fix(replay): Add fallback ordering to replay index page (#103328)

fixes REPLAY-830 

In the replay index page, when sorting by columns that contain duplicate
values (e.g., startedAt, duration, countErrors), the order of rows with
identical values is non-deterministic, which results in inconsistent
pagination. Let's add a fallback ordering on replay_id. We are already
grouping by replay_id so the fallback sort will operate on the
aggregated results.

Author: srest2021

src/sentry/replays/usecases/query/__init__.py

@@ -344,7 +344,11 @@ def _query_using_scalar_strategy(
 
     try:
         where = handle_search_filters(scalar_search_config, search_filters)
-        orderby = handle_ordering(agg_sort_config, sort or "-" + DEFAULT_SORT_FIELD)
+        orderby = handle_ordering(
+            agg_sort_config,
+            sort or "-" + DEFAULT_SORT_FIELD,
+            tiebreaker="replay_id",  # Ensure stable sort when ordering by column with duplicates
+        )
     except RetryAggregated:
         return _query_using_aggregated_strategy(
             search_filters,
@@ -378,7 +382,11 @@ def _query_using_aggregated_strategy(
     period_start: datetime,
     period_stop: datetime,
 ):
-    orderby = handle_ordering(agg_sort_config, sort or "-" + DEFAULT_SORT_FIELD)
+    orderby = handle_ordering(
+        agg_sort_config,
+        sort or "-" + DEFAULT_SORT_FIELD,
+        tiebreaker="replay_id",  # Ensure stable sort when ordering by column with duplicates
+    )
 
     having: list[Condition] = handle_search_filters(agg_search_config, search_filters)
     having.append(Condition(Function("min", parameters=[Column("segment_id")]), Op.EQ, 0))
@@ -459,11 +467,16 @@ def execute_query(query: Query, tenant_id: dict[str, int], referrer: str) -> Map
         raise
 
 
-def handle_ordering(config: dict[str, Expression], sort: str) -> list[OrderBy]:
-    if sort.startswith("-"):
-        return [OrderBy(_get_sort_column(config, sort[1:]), Direction.DESC)]
-    else:
-        return [OrderBy(_get_sort_column(config, sort), Direction.ASC)]
+def handle_ordering(
+    config: dict[str, Expression], sort: str, tiebreaker: str | None = None
+) -> list[OrderBy]:
+    direction = Direction.DESC if sort.startswith("-") else Direction.ASC
+    bare_sort = sort[1:] if sort.startswith("-") else sort
+
+    orderby = [OrderBy(_get_sort_column(config, bare_sort), direction)]
+    if tiebreaker:
+        orderby.append(OrderBy(Column(tiebreaker), direction))
+    return orderby
 
 
 def _get_sort_column(config: dict[str, Expression], column_name: str) -> Function:

tests/sentry/replays/endpoints/test_organization_replay_index.py

@@ -485,6 +485,30 @@ def test_get_replays_duration_sorted(self) -> None:
             assert response_data["data"][0]["id"] == replay2_id
             assert response_data["data"][1]["id"] == replay1_id
 
+    def test_get_replays_duration_sorted_tiebreaker(self) -> None:
+        """Test that replays with identical durations have deterministic order when ordering by duration."""
+        project = self.create_project(teams=[self.team])
+        replay_ids = [uuid.uuid4().hex for _ in range(5)]
+
+        timestamp_start = datetime.datetime.now() - datetime.timedelta(seconds=10)
+        timestamp_end = datetime.datetime.now() - datetime.timedelta(seconds=5)
+
+        for replay_id in replay_ids:
+            self.store_replays(mock_replay(timestamp_start, project.id, replay_id, segment_id=0))
+            self.store_replays(mock_replay(timestamp_end, project.id, replay_id, segment_id=1))
+
+        with self.feature(self.features):
+            response = self.client.get(self.url + "?orderBy=duration")
+            assert response.status_code == 200, response
+            asc_order = [r["id"] for r in response.json()["data"]]
+
+            response = self.client.get(self.url + "?orderBy=-duration")
+            assert response.status_code == 200, response
+            desc_order = [r["id"] for r in response.json()["data"]]
+
+            assert desc_order == list(reversed(asc_order))
+            assert set(asc_order) == set(replay_ids)
+
     def test_get_replays_pagination(self) -> None:
         """Test replays can be paginated."""
         project = self.create_project(teams=[self.team])