Bug#50402 Optimizer producing wrong results when using Index Merge on InnoDB

Subselect executes twice, at JOIN::optimize stage
and at JOIN::execute stage. At optimize stage
Innodb prebuilt struct which is used for the
retrieval of column values is initialized in.
ha_innobase::index_read(), prebuilt->sql_stat_start is true.
After QUICK_ROR_INTERSECT_SELECT finished his job it
restores read_set/write_set bitmaps with initial values
and deactivates one of the handlers used by
QUICK_ROR_INTERSECT_SELECT in JOIN::cleanup
(it's the case when we reuse original handler as one of
 handlers required by QUICK_ROR_INTERSECT_SELECT object).
On second subselect execution inactive handler is activated
in  QUICK_RANGE_SELECT::reset, file->ha_index_init().
In ha_index_init Innodb prebuilt struct is reinitialized
with inappropriate read_set/write_set bitmaps. Further
reinitialization in ha_innobase::index_read() does not
happen as prebuilt->sql_stat_start is false.
It leads to partial retrieval of required field values
and we get a mix of field values from different records
in the record buffer.
The fix is to reset
read_set/write_set bitmaps as these values
are required for proper intialization of
internal InnoDB struct which is used for
the retrieval of column values
(see build_template(), ha_innodb.cc)

mysql-test/include/index_merge_ror_cpk.inc

@@ -126,3 +126,19 @@ WHERE
 
 drop table t1;
 
+--echo #
+--echo # Bug#50402 Optimizer producing wrong results when using Index Merge on InnoDB
+--echo #
+CREATE TABLE t1 (f1 INT, PRIMARY KEY (f1));
+INSERT INTO t1 VALUES (2);
+CREATE TABLE t2 (f1 INT, f2 INT, f3 char(1),
+                 PRIMARY KEY (f1), KEY (f2), KEY (f3) );
+INSERT INTO t2 VALUES (1, 1, 'h'), (2, 3, 'h'), (3, 2, ''), (4, 2, '');
+
+SELECT t1.f1 FROM t1
+WHERE (SELECT COUNT(*) FROM t2 WHERE t2.f3 = 'h' AND t2.f2 = t1.f1) = 0 AND t1.f1 = 2;
+
+EXPLAIN SELECT t1.f1 FROM t1
+WHERE (SELECT COUNT(*) FROM t2 WHERE t2.f3 = 'h' AND t2.f2 = t1.f1) = 0 AND t1.f1 = 2;
+
+DROP TABLE t1,t2;

mysql-test/r/index_merge_innodb.result

@@ -581,3 +581,21 @@ WHERE
 `RUNID`= '' AND `SUBMITNR`= '' AND `ORDERNR`='' AND `PROGRAMM`='' AND
 `TESTID`='' AND `UCCHECK`='';
 drop table t1;
+#
+# Bug#50402 Optimizer producing wrong results when using Index Merge on InnoDB
+#
+CREATE TABLE t1 (f1 INT, PRIMARY KEY (f1));
+INSERT INTO t1 VALUES (2);
+CREATE TABLE t2 (f1 INT, f2 INT, f3 char(1),
+PRIMARY KEY (f1), KEY (f2), KEY (f3) );
+INSERT INTO t2 VALUES (1, 1, 'h'), (2, 3, 'h'), (3, 2, ''), (4, 2, '');
+SELECT t1.f1 FROM t1
+WHERE (SELECT COUNT(*) FROM t2 WHERE t2.f3 = 'h' AND t2.f2 = t1.f1) = 0 AND t1.f1 = 2;
+f1
+2
+EXPLAIN SELECT t1.f1 FROM t1
+WHERE (SELECT COUNT(*) FROM t2 WHERE t2.f3 = 'h' AND t2.f2 = t1.f1) = 0 AND t1.f1 = 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	const	PRIMARY	PRIMARY	4	const	1	Using index
+2	DEPENDENT SUBQUERY	t2	index_merge	f2,f3	f3,f2	2,5	NULL	1	Using intersect(f3,f2); Using where; Using index
+DROP TABLE t1,t2;

mysql-test/r/index_merge_myisam.result

@@ -1416,6 +1416,24 @@ WHERE
 `TESTID`='' AND `UCCHECK`='';
 drop table t1;
 #
+# Bug#50402 Optimizer producing wrong results when using Index Merge on InnoDB
+#
+CREATE TABLE t1 (f1 INT, PRIMARY KEY (f1));
+INSERT INTO t1 VALUES (2);
+CREATE TABLE t2 (f1 INT, f2 INT, f3 char(1),
+PRIMARY KEY (f1), KEY (f2), KEY (f3) );
+INSERT INTO t2 VALUES (1, 1, 'h'), (2, 3, 'h'), (3, 2, ''), (4, 2, '');
+SELECT t1.f1 FROM t1
+WHERE (SELECT COUNT(*) FROM t2 WHERE t2.f3 = 'h' AND t2.f2 = t1.f1) = 0 AND t1.f1 = 2;
+f1
+2
+EXPLAIN SELECT t1.f1 FROM t1
+WHERE (SELECT COUNT(*) FROM t2 WHERE t2.f3 = 'h' AND t2.f2 = t1.f1) = 0 AND t1.f1 = 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	system	PRIMARY	NULL	NULL	NULL	1	
+2	DEPENDENT SUBQUERY	t2	ref	f2,f3	f2	5		1	Using where
+DROP TABLE t1,t2;
+#
 # Generic @@optimizer_switch tests (move those into a separate file if
 #  we get another @@optimizer_switch user)
 #

sql/opt_range.cc

@@ -8451,9 +8451,14 @@ int QUICK_RANGE_SELECT::reset()
   in_range= FALSE;
   cur_range= (QUICK_RANGE**) ranges.buffer;
 
-  if (file->inited == handler::NONE && (error= file->ha_index_init(index,1)))
-    DBUG_RETURN(error);
- 
+  if (file->inited == handler::NONE)
+  {
+    if (in_ror_merged_scan)
+      head->column_bitmaps_set_no_signal(&column_bitmap, &column_bitmap);
+    if ((error= file->ha_index_init(index,1)))
+        DBUG_RETURN(error);
+  }
+
   /* Do not allocate the buffers twice. */
   if (multi_range_length)
   {