MDEV-13784: query causes seg fault

When we have a nested subquery then a subquery that was a dependent subquery
may change to an independent one when we optimizer the inner subqueries.
This is handled st_select_lex::optimize_unflattened_subqueries.
Currently a subquery that was changed to independent from dependent after optimization
phase incorrectly shows dependent in the output of Explain, this happens because we
don't update used_tables for the WHERE clause, ON clause, etc after the optimization phase.

mysql-test/r/subselect_exists2in.result

@@ -330,7 +330,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 3	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
 Warnings:
 Note	1276	Field or reference 'test.t2.b' of SELECT #3 was resolved in SELECT #2
-Note	1003	select (select 1 from dual where (not(((1 is not null) and <in_optimizer>(1,1 in ( <materialize> (select `test`.`t3`.`c` from `test`.`t3` where (`test`.`t3`.`c` is not null) ), <primary_index_lookup>(1 in <temporary table> on distinct_key where ((1 = `<subquery3>`.`c`))))))))) AS `( SELECT b FROM t2 WHERE NOT EXISTS ( SELECT c FROM t3 WHERE c = b ) )` from `test`.`t1`
+Note	1003	select (select 1 from dual where (not(((1 is not null) and <in_optimizer>(1,1 in (<primary_index_lookup>(1 in <temporary table> on distinct_key where ((1 = `<subquery3>`.`c`))))))))) AS `( SELECT b FROM t2 WHERE NOT EXISTS ( SELECT c FROM t3 WHERE c = b ) )` from `test`.`t1`
 SELECT ( SELECT b FROM t2 WHERE NOT EXISTS ( SELECT c FROM t3 WHERE c = b ) ) FROM t1;
 ( SELECT b FROM t2 WHERE NOT EXISTS ( SELECT c FROM t3 WHERE c = b ) )
 1
@@ -344,7 +344,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 3	MATERIALIZED	t3	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
 Warnings:
 Note	1276	Field or reference 'test.t2.b' of SELECT #3 was resolved in SELECT #2
-Note	1003	select (select 1 from dual where (not(((1 is not null) and <in_optimizer>(1,1 in ( <materialize> (select `test`.`t3`.`c` from `test`.`t3` where (`test`.`t3`.`c` is not null) ), <primary_index_lookup>(1 in <temporary table> on distinct_key where ((1 = `<subquery3>`.`c`))))))))) AS `( SELECT b FROM t2 WHERE NOT EXISTS ( SELECT c FROM t3 WHERE c = b ) )` from `test`.`t1`
+Note	1003	select (select 1 from dual where (not(((1 is not null) and <in_optimizer>(1,1 in (<primary_index_lookup>(1 in <temporary table> on distinct_key where ((1 = `<subquery3>`.`c`))))))))) AS `( SELECT b FROM t2 WHERE NOT EXISTS ( SELECT c FROM t3 WHERE c = b ) )` from `test`.`t1`
 SELECT ( SELECT b FROM t2 WHERE NOT EXISTS ( SELECT c FROM t3 WHERE c = b ) ) FROM t1;
 ( SELECT b FROM t2 WHERE NOT EXISTS ( SELECT c FROM t3 WHERE c = b ) )
 1

mysql-test/r/union.result

@@ -2049,3 +2049,41 @@ a
 1000003.0
 1.0
 End of 5.5 tests
+#
+# MDEV-13784: query causes seg fault
+#
+CREATE TABLE t1 (`bug_id` int NOT NULL PRIMARY KEY, `product_id` int NOT NULL);
+INSERT INTO t1 VALUES (45199,1184);
+CREATE TABLE t2 (`product_id` int NOT NULL,`userid` int NOT NULL, PRIMARY KEY (`product_id`,`userid`));
+INSERT INTO t2 VALUES (1184,103),(1184,624),(1184,1577),(1184,1582);
+CREATE TABLE t3 (`id` int NOT NULL  PRIMARY KEY,`name` varchar(64));
+CREATE TABLE t4 ( `userid` int NOT NULL PRIMARY KEY, `login_name` varchar(255));
+INSERT INTO t4 VALUES (103,'foo'),(624,'foo'),(1577,'foo'),(1582,'foo');
+CREATE TABLE t5 (`id` int NOT NULL PRIMARY KEY, `name` varchar(64));
+explain select
+(
+select login_name from t4 where userId = (
+select userid from t2 where product_id = t1.product_id
+union
+select userid from t2 where product_id = (
+select id from t5 where name = (select name from t3 where id = t1.product_id)) limit 1 )
+) as x  from t1 where (t1.bug_id=45199);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	system	PRIMARY	NULL	NULL	NULL	1	
+2	SUBQUERY	t4	eq_ref	PRIMARY	PRIMARY	4	func	1	Using where
+3	SUBQUERY	t2	ref	PRIMARY	PRIMARY	4	const	3	Using index
+4	UNION	t2	ref	PRIMARY	PRIMARY	4	func	1	Using where; Using index
+5	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+6	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+NULL	UNION RESULT	<union3,4>	ALL	NULL	NULL	NULL	NULL	NULL	
+select
+(
+select login_name from t4 where userId = (
+select userid from t2 where product_id = t1.product_id
+union
+select userid from t2 where product_id = (
+select id from t5 where name = (select name from t3 where id = t1.product_id)) limit 1 )
+) as x  from t1 where (t1.bug_id=45199);
+x
+foo
+drop table t1, t2, t3, t4, t5;

