Fixed LP bug #934342.

An outer join query with a semi-join subquery could return a wrong result
if the optimizer chose to materialize the subquery.
It happened because when substituting for the best field into a ref item
used to build access keys not all COND_EQUAL objects that could be employed
at substitution were checked.

Also refined some code in the function check_join_cache_usage to make it
safer. 

mysql-test/r/subselect_sj_jcl6.result

@@ -2753,6 +2753,86 @@ DROP table t1, t2;
 set @@optimizer_switch= @os_912513;
 set @@join_cache_level= @jcl_912513;
 # End
+#
+# BUG#934342: outer join + semijoin materialization 
+#             + join_cache_level > 2
+#
+CREATE TABLE t1 (a varchar(1), b varchar(1), INDEX idx_a(a) );
+INSERT INTO t1 VALUES ('v','v'), ('w','w'), ('t','t');
+CREATE TABLE t2 (c varchar(1), INDEX idx_c(c) );
+INSERT INTO t2 VALUES ('v'), ('v'), ('s'), ('j');
+CREATE TABLE t3 (c varchar(1), d varchar(1), INDEX idx_c(c) );
+INSERT INTO t3 VALUES ('v','v'), ('v','v'), ('s','s'), ('j','j');
+INSERT INTO t3 VALUES ('m','m'), ('d','d'), ('k','k'), ('m','m');
+set @tmp_otimizer_switch= @@optimizer_switch;
+set @tmp_join_cache_level=@@join_cache_level;
+set optimizer_switch = 'materialization=on,semijoin=on,join_cache_hashed=on';
+set join_cache_level=0;
+EXPLAIN
+SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
+WHERE (a, b) IN (SELECT a, b FROM t1 t);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	idx_a	NULL	NULL	NULL	3	
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	10	func,func	1	
+1	PRIMARY	t2	ref	idx_c	idx_c	4	test.t1.b	2	Using where; Using index
+2	MATERIALIZED	t	ALL	idx_a	NULL	NULL	NULL	3	
+SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
+WHERE (a, b) IN (SELECT a, b FROM t1 t);
+a	b	c
+v	v	v
+v	v	v
+w	w	NULL
+t	t	NULL
+EXPLAIN
+SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
+WHERE (a, b) IN (SELECT a, b FROM t1 t);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	idx_a	NULL	NULL	NULL	3	
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	10	func,func	1	
+1	PRIMARY	t3	ref	idx_c	idx_c	4	test.t1.b	2	Using where
+2	MATERIALIZED	t	ALL	idx_a	NULL	NULL	NULL	3	
+SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
+WHERE (a, b) IN (SELECT a, b FROM t1 t);
+a	b	c	d
+v	v	v	v
+v	v	v	v
+w	w	NULL	NULL
+t	t	NULL	NULL
+set join_cache_level=6;
+EXPLAIN
+SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
+WHERE (a, b) IN (SELECT a, b FROM t1 t);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	idx_a	NULL	NULL	NULL	3	
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	10	func,func	1	
+1	PRIMARY	t2	ref	idx_c	idx_c	4	test.t1.b	2	Using where; Using index
+2	MATERIALIZED	t	ALL	idx_a	NULL	NULL	NULL	3	
+SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
+WHERE (a, b) IN (SELECT a, b FROM t1 t);
+a	b	c
+v	v	v
+v	v	v
+w	w	NULL
+t	t	NULL
+EXPLAIN
+SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
+WHERE (a, b) IN (SELECT a, b FROM t1 t);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	idx_a	NULL	NULL	NULL	3	
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	10	func,func	1	
+1	PRIMARY	t3	ref	idx_c	idx_c	4	test.t1.b	2	Using where; Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan
+2	MATERIALIZED	t	ALL	idx_a	NULL	NULL	NULL	3	
+SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
+WHERE (a, b) IN (SELECT a, b FROM t1 t);
+a	b	c	d
+v	v	v	v
+v	v	v	v
+w	w	NULL	NULL
+t	t	NULL	NULL
+set optimizer_switch=@tmp_optimizer_switch;
+set join_cache_level=@tmp_join_cache_level;
+DROP TABLE t1,t2,t3;
+# End
 set join_cache_level=default;
 show variables like 'join_cache_level';
 Variable_name	Value

mysql-test/t/subselect_sj_jcl6.test

@@ -116,6 +116,60 @@ set @@join_cache_level= @jcl_912513;
 
