mariadb/sql/sql_sequence.cc

/*
   Copyright (c) 2017, MariaDB Corporation, Alibaba Corporation
   Copyrgiht (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 St, Fifth Floor, Boston, MA 02110-1301  USA
*/

#include "mariadb.h"
#include "sql_class.h"
#include "sql_list.h"
#include "sql_sequence.h"
#include "ha_sequence.h"
#include "sql_base.h"
#include "sql_table.h"                          // write_bin_log
#include "transaction.h"
#include "lock.h"
#include "sql_acl.h"
#ifdef WITH_WSREP
#include "wsrep_mysqld.h"
bool wsrep_check_sequence(THD* thd,
                          const sequence_definition *seq,
                          const bool used_engine);
#endif

#define MAX_AUTO_INCREMENT_VALUE 65535

/**
  Structure for SEQUENCE tables of a certain value type

  @param in  handler   The handler of a sequence value type

  @return              The sequence table structure given the value type
*/
Sequence_row_definition sequence_structure(const Type_handler* handler)
{
  /*
    We don't really care about src because it is unused in
    max_display_length_for_field().
  */
  const Conv_source src(handler, 0, system_charset_info);
  const uint32 len= handler->max_display_length_for_field(src) + 1;
  const LEX_CSTRING empty= {STRING_WITH_LEN("")};
  const uint flag_unsigned= handler->is_unsigned() ? UNSIGNED_FLAG : 0;
#define FNND (NOT_NULL_FLAG | NO_DEFAULT_VALUE_FLAG)
#define FNNDFU (NOT_NULL_FLAG | NO_DEFAULT_VALUE_FLAG | flag_unsigned)
  return {{{"next_not_cached_value", len, handler, empty, FNNDFU},
           {"minimum_value", len, handler, empty, FNNDFU},
           {"maximum_value", len, handler, empty, FNNDFU},
           {"start_value", len, handler,
            {STRING_WITH_LEN("start value when sequences is created or value "
                             "if RESTART is used")}, FNNDFU},
           {"increment", 21, &type_handler_slonglong,
            {STRING_WITH_LEN("increment value")}, FNND},
           {"cache_size", 21, &type_handler_ulonglong, empty,
            FNND | UNSIGNED_FLAG},
           {"cycle_option", 1, &type_handler_utiny,
            {STRING_WITH_LEN("0 if no cycles are allowed, 1 if the sequence "
                             "should begin a new cycle when maximum_value is "
                             "passed")}, FNND | UNSIGNED_FLAG},
           {"cycle_count", 21, &type_handler_slonglong,
            {STRING_WITH_LEN("How many cycles have been done")}, FNND},
           {NULL, 0, &type_handler_slonglong, {STRING_WITH_LEN("")}, 0}}};
#undef FNNDFU
#undef FNND
}

/**
  Whether a type is allowed as a sequence value type.

  @param in  type   The type to check

  @retval    true   allowed
             false  not allowed
*/
bool sequence_definition::is_allowed_value_type(enum_field_types type)
{
  switch (type)
  {
  case MYSQL_TYPE_TINY:
  case MYSQL_TYPE_SHORT:
  case MYSQL_TYPE_LONG:
  case MYSQL_TYPE_INT24:
  case MYSQL_TYPE_LONGLONG:
    return true;
  default:
    return false;
  }
}

/*
  Get the type handler for the value type of a sequence.
*/
Type_handler const *sequence_definition::value_type_handler()
{
  const Type_handler *handler=
    Type_handler::get_handler_by_field_type(value_type);
  return is_unsigned ? handler->type_handler_unsigned() : handler;
}

/*
  Get the upper bound for a sequence value type.
*/
longlong sequence_definition::value_type_max()
{
  /*
    Use value_type != MYSQL_TYPE_LONGLONG to avoid undefined behaviour
    https://stackoverflow.com/questions/9429156/by-left-shifting-can-a-number-be-set-to-zero
  */
  return is_unsigned && value_type != MYSQL_TYPE_LONGLONG ?
    ~(~0ULL << 8 * value_type_handler()->calc_pack_length(0)) :
    ~value_type_min();
}

/*
  Get the lower bound for a sequence value type.
*/
longlong sequence_definition::value_type_min() {
  return is_unsigned ? 0 :
    ~0ULL << (8 * value_type_handler()->calc_pack_length(0) - 1);
}

/**
  Truncate a Longlong_hybrid.
  
  If `original` is greater than value_type_max(), truncate down to
  value_type_max()

  If `original` is less than value_type_min(), truncate up to
  value_type_min()

  Whenever a truncation happens, the resulting value is just out of
  bounds for sequence values because value_type_max() is the maximum
  possible sequence value + 1, and the same applies to
  value_type_min().

  @param in  original   The value to truncate

  @return               The truncated value
*/
longlong sequence_definition::truncate_value(const Longlong_hybrid& original)
{
  if (is_unsigned)
    return original.to_ulonglong(value_type_max());
  if (original.is_unsigned_outside_of_signed_range())
    return value_type_max();
  const longlong value= original.value();
  return (value > value_type_max() ? value_type_max() :
          value < value_type_min() ? value_type_min() : value);
}

/**
  Check whether sequence values are valid.
  
  Sets default values for fields that are not used, according to Oracle spec.

