mariadb/storage/heap/ha_heap.cc

/*
   Copyright (c) 2000, 2011, Oracle and/or its affiliates

   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 02110-1335  USA */


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

#define MYSQL_SERVER 1
#include "heapdef.h"
#include "sql_priv.h"
#include "sql_plugin.h"
#include "ha_heap.h"
#include "sql_base.h"

static handler *heap_create_handler(handlerton *, TABLE_SHARE *, MEM_ROOT *);
static int heap_prepare_hp_create_info(TABLE *, bool, HP_CREATE_INFO *);


static int heap_panic(handlerton *hton, ha_panic_function flag)
{
  return hp_panic(flag);
}


static int heap_drop_table(handlerton *hton, const char *path)
{
  int error= heap_delete_table(path);
  return error == ENOENT ? -1 : error;
}

/* See optimizer_costs.txt for how the following values where calculated */
#define HEAP_ROW_NEXT_FIND_COST  8.0166e-06           // For table scan
#define BTREE_KEY_NEXT_FIND_COST 0.00007739           // For binary tree scan
#define HEAP_LOOKUP_COST         0.00016097           // Heap lookup cost

static void heap_update_optimizer_costs(OPTIMIZER_COSTS *costs)
{
  /*
    A lot of values are 0 as heap supports all needed xxx_time() functions
  */
  costs->disk_read_cost=0;          // All data in memory
  costs->disk_read_ratio= 0.0;      // All data in memory
  costs->key_next_find_cost= 0;
  costs->key_copy_cost= 0;          // Set in keyread_time()
  costs->row_copy_cost= 2.334e-06;  // This is small as its just a memcpy
  costs->row_lookup_cost= 0;        // Direct pointer
  costs->row_next_find_cost= HEAP_ROW_NEXT_FIND_COST;
  costs->key_lookup_cost= 0;
  costs->key_next_find_cost= 0;
  costs->index_block_copy_cost= 0;
}

int heap_init(void *p)
{
  handlerton *heap_hton;

  init_heap_psi_keys();

  heap_hton= (handlerton *)p;
  heap_hton->db_type=    DB_TYPE_HEAP;
  heap_hton->create=     heap_create_handler;
  heap_hton->panic=      heap_panic;
  heap_hton->drop_table= heap_drop_table;
  heap_hton->update_optimizer_costs= heap_update_optimizer_costs;
  heap_hton->flags=      HTON_CAN_RECREATE;

  return 0;
}

static handler *heap_create_handler(handlerton *hton,
                                    TABLE_SHARE *table, 
                                    MEM_ROOT *mem_root)
{
  return new (mem_root) ha_heap(hton, table);
}


/*****************************************************************************
** HEAP tables
*****************************************************************************/

ha_heap::ha_heap(handlerton *hton, TABLE_SHARE *table_arg)
  :handler(hton, table_arg), file(0), records_changed(0), key_stat_version(0), 
  internal_table(0)
{
}

/*
  Hash index statistics is updated (copied from HP_KEYDEF::hash_buckets to 
  rec_per_key) after 1/HEAP_STATS_UPDATE_THRESHOLD fraction of table records 
  have been inserted/updated/deleted. delete_all_rows() and table flush cause 
  immediate update.

  NOTE
   hash index statistics must be updated when number of table records changes
   from 0 to non-zero value and vice versa. Otherwise records_in_range may 
   erroneously return 0 and 'range' may miss records.
*/
#define HEAP_STATS_UPDATE_THRESHOLD 10

int ha_heap::open(const char *name, int mode, uint test_if_locked)
{
  internal_table= MY_TEST(test_if_locked & HA_OPEN_INTERNAL_TABLE);
  if (internal_table || (!(file= heap_open(name, mode)) && my_errno == ENOENT))
  {
    HP_CREATE_INFO create_info;
    my_bool created_new_share;
    int rc;
    file= 0;
    if (heap_prepare_hp_create_info(table, internal_table, &create_info))
      goto end;
    create_info.pin_share= TRUE;

