perf(dashboard): Batch RLS filter lookups for dashboard digest computation (#37941)

tests/unit_tests/thumbnails/test_digest.py

@@ -433,3 +433,52 @@ def test_chart_digest(
         )
         with cm:
             assert get_chart_digest(chart=chart) == expected_result
+
+
+def test_dashboard_digest_prefetches_rls_filters(
+    app_context: None,
+) -> None:
+    """
+    Test that _adjust_string_with_rls calls prefetch_rls_filters with
+    table IDs from RLS-supporting datasources before iterating.
+    """
+    from superset import security_manager
+    from superset.models.dashboard import Dashboard
+    from superset.models.slice import Slice
+    from superset.thumbnails.digest import get_dashboard_digest
+
+    kwargs = {**_DEFAULT_DASHBOARD_KWARGS}
+    slices = [Slice(**slice_kwargs) for slice_kwargs in kwargs.pop("slices")]
+    dashboard = Dashboard(**kwargs, slices=slices)
+
+    datasources = []
+    for ds_id, rls_supported in [(10, True), (20, True), (30, False)]:
+        ds = MagicMock(spec=BaseDatasource)
+        ds.id = ds_id
+        ds.is_rls_supported = rls_supported
+        ds.get_sqla_row_level_filters = MagicMock(return_value=[])
+        datasources.append(ds)
+
+    user = User(id=1, username="1")
+
+    with (
+        patch.dict(
+            current_app.config,
+            {
+                "THUMBNAIL_EXECUTORS": [ExecutorType.CURRENT_USER],
+                "THUMBNAIL_DASHBOARD_DIGEST_FUNC": None,
+            },
+        ),
+        patch.object(
+            type(dashboard),
+            "datasources",
+            new_callable=PropertyMock,
+            return_value=datasources,
+        ),
+        patch.object(security_manager, "find_user", return_value=user),
+        patch.object(security_manager, "prefetch_rls_filters") as mock_prefetch,
+        override_user(user),
+    ):
+        get_dashboard_digest(dashboard=dashboard)
+        # Should be called with only the RLS-supporting datasource IDs
+        mock_prefetch.assert_called_once_with([10, 20])