Fixed LP bug #891995.

This bug in the function setup_semijoin_dups_elimination() could 
lead to invalid choice of the sequence of tables for which semi-join
duplicate elimination was applied.

mysql-test/r/subselect_sj_jcl6.result

@@ -2094,6 +2094,54 @@ a
 3
 set optimizer_switch=@save_optimizer_switch;
 drop table t0, t1, t2;
+#
+# Bug #891995: IN subquery with join_cache_level >= 3
+#
+CREATE TABLE t1 (a varchar(1));
+INSERT INTO t1 VALUES ('w'),('q');
+CREATE TABLE t2 (a int NOT NULL, b time, PRIMARY KEY (a));
+INSERT INTO t2 VALUES
+(2,'18:56:33'), (5,'19:11:10'), (3,'18:56:33'), (7,'19:11:10');
+CREATE TABLE t3 (
+a int NOT NULL, b int, c int, d varchar(1), PRIMARY KEY (a), KEY (d,c)
+);
+INSERT INTO t3 VALUES
+(25,158,10,'f'), (26,5,2,'v'), (27,163,103,'f'), (28,2,3,'q'), (29,8,6,'y');
+set @save_optimizer_switch=@@optimizer_switch;
+SET SESSION optimizer_switch='semijoin=on';
+SET SESSION optimizer_switch='join_cache_hashed=on';
+SET SESSION join_cache_level=3;
+EXPLAIN
+SELECT * FROM t1, t2
+WHERE t2.a IN (SELECT b FROM t3 WHERE t3.d <= t1.a);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	Start temporary
+1	PRIMARY	t3	ALL	d	NULL	NULL	NULL	5	Range checked for each record (index map: 0x2)
+1	PRIMARY	t2	hash_ALL	PRIMARY	#hash#PRIMARY	4	test.t3.b	4	End temporary; Using join buffer (flat, BNLH join)
+SELECT * FROM t1, t2
+WHERE t2.a IN (SELECT b FROM t3 WHERE t3.d <= t1.a);
+a	a	b
+w	2	18:56:33
+q	2	18:56:33
+w	5	19:11:10
+SET SESSION optimizer_switch='mrr=on';
+SET SESSION join_cache_level=6;
+EXPLAIN
+SELECT * FROM t1, t2
+WHERE t2.a IN (SELECT b FROM t3 WHERE t3.d <= t1.a);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	Start temporary
+1	PRIMARY	t3	ALL	d	NULL	NULL	NULL	5	Range checked for each record (index map: 0x2)
+1	PRIMARY	t2	eq_ref	PRIMARY	PRIMARY	4	test.t3.b	1	End temporary; Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan
+SELECT * FROM t1, t2
+WHERE t2.a IN (SELECT b FROM t3 WHERE t3.d <= t1.a);
+a	a	b
+w	2	18:56:33
+q	2	18:56:33
+w	5	19:11:10
+set optimizer_switch=@save_optimizer_switch;
+set join_cache_level=default;
+DROP TABLE t1,t2,t3;
 # End
 set join_cache_level=default;
 show variables like 'join_cache_level';

mysql-test/t/subselect_sj_jcl6.test

@@ -43,6 +43,48 @@ SELECT * FROM t0 WHERE t0.a IN
 set optimizer_switch=@save_optimizer_switch;
 drop table t0, t1, t2;
 
+--echo #
+--echo # Bug #891995: IN subquery with join_cache_level >= 3
+--echo #
+
+CREATE TABLE t1 (a varchar(1));
+INSERT INTO t1 VALUES ('w'),('q');
+
+CREATE TABLE t2 (a int NOT NULL, b time, PRIMARY KEY (a));
+INSERT INTO t2 VALUES
+  (2,'18:56:33'), (5,'19:11:10'), (3,'18:56:33'), (7,'19:11:10');
+
+CREATE TABLE t3 (
+  a int NOT NULL, b int, c int, d varchar(1), PRIMARY KEY (a), KEY (d,c)
+);
+INSERT INTO t3 VALUES
+  (25,158,10,'f'), (26,5,2,'v'), (27,163,103,'f'), (28,2,3,'q'), (29,8,6,'y');
+
+set @save_optimizer_switch=@@optimizer_switch;
+SET SESSION optimizer_switch='semijoin=on';
+
+SET SESSION optimizer_switch='join_cache_hashed=on';
+SET SESSION join_cache_level=3;
+EXPLAIN
+SELECT * FROM t1, t2
+  WHERE t2.a IN (SELECT b FROM t3 WHERE t3.d <= t1.a);
+SELECT * FROM t1, t2
+  WHERE t2.a IN (SELECT b FROM t3 WHERE t3.d <= t1.a);
+
+
+SET SESSION optimizer_switch='mrr=on';
+SET SESSION join_cache_level=6;
+EXPLAIN
+SELECT * FROM t1, t2
+  WHERE t2.a IN (SELECT b FROM t3 WHERE t3.d <= t1.a);
+SELECT * FROM t1, t2
+  WHERE t2.a IN (SELECT b FROM t3 WHERE t3.d <= t1.a);
+
+set optimizer_switch=@save_optimizer_switch;
+set join_cache_level=default;
+
+DROP TABLE t1,t2,t3;
+
 --echo # End
 
 set join_cache_level=default;

sql/opt_subselect.cc

@@ -3921,8 +3921,8 @@ int setup_semijoin_dups_elimination(JOIN *join, ulonglong options,
           if (j != join->const_tables && js_tab->use_quick != 2 &&
               j <= no_jbuf_after &&
               ((js_tab->type == JT_ALL && join_cache_level != 0) ||
-               (join_cache_level > 2 && (tab->type == JT_REF || 
-                                         tab->type == JT_EQ_REF))))
+               (join_cache_level > 2 && (js_tab->type == JT_REF || 
+                                         js_tab->type == JT_EQ_REF))))
           {
             /* Looks like we'll be using join buffer */
             first_table= join->const_tables;