diff options
Diffstat (limited to 'storage/maria/ma_rprev.c')
| -rw-r--r-- | storage/maria/ma_rprev.c | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/storage/maria/ma_rprev.c b/storage/maria/ma_rprev.c new file mode 100644 index 00000000..15010d96 --- /dev/null +++ b/storage/maria/ma_rprev.c @@ -0,0 +1,106 @@ +/* Copyright (C) 2006 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; 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 Street, Fifth Floor, Boston, MA 02110-1335 USA */ + +#include "maria_def.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 maria_rprev(MARIA_HA *info, uchar *buf, int inx) +{ + int error,changed; + register uint flag; + MARIA_SHARE *share= info->s; + MARIA_KEYDEF *keyinfo; + check_result_t check= CHECK_POS; + DBUG_ENTER("maria_rprev"); + + if ((inx = _ma_check_index(info,inx)) < 0) + DBUG_RETURN(my_errno); + flag=SEARCH_SMALLER; /* Read previous */ + if (info->cur_row.lastpos == HA_OFFSET_ERROR && + info->update & HA_STATE_NEXT_FOUND) + flag=0; /* Read last */ + + if (fast_ma_readinfo(info)) + DBUG_RETURN(my_errno); + keyinfo= share->keyinfo + inx; + changed= _ma_test_if_changed(info); + if (share->lock_key_trees) + mysql_rwlock_rdlock(&keyinfo->root_lock); + if (!flag) + error= _ma_search_last(info, keyinfo, share->state.key_root[inx]); + else if (!changed) + error= _ma_search_next(info, &info->last_key, + flag | info->last_key.flag, + share->state.key_root[inx]); + else + error= _ma_search(info, &info->last_key, flag | info->last_key.flag, + share->state.key_root[inx]); + + if (!error) + { + my_off_t cur_keypage= info->last_keypage; + while (!(*share->row_is_visible)(info) || + ((check= ma_check_index_cond(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 (ma_yield_and_check_if_killed(info, inx)) + { + error= 1; + break; + } + } + + /* Skip rows that are inserted by other threads since we got a lock */ + if ((error= _ma_search_next(info, &info->last_key, + SEARCH_SMALLER, + share->state.key_root[inx]))) + break; + } + } + if (share->lock_key_trees) + mysql_rwlock_unlock(&keyinfo->root_lock); + info->update&= (HA_STATE_CHANGED | HA_STATE_ROW_CHANGED); + info->update|= HA_STATE_PREV_FOUND; + + if (error || check != CHECK_POS) + { + fast_ma_writeinfo(info); + if (my_errno == HA_ERR_KEY_NOT_FOUND) + my_errno= HA_ERR_END_OF_FILE; + } + else if (!buf) + { + fast_ma_writeinfo(info); + DBUG_RETURN(info->cur_row.lastpos == HA_OFFSET_ERROR ? my_errno : 0); + } + else if (!(*info->read_record)(info, buf, info->cur_row.lastpos)) + { + info->update|= HA_STATE_AKTIV; /* Record is read */ + DBUG_RETURN(0); + } + DBUG_RETURN(my_errno); +} /* maria_rprev */ |