_gl_index_id);
      if (keydef) {
        keydef->m_stats.m_distinct_keys_per_prefix.resize(
            keydef->get_key_parts());
        keydef->m_stats.merge(src, i == 0, keydef->max_storage_fmt_length());
        m_stats2store[keydef->m_stats.m_gl_index_id] = keydef->m_stats;
      }
    }
    i++;
  }
  const bool should_save_stats = !m_stats2store.empty();
  mysql_rwlock_unlock(&m_rwlock);
  if (should_save_stats) {
    // Queue an async persist_stats(false) call to the background thread.
    rdb_queue_save_stats_request();
  }
}

void Rdb_ddl_manager::persist_stats(const bool sync) {
  mysql_rwlock_wrlock(&m_rwlock);
  const auto local_stats2store = std::move(m_stats2store);
  m_stats2store.clear();
  mysql_rwlock_unlock(&m_rwlock);

  // Persist stats
  const std::unique_ptr<rocksdb::WriteBatch> wb = m_dict->begin();
  std::vector<Rdb_index_stats> stats;
  std::transform(local_stats2store.begin(), local_stats2store.end(),
                 std::back_inserter(stats),
                 [](const std::pair<GL_INDEX_ID, Rdb_index_stats> &s) {
                   return s.second;
                 });
  m_dict->add_stats(wb.get(), stats);
  m_dict->commit(wb.get(), sync);
}

/*
  Put table definition of `tbl` into the mapping, and also write it to the
  on-disk data dictionary.
*/

int Rdb_ddl_manager::put_and_write(Rdb_tbl_def *const tbl,
                                   rocksdb::WriteBatch *const batch) {
  Rdb_buf_writer<FN_LEN * 2 + Rdb_key_def::INDEX_NUMBER_SIZE> buf_writer;

  buf_writer.write_index(Rdb_key_def::DDL_ENTRY_INDEX_START_NUMBER);

  const std::string &dbname_tablename = tbl->full_tablename();
  buf_writer.write(dbname_tablename.c_str(), dbname_tablename.size());

  int res;
  if ((res = tbl->put_dict(m_dict, batch, buf_writer.to_slice()))) {
    return res;
  }
  if ((res = put(tbl))) {
    return res;
  }
  return HA_EXIT_SUCCESS;
}

/* Return 0 - ok, other value - error */
/* TODO:
  This function modifies m_ddl_map and m_index_num_to_keydef.
  However, these changes need to be reversed if dict_manager.commit fails
  See the discussion here: https://reviews.facebook.net/D35925#inline-259167
  Tracked by https://github.com/facebook/mysql-5.6/issues/33
*/
int Rdb_ddl_manager::put(Rdb_tbl_def *const tbl, const bool lock) {
  Rdb_tbl_def *rec;
  const std::string &dbname_tablename = tbl->full_tablename();

  if (lock) mysql_rwlock_wrlock(&m_rwlock);

  // We have to do this find because 'tbl' is not yet in the list.  We need
  // to find the one we are replacing ('rec')
  rec = find(dbname_tablename, false);
  if (rec) {
    // Free the old record.
    delete rec;
    m_ddl_map.erase(dbname_tablename);
  }
  m_ddl_map.emplace(dbname_tablename, tbl);

  for (uint keyno = 0; keyno < tbl->m_key_count; keyno++) {
    m_index_num_to_keydef[tbl->m_key_descr_arr[keyno]->get_gl_index_id()] =
        std::make_pair(dbname_tablename, keyno);
  }
  tbl->check_and_set_read_free_rpl_table();

  if (lock) mysql_rwlock_unlock(&m_rwlock);
  return 0;
}

void Rdb_ddl_manager::remove(Rdb_tbl_def *const tbl,
                             rocksdb::WriteBatch *const batch,
                             const bool lock) {
  if (lock) mysql_rwlock_wrlock(&m_rwlock);

  Rdb_buf_writer<FN_LEN * 2 + Rdb_key_def::INDEX_NUMBER_SIZE> key_writer;
  key_writer.write_index(Rdb_key_def::DDL_ENTRY_INDEX_START_NUMBER);
  const std::string &dbname_tablename = tbl->full_tablename();
  key_writer.write(dbname_tablename.c_str(), dbname_tablename.size());

  m_dict->delete_key(batch, key_writer.to_slice());

  const auto it = m_ddl_map.find(dbname_tablename);
  if (it != m_ddl_map.end()) {
    // Free Rdb_tbl_def
    delete it->second;

    m_ddl_map.erase(it);
  }

  if (lock) mysql_rwlock_unlock(&m_rwlock);
}

bool Rdb_ddl_manager::rename(const std::string &from, const std::string &to,
                             rocksdb::WriteBatch *const batch) {
  Rdb_tbl_def *rec;
  Rdb_tbl_def *new_rec;
  bool res = true;
  Rdb_buf_writer<FN_LEN * 2 + Rdb_key_def::INDEX_NUMBER_SIZE> new_buf_writer;

  mysql_rwlock_wrlock(&m_rwlock);
  if (!(rec = find(from, false))) {
    mysql_rwlock_unlock(&m_rwlock);
    return true;
  }

  new_rec = new Rdb_tbl_def(to);

  new_rec->m_key_count = rec->m_key_count;
  new_rec->m_auto_incr_val =
      rec->m_auto_incr_val.load(std::memory_order_relaxed);
  new_rec->m_key_descr_arr = rec->m_key_descr_arr;

  new_rec->m_hidden_pk_val =
      rec->m_hidden_pk_val.load(std::memory_order_relaxed);

