Bug #36011: server crash with explain extended on query

   with dependent subqueries
An IN subquery is executed on EXPLAIN when it's not correlated.
If the subquery required a temporary table for its execution
not all the internal structures were restored from pointing to
the items of the temporary table to point back to the items of
the subquery.
Fixed by restoring the ref array when a temp tables were used in
executing the IN subquery during EXPLAIN EXTENDED.


mysql-test/r/subselect.result:
  Bug #36011: test case
mysql-test/t/subselect.test:
  Bug #36011: test case
sql/sql_select.cc:
  Bug #36011: restore the ref array after execution 
  when there were temp tables.

mysql-test/r/subselect.result

@@ -4381,4 +4381,19 @@ t1.a= (select b from t2 limit 1) and not
 t1.a= (select a from t2 limit 1) ;
 a
 drop table t1, t2;
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2);
+EXPLAIN EXTENDED SELECT 1 FROM t1 WHERE 1 IN (SELECT 1 FROM t1 GROUP BY a);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
+2	DEPENDENT SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	Using temporary; Using filesort
+Warnings:
+Note	1003	select 1 AS `1` from `test`.`t1` where <in_optimizer>(1,<exists>(select 1 AS `1` from `test`.`t1` group by `test`.`t1`.`a` having (<cache>(1) = <ref_null_helper>(1))))
+EXPLAIN EXTENDED SELECT 1 FROM t1 WHERE 1 IN (SELECT 1 FROM t1 WHERE a > 3 GROUP BY a);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+2	DEPENDENT SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	Using where; Using temporary; Using filesort
+Warnings:
+Note	1003	select 1 AS `1` from `test`.`t1` where <in_optimizer>(1,<exists>(select 1 AS `1` from `test`.`t1` where (`test`.`t1`.`a` > 3) group by `test`.`t1`.`a` having (<cache>(1) = <ref_null_helper>(1))))
+DROP TABLE t1;
 End of 5.0 tests.

mysql-test/t/subselect.test

@@ -3271,5 +3271,16 @@ select t1.a from t1 where
 
 drop table t1, t2;
 
+#
+# Bug #36011: Server crash with explain extended on query with dependent
+# subqueries
+#
+
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2);
+EXPLAIN EXTENDED SELECT 1 FROM t1 WHERE 1 IN (SELECT 1 FROM t1 GROUP BY a);
+EXPLAIN EXTENDED SELECT 1 FROM t1 WHERE 1 IN (SELECT 1 FROM t1 WHERE a > 3 GROUP BY a);
+DROP TABLE t1;
+
 --echo End of 5.0 tests.
 

sql/sql_select.cc

@@ -2104,11 +2104,12 @@ JOIN::exec()
   /* 
     With EXPLAIN EXTENDED we have to restore original ref_array
     for a derived table which is always materialized.
+    We also need to do this when we have temp table(s).
     Otherwise we would not be able to print the query correctly.
   */ 
-  if (items0 &&
-      (thd->lex->describe & DESCRIBE_EXTENDED) &&
-      select_lex->linkage == DERIVED_TABLE_TYPE)      
+  if (items0 && (thd->lex->describe & DESCRIBE_EXTENDED) &&
+      (select_lex->linkage == DERIVED_TABLE_TYPE ||
+       exec_tmp_table1 || exec_tmp_table2))
     set_items_ref_array(items0);
 
   DBUG_VOID_RETURN;