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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 "myisamdef.h"
/*
Read previous row with the same key as previous read
One may have done a write, update or delete of the previous row.
NOTE! Even if one changes the previous row, the next read is done
based on the position of the last used key!
*/
int mi_rprev(MI_INFO *info, byte *buf, int inx)
{
int error,changed;
register uint flag;
MYISAM_SHARE *share=info->s;
DBUG_ENTER("mi_rprev");
if ((inx = _mi_check_index(info,inx)) < 0)
DBUG_RETURN(my_errno);
flag=SEARCH_SMALLER; /* Read previous */
if (info->lastpos == HA_OFFSET_ERROR && info->update & HA_STATE_NEXT_FOUND)
flag=0; /* Read last */
if (fast_mi_readinfo(info))
DBUG_RETURN(my_errno);
changed=_mi_test_if_changed(info);
if (share->concurrent_insert)
rw_rdlock(&share->key_root_lock[inx]);
if (!flag)
error=_mi_search_last(info, share->keyinfo+inx,
share->state.key_root[inx]);
else if (!changed)
error=_mi_search_next(info,share->keyinfo+inx,info->lastkey,
info->lastkey_length,flag,
share->state.key_root[inx]);
else
error=_mi_search(info,share->keyinfo+inx,info->lastkey,
USE_WHOLE_KEY, flag, share->state.key_root[inx]);
if (share->concurrent_insert)
{
if (!error)
{
while (info->lastpos >= info->state->data_file_length)
{
/* Skip rows that are inserted by other threads since we got a lock */
if ((error=_mi_search_next(info,share->keyinfo+inx,info->lastkey,
info->lastkey_length,
SEARCH_SMALLER,
share->state.key_root[inx])))
break;
}
}
rw_unlock(&share->key_root_lock[inx]);
}
info->update&= (HA_STATE_CHANGED | HA_STATE_ROW_CHANGED);
info->update|= HA_STATE_PREV_FOUND;
if (error)
{
if (my_errno == HA_ERR_KEY_NOT_FOUND)
my_errno=HA_ERR_END_OF_FILE;
}
else if (!buf)
{
DBUG_RETURN(info->lastpos==HA_OFFSET_ERROR ? my_errno : 0);
}
else if (!(*info->read_record)(info,info->lastpos,buf))
{
info->update|= HA_STATE_AKTIV; /* Record is read */
DBUG_RETURN(0);
}
DBUG_RETURN(my_errno);
} /* mi_rprev */
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