MDEV-7823: Server crashes in next_depth_first_tab on nested IN clauses with SQ inside

Consider a query with subquery in form t.key=(select ...). Suppose, the
parent query uses this equality for ref access.
It will attempt to evaluate the subquery in get_best_combination(),
right before the join->join_tab[...] array is filled.  The problem was
that subquery optimization will attempt to look at parent's join->join_tab
to check how many times subquery will be executed (and crash).

Fixed by not doing that when the subquery is constant (non-constant
subqueries are only be evaluated during join execution, so they are not
affected)

mysql-test/r/subselect_extra_no_semijoin.result

@@ -349,9 +349,9 @@ WHERE t.a IN (SELECT b FROM t1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	system	NULL	NULL	NULL	NULL	1	100.00	
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
-3	MATERIALIZED	t1	system	NULL	NULL	NULL	NULL	1	100.00	
+3	DEPENDENT SUBQUERY	t1	system	NULL	NULL	NULL	NULL	1	100.00	
 Warnings:
-Note	1003	select `test`.`t2`.`a` AS `a`,0 AS `a`,0 AS `b` from `test`.`t2` where <expr_cache><0>(<in_optimizer>(0,0 in ( <materialize> (select 0 from dual ), <primary_index_lookup>(0 in <temporary table> on distinct_key where ((0 = `<subquery3>`.`b`))))))
+Note	1003	select `test`.`t2`.`a` AS `a`,0 AS `a`,0 AS `b` from `test`.`t2` where <expr_cache><0>(<in_optimizer>(0,<exists>(select 0 from dual where (<cache>(0) = 0))))
 SELECT * FROM t2 RIGHT JOIN v1 AS t ON t.a != 0
 WHERE t.a IN (SELECT b FROM t1);
 a	a	b
@@ -362,9 +362,9 @@ WHERE t.a IN (SELECT b FROM t1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	system	NULL	NULL	NULL	NULL	1	100.00	
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
-2	MATERIALIZED	t1	system	NULL	NULL	NULL	NULL	1	100.00	
+2	DEPENDENT SUBQUERY	t1	system	NULL	NULL	NULL	NULL	1	100.00	
 Warnings:
-Note	1003	select `test`.`t2`.`a` AS `a`,0 AS `a`,0 AS `b` from `test`.`t2` where <expr_cache><0>(<in_optimizer>(0,0 in ( <materialize> (select 0 from dual ), <primary_index_lookup>(0 in <temporary table> on distinct_key where ((0 = `<subquery2>`.`b`))))))
+Note	1003	select `test`.`t2`.`a` AS `a`,0 AS `a`,0 AS `b` from `test`.`t2` where <expr_cache><0>(<in_optimizer>(0,<exists>(select 0 from dual where (<cache>(0) = 0))))
 DROP VIEW v1;
 DROP TABLE t1,t2;
 #

mysql-test/r/subselect_sj.result

@@ -2995,4 +2995,30 @@ explain
 select 1 from t1 where _cp932 "1" in (select '1' from t1);
 ERROR HY000: Illegal mix of collations (cp932_japanese_ci,COERCIBLE) and (latin1_swedish_ci,COERCIBLE) for operation '='
 drop table t1;
+#
+# MDEV-7823: Server crashes in next_depth_first_tab on nested IN clauses with SQ inside
+#
+set @tmp_mdev7823=@@optimizer_switch;
+set optimizer_switch=default;
+CREATE TABLE t1 (f1 INT);
+INSERT INTO t1 VALUES (1);
+CREATE TABLE t2 (f2 INT, KEY(f2));
+INSERT INTO t2 VALUES (8),(0);
+CREATE TABLE t3 (f3 INT);
+INSERT INTO t3 VALUES (1),(2);
+CREATE TABLE t4 (f4 INT);
+INSERT INTO t4 VALUES (0),(5);
+explain 
+SELECT * FROM t1, t2, t3 WHERE f2 IN ( f1 IN ( SELECT f4 FROM t4 ) );
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	system	NULL	NULL	NULL	NULL	1	
+1	PRIMARY	t2	ref	f2	f2	5	const	0	Using where; Using index
+1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	2	Using join buffer (flat, BNL join)
+2	DEPENDENT SUBQUERY	t4	ALL	NULL	NULL	NULL	NULL	2	Using where
+SELECT * FROM t1, t2, t3 WHERE f2 IN ( f1 IN ( SELECT f4 FROM t4 ) );
+f1	f2	f3
+1	0	1
+1	0	2
+drop table t1,t2,t3,t4;
+set optimizer_switch= @tmp_mdev7823;
 set optimizer_switch=@subselect_sj_tmp;

