SERVER-30695 uniqueItems must ignore field order when comparing documents

1 files changed, 6 insertions, 3 deletions

diff --git a/src/mongo/db/matcher/schema/expression_internal_schema_unique_items.h b/src/mongo/db/matcher/schema/expression_internal_schema_unique_items.h
index 570cf448f07..07beff92319 100644
--- a/src/mongo/db/matcher/schema/expression_internal_schema_unique_items.h
+++ b/src/mongo/db/matcher/schema/expression_internal_schema_unique_items.h
@@ -30,13 +30,16 @@
 
 #include <utility>
 
-#include "mongo/bson/bsonelement_comparator.h"
+#include "mongo/bson/unordered_fields_bsonelement_comparator.h"
 #include "mongo/db/matcher/expression_array.h"
 
 namespace mongo {
 
 /**
- * Matches arrays whose elements are all unique.
+ * Matches arrays whose elements are all unique. When comparing elements,
+ *
+ *  - strings are always compared using the "simple" string comparator; and
+ *  - objects are compared in a field order-independent manner.
  */
 class InternalSchemaUniqueItemsMatchExpression final : public ArrayMatchingMatchExpression {
 public:
@@ -81,6 +84,6 @@ public:
 
 private:
     // The comparator to use when comparing BSONElements, which will never use a collation.
-    BSONElementComparator _comparator{BSONElementComparator::FieldNamesMode::kIgnore, nullptr};
+    UnorderedFieldsBSONElementComparator _comparator;
 };
 }  // namespace mongo