1 /* Copyright (c) 2000, 2021, Oracle and/or its affiliates.
2
3 This program is free software; you can redistribute it and/or modify
4 it under the terms of the GNU General Public License, version 2.0,
5 as published by the Free Software Foundation.
6
7 This program is also distributed with certain software (including
8 but not limited to OpenSSL) that is licensed under separate terms,
9 as designated in a particular file or component or in included license
10 documentation. The authors of MySQL hereby grant you an additional
11 permission to link the program and your derivative works with the
12 separately licensed software that they have included with MySQL.
13
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License, version 2.0, for more details.
18
19 You should have received a copy of the GNU General Public License
20 along with this program; if not, write to the Free Software
21 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
22
23 #include "myisamdef.h"
24
25 /*
26 Read previous row with the same key as previous read
27 One may have done a write, update or delete of the previous row.
28 NOTE! Even if one changes the previous row, the next read is done
29 based on the position of the last used key!
30 */
31
mi_rprev(MI_INFO * info,uchar * buf,int inx)32 int mi_rprev(MI_INFO *info, uchar *buf, int inx)
33 {
34 int error,changed;
35 uint flag;
36 MYISAM_SHARE *share=info->s;
37 DBUG_ENTER("mi_rprev");
38
39 if ((inx = _mi_check_index(info,inx)) < 0)
40 DBUG_RETURN(my_errno());
41 flag=SEARCH_SMALLER; /* Read previous */
42 if (info->lastpos == HA_OFFSET_ERROR && info->update & HA_STATE_NEXT_FOUND)
43 flag=0; /* Read last */
44
45 if (fast_mi_readinfo(info))
46 DBUG_RETURN(my_errno());
47 changed=_mi_test_if_changed(info);
48 if (share->concurrent_insert)
49 mysql_rwlock_rdlock(&share->key_root_lock[inx]);
50 if (!flag)
51 error=_mi_search_last(info, share->keyinfo+inx,
52 share->state.key_root[inx]);
53 else if (!changed)
54 error=_mi_search_next(info,share->keyinfo+inx,info->lastkey,
55 info->lastkey_length,flag,
56 share->state.key_root[inx]);
57 else
58 error=_mi_search(info,share->keyinfo+inx,info->lastkey,
59 USE_WHOLE_KEY, flag, share->state.key_root[inx]);
60
61 if (!error)
62 {
63 int res= 0;
64 while ((share->concurrent_insert &&
65 info->lastpos >= info->state->data_file_length) ||
66 (info->index_cond_func &&
67 !(res= mi_check_index_cond(info, inx, buf))))
68 {
69 /*
70 Skip rows that are either inserted by other threads since
71 we got a lock or do not match pushed index conditions
72 */
73 if ((error=_mi_search_next(info,share->keyinfo+inx,info->lastkey,
74 info->lastkey_length,
75 SEARCH_SMALLER,
76 share->state.key_root[inx])))
77 break;
78 }
79 if (!error && res == 2)
80 {
81 if (share->concurrent_insert)
82 mysql_rwlock_unlock(&share->key_root_lock[inx]);
83 info->lastpos= HA_OFFSET_ERROR;
84 set_my_errno(HA_ERR_END_OF_FILE);
85 DBUG_RETURN(HA_ERR_END_OF_FILE);
86 }
87 }
88
89 if (share->concurrent_insert)
90 {
91 if (!error)
92 {
93 while (info->lastpos >= info->state->data_file_length)
94 {
95 /* Skip rows that are inserted by other threads since we got a lock */
96 if ((error=_mi_search_next(info,share->keyinfo+inx,info->lastkey,
97 info->lastkey_length,
98 SEARCH_SMALLER,
99 share->state.key_root[inx])))
100 break;
101 }
102 }
103 mysql_rwlock_unlock(&share->key_root_lock[inx]);
104 }
105
106 info->update&= (HA_STATE_CHANGED | HA_STATE_ROW_CHANGED);
107 info->update|= HA_STATE_PREV_FOUND;
108 if (error)
109 {
110 if (my_errno() == HA_ERR_KEY_NOT_FOUND)
111 set_my_errno(HA_ERR_END_OF_FILE);
112 }
113 else if (!buf)
114 {
115 DBUG_RETURN(info->lastpos==HA_OFFSET_ERROR ? my_errno() : 0);
116 }
117 else if (!(*info->read_record)(info,info->lastpos,buf))
118 {
119 info->update|= HA_STATE_AKTIV; /* Record is read */
120 DBUG_RETURN(0);
121 }
122 DBUG_RETURN(my_errno());
123 } /* mi_rprev */
124