MDEV-14779: using left join causes incorrect results with materialization and derived tables

Conversion of a subquery to a semi-join is blocked when we have an
IN subquery predicate in the on_expr of an outer join. Currently this
scenario is handled but the cases when an IN subquery predicate is wrapped
inside a Item_in_optimizer item then this blocking is not done.

mysql-test/r/join_outer.result

@@ -2346,11 +2346,27 @@ CREATE TABLE t1 (b1 BIT NOT NULL);
 INSERT INTO t1 VALUES (0),(1);
 CREATE TABLE t2 (b2 BIT NOT NULL);
 INSERT INTO t2 VALUES (0),(1);
-SET SESSION JOIN_CACHE_LEVEL = 3;
+set @save_join_cache_level= @@join_cache_level;
+SET  @@join_cache_level = 3;
 SELECT t1.b1+'0' , t2.b2 + '0' FROM t1 LEFT JOIN t2 ON b1 = b2;
 t1.b1+'0'	t2.b2 + '0'
 0	0
 1	1
 DROP TABLE t1, t2;
+set @join_cache_level= @save_join_cache_level;
+#
+# MDEV-14779: using left join causes incorrect results with materialization and derived tables
+#
+create table t1(id  int);
+insert into t1 values (1),(2);
+create table t2(sid int, id int);
+insert into t2 values (1,1),(2,2);
+select * from t1 t
+left join (select * from t2 where sid in (select max(sid) from t2 where 0=1 group by id)) r
+on t.id=r.id ;
+id	sid	id
+1	NULL	NULL
+2	NULL	NULL
+drop table t1, t2;
 # end of 5.5 tests
 SET optimizer_switch=@save_optimizer_switch;

mysql-test/r/join_outer_jcl6.result

@@ -2357,12 +2357,28 @@ CREATE TABLE t1 (b1 BIT NOT NULL);
 INSERT INTO t1 VALUES (0),(1);
 CREATE TABLE t2 (b2 BIT NOT NULL);
 INSERT INTO t2 VALUES (0),(1);
-SET SESSION JOIN_CACHE_LEVEL = 3;
+set @save_join_cache_level= @@join_cache_level;
+SET  @@join_cache_level = 3;
 SELECT t1.b1+'0' , t2.b2 + '0' FROM t1 LEFT JOIN t2 ON b1 = b2;
 t1.b1+'0'	t2.b2 + '0'
 0	0
 1	1
 DROP TABLE t1, t2;
+set @join_cache_level= @save_join_cache_level;
+#
+# MDEV-14779: using left join causes incorrect results with materialization and derived tables
+#
+create table t1(id  int);
+insert into t1 values (1),(2);
+create table t2(sid int, id int);
+insert into t2 values (1,1),(2,2);
+select * from t1 t
+left join (select * from t2 where sid in (select max(sid) from t2 where 0=1 group by id)) r
+on t.id=r.id ;
+id	sid	id
+1	NULL	NULL
+2	NULL	NULL
+drop table t1, t2;
 # end of 5.5 tests
 SET optimizer_switch=@save_optimizer_switch;
 set join_cache_level=default;

mysql-test/t/join_outer.test

@@ -1891,9 +1891,25 @@ INSERT INTO t1 VALUES (0),(1);
 CREATE TABLE t2 (b2 BIT NOT NULL);
 INSERT INTO t2 VALUES (0),(1);
 
-SET SESSION JOIN_CACHE_LEVEL = 3;
+set @save_join_cache_level= @@join_cache_level;
+SET  @@join_cache_level = 3;
 SELECT t1.b1+'0' , t2.b2 + '0' FROM t1 LEFT JOIN t2 ON b1 = b2;
 DROP TABLE t1, t2;
+set @join_cache_level= @save_join_cache_level;
+
+--echo #
+--echo # MDEV-14779: using left join causes incorrect results with materialization and derived tables
+--echo #
+
+create table t1(id  int);
+insert into t1 values (1),(2);
+create table t2(sid int, id int);
+insert into t2 values (1,1),(2,2);
+
+select * from t1 t
+ left join (select * from t2 where sid in (select max(sid) from t2 where 0=1 group by id)) r
+ on t.id=r.id ;
+drop table t1, t2;
 
 --echo # end of 5.5 tests
 

sql/item_cmpfunc.h

@@ -255,6 +255,7 @@ class Item_in_optimizer: public Item_bool_func
   bool is_null();
   longlong val_int();
   void cleanup();
+  enum Functype functype() const   { return IN_OPTIMIZER_FUNC; }
   const char *func_name() const { return "<in_optimizer>"; }
   Item_cache **get_cache() { return &cache; }
   void keep_top_level_cache();
@@ -270,6 +271,10 @@ class Item_in_optimizer: public Item_bool_func
   void fix_after_pullout(st_select_lex *new_parent, Item **ref);
   virtual void print(String *str, enum_query_type query_type);
   void restore_first_argument();
+  Item* get_wrapped_in_subselect_item()
+  {
+    return args[1];
+  }
 };
 
 class Comp_creator

sql/item_func.h

@@ -66,7 +66,7 @@ class Item_func :public Item_result_field
                   NOW_FUNC, TRIG_COND_FUNC,
                   SUSERVAR_FUNC, GUSERVAR_FUNC, COLLATE_FUNC,
                   EXTRACT_FUNC, CHAR_TYPECAST_FUNC, FUNC_SP, UDF_FUNC,
-                  NEG_FUNC, GSYSVAR_FUNC };
+                  NEG_FUNC, GSYSVAR_FUNC, IN_OPTIMIZER_FUNC };
   enum optimize_type { OPTIMIZE_NONE,OPTIMIZE_KEY,OPTIMIZE_OP, OPTIMIZE_NULL,
                        OPTIMIZE_EQUAL };
   enum Type type() const { return FUNC_ITEM; }

sql/opt_subselect.cc

@@ -1006,6 +1006,10 @@ bool check_for_outer_joins(List<TABLE_LIST> *join_list)
 void find_and_block_conversion_to_sj(Item *to_find,
 				     List_iterator_fast<Item_in_subselect> &li)
 {
+  if (to_find->type() == Item::FUNC_ITEM &&
+     ((Item_func*)to_find)->functype() == Item_func::IN_OPTIMIZER_FUNC)
+    to_find= ((Item_in_optimizer*)to_find)->get_wrapped_in_subselect_item();
+
   if (to_find->type() != Item::SUBSELECT_ITEM ||
       ((Item_subselect *) to_find)->substype() != Item_subselect::IN_SUBS)
     return;