CREATE TABLE bug13510739 (c INTEGER NOT NULL, PRIMARY KEY (c)) ENGINE=INNODB;
INSERT INTO bug13510739 VALUES (1), (2), (3), (4);
DELETE FROM bug13510739 WHERE c=2;
HANDLER bug13510739 OPEN;
HANDLER bug13510739 READ `primary` = (2);
HANDLER bug13510739 READ `primary` NEXT; <-- crash
The bug is that in the particular testcase row_search_for_mysql() picked up
a delete-marked record and quit, leaving the cursor non-positioned state and
on the subsequent 'get next' call the code crashed because of the
non-positioned cursor.
In row0sel.cc (line numbers from mysql-trunk):
4653 if (rec_get_deleted_flag(rec, comp)) {
...
4679 if (index == clust_index && unique_search) {
4680
4681 err = DB_RECORD_NOT_FOUND;
4682
4683 goto normal_return;
4684 }
it quit from here, not storing the cursor position.
In contrast, if the record=2 is not found at all (e.g. sleep(1) after DELETE
to let the purge wipe it away completely) then 'get = 2' does find record=3
and quits from here:
4366 if (0 != cmp_dtuple_rec(search_tuple, rec, offsets)) {
...
4394 btr_pcur_store_position(pcur, &mtr);
4395
4396 err = DB_RECORD_NOT_FOUND;
4397 #if 0
4398 ut_print_name(stderr, trx, FALSE, index->name);
4399 fputs(" record not found 3\n", stderr);
4400 #endif
4401
4402 goto normal_return;
Another fix could be to extend the condition on line 4366 to hold only if
seach_tuple matches rec AND if rec is not delete marked.
Notice that in the above test case if we wait about 1 second somewhere after
DELETE and before 'get = 2', then the testcase does not crash and returns 4
instead. Not sure if this is the correct behavior, but this bugfix removes
the crash and makes the code return what it also returns in the non-crashing
case (if rec=2 is not found during 'get = 2', e.g. we have sleep(1) there).
Approved by: Marko (http://bur03.no.oracle.com/rb/r/863/)
