Fix reordering products duplicates (#6666)

saleor/graphql/product/sorters.py

@@ -1,7 +1,7 @@
 import graphene
 from django.db.models import Count, F, IntegerField, Min, OuterRef, QuerySet, Subquery
 from django.db.models.expressions import Window
-from django.db.models.functions import Coalesce, RowNumber
+from django.db.models.functions import Coalesce, DenseRank
 
 from ...product.models import Category, Product
 from ..core.types import SortInputObjectType
@@ -140,7 +140,7 @@ class ProductOrderField(graphene.Enum):
     TYPE = ["product_type__name", "name", "slug"]
     PUBLISHED = ["is_published", "name", "slug"]
     PUBLICATION_DATE = ["publication_date", "name", "slug"]
-    COLLECTION = ["row_number"]
+    COLLECTION = ["sort_order"]
 
     @property
     def description(self):
@@ -173,8 +173,8 @@ def qs_with_price(queryset: QuerySet) -> QuerySet:
     @staticmethod
     def qs_with_collection(queryset: QuerySet) -> QuerySet:
         return queryset.annotate(
-            row_number=Window(
-                expression=RowNumber(),
+            sort_order=Window(
+                expression=DenseRank(),
                 order_by=(
                     F("collectionproduct__sort_order").asc(nulls_last=True),
                     F("collectionproduct__id"),

saleor/graphql/product/tests/test_product_sorting.py

@@ -113,16 +113,19 @@ def test_sort_products_within_collection(
 
     variables = {
         "collectionId": collection_id,
-        "moves": [{"productId": product, "sortOrder": 1}],
+        "moves": [
+            {"productId": product, "sortOrder": 1},
+            {"productId": second_product, "sortOrder": -1},
+        ],
     }
     content = get_graphql_content(
         staff_api_client.post_graphql(COLLECTION_RESORT_QUERY, variables)
     )["data"]["collectionReorderProducts"]
 
     products = content["collection"]["products"]["edges"]
     assert products[0]["node"]["id"] == third_product
-    assert products[1]["node"]["id"] == product
-    assert products[2]["node"]["id"] == second_product
+    assert products[1]["node"]["id"] == second_product
+    assert products[2]["node"]["id"] == product
 
 
 GET_SORTED_PRODUCTS_QUERY = """