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101 lines
3.3 KiB
C
101 lines
3.3 KiB
C
/* Copyright (C) 2000-2001, 2004 MySQL AB, 2008-2009 Sun Microsystems, Inc
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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#include "myisamdef.h"
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/*
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Read previous row with the same key as previous read
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One may have done a write, update or delete of the previous row.
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NOTE! Even if one changes the previous row, the next read is done
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based on the position of the last used key!
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*/
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int mi_rprev(MI_INFO *info, uchar *buf, int inx)
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{
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int error,changed;
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register uint flag;
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MYISAM_SHARE *share=info->s;
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DBUG_ENTER("mi_rprev");
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if ((inx = _mi_check_index(info,inx)) < 0)
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DBUG_RETURN(my_errno);
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flag=SEARCH_SMALLER; /* Read previous */
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if (info->lastpos == HA_OFFSET_ERROR && info->update & HA_STATE_NEXT_FOUND)
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flag=0; /* Read last */
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if (fast_mi_readinfo(info))
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DBUG_RETURN(my_errno);
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changed=_mi_test_if_changed(info);
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if (share->concurrent_insert)
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mysql_rwlock_rdlock(&share->key_root_lock[inx]);
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if (!flag)
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error=_mi_search_last(info, share->keyinfo+inx,
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share->state.key_root[inx]);
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else if (!changed)
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error=_mi_search_next(info,share->keyinfo+inx,info->lastkey,
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info->lastkey_length,flag,
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share->state.key_root[inx]);
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else
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error=_mi_search(info,share->keyinfo+inx,info->lastkey,
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USE_WHOLE_KEY, flag, share->state.key_root[inx]);
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if (!error)
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{
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int res= 0;
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while ((share->concurrent_insert &&
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info->lastpos >= info->state->data_file_length) ||
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(info->index_cond_func &&
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!(res= mi_check_index_cond(info, inx, buf))))
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{
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/*
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Skip rows that are either inserted by other threads since
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we got a lock or do not match pushed index conditions
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*/
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if ((error=_mi_search_next(info,share->keyinfo+inx,info->lastkey,
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info->lastkey_length,
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SEARCH_SMALLER,
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share->state.key_root[inx])))
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break;
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}
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if (!error && res == 2)
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{
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if (share->concurrent_insert)
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rw_unlock(&share->key_root_lock[inx]);
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info->lastpos= HA_OFFSET_ERROR;
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DBUG_RETURN(my_errno= HA_ERR_END_OF_FILE);
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}
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}
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if (share->concurrent_insert)
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mysql_rwlock_unlock(&share->key_root_lock[inx]);
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info->update&= (HA_STATE_CHANGED | HA_STATE_ROW_CHANGED);
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info->update|= HA_STATE_PREV_FOUND;
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if (error)
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{
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if (my_errno == HA_ERR_KEY_NOT_FOUND)
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my_errno=HA_ERR_END_OF_FILE;
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}
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else if (!buf)
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{
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DBUG_RETURN(info->lastpos==HA_OFFSET_ERROR ? my_errno : 0);
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}
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else if (!(*info->read_record)(info,info->lastpos,buf))
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{
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info->update|= HA_STATE_AKTIV; /* Record is read */
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DBUG_RETURN(0);
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}
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DBUG_RETURN(my_errno);
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} /* mi_rprev */
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