  @param in   thd                 The connection
  @param in   set_reserved_until  Whether to set reserved_until to start
  
  @retval     false               valid
              true                invalid
*/
bool sequence_definition::check_and_adjust(THD *thd, bool set_reserved_until)
{
  DBUG_ENTER("sequence_definition::check_and_adjust");

  /* Easy error to detect. */
  if (!is_allowed_value_type(value_type) || cache < 0)
    DBUG_RETURN(TRUE);

  if (!(real_increment= increment))
    real_increment= global_system_variables.auto_increment_increment;

  /*
    If min_value is not set, in case of signed sequence, set it to
    value_type_min()+1 or 1, depending on real_increment, and in case
    of unsigned sequence, set it to value_type_min()+1
  */
  if (!(used_fields & seq_field_specified_min_value))
    min_value= real_increment < 0 || is_unsigned ? value_type_min()+1 : 1;
  else
  {
    min_value= truncate_value(min_value_from_parser);
    if ((is_unsigned &&
         (ulonglong) min_value <= (ulonglong) value_type_min()) ||
        (!is_unsigned && min_value <= value_type_min()))
    {
      push_warning_printf(
          thd, Sql_condition::WARN_LEVEL_NOTE, ER_TRUNCATED_WRONG_VALUE,
          ER_THD(thd, ER_TRUNCATED_WRONG_VALUE), "INTEGER", "MINVALUE");
      min_value= value_type_min() + 1;
    }
  }

  /*
    If max_value is not set, in case of signed sequence set it to
    value_type_max()-1 or -1, depending on real_increment, and in case
    of unsigned sequence, set it to value_type_max()-1
  */
  if (!(used_fields & seq_field_specified_max_value))
    max_value= real_increment > 0 || is_unsigned ? value_type_max()-1 : -1;
  else
  {
    max_value= truncate_value(max_value_from_parser);
    if ((is_unsigned &&
         (ulonglong) max_value >= (ulonglong) value_type_max()) ||
        (!is_unsigned && max_value >= value_type_max()))
    {
      push_warning_printf(
          thd, Sql_condition::WARN_LEVEL_NOTE, ER_TRUNCATED_WRONG_VALUE,
          ER_THD(thd, ER_TRUNCATED_WRONG_VALUE), "INTEGER", "MAXVALUE");
      max_value= value_type_max() - 1;
    }
  }

  if (!(used_fields & seq_field_used_start))
  {
    /* Use min_value or max_value for start depending on real_increment */
    start= real_increment < 0 ? max_value : min_value;
  } else
    /*
      If the supplied start value is out of range for the value type,
      instead of immediately reporting error, we truncate it to
      value_type_min or value_type_max depending on which side it is
      one. Whenever such truncation happens, the condition that
      max_value >= start >= min_value will be violated, and the error
      will be reported then.
    */
    start= truncate_value(start_from_parser);

  if (set_reserved_until)
    reserved_until= start;

  adjust_values(reserved_until);

  /* To ensure that cache * real_increment will never overflow */
  const longlong max_increment= (real_increment ?
                                 llabs(real_increment) :
                                 MAX_AUTO_INCREMENT_VALUE);

  /*
    To ensure that cache * real_increment will never overflow. See the
    calculation of add_to below in SEQUENCE::next_value(). We need
    this for unsigned too, because otherwise we will need to handle
    add_to as an equivalent of Longlong_hybrid type in
    SEQUENCE::increment_value().
  */
  if (cache >= (LONGLONG_MAX - max_increment) / max_increment)
    DBUG_RETURN(TRUE);

  if (is_unsigned && (ulonglong) max_value >= (ulonglong) start &&
      (ulonglong) max_value > (ulonglong) min_value &&
      (ulonglong) start >= (ulonglong) min_value &&
      ((real_increment > 0 &&
        (ulonglong) reserved_until >= (ulonglong) min_value) ||
       (real_increment < 0 &&
        (ulonglong) reserved_until <= (ulonglong) max_value)))
    DBUG_RETURN(FALSE);

  if (!is_unsigned && max_value >= start && max_value > min_value &&
      start >= min_value &&
      ((real_increment > 0 && reserved_until >= min_value) ||
       (real_increment < 0 && reserved_until <= max_value)))
    DBUG_RETURN(FALSE);

  DBUG_RETURN(TRUE);                           // Error
}


/*
  Read sequence values from a table
*/

void sequence_definition::read_fields(TABLE *table)
{
  MY_BITMAP *old_map= dbug_tmp_use_all_columns(table, &table->read_set);
  reserved_until= table->field[0]->val_int();
  min_value=      table->field[1]->val_int();
  max_value=      table->field[2]->val_int();
  start=          table->field[3]->val_int();
  increment=      table->field[4]->val_int();
  cache=          table->field[5]->val_int();
  cycle=          table->field[6]->val_int();
  round=          table->field[7]->val_int();
  value_type=     table->field[0]->type();
  is_unsigned=    table->field[0]->is_unsigned();
  min_value_from_parser= Longlong_hybrid(min_value, is_unsigned);
  max_value_from_parser= Longlong_hybrid(max_value, is_unsigned);
  start_from_parser= Longlong_hybrid(start, is_unsigned);
  dbug_tmp_restore_column_map(&table->read_set, old_map);
  used_fields= ~(uint) 0;
  print_dbug();
}