  // so that it's not free'd when deleting the old rec
  rec->m_key_descr_arr = nullptr;

  // Create a new key
  new_buf_writer.write_index(Rdb_key_def::DDL_ENTRY_INDEX_START_NUMBER);

  const std::string &dbname_tablename = new_rec->full_tablename();
  new_buf_writer.write(dbname_tablename.c_str(), dbname_tablename.size());

  // Create a key to add
  if (!new_rec->put_dict(m_dict, batch, new_buf_writer.to_slice())) {
    remove(rec, batch, false);
    put(new_rec, false);
    res = false;  // ok
  }

  mysql_rwlock_unlock(&m_rwlock);
  return res;
}

void Rdb_ddl_manager::cleanup() {
  for (const auto &kv : m_ddl_map) {
    delete kv.second;
  }
  m_ddl_map.clear();

  mysql_rwlock_destroy(&m_rwlock);
  m_sequence.cleanup();
}

int Rdb_ddl_manager::scan_for_tables(Rdb_tables_scanner *const tables_scanner) {
  int ret;
  Rdb_tbl_def *rec;

  DBUG_ASSERT(tables_scanner != nullptr);

  mysql_rwlock_rdlock(&m_rwlock);

  ret = 0;

  for (const auto &kv : m_ddl_map) {
    rec = kv.second;
    ret = tables_scanner->add_table(rec);
    if (ret) break;
  }

  mysql_rwlock_unlock(&m_rwlock);
  return ret;
}

/*
  Rdb_binlog_manager class implementation
*/

bool Rdb_binlog_manager::init(Rdb_dict_manager *const dict_arg) {
  DBUG_ASSERT(dict_arg != nullptr);
  m_dict = dict_arg;

  m_key_writer.reset();
  m_key_writer.write_index(Rdb_key_def::BINLOG_INFO_INDEX_NUMBER);
  m_key_slice = m_key_writer.to_slice();
  return false;
}

void Rdb_binlog_manager::cleanup() {}

/**
  Set binlog name, pos and optionally gtid into WriteBatch.
  This function should be called as part of transaction commit,
  since binlog info is set only at transaction commit.
  Actual write into RocksDB is not done here, so checking if
  write succeeded or not is not possible here.
  @param binlog_name   Binlog name
  @param binlog_pos    Binlog pos
  @param batch         WriteBatch
*/
void Rdb_binlog_manager::update(const char *const binlog_name,
                                const my_off_t binlog_pos,
                                rocksdb::WriteBatchBase *const batch) {
  if (binlog_name && binlog_pos) {
    // max binlog length (512) + binlog pos (4) + binlog gtid (57) < 1024
    const size_t RDB_MAX_BINLOG_INFO_LEN = 1024;
    Rdb_buf_writer<RDB_MAX_BINLOG_INFO_LEN> value_writer;

    // store version
    value_writer.write_uint16(Rdb_key_def::BINLOG_INFO_INDEX_NUMBER_VERSION);

    // store binlog file name length
    DBUG_ASSERT(strlen(binlog_name) <= FN_REFLEN);
    const uint16_t binlog_name_len = strlen(binlog_name);
    value_writer.write_uint16(binlog_name_len);

    // store binlog file name
    value_writer.write(binlog_name, binlog_name_len);

    // store binlog pos
    value_writer.write_uint32(binlog_pos);

#ifdef MARIADB_MERGE_2019
    // store binlog gtid length.
    // If gtid was not set, store 0 instead
    const uint16_t binlog_max_gtid_len =
        binlog_max_gtid ? strlen(binlog_max_gtid) : 0;
    value_writer.write_uint16(binlog_max_gtid_len);

    if (binlog_max_gtid_len > 0) {
      // store binlog gtid
      value_writer.write(binlog_max_gtid, binlog_max_gtid_len);
    }
#endif    

    m_dict->put_key(batch, m_key_slice, value_writer.to_slice());
  }
}

/**
  Read binlog committed entry stored in RocksDB, then unpack
  @param[OUT] binlog_name  Binlog name
  @param[OUT] binlog_pos   Binlog pos
  @param[OUT] binlog_gtid  Binlog GTID
  @return
    true is binlog info was found (valid behavior)
    false otherwise
*/
bool Rdb_binlog_manager::read(char *const binlog_name,
                              my_off_t *const binlog_pos,
                              char *const binlog_gtid) const {
  bool ret = false;
  if (binlog_name) {
    std::string value;
    rocksdb::Status status = m_dict->get_value(m_key_slice, &value);
    if (status.ok()) {
      if (!unpack_value((const uchar *)value.c_str(), value.size(), binlog_name, binlog_pos,
                        binlog_gtid)) {
        ret = true;
      }
    }
  }
  return ret;
}

/**
  Unpack value then split into binlog_name, binlog_pos (and binlog_gtid)
  @param[IN]  value        Binlog state info fetched from RocksDB
  @param[OUT] binlog_name  Binlog name
  @param[OUT] binlog_pos   Binlog pos
  @param[OUT] binlog_gtid  Binlog GTID
  @return     true on error
*/
bool Rdb_binlog_manager::unpack_value(const uchar *const value,
                                      size_t value_size_arg,
                                      char *const binlog_name,
                                      my_off_t *const binlog_pos,
                                      char *const binlog_gtid) const {
  uint pack_len = 0;
  intmax_t value_size= value_size_arg;

