maria-developers team mailing list archive

[Kristian Nielsen <knielsen@xxxxxxxxxxxxxxx>]

Hi Igor, Timour, Sergey,

Can one of you please check this patch from MySQL 5.1.46? It is a commit to
fix http://bugs.mysql.com/bug.php?id=51494

This patch introduces a regression:

    http://bugs.mysql.com/bug.php?id=53334

If I revert the patch, the regression disappears. And interestingly, the
included test case does not fail even when the fix is reverted (go figure...)

So it would be good if one of you could check the patch and check what is
wrong with it, and if a different fix for Bug#51494 is needed.

(needed to complete merge of MySQL 5.1.46).

Thanks,

 - Kristian.

------------------------------------------------------------
revno: 3407.1.1
revision-id: sergey.glukhov@xxxxxxx-20100319060102-57ykzjf4pc93avy1
parent: omer@xxxxxxxxx-20100318064207-l3ap0mpxt510b4n3
committer: Sergey Glukhov <Sergey.Glukhov@xxxxxxx>
branch nick: mysql-5.1-bugteam
timestamp: Fri 2010-03-19 10:01:02 +0400
message:
  Bug#51494 crash with join, explain and 'sounds like' operator
  The crash happens because of discrepancy between values of
  conts_tables and join->const_table_map(make_join_statisctics).
  Calculation of conts_tables used condition with
  HA_STATS_RECORDS_IS_EXACT flag check. Calculation of
  join->const_table_map does not use this flag check.
  In case of MERGE table without union with index
  the table does not become const table and
  thus join_read_const_table() is not called
  for the table. join->const_table_map supposes
  this table is const and later in make_join_select
  this table is used for making&calculation const
  condition. As table record buffer is not populated
  it leads to crash.
  The fix is adding a check if an engine supports
  HA_STATS_RECORDS_IS_EXACT flag before updating
  join->const_table_map.
diff:
=== modified file 'sql/sql_select.cc'
--- sql/sql_select.cc	2010-03-14 16:01:45 +0000
+++ sql/sql_select.cc	2010-03-19 06:01:02 +0000
@@ -2943,7 +2943,8 @@
       s->quick=select->quick;
       s->needed_reg=select->needed_reg;
       select->quick=0;
-      if (records == 0 && s->table->reginfo.impossible_range)
+      if (records == 0 && s->table->reginfo.impossible_range &&
+          (s->table->file->ha_table_flags() & HA_STATS_RECORDS_IS_EXACT))
       {
 	/*
 	  Impossible WHERE or ON expression
=== modified file 'mysql-test/r/merge.result'
--- mysql-test/r/merge.result	2010-03-03 10:49:03 +0000
+++ mysql-test/r/merge.result	2010-03-19 06:01:02 +0000
@@ -2286,4 +2286,16 @@
 DROP TABLE m1;
 DROP TABLE `test@1`.`t@1`;
 DROP DATABASE `test@1`;
+#
+# Bug#51494c rash with join, explain and 'sounds like' operator
+#
+CREATE TABLE t1 (a INT) ENGINE=MYISAM;
+INSERT INTO t1 VALUES(1);
+CREATE TABLE t2 (b INT NOT NULL,c INT,d INT,e BLOB NOT NULL,
+KEY idx0 (d, c)) ENGINE=MERGE;
+EXPLAIN SELECT * FROM t1 NATURAL RIGHT JOIN
+t2 WHERE b SOUNDS LIKE e AND d = 1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+DROP TABLE t2, t1;
 End of 5.1 tests

=== modified file 'mysql-test/t/merge.test'
--- mysql-test/t/merge.test	2010-03-03 10:49:03 +0000
+++ mysql-test/t/merge.test	2010-03-19 06:01:02 +0000
@@ -1690,4 +1690,19 @@
 DROP TABLE `test@1`.`t@1`;
 DROP DATABASE `test@1`;
 
+--echo #
+--echo # Bug#51494c rash with join, explain and 'sounds like' operator
+--echo #
+
+CREATE TABLE t1 (a INT) ENGINE=MYISAM;
+INSERT INTO t1 VALUES(1);
+
+CREATE TABLE t2 (b INT NOT NULL,c INT,d INT,e BLOB NOT NULL,
+KEY idx0 (d, c)) ENGINE=MERGE;
+
+EXPLAIN SELECT * FROM t1 NATURAL RIGHT JOIN
+t2 WHERE b SOUNDS LIKE e AND d = 1;
+
+DROP TABLE t2, t1;
+
 --echo End of 5.1 tests