diff options
Diffstat (limited to 'storage/myisam/mi_rprev.c')
| -rw-r--r-- | storage/myisam/mi_rprev.c | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/storage/myisam/mi_rprev.c b/storage/myisam/mi_rprev.c new file mode 100644 index 00000000..698e3b59 --- /dev/null +++ b/storage/myisam/mi_rprev.c @@ -0,0 +1,112 @@ +/* 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 */ |