    rc= heap_create(name, &create_info, &internal_share, &created_new_share);
    my_free(create_info.keydef);
    if (rc)
      goto end;

    implicit_emptied= MY_TEST(created_new_share);
    if (internal_table)
      file= heap_open_from_share(internal_share, mode);
    else
      file= heap_open_from_share_and_register(internal_share, mode);

    if (!file)
    {
      heap_release_share(internal_share, internal_table);
      goto end;
    }
  }

  ref_length= sizeof(HEAP_PTR);
  /*
    We cannot run update_key_stats() here because we do not have a
    lock on the table. The 'records' count might just be changed
    temporarily at this moment and we might get wrong statistics (Bug
    #10178). Instead we request for update. This will be done in
    ha_heap::info(), which is always called before key statistics are
    used.
    */
  key_stat_version= file->s->key_stat_version-1;
end:
  return (file ? 0 : 1);
}

int ha_heap::close(void)
{
  return internal_table ? hp_close(file) : heap_close(file);
}


/*
  Create a copy of this table

  DESCRIPTION
    Do same as default implementation but use file->s->name instead of 
    table->s->path. This is needed by Windows where the clone() call sees
    '/'-delimited path in table->s->path, while ha_heap::open() was called 
    with '\'-delimited path.
*/

handler *ha_heap::clone(const char *name, MEM_ROOT *mem_root)
{
  handler *new_handler= get_new_handler(table->s, mem_root, ht);
  if (new_handler && !new_handler->ha_open(table, file->s->name, table->db_stat,
                                           HA_OPEN_IGNORE_IF_LOCKED))
    return new_handler;
  return NULL;  /* purecov: inspected */
}


/*
  Return set of keys usable for scanning

  SYNOPSIS
    keys_to_use_for_scanning()
    (no parameters)

  DESCRIPTION
    This function populates the bitmap `btree_keys`, where each bit represents
    a key that can be used for scanning the table. The bitmap is dynamically
    updated on every call, ensuring it reflects the current state of the
    table's keys. Caching is avoided because the set of usable keys for
    MEMORY tables may change during optimization or execution.

  RETURN
    Pointer to the updated bitmap of keys (`btree_keys`)
*/

const key_map *ha_heap::keys_to_use_for_scanning()
{
  btree_keys.clear_all();
  for (uint i= 0 ; i < table->s->keys ; i++)
  {
    if (table->key_info[i].algorithm == HA_KEY_ALG_BTREE)
      btree_keys.set_bit(i);
  }
  return &btree_keys;
}

int ha_heap::can_continue_handler_scan()
{
  int error= 0;
  if ((file->key_version != file->s->key_version && inited == INDEX) ||
      (file->file_version != file->s->file_version && inited == RND))
  {
    /* Data changed, not safe to do index or rnd scan */
    error= HA_ERR_RECORD_CHANGED;
  }
  return error;
}


void ha_heap::update_key_stats()
{
  for (uint i= 0; i < table->s->keys; i++)
  {
    KEY *key=table->key_info+i;
    if (!key->rec_per_key)
      continue;
    if (key->algorithm != HA_KEY_ALG_BTREE)
    {
      if (key->flags & HA_NOSAME)
        key->rec_per_key[key->user_defined_key_parts-1]= 1;
      else
      {
        ha_rows hash_buckets= file->s->keydef[i].hash_buckets;
        ulong no_records= hash_buckets ? (ulong)(file->s->records/hash_buckets) : 2;
        if (no_records < 2)
          no_records= 2;
        key->rec_per_key[key->user_defined_key_parts-1]= no_records;
      }
    }
  }
  records_changed= 0;
  /* At the end of update_key_stats() we can proudly claim they are OK. */
  key_stat_version= file->s->key_stat_version;
}


