MDEV-16225: wrong resultset from query with semijoin=on

For non-semi-join subquery optimization we do a cost based decision between
Materialisation and IN -> EXIST transformation. The issue in this case is that for IN->EXIST transformation
we run JOIN::reoptimize with the IN->EXISt conditions and we come up with a new query plan. But when we compare
the cost with Materialization, we make the decision to chose Materialization so we need to restore the query plan
for Materilization.
The saving and restoring for keyuse array and join_tab keyuse is only done when we have atleast
one element in the keyuse_array , we are now changing to do it even for 0 elements to main the generality.

mysql-test/r/subselect_sj2_mat.result

@@ -1601,3 +1601,60 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	11	func	1	
 2	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	3	Using where
 DROP TABLE t1,t2;
+#
+# MDEV-16225: wrong resultset from query with semijoin=on
+#
+CREATE TABLE t1 (
+`id` int(10)  NOT NULL AUTO_INCREMENT,
+`local_name` varchar(64) NOT NULL,
+PRIMARY KEY (`id`)
+) ENGINE=InnoDB AUTO_INCREMENT=14 DEFAULT CHARSET=latin1;
+insert  into t1(`id`,`local_name`) values
+(1,'Cash Advance'),
+(2,'Cash Advance'),
+(3,'Rollover'),
+(4,'AL Installment'),
+(5,'AL Installment'),
+(6,'AL Installment'),
+(7,'AL Installment'),
+(8,'AL Installment'),
+(9,'AL Installment'),
+(10,'Internet Payday'),
+(11,'Rollover - Internet Payday'),
+(12,'AL Monthly Installment'),
+(13,'AL Semi-Monthly Installment');
+explain
+SELECT SQL_NO_CACHE t.id
+FROM t1 t
+WHERE (
+t.id IN (SELECT A.id FROM t1 AS A WHERE A.local_name IN (SELECT B.local_name FROM t1 AS B WHERE B.id IN (0,4,12,13,1,10,3,11)))
+OR
+(t.id IN (0,4,12,13,1,10,3,11))
+);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t	index	PRIMARY	PRIMARY	4	NULL	13	Using where; Using index
+2	MATERIALIZED	<subquery3>	ALL	distinct_key	NULL	NULL	NULL	8	
+2	MATERIALIZED	A	ALL	PRIMARY	NULL	NULL	NULL	13	Using where; Using join buffer (flat, BNL join)
+3	MATERIALIZED	B	ALL	PRIMARY	NULL	NULL	NULL	13	Using where
+SELECT SQL_NO_CACHE t.id
+FROM t1 t
+WHERE (
+t.id IN (SELECT A.id FROM t1 AS A WHERE A.local_name IN (SELECT B.local_name FROM t1 AS B WHERE B.id IN (0,4,12,13,1,10,3,11)))
+OR
+(t.id IN (0,4,12,13,1,10,3,11))
+);
+id
+1
+2
+3
+4
+5
+6
+7
+8
+9
+10
+11
+12
+13
+drop table t1;

mysql-test/t/subselect_sj2_mat.test

@@ -303,3 +303,45 @@ eval $q;
 eval explain $q;
 