  DBUG_ASSERT(binlog_pos != nullptr);

  if ((value_size -= Rdb_key_def::VERSION_SIZE) < 0)
    return true;
  // read version
  const uint16_t version = rdb_netbuf_to_uint16(value);

  pack_len += Rdb_key_def::VERSION_SIZE;
  if (version != Rdb_key_def::BINLOG_INFO_INDEX_NUMBER_VERSION) return true;

  if ((value_size -= sizeof(uint16)) < 0)
    return true;

  // read binlog file name length
  const uint16_t binlog_name_len = rdb_netbuf_to_uint16(value + pack_len);
  pack_len += sizeof(uint16);

  if (binlog_name_len >= (FN_REFLEN+1))
    return true;

  if ((value_size -= binlog_name_len) < 0)
    return true;

  if (binlog_name_len) {
    // read and set binlog name
    memcpy(binlog_name, value + pack_len, binlog_name_len);
    binlog_name[binlog_name_len] = '\0';
    pack_len += binlog_name_len;

    if ((value_size -= sizeof(uint32)) < 0)
      return true;
    // read and set binlog pos
    *binlog_pos = rdb_netbuf_to_uint32(value + pack_len);
    pack_len += sizeof(uint32);

    if ((value_size -= sizeof(uint16)) < 0)
      return true;
    // read gtid length
    const uint16_t binlog_gtid_len = rdb_netbuf_to_uint16(value + pack_len);
    pack_len += sizeof(uint16);

    if (binlog_gtid_len >= GTID_BUF_LEN)
      return true;
    if ((value_size -= binlog_gtid_len) < 0)
      return true;

    if (binlog_gtid && binlog_gtid_len > 0) {
      // read and set gtid
      memcpy(binlog_gtid, value + pack_len, binlog_gtid_len);
      binlog_gtid[binlog_gtid_len] = '\0';
      pack_len += binlog_gtid_len;
    }
  }
  return false;
}

/**
  Inserts a row into mysql.slave_gtid_info table. Doing this inside
  storage engine is more efficient than inserting/updating through MySQL.

  @param[IN] id Primary key of the table.
  @param[IN] db Database name. This is column 2 of the table.
  @param[IN] gtid Gtid in human readable form. This is column 3 of the table.
  @param[IN] write_batch Handle to storage engine writer.
*/
void Rdb_binlog_manager::update_slave_gtid_info(
    const uint id, const char *const db, const char *const gtid,
    rocksdb::WriteBatchBase *const write_batch) {
  if (id && db && gtid) {
    // Make sure that if the slave_gtid_info table exists we have a
    // pointer to it via m_slave_gtid_info_tbl.
    if (!m_slave_gtid_info_tbl.load()) {
      m_slave_gtid_info_tbl.store(
          rdb_get_ddl_manager()->find("mysql.slave_gtid_info"));
    }
    if (!m_slave_gtid_info_tbl.load()) {
      // slave_gtid_info table is not present. Simply return.
      return;
    }
    DBUG_ASSERT(m_slave_gtid_info_tbl.load()->m_key_count == 1);

    const std::shared_ptr<const Rdb_key_def> &kd =
        m_slave_gtid_info_tbl.load()->m_key_descr_arr[0];
    String value;

    // Build key
    Rdb_buf_writer<Rdb_key_def::INDEX_NUMBER_SIZE + 4> key_writer;
    key_writer.write_index(kd->get_index_number());
    key_writer.write_uint32(id);

    // Build value
    Rdb_buf_writer<128> value_writer;
    DBUG_ASSERT(gtid);
    const uint db_len = strlen(db);
    const uint gtid_len = strlen(gtid);
    // 1 byte used for flags. Empty here.
    value_writer.write_byte(0);

    // Write column 1.
    DBUG_ASSERT(strlen(db) <= 64);
    value_writer.write_byte(db_len);
    value_writer.write(db, db_len);

    // Write column 2.
    DBUG_ASSERT(gtid_len <= 56);
    value_writer.write_byte(gtid_len);
    value_writer.write(gtid, gtid_len);

    write_batch->Put(kd->get_cf(), key_writer.to_slice(),
                     value_writer.to_slice());
  }
}

bool Rdb_dict_manager::init(rocksdb::TransactionDB *const rdb_dict,
                            Rdb_cf_manager *const cf_manager) {
  DBUG_ASSERT(rdb_dict != nullptr);
  DBUG_ASSERT(cf_manager != nullptr);

  mysql_mutex_init(0, &m_mutex, MY_MUTEX_INIT_FAST);

  m_db = rdb_dict;

  m_system_cfh = cf_manager->get_or_create_cf(m_db, DEFAULT_SYSTEM_CF_NAME);
  rocksdb::ColumnFamilyHandle *default_cfh =
      cf_manager->get_cf(DEFAULT_CF_NAME);

  // System CF and default CF should be initialized
  if (m_system_cfh == nullptr || default_cfh == nullptr) {
    return HA_EXIT_FAILURE;
  }

  rdb_netbuf_store_index(m_key_buf_max_index_id, Rdb_key_def::MAX_INDEX_ID);

  m_key_slice_max_index_id =
      rocksdb::Slice(reinterpret_cast<char *>(m_key_buf_max_index_id),
                     Rdb_key_def::INDEX_NUMBER_SIZE);

  resume_drop_indexes();
  rollback_ongoing_index_creation();