IO_AND_CPU_COST ha_heap::keyread_time(uint index, ulong ranges, ha_rows rows,
                                      ulonglong blocks)
{
  KEY *key=table->key_info+index;
  if (key->algorithm == HA_KEY_ALG_BTREE)
  {
    double lookup_cost;
    lookup_cost= ranges * costs->key_cmp_cost * log2(stats.records+1);
    return {0, ranges * lookup_cost + (rows-ranges) * BTREE_KEY_NEXT_FIND_COST };
  }
  else
  {
    return {0, (ranges * HEAP_LOOKUP_COST +
                (rows-ranges) * BTREE_KEY_NEXT_FIND_COST) };
  }
}


IO_AND_CPU_COST ha_heap::scan_time()
{
  /* The caller ha_scan_time() handles stats.records */

  return {0, (double) stats.deleted * HEAP_ROW_NEXT_FIND_COST };
}


IO_AND_CPU_COST ha_heap::rnd_pos_time(ha_rows rows)
{
  /*
    The row pointer is a direct pointer to the block. Thus almost instant
    in practice.
    Note that ha_rnd_pos_time() will add ROW_COPY_COST to this result
  */
  return { 0, 0 };
}


int ha_heap::write_row(const uchar * buf)
{
  int res;
  if (table->next_number_field && buf == table->record[0])
  {
    if ((res= update_auto_increment()))
      return res;
  }
  res= heap_write(file,buf);
  if (!res && (++records_changed*HEAP_STATS_UPDATE_THRESHOLD > 
               file->s->records))
  {
    /*
       We can perform this safely since only one writer at the time is
       allowed on the table.
    */
    records_changed= 0;
    file->s->key_stat_version++;
  }
  return res;
}

int ha_heap::update_row(const uchar * old_data, const uchar * new_data)
{
  int res;
  res= heap_update(file,old_data,new_data);
  if (!res && ++records_changed*HEAP_STATS_UPDATE_THRESHOLD > 
              file->s->records)
  {
    /*
       We can perform this safely since only one writer at the time is
       allowed on the table.
    */
    records_changed= 0;
    file->s->key_stat_version++;
  }
  return res;
}

int ha_heap::delete_row(const uchar * buf)
{
  int res;
  res= heap_delete(file,buf);
  if (!res && table->s->tmp_table == NO_TMP_TABLE && 
      ++records_changed*HEAP_STATS_UPDATE_THRESHOLD > file->s->records)
  {
    /*
       We can perform this safely since only one writer at the time is
       allowed on the table.
    */
    records_changed= 0;
    file->s->key_stat_version++;
  }
  return res;
}

int ha_heap::index_read_map(uchar *buf, const uchar *key,
                            key_part_map keypart_map,
                            enum ha_rkey_function find_flag)
{
  DBUG_ASSERT(inited==INDEX);
  int error = heap_rkey(file,buf,active_index, key, keypart_map, find_flag);
  return error;
}

int ha_heap::index_read_last_map(uchar *buf, const uchar *key,
                                 key_part_map keypart_map)
{
  DBUG_ASSERT(inited==INDEX);
  int error= heap_rkey(file, buf, active_index, key, keypart_map,
		       HA_READ_PREFIX_LAST);
  return error;
}

int ha_heap::index_read_idx_map(uchar *buf, uint index, const uchar *key,
                                key_part_map keypart_map,
                                enum ha_rkey_function find_flag)
{
  int error = heap_rkey(file, buf, index, key, keypart_map, find_flag);
  return error;
}

int ha_heap::index_next(uchar * buf)
{
  DBUG_ASSERT(inited==INDEX);
  int error=heap_rnext(file,buf);
  return error;
}

int ha_heap::index_prev(uchar * buf)
{
  DBUG_ASSERT(inited==INDEX);
  int error=heap_rprev(file,buf);
  return error;
}

int ha_heap::index_first(uchar * buf)
{
  DBUG_ASSERT(inited==INDEX);
  int error=heap_rfirst(file, buf, active_index);
  return error;
}