/*
  Store sequence into a table row
*/

void sequence_definition::store_fields(TABLE *table)
{
  MY_BITMAP *old_map= dbug_tmp_use_all_columns(table, &table->write_set);

  /* zero possible delete markers & null bits */
  memcpy(table->record[0], table->s->default_values, table->s->null_bytes);
  table->field[0]->store(reserved_until, is_unsigned);
  table->field[1]->store(min_value, is_unsigned);
  table->field[2]->store(max_value, is_unsigned);
  table->field[3]->store(start, is_unsigned);
  table->field[4]->store(increment, 0);
  table->field[5]->store(cache, 0);
  table->field[6]->store((longlong) cycle != 0, 0);
  table->field[7]->store((longlong) round, 1);

  dbug_tmp_restore_column_map(&table->write_set, old_map);
  print_dbug();
}


/*
  Check the sequence fields through seq_fields when creating a sequence.

  RETURN VALUES
    false       Success
    true        Failure
*/

bool check_sequence_fields(LEX *lex, List<Create_field> *fields,
                           const LEX_CSTRING db, const LEX_CSTRING table_name)
{
  Create_field *field;
  List_iterator_fast<Create_field> it(*fields);
  uint field_count;
  uint field_no;
  const char *reason;
  Sequence_row_definition row_structure;
  DBUG_ENTER("check_sequence_fields");

  field_count= fields->elements;
  if (!field_count)
  {
    reason= my_get_err_msg(ER_SEQUENCE_TABLE_HAS_WRONG_NUMBER_OF_COLUMNS);
    goto err;
  }
  if (!sequence_definition::is_allowed_value_type(
        fields->head()->type_handler()->field_type()))
  {
    reason= fields->head()->field_name.str;
    goto err;
  }
  row_structure= sequence_structure(fields->head()->type_handler());
  if (field_count != array_elements(row_structure.fields)-1)
  {
    reason= my_get_err_msg(ER_SEQUENCE_TABLE_HAS_WRONG_NUMBER_OF_COLUMNS);
    goto err;
  }
  if (lex->alter_info.key_list.elements > 0)
  {
    reason= my_get_err_msg(ER_SEQUENCE_TABLE_CANNOT_HAVE_ANY_KEYS);
    goto err;
  }
  if (lex->alter_info.check_constraint_list.elements > 0)
  {
    reason= my_get_err_msg(ER_SEQUENCE_TABLE_CANNOT_HAVE_ANY_CONSTRAINTS);
    goto err;
  }
  if (lex->alter_info.flags & ALTER_ORDER)
  {
    reason= my_get_err_msg(ER_SEQUENCE_TABLE_ORDER_BY);
    goto err;
  }

  for (field_no= 0; (field= it++); field_no++)
  {
    const Sequence_field_definition *field_def= &row_structure.fields[field_no];
    if (!field->field_name.streq(Lex_cstring_strlen(field_def->field_name)) ||
        field->flags != field_def->flags ||
        field->type_handler() != field_def->type_handler ||
        field->check_constraint || field->vcol_info)
    {
      reason= field->field_name.str;
      goto err;
    }
  }
  DBUG_RETURN(FALSE);

err:
  my_error(ER_SEQUENCE_INVALID_TABLE_STRUCTURE, MYF(0),
           db.str, table_name.str, reason);
  DBUG_RETURN(TRUE);
}


/*
  Create the fields for a SEQUENCE TABLE

  RETURN VALUES
    false       Success
    true        Failure (out of memory)
*/

bool sequence_definition::prepare_sequence_fields(List<Create_field> *fields,
                                                  bool alter)
{
  DBUG_ENTER("prepare_sequence_fields");
  const Sequence_row_definition row_def=
    sequence_structure(value_type_handler());

  for (const Sequence_field_definition *field_info= row_def.fields;
       field_info->field_name; field_info++)
  {
    Create_field *new_field;
    const Lex_ident_column field_name= Lex_cstring_strlen(field_info->
                                                            field_name);

    if (unlikely(!(new_field= new Create_field())))
      DBUG_RETURN(TRUE); /* purify inspected */

    new_field->field_name=  field_name;
    new_field->set_handler(field_info->type_handler);
    new_field->length=      field_info->length;
    new_field->char_length= field_info->length;
    new_field->comment=     field_info->comment;
    new_field->flags=       field_info->flags;
    if (alter)
      new_field->change =   field_name;
    if (unlikely(fields->push_back(new_field)))
      DBUG_RETURN(TRUE); /* purify inspected */
  }
  DBUG_RETURN(FALSE);
}

/*
  Initialize the sequence table record as part of CREATE SEQUENCE

  Store one row with sequence information.

  RETURN VALUES
    false       Success
    true        Failure. Error reported.

