BUG#978479: Wrong result (extra rows) with derived_with_keys+loosescan+semijoin=ON, materialization=OFF

Part#1: make EXPLAIN's plan match the one by actual execution: 
Item_subselect::used_tables() should return the same value irrespectively 
of whether we're running an EXPLAIN or a SELECT.

1 files changed, 27 insertions, 0 deletions

diff --git a/mysql-test/r/subselect_sj_jcl6.result b/mysql-test/r/subselect_sj_jcl6.result
index 704cde2afd2..454e0e36ed7 100644
--- a/mysql-test/r/subselect_sj_jcl6.result
+++ b/mysql-test/r/subselect_sj_jcl6.result
@@ -2675,6 +2675,33 @@ a
 DEALLOCATE PREPARE pstmt;
 DROP VIEW v1;
 DROP TABLE t1, t2;
+#
+# BUG#978479: Wrong result (extra rows) with derived_with_keys+loosescan+semijoin=ON, materialization=OFF
+#
+set @tmp_jcl_978479= @@join_cache_level;
+set join_cache_level=0;
+set @tmp_os_978479= @@optimizer_switch;
+set optimizer_switch = 'derived_with_keys=on,loosescan=on,semijoin=on,materialization=off';
+# Part#1: make sure EXPLAIN is using LooseScan:
+CREATE TABLE t1 ( a INT, b INT );
+INSERT INTO t1 VALUES
+(4,0),(6,8),(3,1),(5,8),(3,9),(2,4),
+(2,6),(9,1),(5,4),(7,7),(5,4);
+CREATE ALGORITHM=TEMPTABLE
+VIEW v1 AS SELECT * FROM t1;
+# This will use LooseScan:
+EXPLAIN
+SELECT * FROM t1 AS t1_1, t1 AS t1_2
+WHERE (t1_1.a, t1_2.a) IN ( SELECT a, b FROM v1 );
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1	ALL	NULL	NULL	NULL	NULL	11	
+1	PRIMARY	<derived3>	ALL	NULL	NULL	NULL	NULL	11	Using where; LooseScan
+1	PRIMARY	t1_2	ALL	NULL	NULL	NULL	NULL	11	Using where
+3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	11	
+DROP VIEW v1;
+DROP TABLE t1;
+set @@join_cache_level= @tmp_jcl_978479;
+set @@optimizer_switch= @tmp_os_978479;
 set optimizer_switch=@subselect_sj_tmp;
 #
 # BUG#49129: Wrong result with IN-subquery with join_cache_level=6 and firstmatch=off