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.

1 files changed, 6 insertions, 3 deletions

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)
       {
-        embedding->on_expr->update_used_tables();
-        embedding->on_expr->walk(&Item::eval_not_null_tables, 0, NULL);
+        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;