 DROP TABLE t1,t2;
+
+--echo #
+--echo # MDEV-16225: wrong resultset from query with semijoin=on
+--echo #
+
+CREATE TABLE t1 (
+  `id` int(10)  NOT NULL AUTO_INCREMENT,
+  `local_name` varchar(64) NOT NULL,
+  PRIMARY KEY (`id`)
+) ENGINE=InnoDB AUTO_INCREMENT=14 DEFAULT CHARSET=latin1;
+
+insert  into t1(`id`,`local_name`) values
+(1,'Cash Advance'),
+(2,'Cash Advance'),
+(3,'Rollover'),
+(4,'AL Installment'),
+(5,'AL Installment'),
+(6,'AL Installment'),
+(7,'AL Installment'),
+(8,'AL Installment'),
+(9,'AL Installment'),
+(10,'Internet Payday'),
+(11,'Rollover - Internet Payday'),
+(12,'AL Monthly Installment'),
+(13,'AL Semi-Monthly Installment');
+
+explain
+SELECT SQL_NO_CACHE t.id
+FROM t1 t
+WHERE (
+        t.id IN (SELECT A.id FROM t1 AS A WHERE A.local_name IN (SELECT B.local_name FROM t1 AS B WHERE B.id IN (0,4,12,13,1,10,3,11)))
+        OR
+        (t.id IN (0,4,12,13,1,10,3,11))
+);
+SELECT SQL_NO_CACHE t.id
+FROM t1 t
+WHERE (
+        t.id IN (SELECT A.id FROM t1 AS A WHERE A.local_name IN (SELECT B.local_name FROM t1 AS B WHERE B.id IN (0,4,12,13,1,10,3,11)))
+        OR
+        (t.id IN (0,4,12,13,1,10,3,11))
+);
+drop table t1;

sql/sql_select.cc

@@ -23739,21 +23739,18 @@ void JOIN::set_allowed_join_cache_types()
 
 void JOIN::save_query_plan(Join_plan_state *save_to)
 {
-  if (keyuse.elements)
-  {
-    DYNAMIC_ARRAY tmp_keyuse;
-    /* Swap the current and the backup keyuse internal arrays. */
-    tmp_keyuse= keyuse;
-    keyuse= save_to->keyuse; /* keyuse is reset to an empty array. */
-    save_to->keyuse= tmp_keyuse;
+  DYNAMIC_ARRAY tmp_keyuse;
+  /* Swap the current and the backup keyuse internal arrays. */
+  tmp_keyuse= keyuse;
+  keyuse= save_to->keyuse; /* keyuse is reset to an empty array. */
+  save_to->keyuse= tmp_keyuse;
 
-    for (uint i= 0; i < table_count; i++)
-    {
-      save_to->join_tab_keyuse[i]= join_tab[i].keyuse;
-      join_tab[i].keyuse= NULL;
-      save_to->join_tab_checked_keys[i]= join_tab[i].checked_keys;
-      join_tab[i].checked_keys.clear_all();
-    }
+  for (uint i= 0; i < table_count; i++)
+  {
+    save_to->join_tab_keyuse[i]= join_tab[i].keyuse;
+    join_tab[i].keyuse= NULL;
+    save_to->join_tab_checked_keys[i]= join_tab[i].checked_keys;
+    join_tab[i].checked_keys.clear_all();
   }
   memcpy((uchar*) save_to->best_positions, (uchar*) best_positions,
          sizeof(POSITION) * (table_count + 1));
@@ -23791,20 +23788,17 @@ void JOIN::reset_query_plan()
 
 void JOIN::restore_query_plan(Join_plan_state *restore_from)
 {
-  if (restore_from->keyuse.elements)
-  {
-    DYNAMIC_ARRAY tmp_keyuse;
-    tmp_keyuse= keyuse;
-    keyuse= restore_from->keyuse;
-    restore_from->keyuse= tmp_keyuse;
-
-    for (uint i= 0; i < table_count; i++)
-    {
-      join_tab[i].keyuse= restore_from->join_tab_keyuse[i];
-      join_tab[i].checked_keys= restore_from->join_tab_checked_keys[i];
-    }
+  DYNAMIC_ARRAY tmp_keyuse;
+  tmp_keyuse= keyuse;
+  keyuse= restore_from->keyuse;
+  restore_from->keyuse= tmp_keyuse;
 
+  for (uint i= 0; i < table_count; i++)
+  {
+    join_tab[i].keyuse= restore_from->join_tab_keyuse[i];
+    join_tab[i].checked_keys= restore_from->join_tab_checked_keys[i];
   }
+
   memcpy((uchar*) best_positions, (uchar*) restore_from->best_positions,
          sizeof(POSITION) * (table_count + 1));
   /* Restore SJM nests */