Fixed the bug mdev-12812.

This is another correction of the patch for bug mdev-12670.
If a derived table is merged into a select with STRAIGHT_JOIN
modifier all IN subquery predicates contained in the
specification of the derived table cannot be subject to
conversion to semi-joins.

mysql-test/r/derived_view.result

@@ -2617,5 +2617,26 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	ref	idx	idx	5	test.t1.a	140	Using index; FirstMatch(t1)
 drop view v1;
 drop table t1,t2;
+#
+# Bug mdev-12812: mergeable derived / view with subqueries
+#                 NOT subject to semi-join optimizations
+#
+CREATE TABLE t1 (c1 varchar(3)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES ('foo'),('foo');
+CREATE TABLE t2 (c2 varchar(3)) ENGINE=MyISAM;
+INSERT INTO t2 VALUES ('bar'),('qux'),('foo');
+SELECT STRAIGHT_JOIN * 
+FROM ( SELECT * FROM t1 WHERE c1 IN ( SELECT c2 FROM t2 ) ) AS sq;
+c1
+foo
+foo
+EXPLAIN EXTENDED SELECT STRAIGHT_JOIN * 
+FROM ( SELECT * FROM t1 WHERE c1 IN ( SELECT c2 FROM t2 ) ) AS sq;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+3	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
+Warnings:
+Note	1003	select straight_join `test`.`t1`.`c1` AS `c1` from `test`.`t1` where <in_optimizer>(`test`.`t1`.`c1`,<exists>(select `test`.`t2`.`c2` from `test`.`t2` where (<cache>(`test`.`t1`.`c1`) = `test`.`t2`.`c2`)))
+DROP TABLE t1, t2;
 set optimizer_switch=@exit_optimizer_switch;
 set join_cache_level=@exit_join_cache_level;

mysql-test/t/derived_view.test

@@ -1911,6 +1911,26 @@ explain select * from v1;
 drop view v1;
 drop table t1,t2;
 
+--echo #
+--echo # Bug mdev-12812: mergeable derived / view with subqueries
+--echo #                 NOT subject to semi-join optimizations
+--echo #
+
+CREATE TABLE t1 (c1 varchar(3)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES ('foo'),('foo');
+
+CREATE TABLE t2 (c2 varchar(3)) ENGINE=MyISAM;
+INSERT INTO t2 VALUES ('bar'),('qux'),('foo');
+
+let $q=
+SELECT STRAIGHT_JOIN * 
+  FROM ( SELECT * FROM t1 WHERE c1 IN ( SELECT c2 FROM t2 ) ) AS sq;
+
+eval $q;
+eval EXPLAIN EXTENDED $q;
+
+DROP TABLE t1, t2;
+
 # The following command must be the last one the file 
 set optimizer_switch=@exit_optimizer_switch;
 set join_cache_level=@exit_join_cache_level;

sql/opt_subselect.cc

@@ -1161,6 +1161,16 @@ bool convert_join_subqueries_to_semijoins(JOIN *join)
       in_subq->block_conversion_to_sj();
     }
   }
+
+  if (join->select_options & SELECT_STRAIGHT_JOIN)
+  {
+    /* Block conversion to semijoins for all candidates */ 
+    li.rewind();
+    while ((in_subq= li++))
+    {
+      in_subq->block_conversion_to_sj();
+    }
+  }
 
   li.rewind();
   /* First, convert child join's subqueries. We proceed bottom-up here */