Bug #47106: Crash / segfault on adding EXPLAIN to a non-crashing

 query
      
The fix for bug 46749 removed the check for OUTER_REF_TABLE_BIT 
and substituted it for a check on the presence of 
Item_ident::depended_from.
Removing it altogether was wrong : OUTER_REF_TABLE_BIT should 
still be checked in addition to depended_from (because it's not 
set in all cases and doesn't contradict to the check of depended_from).
Fixed by returning the old condition back as a compliment to the 
new one.

mysql-test/r/subselect4.result

@@ -27,4 +27,35 @@ SELECT 1;
 1
 1
 DROP TABLE t1,t2,t3;
+#
+# Bug #47106: Crash / segfault on adding EXPLAIN to a non-crashing 
+# query
+#
+CREATE TABLE t1 (
+a INT,
+b INT,
+PRIMARY KEY (a),
+KEY b (b)
+);
+INSERT INTO t1 VALUES (1, 1), (2, 1);
+CREATE TABLE t2 LIKE t1;
+INSERT INTO t2 SELECT * FROM t1;
+CREATE TABLE t3 LIKE t1;
+INSERT INTO t3 SELECT * FROM t1;
+# Should not crash.
+# Should have 1 impossible where and 2 dependent subqs.
+EXPLAIN
+SELECT
+(SELECT 1 FROM t1,t2 WHERE t2.b > t3.b)
+FROM t3 WHERE 1 = 0 GROUP BY 1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+2	DEPENDENT SUBQUERY	t1	index	NULL	PRIMARY	4	NULL	2	Using index
+2	DEPENDENT SUBQUERY	t2	index	b	b	5	NULL	2	Using where; Using index
+# should return 0 rows
+SELECT
+(SELECT 1 FROM t1,t2 WHERE t2.b > t3.b)
+FROM t3 WHERE 1 = 0 GROUP BY 1;
+(SELECT 1 FROM t1,t2 WHERE t2.b > t3.b)
+DROP TABLE t1,t2,t3;
 End of 5.0 tests.

mysql-test/t/subselect4.test

@@ -28,5 +28,37 @@ SELECT 1;
 
 DROP TABLE t1,t2,t3;
 
+--echo #
+--echo # Bug #47106: Crash / segfault on adding EXPLAIN to a non-crashing 
+--echo # query
+--echo #
+
+CREATE TABLE t1 (
+  a INT,
+  b INT,
+  PRIMARY KEY (a),
+  KEY b (b)
+);
+INSERT INTO t1 VALUES (1, 1), (2, 1);
+
+CREATE TABLE t2 LIKE t1;
+INSERT INTO t2 SELECT * FROM t1;
+
+CREATE TABLE t3 LIKE t1;
+INSERT INTO t3 SELECT * FROM t1;
+
+--echo # Should not crash.
+--echo # Should have 1 impossible where and 2 dependent subqs.
+EXPLAIN
+SELECT
+  (SELECT 1 FROM t1,t2 WHERE t2.b > t3.b)
+FROM t3 WHERE 1 = 0 GROUP BY 1;
+
+--echo # should return 0 rows
+SELECT
+  (SELECT 1 FROM t1,t2 WHERE t2.b > t3.b)
+FROM t3 WHERE 1 = 0 GROUP BY 1;
+
+DROP TABLE t1,t2,t3;
 
 --echo End of 5.0 tests.

sql/sql_select.cc

@@ -3216,12 +3216,12 @@ add_key_equal_fields(KEY_FIELD **key_fields, uint and_level,
      @retval FALSE  it's something else
 */
 
-inline static bool
+static bool
 is_local_field (Item *field)
 {
-  field= field->real_item();
-  return field->type() == Item::FIELD_ITEM && 
-    !((Item_field *)field)->depended_from;
+  return field->real_item()->type() == Item::FIELD_ITEM
+    && !(field->used_tables() & OUTER_REF_TABLE_BIT)
+    && !((Item_field *)field->real_item())->depended_from;
 }