  NOTES
    This function is called as part of CREATE SEQUENCE. When called
    there are now active transactions and no open tables.
    There is also a MDL lock on the table.
*/

bool sequence_insert(THD *thd, LEX *lex, TABLE_LIST *org_table_list)
{
  int error;
  TABLE *table;
  Reprepare_observer *save_reprepare_observer;
  sequence_definition *seq= lex->create_info.seq_create_info;
  bool temporary_table= org_table_list->table != 0;
  /*
    seq is 0 if sequence was created with CREATE TABLE instead of
    CREATE SEQUENCE
  */
  bool create_new= !seq;
  Open_tables_backup open_tables_backup;
  Query_tables_list query_tables_list_backup;
  TABLE_LIST table_list;                        // For sequence table
  DBUG_ENTER("sequence_insert");
  DBUG_EXECUTE_IF("kill_query_on_sequence_insert",
                  thd->set_killed(KILL_QUERY););

  if (create_new && !(seq= new (thd->mem_root) sequence_definition))
    DBUG_RETURN(TRUE);

  /* If not temporary table */
  if (!temporary_table)
  {
    /*
      The following code works like open_system_tables_for_read()
      The idea is:
      - Copy the table_list object for the sequence that was created
      - Backup the current state of open tables and create a new
        environment for open tables without any tables opened
     - open the newly sequence table for write
     This is safe as the sequence table has a mdl lock thanks to the
     create sequence statement that is calling this function
    */

    table_list.init_one_table(&org_table_list->db,
                              &org_table_list->table_name, 
                              NULL, TL_WRITE_DEFAULT);
    table_list.updating=  1;
    table_list.open_strategy= TABLE_LIST::OPEN_IF_EXISTS;
    table_list.open_type= OT_BASE_ONLY;

    DBUG_ASSERT(!thd->locked_tables_mode ||
                (thd->variables.option_bits & OPTION_TABLE_LOCK));
    lex->reset_n_backup_query_tables_list(&query_tables_list_backup);
    thd->reset_n_backup_open_tables_state(&open_tables_backup);

    /*
      The FOR CREATE flag is needed to ensure that ha_open() doesn't try to
      read the not yet existing row in the sequence table
    */
    thd->open_options|= HA_OPEN_FOR_CREATE;
    /*
      We have to reset the reprepare observer to be able to open the
      table under prepared statements.
    */
    save_reprepare_observer= thd->m_reprepare_observer;
    thd->m_reprepare_observer= 0;
    lex->sql_command= SQLCOM_CREATE_SEQUENCE;
    error= open_and_lock_tables(thd, &table_list, FALSE,
                                MYSQL_LOCK_IGNORE_TIMEOUT |
                                MYSQL_OPEN_HAS_MDL_LOCK);
    thd->open_options&= ~HA_OPEN_FOR_CREATE;
    thd->m_reprepare_observer= save_reprepare_observer;
    if (unlikely(error))
    {
      lex->restore_backup_query_tables_list(&query_tables_list_backup);
      thd->restore_backup_open_tables_state(&open_tables_backup);
      DBUG_RETURN(error);
    }
    table= table_list.table;
  }
  else
    table= org_table_list->table;

  if (create_new)
  {
    seq->value_type= (*table->s->field)->type();
    seq->is_unsigned= (*table->s->field)->is_unsigned();
    /* We set reserved_until when creating a new sequence. */
    if (seq->check_and_adjust(thd, true))
      DBUG_RETURN(TRUE);
  }

  error= seq->write_initial_sequence(table);
  {
    uint save_unsafe_rollback_flags=
      thd->transaction->stmt.m_unsafe_rollback_flags;
    if (trans_commit_stmt(thd))
      error= 1;
    thd->transaction->stmt.m_unsafe_rollback_flags=
      save_unsafe_rollback_flags;
  }
  if (trans_commit_implicit(thd))
    error= 1;

  if (!temporary_table)
  {
    close_thread_tables(thd);
    lex->restore_backup_query_tables_list(&query_tables_list_backup);
    thd->restore_backup_open_tables_state(&open_tables_backup);

    /* OPTION_TABLE_LOCK was reset in trans_commit_implicit */
    if (thd->locked_tables_mode)
      thd->variables.option_bits|= OPTION_TABLE_LOCK;
  }
  DBUG_RETURN(error);
}


/* Create a SQUENCE object */

SEQUENCE::SEQUENCE() :all_values_used(0), initialized(SEQ_UNINTIALIZED)
{
  mysql_rwlock_init(key_LOCK_SEQUENCE, &mutex);
}

SEQUENCE::~SEQUENCE()
{
  mysql_rwlock_destroy(&mutex);
}

/*
  The following functions is to ensure that we when reserve new values
  trough sequence object sequence we have only one writer at at time.
  A sequence table can have many readers (trough normal SELECT's).

  We mark that we have a write lock in the table object so that
  ha_sequence::write_row() can check if we have a lock. If already locked, then
  ha_write() knows that we are running a sequence operation. If not, then
  ha_write() knows that it's an INSERT statement.
*/

void SEQUENCE::write_lock(TABLE *table)
{
  DBUG_ASSERT(((ha_sequence*) table->file)->is_locked() == 0);
  mysql_rwlock_wrlock(&mutex);
  ((ha_sequence*) table->file)->write_lock();
}
void SEQUENCE::write_unlock(TABLE *table)
{
  ((ha_sequence*) table->file)->unlock();
  mysql_rwlock_unlock(&mutex);
}
void SEQUENCE::read_lock(TABLE *table)
{
  if (!((ha_sequence*) table->file)->is_locked())
    mysql_rwlock_rdlock(&mutex);
}
void SEQUENCE::read_unlock(TABLE *table)
{
  if (!((ha_sequence*) table->file)->is_locked())
    mysql_rwlock_unlock(&mutex);
}