int ha_heap::index_last(uchar * buf)
{
  DBUG_ASSERT(inited==INDEX);
  int error=heap_rlast(file, buf, active_index);
  return error;
}

int ha_heap::rnd_init(bool scan)
{
  return scan ? heap_scan_init(file) : 0;
}

int ha_heap::rnd_next(uchar *buf)
{
  int error=heap_scan(file, buf);
  return error;
}

int ha_heap::rnd_pos(uchar * buf, uchar *pos)
{
  int error;
  HEAP_PTR heap_position;
  memcpy(&heap_position, pos, sizeof(HEAP_PTR));
  error=heap_rrnd(file, buf, heap_position);
  return error;
}

void ha_heap::position(const uchar *record)
{
  *(HEAP_PTR*) ref= heap_position(file);	// Ref is aligned
}

int ha_heap::info(uint flag)
{
  HEAPINFO hp_info;

  (void) heap_info(file,&hp_info,flag);

  errkey=                     hp_info.errkey;
  stats.records=              hp_info.records;
  stats.deleted=              hp_info.deleted;
  stats.mean_rec_length=      hp_info.reclength;
  stats.data_file_length=     hp_info.data_length;
  stats.index_file_length=    hp_info.index_length;
  stats.max_data_file_length= hp_info.max_records * hp_info.reclength;
  stats.delete_length=        hp_info.deleted * hp_info.reclength;
  stats.create_time=          (ulong) hp_info.create_time;
  if (flag & HA_STATUS_AUTO)
    stats.auto_increment_value= hp_info.auto_increment;
  /*
    If info() is called for the first time after open(), we will still
    have to update the key statistics. Hoping that a table lock is now
    in place.
  */
  if (key_stat_version != file->s->key_stat_version)
    update_key_stats();
  return 0;
}


int ha_heap::extra(enum ha_extra_function operation)
{
  return heap_extra(file,operation);
}


int ha_heap::reset()
{
  return heap_reset(file);
}


int ha_heap::delete_all_rows()
{
  heap_clear(file);
  if (table->s->tmp_table == NO_TMP_TABLE)
  {
    /*
       We can perform this safely since only one writer at the time is
       allowed on the table.
    */
    file->s->key_stat_version++;
  }
  return 0;
}


int ha_heap::reset_auto_increment(ulonglong value)
{
  file->s->auto_increment= value;
  return 0;
}


int ha_heap::external_lock(THD *thd, int lock_type)
{
#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
  if (lock_type == F_UNLCK && file->s->changed && heap_check_heap(file, 0))
    return HA_ERR_CRASHED;
#endif
  return 0;					// No external locking
}


/*
  Disable indexes.

  SYNOPSIS
    disable_indexes()

  DESCRIPTION
    See handler::ha_disable_indexes()

  RETURN
    0  ok
    HA_ERR_WRONG_COMMAND  mode not implemented.
*/

int ha_heap::disable_indexes(key_map map, bool persist)
{
  int error;

  if (!persist)
  {
    DBUG_ASSERT(map.is_clear_all());
    error= heap_disable_indexes(file);
  }
  else
  {
    /* mode not implemented */
    error= HA_ERR_WRONG_COMMAND;
  }
  return error;
}


/*
  Enable indexes.

  SYNOPSIS
    enable_indexes()

  DESCRIPTION
    Enable indexes taht might have been disabled by disable_index() before.
    The function works only if both data and indexes are empty,
    since the heap storage engine cannot repair the indexes.
    To be sure, call handler::delete_all_rows() before.

    See also handler::ha_enable_indexes()

  RETURN
    0  ok
    HA_ERR_CRASHED  data or index is non-empty. Delete all rows and retry.
    HA_ERR_WRONG_COMMAND  mode not implemented.
*/

int ha_heap::enable_indexes(key_map map, bool persist)
{
  int error;

  if (!persist)
  {
    DBUG_ASSERT(map.is_prefix(table->s->keys));
    error= heap_enable_indexes(file);
  }
  else
  {
    /* mode not implemented */
    error= HA_ERR_WRONG_COMMAND;
  }
  return error;
}


/*
  Test if indexes are disabled.

  SYNOPSIS
    indexes_are_disabled()
    no parameters

  RETURN
    0  indexes are not disabled
    1  all indexes are disabled
   [2  non-unique indexes are disabled - NOT YET IMPLEMENTED]
*/

int ha_heap::indexes_are_disabled(void)
{
  return heap_indexes_are_disabled(file);
}

THR_LOCK_DATA **ha_heap::store_lock(THD *thd,
				    THR_LOCK_DATA **to,
				    enum thr_lock_type lock_type)
{
  if (lock_type != TL_IGNORE && file->lock.type == TL_UNLOCK)
    file->lock.type=lock_type;
  *to++= &file->lock;
  return to;
}

/*
  We have to ignore ENOENT entries as the HEAP table is created on open and
  not when doing a CREATE on the table.
*/

int ha_heap::delete_table(const char *name)
{
  return heap_drop_table(0, name);
}


void ha_heap::drop_table(const char *name)
{
  file->s->delete_on_close= 1;
  ha_close();
}


int ha_heap::rename_table(const char * from, const char * to)
{
  return heap_rename(from,to);
}


ha_rows ha_heap::records_in_range(uint inx, const key_range *min_key,
                                  const key_range *max_key, page_range *pages)
{
  KEY *key=table->key_info+inx;
  if (key->algorithm == HA_KEY_ALG_BTREE)
    return hp_rb_records_in_range(file, inx, min_key, max_key);

  if (!min_key || !max_key ||
      min_key->length != max_key->length ||
      min_key->length != key->key_length ||
      min_key->flag != HA_READ_KEY_EXACT ||
      max_key->flag != HA_READ_AFTER_KEY)
    return HA_POS_ERROR;			// Can only use exact keys

  if (stats.records <= 1)
    return stats.records;

  /* Assert that info() did run. We need current statistics here. */
  DBUG_ASSERT(key_stat_version == file->s->key_stat_version);
  return key->rec_per_key[key->user_defined_key_parts-1];
}


static int heap_prepare_hp_create_info(TABLE *table_arg, bool internal_table,
                                       HP_CREATE_INFO *hp_create_info)
{
  TABLE_SHARE *share= table_arg->s;
  uint key, parts, mem_per_row= 0, keys= share->keys;
  uint auto_key= 0, auto_key_type= 0;
  ha_rows max_rows;
  HP_KEYDEF *keydef;
  HA_KEYSEG *seg;
  bool found_real_auto_increment= 0;

  bzero(hp_create_info, sizeof(*hp_create_info));

  for (key= parts= 0; key < keys; key++)
    parts+= table_arg->key_info[key].user_defined_key_parts;

  if (!my_multi_malloc(hp_key_memory_HP_KEYDEF,
                       MYF(MY_WME | MY_THREAD_SPECIFIC),
                       &keydef, keys * sizeof(HP_KEYDEF),
                       &seg, parts * sizeof(HA_KEYSEG),
                       NULL))
    return my_errno;
  for (key= 0; key < keys; key++)
  {
    KEY *pos= table_arg->key_info+key;
    KEY_PART_INFO *key_part=     pos->key_part;
    KEY_PART_INFO *key_part_end= key_part + pos->user_defined_key_parts;

    keydef[key].keysegs=   (uint) pos->user_defined_key_parts;
    keydef[key].flag=      (pos->flags & (HA_NOSAME | HA_NULL_ARE_EQUAL));
    keydef[key].seg=       seg;

    switch (pos->algorithm) {
    case HA_KEY_ALG_UNDEF:
    case HA_KEY_ALG_HASH:
      keydef[key].algorithm= HA_KEY_ALG_HASH;
      mem_per_row+= sizeof(HASH_INFO);
      break;
    case HA_KEY_ALG_BTREE:
      keydef[key].algorithm= HA_KEY_ALG_BTREE;
      mem_per_row+=sizeof(TREE_ELEMENT)+pos->key_length+sizeof(char*);
      break;
    default:
      DBUG_ASSERT(0); // cannot happen
    }