mysql-test/r/view.result

@@ -4633,7 +4633,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 2	DEPENDENT SUBQUERY	t4	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
 Warnings:
 Note	1276	Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
-Note	1003	select `test`.`t1`.`a` AS `a`,10 AS `a` from `test`.`t1` where (not(<expr_cache><10,`test`.`t1`.`a`>(<in_optimizer>(10,<exists>(select NULL from `test`.`t4` where ((`test`.`t4`.`a` >= `test`.`t1`.`a`) and trigcond(((<cache>(10) = NULL) or <cache>(isnull(NULL))))) having trigcond(<is_not_null_test>(NULL)))))))
+Note	1003	select `test`.`t1`.`a` AS `a`,10 AS `a` from `test`.`t1` where (not(<expr_cache><10,`test`.`t1`.`a`>(<in_optimizer>(10,<exists>(select NULL from `test`.`t4` where ((`test`.`t4`.`a` >= `test`.`t1`.`a`) and trigcond(((<cache>(10) = NULL) or 1))) having trigcond(<is_not_null_test>(NULL)))))))
 SELECT * FROM t1, t2
 WHERE t2.a NOT IN (SELECT t3.b FROM t3 RIGHT JOIN t4 ON (t4.a = t3.a)
 WHERE t4.a >= t1.a);
@@ -4649,7 +4649,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 2	DEPENDENT SUBQUERY	t4	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
 Warnings:
 Note	1276	Field or reference 'v1.a' of SELECT #2 was resolved in SELECT #1
-Note	1003	select `test`.`t1`.`a` AS `a`,10 AS `a` from `test`.`t1` where (not(<expr_cache><10,`test`.`t1`.`a`>(<in_optimizer>(10,<exists>(select NULL from `test`.`t4` where ((`test`.`t4`.`a` >= `test`.`t1`.`a`) and trigcond(((<cache>(10) = NULL) or <cache>(isnull(NULL))))) having trigcond(<is_not_null_test>(NULL)))))))
+Note	1003	select `test`.`t1`.`a` AS `a`,10 AS `a` from `test`.`t1` where (not(<expr_cache><10,`test`.`t1`.`a`>(<in_optimizer>(10,<exists>(select NULL from `test`.`t4` where ((`test`.`t4`.`a` >= `test`.`t1`.`a`) and trigcond(((<cache>(10) = NULL) or 1))) having trigcond(<is_not_null_test>(NULL)))))))
 SELECT * FROM v1, t2
 WHERE t2.a NOT IN (SELECT t3.b FROM t3 RIGHT JOIN t4 ON (t4.a = t3.a)
 WHERE t4.a >= v1.a);

mysql-test/t/union.test

@@ -1437,3 +1437,38 @@ SET @advertAcctId = 1000003;
 select @advertAcctId as a from dual union all select 1.0 from dual;
 
 --echo End of 5.5 tests
+
+--echo #
+--echo # MDEV-13784: query causes seg fault
+--echo #
+
+CREATE TABLE t1 (`bug_id` int NOT NULL PRIMARY KEY, `product_id` int NOT NULL);
+INSERT INTO t1 VALUES (45199,1184);
+
+CREATE TABLE t2 (`product_id` int NOT NULL,`userid` int NOT NULL, PRIMARY KEY (`product_id`,`userid`));
+INSERT INTO t2 VALUES (1184,103),(1184,624),(1184,1577),(1184,1582);
+
+CREATE TABLE t3 (`id` int NOT NULL  PRIMARY KEY,`name` varchar(64));
+
+
+CREATE TABLE t4 ( `userid` int NOT NULL PRIMARY KEY, `login_name` varchar(255));
+INSERT INTO t4 VALUES (103,'foo'),(624,'foo'),(1577,'foo'),(1582,'foo');
+CREATE TABLE t5 (`id` int NOT NULL PRIMARY KEY, `name` varchar(64));
+
+explain select
+(
+  select login_name from t4 where userId = (
+    select userid from t2 where product_id = t1.product_id
+    union
+    select userid from t2 where product_id = (
+      select id from t5 where name = (select name from t3 where id = t1.product_id)) limit 1 )
+) as x  from t1 where (t1.bug_id=45199);
+select
+(
+  select login_name from t4 where userId = (
+    select userid from t2 where product_id = t1.product_id
+    union
+    select userid from t2 where product_id = (
+      select id from t5 where name = (select name from t3 where id = t1.product_id)) limit 1 )
+) as x  from t1 where (t1.bug_id=45199);
+drop table t1, t2, t3, t4, t5;

sql/sql_lex.cc

@@ -3551,6 +3551,7 @@ bool st_select_lex::optimize_unflattened_subqueries(bool const_only)
           inner_join->select_options|= SELECT_DESCRIBE;
         }
         res= inner_join->optimize();
+        sl->update_used_tables();
         sl->update_correlated_cache();
         is_correlated_unit|= sl->is_correlated;
         inner_join->select_options= save_options;