 --echo # End
 
+--echo #
+--echo # BUG#934342: outer join + semijoin materialization 
+--echo #             + join_cache_level > 2
+--echo #
+
+CREATE TABLE t1 (a varchar(1), b varchar(1), INDEX idx_a(a) );
+INSERT INTO t1 VALUES ('v','v'), ('w','w'), ('t','t');
+
+CREATE TABLE t2 (c varchar(1), INDEX idx_c(c) );
+INSERT INTO t2 VALUES ('v'), ('v'), ('s'), ('j');
+
+CREATE TABLE t3 (c varchar(1), d varchar(1), INDEX idx_c(c) );
+INSERT INTO t3 VALUES ('v','v'), ('v','v'), ('s','s'), ('j','j');
+INSERT INTO t3 VALUES ('m','m'), ('d','d'), ('k','k'), ('m','m');
+
+set @tmp_otimizer_switch= @@optimizer_switch;
+set @tmp_join_cache_level=@@join_cache_level;
+set optimizer_switch = 'materialization=on,semijoin=on,join_cache_hashed=on';
+
+set join_cache_level=0;
+
+EXPLAIN
+SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
+  WHERE (a, b) IN (SELECT a, b FROM t1 t);
+SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
+  WHERE (a, b) IN (SELECT a, b FROM t1 t);
+
+EXPLAIN
+SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
+  WHERE (a, b) IN (SELECT a, b FROM t1 t);
+SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
+  WHERE (a, b) IN (SELECT a, b FROM t1 t);
+
+set join_cache_level=6;
+
+EXPLAIN
+SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
+  WHERE (a, b) IN (SELECT a, b FROM t1 t);
+SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
+  WHERE (a, b) IN (SELECT a, b FROM t1 t);
+
+EXPLAIN
+SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
+  WHERE (a, b) IN (SELECT a, b FROM t1 t);
+SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
+  WHERE (a, b) IN (SELECT a, b FROM t1 t);
+
+set optimizer_switch=@tmp_optimizer_switch;
+set join_cache_level=@tmp_join_cache_level;
+
+DROP TABLE t1,t2,t3;
+
+--echo # End
+
 set join_cache_level=default;
 show variables like 'join_cache_level';
 

sql/sql_select.cc

@@ -1266,9 +1266,20 @@ JOIN::optimize()
       Item *ref_item= *ref_item_ptr;
       if (!ref_item->used_tables() && !(select_options & SELECT_DESCRIBE))
         continue;
-      COND_EQUAL *equals= tab->first_inner ? tab->first_inner->cond_equal : 
-                                             cond_equal;
-      ref_item= substitute_for_best_equal_field(tab, ref_item, equals, map2table);
+      COND_EQUAL *equals= cond_equal;
+      JOIN_TAB *first_inner= tab->first_inner;
+      while (equals)
+      {
+        ref_item= substitute_for_best_equal_field(tab, ref_item,
+                                                  equals, map2table);
+        if (first_inner)
+	{
+          equals= first_inner->cond_equal;
+          first_inner= first_inner->first_upper;
+        }
+        else
+          equals= 0;
+      }  
       ref_item->update_used_tables();
       if (*ref_item_ptr != ref_item)
       {
@@ -9213,7 +9224,7 @@ uint check_join_cache_usage(JOIN_TAB *tab,
       Check whether table tab and the previous one belong to the same nest of
       inner tables and if so do not use join buffer when joining table tab. 
     */
-    if (tab->first_inner)
+    if (tab->first_inner && tab != tab->first_inner)
     {
       for (JOIN_TAB *first_inner= tab[-1].first_inner;
            first_inner;
@@ -9223,7 +9234,7 @@ uint check_join_cache_usage(JOIN_TAB *tab,
           goto no_join_cache;
       }
     }
-    else if (tab->first_sj_inner_tab &&
+    else if (tab->first_sj_inner_tab && tab != tab->first_sj_inner_tab &&
              tab->first_sj_inner_tab == tab[-1].first_sj_inner_tab)
       goto no_join_cache; 
   }