  // Initialize system CF and default CF flags
  const std::unique_ptr<rocksdb::WriteBatch> wb = begin();
  rocksdb::WriteBatch *const batch = wb.get();

  add_cf_flags(batch, m_system_cfh->GetID(), 0);
  add_cf_flags(batch, default_cfh->GetID(), 0);
  commit(batch);

  return HA_EXIT_SUCCESS;
}

std::unique_ptr<rocksdb::WriteBatch> Rdb_dict_manager::begin() const {
  return std::unique_ptr<rocksdb::WriteBatch>(new rocksdb::WriteBatch);
}

void Rdb_dict_manager::put_key(rocksdb::WriteBatchBase *const batch,
                               const rocksdb::Slice &key,
                               const rocksdb::Slice &value) const {
  batch->Put(m_system_cfh, key, value);
}

rocksdb::Status Rdb_dict_manager::get_value(const rocksdb::Slice &key,
                                            std::string *const value) const {
  rocksdb::ReadOptions options;
  options.total_order_seek = true;
  return m_db->Get(options, m_system_cfh, key, value);
}

void Rdb_dict_manager::delete_key(rocksdb::WriteBatchBase *batch,
                                  const rocksdb::Slice &key) const {
  batch->Delete(m_system_cfh, key);
}

rocksdb::Iterator *Rdb_dict_manager::new_iterator() const {
  /* Reading data dictionary should always skip bloom filter */
  rocksdb::ReadOptions read_options;
  read_options.total_order_seek = true;
  return m_db->NewIterator(read_options, m_system_cfh);
}

int Rdb_dict_manager::commit(rocksdb::WriteBatch *const batch,
                             const bool sync) const {
  if (!batch) return HA_ERR_ROCKSDB_COMMIT_FAILED;
  int res = HA_EXIT_SUCCESS;
  rocksdb::WriteOptions options;
  options.sync = sync;
  rocksdb::TransactionDBWriteOptimizations optimize;
  optimize.skip_concurrency_control = true;
  rocksdb::Status s = m_db->Write(options, optimize, batch);
  res = !s.ok();  // we return true when something failed
  if (res) {
    rdb_handle_io_error(s, RDB_IO_ERROR_DICT_COMMIT);
  }
  batch->Clear();
  return res;
}

void Rdb_dict_manager::dump_index_id(uchar *const netbuf,
                                     Rdb_key_def::DATA_DICT_TYPE dict_type,
                                     const GL_INDEX_ID &gl_index_id) {
  rdb_netbuf_store_uint32(netbuf, dict_type);
  rdb_netbuf_store_uint32(netbuf + Rdb_key_def::INDEX_NUMBER_SIZE,
                          gl_index_id.cf_id);
  rdb_netbuf_store_uint32(netbuf + 2 * Rdb_key_def::INDEX_NUMBER_SIZE,
                          gl_index_id.index_id);
}

void Rdb_dict_manager::delete_with_prefix(
    rocksdb::WriteBatch *const batch, Rdb_key_def::DATA_DICT_TYPE dict_type,
    const GL_INDEX_ID &gl_index_id) const {
  Rdb_buf_writer<Rdb_key_def::INDEX_NUMBER_SIZE * 3> key_writer;
  dump_index_id(&key_writer, dict_type, gl_index_id);

  delete_key(batch, key_writer.to_slice());
}

void Rdb_dict_manager::add_or_update_index_cf_mapping(
    rocksdb::WriteBatch *batch, struct Rdb_index_info *const index_info) const {
  Rdb_buf_writer<Rdb_key_def::INDEX_NUMBER_SIZE * 3> key_writer;
  dump_index_id(&key_writer, Rdb_key_def::INDEX_INFO,
                index_info->m_gl_index_id);

  Rdb_buf_writer<256> value_writer;

  value_writer.write_uint16(Rdb_key_def::INDEX_INFO_VERSION_LATEST);
  value_writer.write_byte(index_info->m_index_type);
  value_writer.write_uint16(index_info->m_kv_version);
  value_writer.write_uint32(index_info->m_index_flags);
  value_writer.write_uint64(index_info->m_ttl_duration);

  batch->Put(m_system_cfh, key_writer.to_slice(), value_writer.to_slice());
}

void Rdb_dict_manager::add_cf_flags(rocksdb::WriteBatch *const batch,
                                    const uint32_t cf_id,
                                    const uint32_t cf_flags) const {
  DBUG_ASSERT(batch != nullptr);

  Rdb_buf_writer<Rdb_key_def::INDEX_NUMBER_SIZE * 2> key_writer;
  key_writer.write_uint32(Rdb_key_def::CF_DEFINITION);
  key_writer.write_uint32(cf_id);

  Rdb_buf_writer<Rdb_key_def::VERSION_SIZE + Rdb_key_def::INDEX_NUMBER_SIZE>
      value_writer;
  value_writer.write_uint16(Rdb_key_def::CF_DEFINITION_VERSION);
  value_writer.write_uint32(cf_flags);

  batch->Put(m_system_cfh, key_writer.to_slice(), value_writer.to_slice());
}

void Rdb_dict_manager::delete_index_info(rocksdb::WriteBatch *batch,
                                         const GL_INDEX_ID &gl_index_id) const {
  delete_with_prefix(batch, Rdb_key_def::INDEX_INFO, gl_index_id);
  delete_with_prefix(batch, Rdb_key_def::INDEX_STATISTICS, gl_index_id);
  delete_with_prefix(batch, Rdb_key_def::AUTO_INC, gl_index_id);
}

bool Rdb_dict_manager::get_index_info(
    const GL_INDEX_ID &gl_index_id,
    struct Rdb_index_info *const index_info) const {
  if (index_info) {
    index_info->m_gl_index_id = gl_index_id;
  }

  bool found = false;
  bool error = false;
  std::string value;
  Rdb_buf_writer<Rdb_key_def::INDEX_NUMBER_SIZE * 3> key_writer;
  dump_index_id(&key_writer, Rdb_key_def::INDEX_INFO, gl_index_id);

