Fixing performance regression in all_resource_timestamps for postgres (#3631)

alexcottner · web-flow · commit 28a86f58a535 · 2026-01-23T17:50:57.000+01:00
diff --git a/kinto/core/storage/postgresql/__init__.py b/kinto/core/storage/postgresql/__init__.py
@@ -252,10 +252,10 @@ def all_resources_timestamps(self, resource_name):
         WITH existing_timestamps AS (
           -- Timestamp of latest object by parent_id.
           (
-            SELECT DISTINCT ON (parent_id) parent_id, last_modified
+            SELECT parent_id, MAX(last_modified) AS last_modified
             FROM objects
             WHERE resource_name = :resource_name
-            ORDER BY parent_id, last_modified DESC
+            GROUP BY parent_id
           )
           -- Timestamp of resources without sub-objects.
           UNION ALL

Original file line number	Diff line number	Diff line change
`@@ -252,10 +252,10 @@ def all_resources_timestamps(self, resource_name):`
`252`	`252`	`WITH existing_timestamps AS (`
`253`	`253`	`-- Timestamp of latest object by parent_id.`
`254`	`254`	`(`
`255`		`- SELECT DISTINCT ON (parent_id) parent_id, last_modified`
	`255`	`+ SELECT parent_id, MAX(last_modified) AS last_modified`
`256`	`256`	`FROM objects`
`257`	`257`	`WHERE resource_name = :resource_name`
`258`		`- ORDER BY parent_id, last_modified DESC`
	`258`	`+ GROUP BY parent_id`
`259`	`259`	`)`
`260`	`260`	`-- Timestamp of resources without sub-objects.`
`261`	`261`	`UNION ALL`