    for (; key_part != key_part_end; key_part++, seg++)
    {
      Field *field= key_part->field;

      if (pos->algorithm == HA_KEY_ALG_BTREE)
	seg->type= field->key_type();
      else
      {
        if ((seg->type = field->key_type()) != (int) HA_KEYTYPE_TEXT &&
            seg->type != HA_KEYTYPE_VARTEXT1 &&
            seg->type != HA_KEYTYPE_VARTEXT2 &&
            seg->type != HA_KEYTYPE_VARBINARY1 &&
            seg->type != HA_KEYTYPE_VARBINARY2 &&
            seg->type != HA_KEYTYPE_BIT)
          seg->type= HA_KEYTYPE_BINARY;
      }
      seg->start=   (uint) key_part->offset;
      seg->length=  (uint) key_part->length;
      seg->flag=    key_part->key_part_flag;

      if (field->flags & (ENUM_FLAG | SET_FLAG))
        seg->charset= &my_charset_bin;
      else
        seg->charset= field->charset_for_protocol();
      if (field->null_ptr)
      {
	seg->null_bit= field->null_bit;
	seg->null_pos= (uint) (field->null_ptr - (uchar*) table_arg->record[0]);
      }
      else
      {
	seg->null_bit= 0;
	seg->null_pos= 0;
      }
      if (field->flags & AUTO_INCREMENT_FLAG &&
          table_arg->found_next_number_field &&
          key == share->next_number_index)
      {
        /*
          Store key number and type for found auto_increment key
          We have to store type as seg->type can differ from it
        */
        auto_key= key+ 1;
	auto_key_type= field->key_type();
      }
      if (seg->type == HA_KEYTYPE_BIT)
      {
        seg->bit_length= ((Field_bit *) field)->bit_len;
        seg->bit_start= ((Field_bit *) field)->bit_ofs;
        seg->bit_pos= (uint) (((Field_bit *) field)->bit_ptr -
                                          (uchar*) table_arg->record[0]);
      }
      else
      {
        seg->bit_length= seg->bit_start= 0;
        seg->bit_pos= 0;
      }
    }
  }
  if (table_arg->found_next_number_field)
  {
    keydef[share->next_number_index].flag|= HA_AUTO_KEY;
    found_real_auto_increment= share->next_number_key_offset == 0;
  }
  hp_create_info->auto_key= auto_key;
  hp_create_info->auto_key_type= auto_key_type;
  hp_create_info->max_table_size= MY_MAX(current_thd->variables.max_heap_table_size, sizeof(HP_PTRS));
  hp_create_info->with_auto_increment= found_real_auto_increment;
  hp_create_info->internal_table= internal_table;

  max_rows= hp_rows_in_memory(share->reclength, mem_per_row,
                              hp_create_info->max_table_size);
#ifdef GIVE_ERROR_IF_NOT_MEMORY_TO_INSERT_ONE_ROW
  /* We do not give the error now but instead give an error on first insert */
  if (!max_rows)
    return HA_WRONG_CREATE_OPTION;
#endif

  if (share->max_rows && share->max_rows < max_rows)
    max_rows= share->max_rows;

  hp_create_info->max_records= (ulong) MY_MIN(max_rows, ULONG_MAX);
  hp_create_info->min_records= (ulong) MY_MIN(share->min_rows, ULONG_MAX);
  hp_create_info->keys= share->keys;
  hp_create_info->reclength= share->reclength;
  hp_create_info->keydef= keydef;
  return 0;
}


int ha_heap::create(const char *name, TABLE *table_arg,
		    HA_CREATE_INFO *create_info)
{
  int error;
  my_bool created;
  HP_CREATE_INFO hp_create_info;