  const rocksdb::Status &status = get_value(key_writer.to_slice(), &value);
  if (status.ok()) {
    if (!index_info) {
      return true;
    }

    const uchar *const val = (const uchar *)value.c_str();
    const uchar *ptr = val;
    index_info->m_index_dict_version = rdb_netbuf_to_uint16(val);
    ptr += RDB_SIZEOF_INDEX_INFO_VERSION;

    switch (index_info->m_index_dict_version) {
      case Rdb_key_def::INDEX_INFO_VERSION_FIELD_FLAGS:
        /* Sanity check to prevent reading bogus TTL record. */
        if (value.size() != RDB_SIZEOF_INDEX_INFO_VERSION +
                                RDB_SIZEOF_INDEX_TYPE + RDB_SIZEOF_KV_VERSION +
                                RDB_SIZEOF_INDEX_FLAGS +
                                ROCKSDB_SIZEOF_TTL_RECORD) {
          error = true;
          break;
        }
        index_info->m_index_type = rdb_netbuf_to_byte(ptr);
        ptr += RDB_SIZEOF_INDEX_TYPE;
        index_info->m_kv_version = rdb_netbuf_to_uint16(ptr);
        ptr += RDB_SIZEOF_KV_VERSION;
        index_info->m_index_flags = rdb_netbuf_to_uint32(ptr);
        ptr += RDB_SIZEOF_INDEX_FLAGS;
        index_info->m_ttl_duration = rdb_netbuf_to_uint64(ptr);
        found = true;
        break;

      case Rdb_key_def::INDEX_INFO_VERSION_TTL:
        /* Sanity check to prevent reading bogus into TTL record. */
        if (value.size() != RDB_SIZEOF_INDEX_INFO_VERSION +
                                RDB_SIZEOF_INDEX_TYPE + RDB_SIZEOF_KV_VERSION +
                                ROCKSDB_SIZEOF_TTL_RECORD) {
          error = true;
          break;
        }
        index_info->m_index_type = rdb_netbuf_to_byte(ptr);
        ptr += RDB_SIZEOF_INDEX_TYPE;
        index_info->m_kv_version = rdb_netbuf_to_uint16(ptr);
        ptr += RDB_SIZEOF_KV_VERSION;
        index_info->m_ttl_duration = rdb_netbuf_to_uint64(ptr);
        if ((index_info->m_kv_version ==
             Rdb_key_def::PRIMARY_FORMAT_VERSION_TTL) &&
            index_info->m_ttl_duration > 0) {
          index_info->m_index_flags = Rdb_key_def::TTL_FLAG;
        }
        found = true;
        break;

      case Rdb_key_def::INDEX_INFO_VERSION_VERIFY_KV_FORMAT:
      case Rdb_key_def::INDEX_INFO_VERSION_GLOBAL_ID:
        index_info->m_index_type = rdb_netbuf_to_byte(ptr);
        ptr += RDB_SIZEOF_INDEX_TYPE;
        index_info->m_kv_version = rdb_netbuf_to_uint16(ptr);
        found = true;
        break;

      default:
        error = true;
        break;
    }

    switch (index_info->m_index_type) {
      case Rdb_key_def::INDEX_TYPE_PRIMARY:
      case Rdb_key_def::INDEX_TYPE_HIDDEN_PRIMARY: {
        error = index_info->m_kv_version >
                Rdb_key_def::PRIMARY_FORMAT_VERSION_LATEST;
        break;
      }
      case Rdb_key_def::INDEX_TYPE_SECONDARY:
        error = index_info->m_kv_version >
                Rdb_key_def::SECONDARY_FORMAT_VERSION_LATEST;
        break;
      default:
        error = true;
        break;
    }
  }

  if (error) {
    // NO_LINT_DEBUG
    sql_print_error(
        "RocksDB: Found invalid key version number (%u, %u, %u, %llu) "
        "from data dictionary. This should never happen "
        "and it may be a bug.",
        index_info->m_index_dict_version, index_info->m_index_type,
        index_info->m_kv_version, index_info->m_ttl_duration);
    abort();
  }

  return found;
}

bool Rdb_dict_manager::get_cf_flags(const uint32_t cf_id,
                                    uint32_t *const cf_flags) const {
  DBUG_ASSERT(cf_flags != nullptr);

  bool found = false;
  std::string value;
  Rdb_buf_writer<Rdb_key_def::INDEX_NUMBER_SIZE * 2> key_writer;

  key_writer.write_uint32(Rdb_key_def::CF_DEFINITION);
  key_writer.write_uint32(cf_id);

  const rocksdb::Status status = get_value(key_writer.to_slice(), &value);

  if (status.ok()) {
    const uchar *val = (const uchar *)value.c_str();
    DBUG_ASSERT(val);

    const uint16_t version = rdb_netbuf_to_uint16(val);

    if (version == Rdb_key_def::CF_DEFINITION_VERSION) {
      *cf_flags = rdb_netbuf_to_uint32(val + Rdb_key_def::VERSION_SIZE);
      found = true;
    }
  }

  return found;
}

/*
  Returning index ids that were marked as deleted (via DROP TABLE) but
  still not removed by drop_index_thread yet, or indexes that are marked as
  ongoing creation.
 */
void Rdb_dict_manager::get_ongoing_index_operation(
    std::unordered_set<GL_INDEX_ID> *gl_index_ids,
    Rdb_key_def::DATA_DICT_TYPE dd_type) const {
  DBUG_ASSERT(dd_type == Rdb_key_def::DDL_DROP_INDEX_ONGOING ||
              dd_type == Rdb_key_def::DDL_CREATE_INDEX_ONGOING);