/**
   Read values from the sequence tables to table_share->sequence.
   This is called from ha_open() when the table is not yet locked
*/

int SEQUENCE::read_initial_values(TABLE *table)
{
  int error= 0;
  enum thr_lock_type save_lock_type;
  MDL_request mdl_request;                      // Empty constructor!
  DBUG_ENTER("SEQUENCE::read_initial_values");

  if (likely(initialized != SEQ_UNINTIALIZED))
    DBUG_RETURN(0);
  write_lock(table);
  if (likely(initialized == SEQ_UNINTIALIZED))
  {
    MYSQL_LOCK *lock;
    bool mdl_lock_used= 0;
    THD *thd= table->in_use;
    bool has_active_transaction= !thd->transaction->stmt.is_empty();
    /*
      There is already a mdl_ticket for this table. However, for list_fields
      the MDL lock is of type MDL_SHARED_HIGH_PRIO which is not usable
      for doing a table lock. Get a proper read lock to solve this.
    */
    if (table->mdl_ticket == 0)
    {
      MDL_request_list mdl_requests;
      mdl_lock_used= 1;
      /*
        This happens if first request is SHOW CREATE TABLE or LIST FIELDS
        where we don't have a mdl lock on the table
      */

      MDL_REQUEST_INIT(&mdl_request, MDL_key::TABLE, table->s->db.str,
                       table->s->table_name.str, MDL_SHARED_READ,
                       MDL_EXPLICIT);
      mdl_requests.push_front(&mdl_request);
      if (thd->mdl_context.acquire_locks(&mdl_requests,
                                         thd->variables.lock_wait_timeout))
      {
        write_unlock(table);
        DBUG_RETURN(HA_ERR_LOCK_WAIT_TIMEOUT);
      }
    }
    save_lock_type= table->reginfo.lock_type;
    table->reginfo.lock_type= TL_READ;
    if (!(lock= mysql_lock_tables(thd, &table, 1,
                                  MYSQL_LOCK_IGNORE_GLOBAL_READ_ONLY)))
    {
      if (mdl_lock_used)
        thd->mdl_context.release_lock(mdl_request.ticket);
      write_unlock(table);

      if (!has_active_transaction && !thd->transaction->stmt.is_empty() &&
          !thd->in_sub_stmt)
        trans_commit_stmt(thd);
      DBUG_RETURN(HA_ERR_LOCK_WAIT_TIMEOUT);
    }
    DBUG_ASSERT(table->reginfo.lock_type == TL_READ);
    if (likely(!(error= read_stored_values(table))))
      initialized= SEQ_READY_TO_USE;
    mysql_unlock_tables(thd, lock);
    if (mdl_lock_used)
      thd->mdl_context.release_lock(mdl_request.ticket);

    /* Reset value to default */
    table->reginfo.lock_type= save_lock_type;
    /*
      Doing mysql_lock_tables() may have started a read only transaction.
      If that happend, it's better that we commit it now, as a lot of
      code assumes that there is no active stmt transaction directly after
      open_tables().
      But we also don't want to commit the stmt transaction while in a
      substatement, see MDEV-15977.
    */
    if (!has_active_transaction && !thd->transaction->stmt.is_empty() &&
        !thd->in_sub_stmt)
      trans_commit_stmt(thd);
  }
  write_unlock(table);
  DBUG_RETURN(error);
}


/*
  Do the actiual reading of data from sequence table and
  update values in the sequence object.

  Called once from when table is opened
*/

int SEQUENCE::read_stored_values(TABLE *table)
{
  int error;
  DBUG_ENTER("SEQUENCE::read_stored_values");

  MY_BITMAP *save_read_set= tmp_use_all_columns(table, &table->read_set);
  error= table->file->ha_read_first_row(table->record[0], MAX_KEY);
  tmp_restore_column_map(&table->read_set, save_read_set);

  if (unlikely(error))
  {
    table->file->print_error(error, MYF(0));
    DBUG_RETURN(error);
  }
  read_fields(table);
  adjust_values(reserved_until);

  all_values_used= 0;
  DBUG_RETURN(0);
}


/*
  Adjust values after reading a the stored state
*/

void sequence_definition::adjust_values(longlong next_value)
{
  next_free_value= next_value;
  if (!(real_increment= increment))
  {
    longlong offset= 0;
    longlong off, to_add;
    /* Use auto_increment_increment and auto_increment_offset */

    if ((real_increment= global_system_variables.auto_increment_increment)
        != 1)
      offset= (global_system_variables.auto_increment_offset %
               global_system_variables.auto_increment_increment);

    /*
      Ensure that next_free_value has the right offset, so that we can
      generate a serie by just adding real_increment. The goal is to
      adjust next_free_value upwards such that

      next_free_value % real_increment == offset
    */
    if (is_unsigned)
      off= (ulonglong) next_free_value % real_increment;
    else
      off= next_free_value % real_increment;
    if (off < 0)
      off+= real_increment;
    to_add= (real_increment + offset - off) % real_increment;

    /*
      Check if add will make next_free_value bigger than max_value,
      taken into account that next_free_value or max_value addition
      may overflow.

