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When data checksums catch corruption, restore from backup or fail over—unless you have neither.

Here is a query that shows up in every analytics workload:

SELECT count(DISTINCT user_id) FROM events;

It looks like the cheapest possible thing: count the distinct users. On a machine with cores to spare you would expect Postgres to throw a few parallel workers at it, the way it does for almost any large scan. It does not. That one keyword, DISTINCT, switches off parallel query for the entire statement, and the larger your table the more it costs you. No setting or index changes that; the reason is in how the aggregate has to execute.

Jacob Jackson at ByteofDev built something I can only describe as admirably irresponsible (and something I wish I had thought of first): claudegres, a “PostgreSQL” in which Claude is the entire backend. Not Claude tuning the database, and not Claude writing queries against the database. Claude as…

Vacuum is not a problem as we can help PostgreSQL avoid it with HOT updates. A HammerDB TPROC-C benchmark shows how tuning fillfactor for tables eliminates vacuum and reduces the bloat growth.

Idle sessions consume connection slots and backend memory—not locks or xmin. Learn when and how to reap them without sabotaging your connection pooler.

#​660 — August 5, 2026

Web Version

Lots of videos from this year's PGConf.dev are now on YouTube and I've rounded up some highlights at the end of the issue!
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Your editor, Peter Cooper

Postgres Weekly

If you are a traditional database administrator (DBA) transitioning to Kubernetes, the cloud-native ecosystem can feel like a series of personal attacks on your workflow.

For years, your terminal was your home. If a query was running slow, you SSH’d into the VM, opened /var/lib/pgsql/data/postgresql.conf in vim, bumped up shared_buffers, and ran a quick pg_ctl reload. If you needed to lock down access for a new application server, you hopped into pg_hba.conf, appended a new host rule, and went about your day.

Replication slots promise to keep WAL forever—until PostgreSQL 18's new `idle_replication_slot_timeout` puts an expiration date on abandoned ones before they…

“The database is locked up.” We heard some version of that sentence more than once this past week, from the same team, about what looked like the same problem. It was not the same problem. Once, Postgres had genuinely stopped responding. Every other time, Postgres was fine, and a connection sitting in the application’s pool had quietly died somewhere between the app and the database.

Idle transactions hold locks and block vacuums, turning one forgotten connection into a cascading outage.

ident_file tells the server where pg_ident.conf lives, but when it's wrong, the server just logs a quiet failure and keeps running.

`hot_standby_feedback` trades primary bloat to prevent query cancellations on standbys—but it only stops cleanup conflicts, not lock or drop conflicts, and…

Your Transaction Boundary Belongs in the Program, Not the Filename#

A phased schema change spans transactional and non-transactional work. Most migration frameworks express that distinction as metadata; pgmi makes it part of the SQL program.

By Alexey Evlampiev

Three facts about PostgreSQL decide how a deployment has to be shaped, and all three are the server’s rules rather than any tool’s.

Your ALTER TABLE Is Fast. The Queue Behind It Is Not.#

A schema change that runs in six milliseconds can still stop every read on the table for sixteen seconds — the damage is done by waiting, not by working.

By Alexey Evlampiev

That's 320 milliseconds vs 671 ms for exact COUNT(DISTINCT) which is about twice as fast on a single scan. Also HLL isn't just about raw speed on one query. The function names are a bit verbose but the pattern is always the same: hash the value, aggregate the hashes into an HLL, then ask for the cardinality.

 

The PostgreSQL Performance Farm is still not quite a reality, but I think there is some hope on the horizon.

On 16th of March 2026, Peter Eisentraut committed patch: SQL Property Graph Queries (SQL/PGQ)   Implementation of SQL property graph queries, according to SQL/PGQ standard (ISO/IEC 9075-16:2023).

I'm pleased to announce that David Rowley will be joining us in September to discuss his talk Optimizing code in the hot path; with examples from tuple deformation. If you're interesting in joining us, please sign up using this form and I will send you an invite to one of the sessions. As always, thanks to David for agreeing to join the sessions.

PostgreSQL 18 adds a Grand Unified Configuration (GUC), , that lets an extension's control and SQL files live outside the server's own directories. Together with Kubernetes's ImageVolume and Docker's , that makes it practical to package an extension as its own small OCI container image and mount it into the PostgreSQL pod at runtime, without rebuilding the server image.The idea is compelling. A fleet of clusters sharing one lean, unmodified PostgreSQL image. Extensions versioned and upgraded independently.

The official logs are still processing, but the raw data is ready.

Welcome to the newest #UNLOGGED drop from WAWTech+Summer 2026 in Warsaw. We traded the classic conference center for an open-air tech festival at Tor Służewiec, and the energy was incredible.