  Rdb_buf_writer<Rdb_key_def::INDEX_NUMBER_SIZE> index_writer;
  index_writer.write_uint32(dd_type);
  const rocksdb::Slice index_slice = index_writer.to_slice();

  rocksdb::Iterator *it = new_iterator();
  for (it->Seek(index_slice); it->Valid(); it->Next()) {
    rocksdb::Slice key = it->key();
    const uchar *const ptr = (const uchar *)key.data();

    /*
      Ongoing drop/create index operations require key to be of the form:
      dd_type + cf_id + index_id (== INDEX_NUMBER_SIZE * 3)

      This may need to be changed in the future if we want to process a new
      ddl_type with different format.
    */
    if (key.size() != Rdb_key_def::INDEX_NUMBER_SIZE * 3 ||
        rdb_netbuf_to_uint32(ptr) != dd_type) {
      break;
    }

    // We don't check version right now since currently we always store only
    // Rdb_key_def::DDL_DROP_INDEX_ONGOING_VERSION = 1 as a value.
    // If increasing version number, we need to add version check logic here.
    GL_INDEX_ID gl_index_id;
    gl_index_id.cf_id =
        rdb_netbuf_to_uint32(ptr + Rdb_key_def::INDEX_NUMBER_SIZE);
    gl_index_id.index_id =
        rdb_netbuf_to_uint32(ptr + 2 * Rdb_key_def::INDEX_NUMBER_SIZE);
    gl_index_ids->insert(gl_index_id);
  }
  delete it;
}

/*
  Returning true if index_id is create/delete ongoing (undergoing creation or
  marked as deleted via DROP TABLE but drop_index_thread has not wiped yet)
  or not.
 */
bool Rdb_dict_manager::is_index_operation_ongoing(
    const GL_INDEX_ID &gl_index_id, Rdb_key_def::DATA_DICT_TYPE dd_type) const {
  DBUG_ASSERT(dd_type == Rdb_key_def::DDL_DROP_INDEX_ONGOING ||
              dd_type == Rdb_key_def::DDL_CREATE_INDEX_ONGOING);

  bool found = false;
  std::string value;
  Rdb_buf_writer<Rdb_key_def::INDEX_NUMBER_SIZE * 3> key_writer;
  dump_index_id(&key_writer, dd_type, gl_index_id);

  const rocksdb::Status status = get_value(key_writer.to_slice(), &value);
  if (status.ok()) {
    found = true;
  }
  return found;
}

/*
  Adding index_id to data dictionary so that the index id is removed
  by drop_index_thread, or to track online index creation.
 */
void Rdb_dict_manager::start_ongoing_index_operation(
    rocksdb::WriteBatch *const batch, const GL_INDEX_ID &gl_index_id,
    Rdb_key_def::DATA_DICT_TYPE dd_type) const {
  DBUG_ASSERT(dd_type == Rdb_key_def::DDL_DROP_INDEX_ONGOING ||
              dd_type == Rdb_key_def::DDL_CREATE_INDEX_ONGOING);

  Rdb_buf_writer<Rdb_key_def::INDEX_NUMBER_SIZE * 3> key_writer;
  Rdb_buf_writer<Rdb_key_def::VERSION_SIZE> value_writer;

  dump_index_id(&key_writer, dd_type, gl_index_id);

  // version as needed
  if (dd_type == Rdb_key_def::DDL_DROP_INDEX_ONGOING) {
    value_writer.write_uint16(Rdb_key_def::DDL_DROP_INDEX_ONGOING_VERSION);
  } else {
    value_writer.write_uint16(Rdb_key_def::DDL_CREATE_INDEX_ONGOING_VERSION);
  }

  batch->Put(m_system_cfh, key_writer.to_slice(), value_writer.to_slice());
}

/*
  Removing index_id from data dictionary to confirm drop_index_thread
  completed dropping entire key/values of the index_id
 */
void Rdb_dict_manager::end_ongoing_index_operation(
    rocksdb::WriteBatch *const batch, const GL_INDEX_ID &gl_index_id,
    Rdb_key_def::DATA_DICT_TYPE dd_type) const {
  DBUG_ASSERT(dd_type == Rdb_key_def::DDL_DROP_INDEX_ONGOING ||
              dd_type == Rdb_key_def::DDL_CREATE_INDEX_ONGOING);

  delete_with_prefix(batch, dd_type, gl_index_id);
}

/*
  Returning true if there is no target index ids to be removed
  by drop_index_thread
 */
bool Rdb_dict_manager::is_drop_index_empty() const {
  std::unordered_set<GL_INDEX_ID> gl_index_ids;
  get_ongoing_drop_indexes(&gl_index_ids);
  return gl_index_ids.empty();
}

/*
  This function is supposed to be called by DROP TABLE. Logging messages
  that dropping indexes started, and adding data dictionary so that
  all associated indexes to be removed
 */
void Rdb_dict_manager::add_drop_table(
    std::shared_ptr<Rdb_key_def> *const key_descr, const uint32 n_keys,
    rocksdb::WriteBatch *const batch) const {
  std::unordered_set<GL_INDEX_ID> dropped_index_ids;
  for (uint32 i = 0; i < n_keys; i++) {
    dropped_index_ids.insert(key_descr[i]->get_gl_index_id());
  }

  add_drop_index(dropped_index_ids, batch);
}

/*
  Called during inplace index drop operations. Logging messages
  that dropping indexes started, and adding data dictionary so that
  all associated indexes to be removed
 */
void Rdb_dict_manager::add_drop_index(
    const std::unordered_set<GL_INDEX_ID> &gl_index_ids,
    rocksdb::WriteBatch *const batch) const {
  for (const auto &gl_index_id : gl_index_ids) {
    log_start_drop_index(gl_index_id, "Begin");
    start_drop_index(batch, gl_index_id);
  }
}