mysql-test/r/subselect_sj_jcl6.result

@@ -3009,6 +3009,32 @@ explain
 select 1 from t1 where _cp932 "1" in (select '1' from t1);
 ERROR HY000: Illegal mix of collations (cp932_japanese_ci,COERCIBLE) and (latin1_swedish_ci,COERCIBLE) for operation '='
 drop table t1;
+#
+# MDEV-7823: Server crashes in next_depth_first_tab on nested IN clauses with SQ inside
+#
+set @tmp_mdev7823=@@optimizer_switch;
+set optimizer_switch=default;
+CREATE TABLE t1 (f1 INT);
+INSERT INTO t1 VALUES (1);
+CREATE TABLE t2 (f2 INT, KEY(f2));
+INSERT INTO t2 VALUES (8),(0);
+CREATE TABLE t3 (f3 INT);
+INSERT INTO t3 VALUES (1),(2);
+CREATE TABLE t4 (f4 INT);
+INSERT INTO t4 VALUES (0),(5);
+explain 
+SELECT * FROM t1, t2, t3 WHERE f2 IN ( f1 IN ( SELECT f4 FROM t4 ) );
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	system	NULL	NULL	NULL	NULL	1	
+1	PRIMARY	t2	ref	f2	f2	5	const	0	Using where; Using index
+1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	2	Using join buffer (flat, BNL join)
+2	DEPENDENT SUBQUERY	t4	ALL	NULL	NULL	NULL	NULL	2	Using where
+SELECT * FROM t1, t2, t3 WHERE f2 IN ( f1 IN ( SELECT f4 FROM t4 ) );
+f1	f2	f3
+1	0	1
+1	0	2
+drop table t1,t2,t3,t4;
+set optimizer_switch= @tmp_mdev7823;
 set optimizer_switch=@subselect_sj_tmp;
 #
 # BUG#49129: Wrong result with IN-subquery with join_cache_level=6 and firstmatch=off

mysql-test/t/subselect_sj.test

@@ -2700,5 +2700,30 @@ explain
 select 1 from t1 where _cp932 "1" in (select '1' from t1);
 drop table t1;
 
+--echo #
+--echo # MDEV-7823: Server crashes in next_depth_first_tab on nested IN clauses with SQ inside
+--echo #
+set @tmp_mdev7823=@@optimizer_switch;
+set optimizer_switch=default;
+CREATE TABLE t1 (f1 INT);
+INSERT INTO t1 VALUES (1);
+
+CREATE TABLE t2 (f2 INT, KEY(f2));
+INSERT INTO t2 VALUES (8),(0);
+
+CREATE TABLE t3 (f3 INT);
+INSERT INTO t3 VALUES (1),(2);
+
+CREATE TABLE t4 (f4 INT);
+INSERT INTO t4 VALUES (0),(5);
+
+explain 
+SELECT * FROM t1, t2, t3 WHERE f2 IN ( f1 IN ( SELECT f4 FROM t4 ) );
+SELECT * FROM t1, t2, t3 WHERE f2 IN ( f1 IN ( SELECT f4 FROM t4 ) );
+
+drop table t1,t2,t3,t4;
+set optimizer_switch= @tmp_mdev7823;
+
+
 # The following command must be the last one the file 
 set optimizer_switch=@subselect_sj_tmp;

sql/opt_subselect.cc

@@ -5463,7 +5463,8 @@ bool JOIN::choose_subquery_plan(table_map join_tables)
           outer join has not been optimized yet).
     */
     if (outer_join && outer_join->table_count > 0 && // (1)
-        outer_join->join_tab)                        // (2)
+        outer_join->join_tab &&                      // (2)
+        !in_subs->const_item())
     {
       /*
         TODO: