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/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
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; either version 2 of the License, or
(at your option) any later version.
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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
#include "mymrgdef.h"
/*
Read previous row with the same key as previous read
*/
int myrg_rprev(MYRG_INFO *info, byte *buf, int inx)
{
MYRG_TABLE *table;
MI_INFO *mi;
byte *key_buff;
uint pack_key_length;
int err;
/* at first, do rnext for the table found before */
err=mi_rprev(info->current_table->table,NULL,inx);
if (err == HA_ERR_END_OF_FILE)
{
queue_remove(&(info->by_key),0);
if (!info->by_key.elements)
return HA_ERR_END_OF_FILE;
}
else if (err)
return err;
else
{
/* Found here, adding to queue */
queue_top(&(info->by_key))=(byte *)(info->current_table);
queue_replaced(&(info->by_key));
}
/* next, let's finish myrg_rkey's initial scan */
table=info->last_used_table+1;
if (table < info->end_table)
{
mi=info->last_used_table->table;
key_buff=(byte*) mi->lastkey+mi->s->base.max_key_length;
pack_key_length=mi->last_rkey_length;
for (; table < info->end_table ; table++)
{
mi=table->table;
err=_mi_rkey(mi,NULL,inx,key_buff,pack_key_length,
HA_READ_KEY_OR_PREV,FALSE);
info->last_used_table=table;
if (err == HA_ERR_KEY_NOT_FOUND)
continue;
if (err)
return err;
/* Found here, adding to queue */
queue_insert(&(info->by_key),(byte *)table);
}
}
/* now, mymerge's read_prev is as simple as one queue_top */
mi=(info->current_table=(MYRG_TABLE *)queue_top(&(info->by_key)))->table;
return mi_rrnd(mi,buf,mi->lastpos);
}
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