/*
  Called during inplace index creation operations. Logging messages
  that adding indexes started, and updates data dictionary with all associated
  indexes to be added.
 */
void Rdb_dict_manager::add_create_index(
    const std::unordered_set<GL_INDEX_ID> &gl_index_ids,
    rocksdb::WriteBatch *const batch) const {
  for (const auto &gl_index_id : gl_index_ids) {
    // NO_LINT_DEBUG
    sql_print_verbose_info("RocksDB: Begin index creation (%u,%u)",
                           gl_index_id.cf_id, gl_index_id.index_id);
    start_create_index(batch, gl_index_id);
  }
}

/*
  This function is supposed to be called by drop_index_thread, when it
  finished dropping any index, or at the completion of online index creation.
 */
void Rdb_dict_manager::finish_indexes_operation(
    const std::unordered_set<GL_INDEX_ID> &gl_index_ids,
    Rdb_key_def::DATA_DICT_TYPE dd_type) const {
  DBUG_ASSERT(dd_type == Rdb_key_def::DDL_DROP_INDEX_ONGOING ||
              dd_type == Rdb_key_def::DDL_CREATE_INDEX_ONGOING);

  const std::unique_ptr<rocksdb::WriteBatch> wb = begin();
  rocksdb::WriteBatch *const batch = wb.get();

  std::unordered_set<GL_INDEX_ID> incomplete_create_indexes;
  get_ongoing_create_indexes(&incomplete_create_indexes);

  for (const auto &gl_index_id : gl_index_ids) {
    if (is_index_operation_ongoing(gl_index_id, dd_type)) {
      end_ongoing_index_operation(batch, gl_index_id, dd_type);

      /*
        Remove the corresponding incomplete create indexes from data
        dictionary as well
      */
      if (dd_type == Rdb_key_def::DDL_DROP_INDEX_ONGOING) {
        if (incomplete_create_indexes.count(gl_index_id)) {
          end_ongoing_index_operation(batch, gl_index_id,
                                      Rdb_key_def::DDL_CREATE_INDEX_ONGOING);
        }
      }
    }

    if (dd_type == Rdb_key_def::DDL_DROP_INDEX_ONGOING) {
      delete_index_info(batch, gl_index_id);
    }
  }
  commit(batch);
}

/*
  This function is supposed to be called when initializing
  Rdb_dict_manager (at startup). If there is any index ids that are
  drop ongoing, printing out messages for diagnostics purposes.
 */
void Rdb_dict_manager::resume_drop_indexes() const {
  std::unordered_set<GL_INDEX_ID> gl_index_ids;
  get_ongoing_drop_indexes(&gl_index_ids);

  uint max_index_id_in_dict = 0;
  get_max_index_id(&max_index_id_in_dict);

  for (const auto &gl_index_id : gl_index_ids) {
    log_start_drop_index(gl_index_id, "Resume");
    if (max_index_id_in_dict < gl_index_id.index_id) {
      // NO_LINT_DEBUG
      sql_print_error(
          "RocksDB: Found max index id %u from data dictionary "
          "but also found dropped index id (%u,%u) from drop_index "
          "dictionary. This should never happen and is possibly a "
          "bug.",
          max_index_id_in_dict, gl_index_id.cf_id, gl_index_id.index_id);
      abort();
    }
  }
}

void Rdb_dict_manager::rollback_ongoing_index_creation() const {
  const std::unique_ptr<rocksdb::WriteBatch> wb = begin();
  rocksdb::WriteBatch *const batch = wb.get();

  std::unordered_set<GL_INDEX_ID> gl_index_ids;
  get_ongoing_create_indexes(&gl_index_ids);

  for (const auto &gl_index_id : gl_index_ids) {
    // NO_LINT_DEBUG
    sql_print_verbose_info("RocksDB: Removing incomplete create index (%u,%u)",
                           gl_index_id.cf_id, gl_index_id.index_id);

    start_drop_index(batch, gl_index_id);
  }

  commit(batch);
}

void Rdb_dict_manager::log_start_drop_table(
    const std::shared_ptr<Rdb_key_def> *const key_descr, const uint32 n_keys,
    const char *const log_action) const {
  for (uint32 i = 0; i < n_keys; i++) {
    log_start_drop_index(key_descr[i]->get_gl_index_id(), log_action);
  }
}

void Rdb_dict_manager::log_start_drop_index(GL_INDEX_ID gl_index_id,
                                            const char *log_action) const {
  struct Rdb_index_info index_info;
  if (!get_index_info(gl_index_id, &index_info)) {
    /*
      If we don't find the index info, it could be that it's because it was a
      partially created index that isn't in the data dictionary yet that needs
      to be rolled back.
    */
    std::unordered_set<GL_INDEX_ID> incomplete_create_indexes;
    get_ongoing_create_indexes(&incomplete_create_indexes);

    if (!incomplete_create_indexes.count(gl_index_id)) {
      /* If it's not a partially created index, something is very wrong. */
      // NO_LINT_DEBUG
      sql_print_error(
          "RocksDB: Failed to get column family info "
          "from index id (%u,%u). MyRocks data dictionary may "
          "get corrupted.",
          gl_index_id.cf_id, gl_index_id.index_id);
      abort();
    }
  }
}

