MDEV-18896 Crash in convert_join_subqueries_to_semijoins

If an IN-subquery is used in a table-less select the current code
should never consider it as candidate for semi-join optimizations.
Yet the function check_and_do_in_subquery_rewrites() improperly
checked the property "to be a table-less select". As a result
such select in IN subquery was used in INSERT .. SELECT then
the IN subquery by mistake was registered as a semi-join subquery
and convert_subq_to_sj() was called for it. However the code of
this function does not assume that the parent select of the subquery
could be a table-less select.

1 files changed, 7 insertions, 0 deletions

diff --git a/mysql-test/r/subselect_sj.result b/mysql-test/r/subselect_sj.result
index 519d53eb98f..73c620b2973 100644
--- a/mysql-test/r/subselect_sj.result
+++ b/mysql-test/r/subselect_sj.result
@@ -3178,5 +3178,12 @@ EXECUTE stmt;
 a
 drop view v3;
 drop table t1,t2,t3;
+#
+# MDEV-18896: IN subquery in WHERE of a table-less query used for INSERT
+#
+create table t1 (a1 varchar(25));
+create table t2 (a2 varchar(25)) ;
+insert into t1 select 'xxx' from dual where 'xxx' in (select a2 from t2);
+drop table t1,t2;
 # End of 5.5 test
 set optimizer_switch=@subselect_sj_tmp;