Hi, Sergei, On May 04, Sergei Petrunia wrote:

revision-id: 4ba5b444b4b (mariadb-10.2.43-97-g4ba5b444b4b) parent(s): 70555454b4c author: Sergei Petrunia committer: Sergei Petrunia timestamp: 2022-05-04 12:24:48 +0300 message:

MDEV-28437: Assertion `!eliminated' failed in Item_subselect::exec

(This is the assert that was added in fix for MDEV-26047)

Table elimination may remove an ON expression from an outer join. However SELECT_LEX::update_used_tables() will still call

item->walk(&Item::eval_not_null_tables)

for eliminated expressions. If the subquery is constant and cheap Item_cond_and will attempt to evaluate it, which will trigger an assert. The fix is not to call update_used_tables() or eval_not_null_tables() for ON expressions that were eliminated.

diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc index 22ee8801e3a..8e718f2a942 100644 --- a/sql/sql_lex.cc +++ b/sql/sql_lex.cc @@ -4229,7 +4229,7 @@ void SELECT_LEX::update_used_tables() } } while ((embedding= embedding->embedding)); - if (tl->on_expr) + if (tl->on_expr && !is_eliminated_table(join->eliminated_tables, tl)) { tl->on_expr->update_used_tables(); tl->on_expr->walk(&Item::eval_not_null_tables, 0, NULL); @@ -4253,8 +4253,11 @@ void SELECT_LEX::update_used_tables() if (embedding->on_expr && embedding->nested_join->join_list.head() == tl) {

can embedding be eliminated? if yes - does it make sense to do anything in tl's below that eliminated embedding? Perhaps it should be (in the do..while above), like do { bool maybe_null; if ((maybe_null= MY_TEST(embedding->outer_join))) { tl->table->maybe_null= maybe_null; break; } + if (is_eliminated_table(join->eliminated_tables, embedding)) + tl= embedding->embedding; } while ((embedding= embedding->embedding));

+ if (!is_eliminated_table(join->eliminated_tables, embedding)) + { embedding->on_expr->update_used_tables(); embedding->on_expr->walk(&Item::eval_not_null_tables, 0, NULL); + } } tl= embedding; embedding= tl->embedding;

Regards, Sergei VP of MariaDB Server Engineering and security@mariadb.org