MDEV-22462: Item_in_subselect::create_single_in_to_exists_cond(JOIN *, Item...

MDEV-22462: Item_in_subselect::create_single_in_to_exists_cond(JOIN *, Item **, Item **): Assertion `false' failed.

Item_in_subselect::create_single_in_to_exists_cond() should handle the
case where the subquery is a table-less select but it is not a result
of a UNION.

(Table-less subqueries like "(SELECT 1)" are "substituted" with their select
list, but table-less subqueries with WHERE or HAVING clause, like
"(SELECT 1 WHERE ...)" are not substituted. They are handled with regular
execution path)

mysql-test/r/subselect4.result

@@ -2721,7 +2721,15 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 SELECT a FROM t1 WHERE (a, a) IN (SELECT 1, 2) AND a = (SELECT MIN(b) FROM t2);
 a
 DROP TABLE t1,t2;
-# End of 10.2 tests
+#
+# MDEV-22462: Item_in_subselect::create_single_in_to_exists_cond(JOIN *, Item **, Item **): Assertion `false' failed.
+#
+select 1 from dual where 1 in (select 5 from dual where 1);
+1
+create table t1 (a int);
+insert into t1 values (1),(2),(3);
+update t1 set a = 2 where a in (select a from dual where a = a);
+drop table t1;
 #
 # MDEV-24925: Server crashes in Item_subselect::init_expr_cache_tracker
 #
@@ -2793,3 +2801,4 @@ FROM (t1 JOIN t1 AS ref_t1 ON
 (t1.i1 > (SELECT ref_t1.i1 AS c0 FROM t1 b ORDER BY -c0)));
 ERROR 21000: Subquery returns more than 1 row
 DROP TABLE t1;
+# End of 10.2 tests

mysql-test/t/subselect4.test

@@ -2236,7 +2236,17 @@ SELECT a FROM t1 WHERE (a, a) IN (SELECT 1, 2) AND a = (SELECT MIN(b) FROM t2);
 
 DROP TABLE t1,t2;
 
---echo # End of 10.2 tests
+--echo #
+--echo # MDEV-22462: Item_in_subselect::create_single_in_to_exists_cond(JOIN *, Item **, Item **): Assertion `false' failed.
+--echo #
+
+select 1 from dual where 1 in (select 5 from dual where 1);
+
+create table t1 (a int);
+insert into t1 values (1),(2),(3);
+
+update t1 set a = 2 where a in (select a from dual where a = a);
+drop table t1;
 
 --echo #
 --echo # MDEV-24925: Server crashes in Item_subselect::init_expr_cache_tracker
@@ -2296,3 +2306,4 @@ FROM (t1 JOIN t1 AS ref_t1 ON
 
 DROP TABLE t1;
 
+--echo # End of 10.2 tests

sql/item_subselect.cc

@@ -2249,7 +2249,8 @@ Item_in_subselect::create_single_in_to_exists_cond(JOIN *join,
     */
     Item *item= (Item*) select_lex->item_list.head();
 
-    if (select_lex->table_list.elements)
+    if (select_lex->table_list.elements ||
+        !(select_lex->master_unit()->is_union()))
     {
       Item *having= item;
       Item *orig_item= item;
@@ -2297,8 +2298,8 @@ Item_in_subselect::create_single_in_to_exists_cond(JOIN *join,
     }
     else
     {
-      if (select_lex->master_unit()->is_union())
-      {
+      DBUG_ASSERT(select_lex->master_unit()->is_union());
+
       Item *new_having=
         func->create(thd, expr,
                      new (thd->mem_root) Item_ref_null_helper(thd,
@@ -2320,9 +2321,6 @@ Item_in_subselect::create_single_in_to_exists_cond(JOIN *join,
         DBUG_RETURN(true);
       *having_item= new_having;
     }
-      else
-        DBUG_ASSERT(false);
-    }
   }
 
   DBUG_RETURN(false);