      0 <= to_add <= auto_increment_increment <= 65535 so we do not
      need to cast to_add.
    */
    if ((is_unsigned &&
         ((ulonglong) next_free_value > (ulonglong) max_value - to_add ||
          (ulonglong) next_free_value + to_add > (ulonglong) max_value ||
          (ulonglong) next_free_value > (ulonglong) max_value)) ||
        (!is_unsigned &&
         (next_free_value > (longlong) ((ulonglong) max_value - to_add) ||
          (longlong) ((ulonglong) next_free_value + to_add) > max_value ||
          next_free_value > max_value)))
      next_free_value= max_value+1;
    else
    {
      next_free_value=
        (longlong) ((ulonglong) next_free_value + (ulonglong) to_add);
      if (is_unsigned)
        DBUG_ASSERT((ulonglong) next_free_value % real_increment ==
                    (ulonglong) offset);
      else
        DBUG_ASSERT(llabs(next_free_value % real_increment) == offset);
    }
  }
}


/**
   Write initial sequence information for CREATE and ALTER to sequence table
*/

int sequence_definition::write_initial_sequence(TABLE *table)
{
  int error;
  MY_BITMAP *save_write_set;

  store_fields(table);
  /* Store the sequence values in table share */
  table->s->sequence->copy(this);
  /*
    Sequence values will be replicated as a statement
    like 'create sequence'. So disable row logging for this table & statement
  */
  table->file->row_logging= table->file->row_logging_init= 0;
  save_write_set= table->write_set;
  table->write_set= &table->s->all_set;
  table->s->sequence->initialized= SEQUENCE::SEQ_IN_PREPARE;
  error= table->file->ha_write_row(table->record[0]);
  table->s->sequence->initialized= SEQUENCE::SEQ_UNINTIALIZED;
  table->write_set= save_write_set;
  if (unlikely(error))
    table->file->print_error(error, MYF(0));
  else
  {
    /*
      Sequence structure is up to date and table has one row,
      sequence is now usable
    */
    table->s->sequence->initialized= SEQUENCE::SEQ_READY_TO_USE;
  }
  return error;
}


/**
   Store current sequence values into the sequence table
*/

int sequence_definition::write(TABLE *table, bool all_fields)
{
  int error;
  MY_BITMAP *save_rpl_write_set, *save_write_set, *save_read_set;
  DBUG_ASSERT(((ha_sequence*) table->file)->is_locked());

  save_rpl_write_set= table->rpl_write_set;
  if (likely(!all_fields))
  {
    /* Only write next_value and round to binary log */
    table->rpl_write_set= &table->def_rpl_write_set;
    bitmap_clear_all(table->rpl_write_set);
    bitmap_set_bit(table->rpl_write_set, NEXT_FIELD_NO);
    bitmap_set_bit(table->rpl_write_set, ROUND_FIELD_NO);
  }
  else
    table->rpl_write_set= &table->s->all_set;

  /* Update table */
  save_write_set= table->write_set;
  save_read_set=  table->read_set;
  table->read_set= table->write_set= &table->s->all_set;
  table->file->column_bitmaps_signal();
  store_fields(table);
  if (unlikely((error= table->file->ha_write_row(table->record[0]))))
    table->file->print_error(error, MYF(0));
  table->rpl_write_set= save_rpl_write_set;
  table->read_set=  save_read_set;
  table->write_set= save_write_set;
  table->file->column_bitmaps_signal();
  return error;
}


/**
   Get next value for sequence

   @param in   table  Sequence table
   @param in   second_round
                      1 if recursive call (out of values once)
   @param out  error  Set this to <> 0 in case of error
                      push_warning_printf(WARN_LEVEL_WARN) has been called


   @retval     0      Next number or error. Check error variable
               #      Next sequence number

   NOTES:
     Return next_free_value and increment next_free_value to next allowed
     value or reserved_value if out of range
     if next_free_value >= reserved_value reserve a new range by writing
     a record to the sequence table.

  The state of the variables:
    next_free_value contains next value to use. It may be
    bigger than max_value or less than min_value if end of sequence.
    reserved_until contains the last value written to the file. All
    values up to this one can be used.
    If next_free_value >= reserved_until we have to reserve new
    values from the sequence.
*/

longlong SEQUENCE::next_value(TABLE *table, bool second_round, int *error)
{
  longlong res_value, org_reserved_until, add_to;
  bool out_of_values;
  THD *thd= table->in_use;
  DBUG_ENTER("SEQUENCE::next_value");
  DBUG_ASSERT(thd);

  *error= 0;
  if (!second_round)
    write_lock(table);

  res_value= next_free_value;
  next_free_value= increment_value(next_free_value, real_increment);

  if (within_bound(res_value, reserved_until, reserved_until,
                    real_increment > 0))
  {
    write_unlock(table);
    DBUG_RETURN(res_value);
  }

  if (all_values_used)
    goto err;

  org_reserved_until= reserved_until;

  /*
    Out of cached values, reserve 'cache' new ones
    The cache value is checked on insert so the following can't
    overflow
  */
  add_to= cache ? real_increment * cache : real_increment;

  reserved_until= increment_value(reserved_until, add_to);
  out_of_values= !within_bound(res_value, max_value + 1, min_value - 1,
                                add_to > 0);
  if (out_of_values)
  {
    if (!cycle || second_round)
      goto err;
    round++;
    reserved_until= real_increment >0 ? min_value : max_value;
    adjust_values(reserved_until);              // Fix next_free_value
    /*
      We have to do everything again to ensure that the given range was
      not empty, which could happen if increment == 0
    */
    DBUG_RETURN(next_value(table, 1, error));
  }

  if (unlikely((*error= write(table, thd->variables.binlog_row_image !=
                                         BINLOG_ROW_IMAGE_MINIMAL))))
  {
    reserved_until= org_reserved_until;
    next_free_value= res_value;
  }

  write_unlock(table);
  DBUG_RETURN(res_value);

err:
  write_unlock(table);
  my_error(ER_SEQUENCE_RUN_OUT, MYF(0), table->s->db.str,
           table->s->table_name.str);
  *error= ER_SEQUENCE_RUN_OUT;
  all_values_used= 1;
  DBUG_RETURN(0);
}


/*
   The following functions is to detect if a table has been dropped
   and re-created since last call to PREVIOUS VALUE.

   This is needed as we don't delete dropped sequences from THD->sequence
   for DROP TABLE.
*/

bool SEQUENCE_LAST_VALUE::check_version(TABLE *table)
{
  DBUG_ASSERT(table->s->tabledef_version.length == MY_UUID_SIZE);
  return memcmp(table->s->tabledef_version.str, table_version,
                MY_UUID_SIZE) != 0;
}

void SEQUENCE_LAST_VALUE::set_version(TABLE *table)
{
  memcpy(table_version, table->s->tabledef_version.str, MY_UUID_SIZE);
}

/**
   Set the next value for sequence

   @param in   table       Sequence table
   @param in   next_val    Next free value
   @param in   next_round  Round for 'next_value' (in case of cycles)
   @param in   is_used     1 if next_val is already used

   @retval     0      ok, value adjusted
               -1     value was less than current value
               1      error when storing value

   @comment
   A new value is set only if "nextval,next_round" is less than
   "next_free_value,round". This is needed as in replication
   setvalue() calls may come out to the slave out-of-order.
   Storing only the highest value ensures that sequence object will always
   contain the highest used value when the slave is promoted to a master.
*/

int SEQUENCE::set_value(TABLE *table, longlong next_val, ulonglong next_round,
                         bool is_used)
{
  int error= -1;
  bool needs_to_be_stored= 0;
  longlong org_reserved_until=  reserved_until;
  longlong org_next_free_value= next_free_value;
  ulonglong org_round= round;
  THD *thd= table->in_use;
  DBUG_ENTER("SEQUENCE::set_value");
  DBUG_ASSERT(thd);

  write_lock(table);
  if (is_used)
    next_val= increment_value(next_val, real_increment);

  if (round > next_round)
    goto end;                                   // error = -1
  if (round == next_round)
  {
    if (within_bound(next_val, next_free_value, next_free_value,
                     real_increment > 0))
      goto end;                                 // error = -1
    if (next_val == next_free_value)
    {
      error= 0;
      goto end;
    }
  }
  else if (cycle == 0)
  {
    // round < next_round && no cycles, which is impossible
    my_error(ER_SEQUENCE_RUN_OUT, MYF(0), table->s->db.str,
             table->s->table_name.str);
    error= 1;
    goto end;
  }
  else
    needs_to_be_stored= 1;

  round= next_round;
  adjust_values(next_val);
  if (within_bound(reserved_until, next_free_value, next_free_value,
                   real_increment > 0) ||
      needs_to_be_stored)
  {
    reserved_until= next_free_value;
    if (write(table,
              thd->variables.binlog_row_image != BINLOG_ROW_IMAGE_MINIMAL))
    {
      reserved_until=  org_reserved_until;
      next_free_value= org_next_free_value;
      round= org_round;
      error= 1;
      goto end;
    }
  }
  error= 0;

end:
  write_unlock(table);
  DBUG_RETURN(error);
}

#if defined(HAVE_REPLICATION)
class wait_for_commit_raii
{
private:
  THD *m_thd;
  wait_for_commit *m_wfc;

public:
  wait_for_commit_raii(THD* thd) :
      m_thd(thd), m_wfc(thd->suspend_subsequent_commits())
    {}
  ~wait_for_commit_raii() { m_thd->resume_subsequent_commits(m_wfc); }
};
#endif

bool Sql_cmd_alter_sequence::execute(THD *thd)
{
  int error= 0;
  int trapped_errors= 0;
  LEX *lex= thd->lex;
  TABLE_LIST *first_table= lex->query_tables;
  TABLE *table;
  sequence_definition *new_seq= lex->create_info.seq_create_info;
  uint saved_used_fields= new_seq->used_fields;
  SEQUENCE *seq;
  No_such_table_error_handler no_such_table_handler;
  DBUG_ENTER("Sql_cmd_alter_sequence::execute");
#if defined(HAVE_REPLICATION)
  /* No wakeup():s of subsequent commits is allowed in this function. */
  wait_for_commit_raii suspend_wfc(thd);
#endif

  if (check_access(thd, ALTER_ACL, first_table->db.str,
                   &first_table->grant.privilege,
                   &first_table->grant.m_internal,
                   0, 0))
    DBUG_RETURN(TRUE);                  /* purecov: inspected */

  if (check_grant(thd, ALTER_ACL, first_table, FALSE, 1, FALSE))
    DBUG_RETURN(TRUE);                  /* purecov: inspected */

#ifdef WITH_WSREP
  if (WSREP(thd) && wsrep_thd_is_local(thd))
  {
    const bool used_engine= lex->create_info.used_fields & HA_CREATE_USED_ENGINE;
    if (wsrep_check_sequence(thd, new_seq, used_engine))
      DBUG_RETURN(TRUE);

    if (wsrep_to_isolation_begin(thd, first_table->db.str,
                                 first_table->table_name.str,
                                 first_table))
    {
      DBUG_RETURN(TRUE);
    }
  }
#endif /* WITH_WSREP */

  if (new_seq->used_fields & seq_field_used_as)
  {
    /* This should have been prevented during parsing. */
    DBUG_ASSERT(!(new_seq->used_fields - seq_field_used_as));

    first_table->lock_type= TL_READ_NO_INSERT;
    first_table->mdl_request.set_type(MDL_SHARED_NO_WRITE);
    Alter_info alter_info;
    alter_info.flags= ALTER_CHANGE_COLUMN;
    if (new_seq->prepare_sequence_fields(&alter_info.create_list, true))
      DBUG_RETURN(TRUE);
    Table_specification_st create_info;
    create_info.init();
    create_info.alter_info= &alter_info;
    if (if_exists())
      thd->push_internal_handler(&no_such_table_handler);
    Recreate_info recreate_info;
    error= mysql_alter_table(thd, &null_clex_str, &null_clex_str,
                             &create_info, first_table, &recreate_info,
                             &alter_info, 0, (ORDER *) 0, 0, 0);
    if (if_exists())
    {
      trapped_errors= no_such_table_handler.safely_trapped_errors();
      thd->pop_internal_handler();
    }
    /* Do we need to store the sequence value in table share, like below? */
    DBUG_RETURN(error);
  }

  if (if_exists())
    thd->push_internal_handler(&no_such_table_handler);
  error= open_and_lock_tables(thd, first_table, FALSE, 0);
  if (if_exists())
  {
    trapped_errors= no_such_table_handler.safely_trapped_errors();
    thd->pop_internal_handler();
  }
  if (unlikely(error))
  {
    if (trapped_errors)
    {
      StringBuffer<FN_REFLEN> tbl_name;
      tbl_name.append(&first_table->db);
      tbl_name.append('.');
      tbl_name.append(&first_table->table_name);
      push_warning_printf(thd, Sql_condition::WARN_LEVEL_NOTE,
                          ER_UNKNOWN_SEQUENCES,
                          ER_THD(thd, ER_UNKNOWN_SEQUENCES),
                          tbl_name.c_ptr_safe());
      my_ok(thd);
      DBUG_RETURN(FALSE);
    }
    DBUG_RETURN(TRUE);
  }

  table= first_table->table;
  seq= table->s->sequence;

  seq->write_lock(table);
  new_seq->reserved_until= seq->reserved_until;

  /* Copy from old sequence those fields that the user didn't specified */
  if (!(new_seq->used_fields & seq_field_used_increment))
    new_seq->increment= seq->increment;
  /*
    We need to assign to foo_from_parser so that things get handled
    properly in check_and_adjust() later
  */
  if (!(new_seq->used_fields & seq_field_used_min_value))
    new_seq->min_value_from_parser= Longlong_hybrid(seq->min_value, seq->is_unsigned);
  if (!(new_seq->used_fields & seq_field_used_max_value))
    new_seq->max_value_from_parser= Longlong_hybrid(seq->max_value, seq->is_unsigned);
  if (!(new_seq->used_fields & seq_field_used_start))
    new_seq->start_from_parser= Longlong_hybrid(seq->start, seq->is_unsigned);
  if (!(new_seq->used_fields & seq_field_used_cache))
    new_seq->cache= seq->cache;
  if (!(new_seq->used_fields & seq_field_used_cycle))
    new_seq->cycle= seq->cycle;
  /* This should have been prevented during parsing. */
  DBUG_ASSERT(!(new_seq->used_fields & seq_field_used_as));
  new_seq->value_type= seq->value_type;
  new_seq->is_unsigned= seq->is_unsigned;

  /* If we should restart from a new value */
  if (new_seq->used_fields & seq_field_used_restart)
  {
    if (!(new_seq->used_fields & seq_field_used_restart_value))
      new_seq->restart_from_parser=      new_seq->start_from_parser;
    /*
      Similar to start, we just need to truncate reserved_until and
      the errors will be reported in check_and_adjust if truncation
      happens on the wrong end.
    */
    new_seq->reserved_until=
      new_seq->truncate_value(new_seq->restart_from_parser);
  }

  /* Let check_and_adjust think all fields are used */
  new_seq->used_fields= ~0;
  if (new_seq->check_and_adjust(thd, 0))
  {
    my_error(ER_SEQUENCE_INVALID_DATA, MYF(0),
             first_table->db.str,
             first_table->table_name.str);
    error= 1;
    seq->write_unlock(table);
    goto end;
  }

  if (likely(!(error= new_seq->write(table, 1))))
  {
    /* Store the sequence values in table share */
    seq->copy(new_seq);
  }
  else
    table->file->print_error(error, MYF(0));
  seq->write_unlock(table);
  if (trans_commit_stmt(thd))
    error= 1;
  if (trans_commit_implicit(thd))
    error= 1;
  DBUG_EXECUTE_IF("hold_worker_on_schedule",
                  {
                    /* delay binlogging of a parent trx in rpl_parallel_seq */
                    my_sleep(100000);
                  });
  if (likely(!error))
    error= write_bin_log(thd, 1, thd->query(), thd->query_length());
  if (likely(!error))
    my_ok(thd);

end:
  new_seq->used_fields= saved_used_fields;
  DBUG_RETURN(error);
}