MDEV-35105 Assertion `tab->join->order' fails upon vector search with DISTINCT

don't apply distinct optimization to order by a vector index

Author: vuvova

mysql-test/main/vector2.result

@@ -95,3 +95,12 @@ t	CREATE TABLE `t` (
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci
 drop table t;
 set mhnsw_distance_function= default;
+#
+# MDEV-35105 Assertion `tab->join->order' fails upon vector search with DISTINCT
+#
+create table t (a int, v blob not null, vector(v));
+insert into t values(1,x'00000000'),(2,x'00000000');
+select distinct a from t order by vec_distance_euclidean(v,vec_fromtext('[1]')) limit 1;
+a
+#
+drop table t;

mysql-test/main/vector2.test

@@ -82,3 +82,12 @@ execute stmt;
 show create table t;
 drop table t;
 set mhnsw_distance_function= default;
+
+--echo #
+--echo # MDEV-35105 Assertion `tab->join->order' fails upon vector search with DISTINCT
+--echo #
+create table t (a int, v blob not null, vector(v));
+insert into t values(1,x'00000000'),(2,x'00000000');
+--replace_column 1 #
+select distinct a from t order by vec_distance_euclidean(v,vec_fromtext('[1]')) limit 1;
+drop table t;

sql/sql_select.cc

@@ -4402,7 +4402,8 @@ JOIN::optimize_distinct()
   }
 
   /* Optimize "select distinct b from t1 order by key_part_1 limit #" */
-  if (order && skip_sort_order && !unit->lim.is_with_ties())
+  if (order && skip_sort_order && !unit->lim.is_with_ties()
+      && (*order->item)->type() == Item::FIELD_ITEM)
   {
     /* Should already have been optimized away */
     DBUG_ASSERT(ordered_index_usage == ordered_index_order_by);