BUG#20420: optimizer reports wrong keys on left join with IN

 When checking if an IN predicate can be evaluated using a key
 the optimizer makes sure that all the arguments of IN are of
 the same result type. To assure that it check whether 
 Item_func_in::array is filled in. 
 However Item_func_in::array is set if the types are
 the same AND all the arguments are compile time constants.
 Fixed by introducing Item_func_in::arg_types_compatible
 flag to allow correct checking of the desired condition.

mysql-test/r/func_in.result

@@ -351,6 +351,50 @@ some_id
 1
 2
 drop table t1;
+CREATE TABLE t1 (a int, b int, PRIMARY KEY (a));
+INSERT INTO t1 VALUES (1,1),(2,1),(3,1),(4,1),(5,1),(6,1);
+CREATE TABLE t2 (a int, b int, PRIMARY KEY (a));
+INSERT INTO t2 VALUES (3,2),(4,2),(100,100),(101,201),(102,102);
+CREATE TABLE t3 (a int PRIMARY KEY);
+INSERT INTO t3 VALUES (1),(2),(3),(4);
+CREATE TABLE t4 (a int PRIMARY KEY,b int);
+INSERT INTO t4 VALUES (1,1),(2,2),(1000,1000),(1001,1001),(1002,1002),
+(1003,1003),(1004,1004);
+EXPLAIN SELECT STRAIGHT_JOIN * FROM t3 
+JOIN t1 ON t3.a=t1.a 
+JOIN t2 ON t3.a=t2.a
+JOIN t4 WHERE t4.a IN (t1.b, t2.b);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t3	index	PRIMARY	PRIMARY	4	NULL	4	Using index
+1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t3.a	1	
+1	SIMPLE	t2	eq_ref	PRIMARY	PRIMARY	4	test.t3.a	1	
+1	SIMPLE	t4	ALL	PRIMARY	NULL	NULL	NULL	7	Range checked for each record (index map: 0x1)
+SELECT STRAIGHT_JOIN * FROM t3 
+JOIN t1 ON t3.a=t1.a 
+JOIN t2 ON t3.a=t2.a
+JOIN t4 WHERE t4.a IN (t1.b, t2.b);
+a	a	b	a	b	a	b
+3	3	1	3	2	1	1
+3	3	1	3	2	2	2
+4	4	1	4	2	1	1
+4	4	1	4	2	2	2
+EXPLAIN SELECT STRAIGHT_JOIN 
+(SELECT SUM(t4.a) FROM t4 WHERE t4.a IN (t1.b, t2.b)) 
+FROM t3, t1, t2
+WHERE t3.a=t1.a AND t3.a=t2.a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t3	index	PRIMARY	PRIMARY	4	NULL	4	Using index
+1	PRIMARY	t1	eq_ref	PRIMARY	PRIMARY	4	test.t3.a	1	
+1	PRIMARY	t2	eq_ref	PRIMARY	PRIMARY	4	test.t3.a	1	
+2	DEPENDENT SUBQUERY	t4	index	NULL	PRIMARY	4	NULL	7	Using where; Using index
+SELECT STRAIGHT_JOIN 
+(SELECT SUM(t4.a) FROM t4 WHERE t4.a IN (t1.b, t2.b)) 
+FROM t3, t1, t2
+WHERE t3.a=t1.a AND t3.a=t2.a;
+(SELECT SUM(t4.a) FROM t4 WHERE t4.a IN (t1.b, t2.b))
+3
+3
+DROP TABLE t1,t2,t3,t4;
 End of 5.0 tests
 create table t1(f1 char(1));
 insert into t1 values ('a'),('b'),('1');

mysql-test/t/func_in.test

@@ -254,44 +254,43 @@ select some_id from t1 where some_id not in(-4,-1,-4);
 select some_id from t1 where some_id not in(-4,-1,3423534,2342342);
 drop table t1;
 