  error= heap_prepare_hp_create_info(table_arg, internal_table,
                                     &hp_create_info);
  if (error)
    return error;
  hp_create_info.auto_increment= (create_info->auto_increment_value ?
				  create_info->auto_increment_value - 1 : 0);
  error= heap_create(name, &hp_create_info, &internal_share, &created);
  my_free(hp_create_info.keydef);
  DBUG_ASSERT(file == 0);
  return (error);
}


void ha_heap::update_create_info(HA_CREATE_INFO *create_info)
{
  table->file->info(HA_STATUS_AUTO);
  if (!(create_info->used_fields & HA_CREATE_USED_AUTO))
    create_info->auto_increment_value= stats.auto_increment_value;
}

void ha_heap::get_auto_increment(ulonglong offset, ulonglong increment,
                                 ulonglong nb_desired_values,
                                 ulonglong *first_value,
                                 ulonglong *nb_reserved_values)
{
  ha_heap::info(HA_STATUS_AUTO);
  *first_value= stats.auto_increment_value;
  /* such table has only table-level locking so reserves up to +inf */
  *nb_reserved_values= ULONGLONG_MAX;
}


bool ha_heap::check_if_incompatible_data(HA_CREATE_INFO *info,
					 uint table_changes)
{
  /* Check that auto_increment value was not changed */
  if ((info->used_fields & HA_CREATE_USED_AUTO &&
       info->auto_increment_value != 0) ||
      table_changes == IS_EQUAL_NO ||
      table_changes & IS_EQUAL_PACK_LENGTH) // Not implemented yet
    return COMPATIBLE_DATA_NO;
  return COMPATIBLE_DATA_YES;
}


/**
  Find record by unique index (used in temporary tables with the index)

  @param record          (IN|OUT) the record to find
  @param unique_idx      (IN) number of index (for this engine)

  @note It is like hp_search but uses function for raw where hp_search
        uses functions for index.

  @retval  0 OK
  @retval  1 Not found
  @retval -1 Error
*/

int ha_heap::find_unique_row(uchar *record, uint unique_idx)
{
  DBUG_ENTER("ha_heap::find_unique_row");
  HP_SHARE *share= file->s;
  DBUG_ASSERT(inited==NONE);
  HP_KEYDEF *keyinfo= share->keydef + unique_idx;
  DBUG_ASSERT(keyinfo->algorithm == HA_KEY_ALG_HASH);
  DBUG_ASSERT(keyinfo->flag & HA_NOSAME);
  if (!share->records)
    DBUG_RETURN(1); // not found
  HASH_INFO *pos= hp_find_hash(&keyinfo->block,
                               hp_mask(hp_rec_hashnr(keyinfo, record),
                                       share->blength, share->records));
  do
  {
    if (!hp_rec_key_cmp(keyinfo, pos->ptr_to_rec, record))
    {
      file->current_hash_ptr= pos;
      file->current_ptr= pos->ptr_to_rec;
      file->update = HA_STATE_AKTIV;
      /*
        We compare it only by record in the index, so better to read all
        records.
      */
      memcpy(record, file->current_ptr, (size_t) share->reclength);

      DBUG_RETURN(0); // found and position set
    }
  }
  while ((pos= pos->next_key));
  DBUG_RETURN(1); // not found
}

struct st_mysql_storage_engine heap_storage_engine=
{ MYSQL_HANDLERTON_INTERFACE_VERSION };

maria_declare_plugin(heap)
{
  MYSQL_STORAGE_ENGINE_PLUGIN,
  &heap_storage_engine,
  "MEMORY",
  "MySQL AB",
  "Hash based, stored in memory, useful for temporary tables",
  PLUGIN_LICENSE_GPL,
  heap_init,
  NULL,
  0x0100, /* 1.0 */
  NULL,                       /* status variables                */
  NULL,                       /* system variables                */
  "1.0",                      /* string version */
  MariaDB_PLUGIN_MATURITY_STABLE /* maturity */
}
maria_declare_plugin_end;