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/* Copyright (c) 2000, 2001, 2004-2007 MySQL AB, 2009 Sun Microsystems, Inc.
Use is subject to license terms.
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 */
#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, uchar *buf, int inx)
{
int error,changed;
register uint flag;
MYISAM_SHARE *share=info->s;
check_result_t check= CHECK_POS;
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)
mysql_rwlock_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 (!error)
{
my_off_t cur_keypage= info->last_keypage;
while ((share->concurrent_insert &&
info->lastpos >= info->state->data_file_length) ||
(check= mi_check_index_tuple(info, inx, buf)) == CHECK_NEG)
{
/*
If we are at the last (i.e. first?) key on the key page,
allow writers to access the index.
*/
if (info->last_keypage != cur_keypage)
{
cur_keypage= info->last_keypage;
if (mi_yield_and_check_if_killed(info, inx))
{
error= 1;
break;
}
}
/*
Skip rows that are either inserted by other threads since
we got a lock or do not match pushed index conditions
*/
if ((error=_mi_search_next(info,share->keyinfo+inx,info->lastkey,
info->lastkey_length,
SEARCH_SMALLER,
share->state.key_root[inx])))
break;
}
}
if (share->concurrent_insert)
mysql_rwlock_unlock(&share->key_root_lock[inx]);
info->update&= (HA_STATE_CHANGED | HA_STATE_ROW_CHANGED);
info->update|= HA_STATE_PREV_FOUND;
if (error || check != CHECK_POS)
{
fast_mi_writeinfo(info);
if (my_errno == HA_ERR_KEY_NOT_FOUND)
my_errno=HA_ERR_END_OF_FILE;
}
else if (!buf)
{
fast_mi_writeinfo(info);
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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