myrg_queue.c

/* Copyright (c) 2000, 2023, 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, version 2.0,
   as published by the Free Software Foundation.

   This program is also distributed with certain software (including
   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have included with MySQL.

   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, version 2.0, 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 "myrg_def.h"

static int queue_key_cmp(void *keyseg, uchar *a, uchar *b)
{
  MYRG_TABLE *ma= (MYRG_TABLE *)a;
  MYRG_TABLE *mb= (MYRG_TABLE *)b;
  MI_INFO *aa= ma->table;
  MI_INFO *bb= mb->table;
  uint not_used[2];
  int ret= ha_key_cmp((HA_KEYSEG *)keyseg, aa->lastkey, bb->lastkey,
		       USE_WHOLE_KEY, SEARCH_FIND, not_used);
  if (ret < 0)
    return -1;
  if (ret > 0)
    return 1;
 
  /*
    If index tuples have the same values, let the record with least rowid
    value be "smaller", so index scans return records ordered by (keytuple,
    rowid). This is used by index_merge access method, grep for ROR in
    sql/opt_range.cc for details.
  */
  return (ma->file_offset < mb->file_offset)? -1 : (ma->file_offset > 
                                                    mb->file_offset) ? 1 : 0;
} /* queue_key_cmp */


int _myrg_init_queue(MYRG_INFO *info,int inx,enum ha_rkey_function search_flag)
{
  int error=0;
  QUEUE *q= &(info->by_key);

  if (inx < (int) info->keys)
  {
    if (!is_queue_inited(q))
    {
      if (init_queue(q,info->tables, 0,
		     (myisam_readnext_vec[search_flag] == SEARCH_SMALLER),
		     queue_key_cmp,
		     info->open_tables->table->s->keyinfo[inx].seg))
	error=my_errno();
    }
    else
    {
      if (reinit_queue(q,info->tables, 0,
		       (myisam_readnext_vec[search_flag] == SEARCH_SMALLER),
		       queue_key_cmp,
		       info->open_tables->table->s->keyinfo[inx].seg))
	error=my_errno();
    }
  }
  else
  {
    /*
      inx may be bigger than info->keys if there are no underlying tables
      defined. In this case we should return empty result. As we check for
      underlying tables conformance when we open a table, we may not enter
      this branch with underlying table that has less keys than merge table
      have.
    */
    assert(!info->tables);
    error= HA_ERR_END_OF_FILE;
    set_my_errno(error);
  }
  return error;
}

int _myrg_mi_read_record(MI_INFO *info, uchar *buf)
{
  if (!(*info->read_record)(info,info->lastpos,buf))
  {
    info->update|= HA_STATE_AKTIV;		/* Record is read */
    return 0;
  }
  return my_errno();
}