Subscription on kylorend3r Bloghttps://kylorend3r.github.io/tags/subscription/Recent content in Subscription on kylorend3r Blogkylorend3r Bloghttps://kylorend3r.github.io/og-image.pnghttps://kylorend3r.github.io/og-image.pngHugo -- 0.146.0en-usWed, 29 Jul 2026 00:00:00 +0000Upgrading a PostgreSQL Subscriber to Avoid Replaying WAL You Already Appliedhttps://kylorend3r.github.io/posts/upgrading-postgresql-logical-replication-subscribers-with-pg-upgrade/Wed, 29 Jul 2026 00:00:00 +0000https://kylorend3r.github.io/posts/upgrading-postgresql-logical-replication-subscribers-with-pg-upgrade/<p><strong>Summary:</strong> Running <code>pg_upgrade</code> on a logical replication subscriber that&rsquo;s older than PostgreSQL 17 silently drops the subscription&rsquo;s replication origin — the bookmark tracking how far it has replayed. The publisher never finds out, so it replays WAL the subscriber already applied, surfacing as duplicate-key errors after an otherwise clean upgrade. This post covers why that happens, what PostgreSQL 17 changed to fix it, a manual procedure to protect subscribers on older versions, and the separate considerations for upgrading the publisher side, where publications survive the upgrade but replication slots never do.</p>