Bug #44290: explain crashes for subquery with distinct in

            SQL_SELECT::test_quick_select

The crash was caused by an incomplete cleanup of JOIN_TAB::select
during the filesort of rows for GROUP BY clause inside a subquery.
Queries where a quick index access is replaced with filesort was
was affected. For example:

  SELECT 1 FROM
    (SELECT COUNT(DISTINCT c1) FROM t1
       WHERE c2 IN (1, 1) AND c3 = 2 GROUP BY c2) x

Quick index access related data in the SQL_SELECT::test_quick_select
function was inconsistent after an incomplete cleanup.
This function has been completed to prevent crashes in the
SQL_SELECT::test_quick_select function.

mysql-test/include/mix1.inc

@@ -1516,4 +1516,23 @@ DROP TABLE t1;
 # DROP TABLE t1;
 #
 
+--echo #
+--echo # Bug #44290: explain crashes for subquery with distinct in
+--echo #             SQL_SELECT::test_quick_select
+--echo #             (reproduced only with InnoDB tables)
+--echo #
+
+eval
+CREATE TABLE t1 (c1 INT, c2 INT, c3 INT, KEY (c3), KEY (c2, c3))
+  ENGINE=$engine_type;
+INSERT INTO t1 VALUES (1,1,1), (1,1,1), (1,1,2), (1,1,1), (1,1,2);
+
+SELECT 1 FROM (SELECT COUNT(DISTINCT c1) 
+                 FROM t1 WHERE c2 IN (1, 1) AND c3 = 2 GROUP BY c2) x;
+EXPLAIN 
+SELECT 1 FROM (SELECT COUNT(DISTINCT c1) 
+                 FROM t1 WHERE c2 IN (1, 1) AND c3 = 2 GROUP BY c2) x;
+
+DROP TABLE t1;
+
 --echo End of 5.1 tests

mysql-test/r/innodb_mysql.result

@@ -1687,6 +1687,25 @@ vid	tid	idx	name	type
 3	1	2	c1	NULL
 3	1	1	pk	NULL
 DROP TABLE t1;
+#
+# Bug #44290: explain crashes for subquery with distinct in
+#             SQL_SELECT::test_quick_select
+#             (reproduced only with InnoDB tables)
+#
+CREATE TABLE t1 (c1 INT, c2 INT, c3 INT, KEY (c3), KEY (c2, c3))
+ENGINE=InnoDB;
+INSERT INTO t1 VALUES (1,1,1), (1,1,1), (1,1,2), (1,1,1), (1,1,2);
+SELECT 1 FROM (SELECT COUNT(DISTINCT c1) 
+FROM t1 WHERE c2 IN (1, 1) AND c3 = 2 GROUP BY c2) x;
+1
+1
+EXPLAIN 
+SELECT 1 FROM (SELECT COUNT(DISTINCT c1) 
+FROM t1 WHERE c2 IN (1, 1) AND c3 = 2 GROUP BY c2) x;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	<derived2>	system	NULL	NULL	NULL	NULL	1	
+2	DERIVED	t1	index	c3,c2	c2	10	NULL	5	
+DROP TABLE t1;
 End of 5.1 tests
 drop table if exists t1, t2, t3;
 create table t1(a int);

sql/sql_select.cc

@@ -13481,6 +13481,7 @@ create_sort_index(THD *thd, JOIN *join, ORDER *order,
   {
     select->cleanup();				// filesort did select
     tab->select= 0;
+    table->quick_keys.clear_all();  // as far as we cleanup select->quick
   }
   tab->select_cond=0;
   tab->last_inner= 0;