-# TODO:Disabled until re-resolution of bug #20420 for 5.1.
-# Results must be the same as in 5.0
-##
-## BUG#20420: optimizer reports wrong keys on left join with IN
-##
-#CREATE TABLE t1 (a int, b int, PRIMARY KEY (a));
-#INSERT INTO t1 VALUES (1,1),(2,1),(3,1),(4,1),(5,1),(6,1);
 #
-#CREATE TABLE t2 (a int, b int, PRIMARY KEY (a));
-#INSERT INTO t2 VALUES (3,2),(4,2),(100,100),(101,201),(102,102);
+# BUG#20420: optimizer reports wrong keys on left join with IN
 #
-#CREATE TABLE t3 (a int PRIMARY KEY);
-#INSERT INTO t3 VALUES (1),(2),(3),(4);
-#
-#CREATE TABLE t4 (a int PRIMARY KEY,b int);
-#INSERT INTO t4 VALUES (1,1),(2,2),(1000,1000),(1001,1001),(1002,1002),(1003,1003),(1004,1004);
-#
-#EXPLAIN SELECT STRAIGHT_JOIN * FROM t3 
-#  JOIN t1 ON t3.a=t1.a 
-#  JOIN t2 ON t3.a=t2.a
-#  JOIN t4 WHERE t4.a IN (t1.b, t2.b);
-#
-#SELECT STRAIGHT_JOIN * FROM t3 
-#  JOIN t1 ON t3.a=t1.a 
-#  JOIN t2 ON t3.a=t2.a
-#  JOIN t4 WHERE t4.a IN (t1.b, t2.b);
-#
-#EXPLAIN SELECT STRAIGHT_JOIN 
-#   (SELECT SUM(t4.a) FROM t4 WHERE t4.a IN (t1.b, t2.b)) 
-#  FROM t3, t1, t2
-#  WHERE t3.a=t1.a AND t3.a=t2.a;
-#
-#SELECT STRAIGHT_JOIN 
-#   (SELECT SUM(t4.a) FROM t4 WHERE t4.a IN (t1.b, t2.b)) 
-#  FROM t3, t1, t2
-#  WHERE t3.a=t1.a AND t3.a=t2.a;
-#
-#DROP TABLE t1,t2,t3,t4;  
+CREATE TABLE t1 (a int, b int, PRIMARY KEY (a));
+INSERT INTO t1 VALUES (1,1),(2,1),(3,1),(4,1),(5,1),(6,1);
+
+CREATE TABLE t2 (a int, b int, PRIMARY KEY (a));
+INSERT INTO t2 VALUES (3,2),(4,2),(100,100),(101,201),(102,102);
+
+CREATE TABLE t3 (a int PRIMARY KEY);
+INSERT INTO t3 VALUES (1),(2),(3),(4);
+
+CREATE TABLE t4 (a int PRIMARY KEY,b int);
+INSERT INTO t4 VALUES (1,1),(2,2),(1000,1000),(1001,1001),(1002,1002),
+       (1003,1003),(1004,1004);
+
+EXPLAIN SELECT STRAIGHT_JOIN * FROM t3 
+  JOIN t1 ON t3.a=t1.a 
+  JOIN t2 ON t3.a=t2.a
+  JOIN t4 WHERE t4.a IN (t1.b, t2.b);
+
+SELECT STRAIGHT_JOIN * FROM t3 
+  JOIN t1 ON t3.a=t1.a 
+  JOIN t2 ON t3.a=t2.a
+  JOIN t4 WHERE t4.a IN (t1.b, t2.b);
+
+EXPLAIN SELECT STRAIGHT_JOIN 
+   (SELECT SUM(t4.a) FROM t4 WHERE t4.a IN (t1.b, t2.b)) 
+  FROM t3, t1, t2
+  WHERE t3.a=t1.a AND t3.a=t2.a;
+
+SELECT STRAIGHT_JOIN 
+   (SELECT SUM(t4.a) FROM t4 WHERE t4.a IN (t1.b, t2.b)) 
+  FROM t3, t1, t2
+  WHERE t3.a=t1.a AND t3.a=t2.a;
+
+DROP TABLE t1,t2,t3,t4;  
 
 --echo End of 5.0 tests
 

sql/item_cmpfunc.cc

@@ -2484,6 +2484,7 @@ void Item_func_in::fix_length_and_dec()
   THD *thd= current_thd;
   uint found_types= 0;
   uint type_cnt= 0, i;
+  Item_result cmp_type;
   left_result_type= args[0]->result_type();
   found_types= collect_cmp_types(args, arg_count);
   
@@ -2498,25 +2499,28 @@ void Item_func_in::fix_length_and_dec()
   for (i= 0; i <= (uint)DECIMAL_RESULT; i++)
   {
     if (found_types & 1 << i)
+    {
       (type_cnt)++;
+      cmp_type= (Item_result) i;
     }
+  }
+
+  if (type_cnt == 1)
+  {
+    if (cmp_type == STRING_RESULT && 
+        agg_arg_charsets(cmp_collation, args, arg_count, MY_COLL_CMP_CONV, 1))
+      return;
+    arg_types_compatible= TRUE;
+  }
+
   /*
     Row item with NULLs inside can return NULL or FALSE =>
     they can't be processed as static
   */
   if (type_cnt == 1 && const_itm && !nulls_in_row())
   {
-    uint tmp_type;
-    Item_result cmp_type;
-    /* Only one cmp type was found. Extract it here */
-    for (tmp_type= 0; found_types - 1; found_types>>= 1)
-      tmp_type++;
-    cmp_type= (Item_result)tmp_type;
-
     switch (cmp_type) {
     case STRING_RESULT:
-      if (agg_arg_charsets(cmp_collation, args, arg_count, MY_COLL_CMP_CONV, 1))
-        return;
       array=new in_string(arg_count - 1,(qsort2_cmp) srtcmp_in,
 			  cmp_collation.collation);
       break;

sql/item_cmpfunc.h

@@ -1041,12 +1041,18 @@ public:
   */
   in_vector *array;
   bool have_null;
+  /* 
+    true when all arguments of the IN clause are of compatible types
+    and can be used safely as comparisons for key conditions
+  */
+  bool arg_types_compatible;
   Item_result left_result_type;
   cmp_item *cmp_items[5]; /* One cmp_item for each result type */
   DTCollation cmp_collation;
 
   Item_func_in(List<Item> &list)
-    :Item_func_opt_neg(list), array(0), have_null(0)
+    :Item_func_opt_neg(list), array(0), have_null(0),
+    arg_types_compatible(FALSE)
   {
     bzero(&cmp_items, sizeof(cmp_items));
     allowed_arg_cols= 0;  // Fetch this value from first argument

sql/opt_range.cc

@@ -4928,7 +4928,7 @@ static SEL_TREE *get_func_mm_tree(RANGE_OPT_PARAM *param, Item_func *cond_func,
       type. Tree won't be built for values with different result types,
       so we check it here to avoid unnecessary work.
     */
-    if (!func->array)
+    if (!func->arg_types_compatible)
       break;     
 
     if (inv)