bool Rdb_dict_manager::get_max_index_id(uint32_t *const index_id) const {
  bool found = false;
  std::string value;

  const rocksdb::Status status = get_value(m_key_slice_max_index_id, &value);
  if (status.ok()) {
    const uchar *const val = (const uchar *)value.c_str();
    const uint16_t version = rdb_netbuf_to_uint16(val);
    if (version == Rdb_key_def::MAX_INDEX_ID_VERSION) {
      *index_id = rdb_netbuf_to_uint32(val + Rdb_key_def::VERSION_SIZE);
      found = true;
    }
  }
  return found;
}

bool Rdb_dict_manager::update_max_index_id(rocksdb::WriteBatch *const batch,
                                           const uint32_t index_id) const {
  DBUG_ASSERT(batch != nullptr);

  uint32_t old_index_id = -1;
  if (get_max_index_id(&old_index_id)) {
    if (old_index_id > index_id) {
      // NO_LINT_DEBUG
      sql_print_error(
          "RocksDB: Found max index id %u from data dictionary "
          "but trying to update to older value %u. This should "
          "never happen and possibly a bug.",
          old_index_id, index_id);
      return true;
    }
  }

  Rdb_buf_writer<Rdb_key_def::VERSION_SIZE + Rdb_key_def::INDEX_NUMBER_SIZE>
      value_writer;
  value_writer.write_uint16(Rdb_key_def::MAX_INDEX_ID_VERSION);
  value_writer.write_uint32(index_id);

  batch->Put(m_system_cfh, m_key_slice_max_index_id, value_writer.to_slice());
  return false;
}

void Rdb_dict_manager::add_stats(
    rocksdb::WriteBatch *const batch,
    const std::vector<Rdb_index_stats> &stats) const {
  DBUG_ASSERT(batch != nullptr);

  for (const auto &it : stats) {
    Rdb_buf_writer<Rdb_key_def::INDEX_NUMBER_SIZE * 3> key_writer;
    dump_index_id(&key_writer, Rdb_key_def::INDEX_STATISTICS, it.m_gl_index_id);

    // IndexStats::materialize takes complete care of serialization including
    // storing the version
    const auto value =
        Rdb_index_stats::materialize(std::vector<Rdb_index_stats>{it});

    batch->Put(m_system_cfh, key_writer.to_slice(), value);
  }
}

Rdb_index_stats Rdb_dict_manager::get_stats(GL_INDEX_ID gl_index_id) const {
  Rdb_buf_writer<Rdb_key_def::INDEX_NUMBER_SIZE * 3> key_writer;
  dump_index_id(&key_writer, Rdb_key_def::INDEX_STATISTICS, gl_index_id);

  std::string value;
  const rocksdb::Status status = get_value(key_writer.to_slice(), &value);
  if (status.ok()) {
    std::vector<Rdb_index_stats> v;
    // unmaterialize checks if the version matches
    if (Rdb_index_stats::unmaterialize(value, &v) == 0 && v.size() == 1) {
      return v[0];
    }
  }

  return Rdb_index_stats();
}

rocksdb::Status Rdb_dict_manager::put_auto_incr_val(
    rocksdb::WriteBatchBase *batch, const GL_INDEX_ID &gl_index_id,
    ulonglong val, bool overwrite) const {
  Rdb_buf_writer<Rdb_key_def::INDEX_NUMBER_SIZE * 3> key_writer;
  dump_index_id(&key_writer, Rdb_key_def::AUTO_INC, gl_index_id);

  // Value is constructed by storing the version and the value.
  Rdb_buf_writer<RDB_SIZEOF_AUTO_INCREMENT_VERSION +
                 ROCKSDB_SIZEOF_AUTOINC_VALUE>
      value_writer;
  value_writer.write_uint16(Rdb_key_def::AUTO_INCREMENT_VERSION);
  value_writer.write_uint64(val);

  if (overwrite) {
    return batch->Put(m_system_cfh, key_writer.to_slice(),
                      value_writer.to_slice());
  }
  return batch->Merge(m_system_cfh, key_writer.to_slice(),
                      value_writer.to_slice());
}

bool Rdb_dict_manager::get_auto_incr_val(const GL_INDEX_ID &gl_index_id,
                                         ulonglong *new_val) const {
  Rdb_buf_writer<Rdb_key_def::INDEX_NUMBER_SIZE * 3> key_writer;
  dump_index_id(&key_writer, Rdb_key_def::AUTO_INC, gl_index_id);

  std::string value;
  const rocksdb::Status status = get_value(key_writer.to_slice(), &value);

  if (status.ok()) {
    const uchar *const val = reinterpret_cast<const uchar *>(value.data());

    if (rdb_netbuf_to_uint16(val) <= Rdb_key_def::AUTO_INCREMENT_VERSION) {
      *new_val = rdb_netbuf_to_uint64(val + RDB_SIZEOF_AUTO_INCREMENT_VERSION);
      return true;
    }
  }
  return false;
}

uint Rdb_seq_generator::get_and_update_next_number(
    Rdb_dict_manager *const dict) {
  DBUG_ASSERT(dict != nullptr);

  uint res;
  RDB_MUTEX_LOCK_CHECK(m_mutex);

  res = m_next_number++;

  const std::unique_ptr<rocksdb::WriteBatch> wb = dict->begin();
  rocksdb::WriteBatch *const batch = wb.get();

  DBUG_ASSERT(batch != nullptr);
  dict->update_max_index_id(batch, res);
  dict->commit(batch);

  RDB_MUTEX_UNLOCK_CHECK(m_mutex);

  return res;
}

}  // namespace myrocks