Postgres FM

Nik and Michael discuss query level comments, object level comments, and another way of adding object level metadata.
 
Here are some links to things they mentioned: 

• Object comments https://www.postgresql.org/docs/current/sql-comment.html
• Query comment syntax (from an old version of the docs) https://www.postgresql.org/docs/7.0/syntax519.htm
• SQL Comments, Please! (Post by Markus Winand) https://modern-sql.com/caniuse/comments
• “While C-style block comments are passed to the server for processing and removal, SQL-standard comments are removed by psql.” https://www.postgresql.org/docs/current/app-psql.html
• marginalia https://github.com/basecamp/marginalia
• track_activity_query_size https://www.postgresql.org/docs/current/runtime-config-statistics.html#GUC-TRACK-ACTIVITY-QUERY-SIZE
• Custom Properties for Database Objects Using SECURITY LABELS (post by Andrei Lepikhov) https://www.pgedge.com/blog/custom-properties-for-postgresql-database-objects-without-core-patches

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What did you like or not like? What should we discuss next time? Let us know via a YouTube comment, on social media, or by commenting on our Google doc!

~~~

Postgres FM is produced by:

• Michael Christofides, founder of pgMustard
• Nikolay Samokhvalov, founder of Postgres.ai

With credit to:

• Jessie Draws for the elephant artwork

Nik and Michael are joined by Lev Kokotov for an update on all things PgDog.
 
Here are some links to things they mentioned:

• Lev Kokotov https://postgres.fm/people/lev-kokotov
• PgDog https://github.com/pgdogdev/pgdog
• Our first PgDog episode (March 2025) https://postgres.fm/episodes/pgdog
• Sharding pgvector (blog post by Lev) https://pgdog.dev/blog/sharding-pgvector
• Prepared statements and partitioned table lock explosion (series by Nik) https://postgres.ai/blog/20251028-postgres-marathon-2-009

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What did you like or not like? What should we discuss next time? Let us know via a YouTube comment, on social media, or by commenting on our Google doc!

~~~

Postgres FM is produced by:

• Michael Christofides, founder of pgMustard
• Nikolay Samokhvalov, founder of Postgres.ai

With credit to:

• Jessie Draws for the elephant artwork

Nik and Michael are joined by Radim Marek from boringSQL to talk about RegreSQL, a regression testing tool for SQL queries they forked and improved recently.
 
Here are some links to things they mentioned:

• Radim Marek https://postgres.fm/people/radim-marek
• boringSQL https://boringsql.com
• RegreSQL: Regression Testing for PostgreSQL Queries (blog post by Radim) https://boringsql.com/posts/regresql-testing-queries
• Discussion on Hacker News https://news.ycombinator.com/item?id=45924619 
• Radim’s fork of RegreSQL on GitHub https://github.com/boringSQL/regresql 
• Original RegreSQL on GitHub (by Dimitri Fontaine) https://github.com/dimitri/regresql 
• The Art of PostgreSQL (book) https://theartofpostgresql.com
• How to make the non-production Postgres planner behave like in production (how-to post by Nik) https://postgres.ai/docs/postgres-howtos/performance-optimization/query-tuning/how-to-imitate-production-planner 
• Just because you’re getting an index scan, doesn't mean you can’t do better! (Blog post by Michael) https://www.pgmustard.com/blog/index-scan-doesnt-mean-its-fast
• boringSQL Labs https://labs.boringsql.com

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What did you like or not like? What should we discuss next time? Let us know via a YouTube comment, on social media, or by commenting on our Google doc!

~~~

Postgres FM is produced by:

• Michael Christofides, founder of pgMustard
• Nikolay Samokhvalov, founder of Postgres.ai

With credit to:

• Jessie Draws for the elephant artwork

Nik and Michael discuss the events and trends they thought were most important in the Postgres ecosystem in 2025.
 
Here are some links to things they mentioned: 

• Postgres 18 release notes https://www.postgresql.org/docs/18/release-18.html
• Our episode on Postgres 18 https://postgres.fm/episodes/postgres-18
• LWLock:LockManager benchmarks for Postgres 18 (blog post by Nik) https://postgres.ai/blog/20251009-postgres-marathon-2-005
• PostgreSQL bug tied to zero-day attack on US Treasury https://www.theregister.com/2025/02/14/postgresql_bug_treasury
• PgDog episode https://postgres.fm/episodes/pgdog
• Multigres episode https://postgres.fm/episodes/multigres
• Neki announcement https://planetscale.com/blog/announcing-neki
• Our 100TB episode from 2024 https://postgres.fm/episodes/to-100tb-and-beyond
• PlanetScale for Postgres https://planetscale.com/blog/planetscale-for-postgres
• Oracle's MySQL job cuts https://www.theregister.com/2025/09/11/oracle_slammed_for_mysql_job
• Amazon Aurora DSQL is now generally available https://aws.amazon.com/about-aws/whats-new/2025/05/amazon-aurora-dsql-generally-available
• Announcing Azure HorizonDB https://techcommunity.microsoft.com/blog/adforpostgresql/announcing-azure-horizondb/4469710
• Lessons from Replit and Tiger Data on Storage for Agentic Experimentation https://www.tigerdata.com/blog/lessons-replit-tiger-data-storage-agentic-experimentation
• Instant database clones with PostgreSQL 18 https://boringsql.com/posts/instant-database-clones
• turbopuffer episode https://postgres.fm/episodes/turbopuffer
• Crunchy joins Snowflake https://www.crunchydata.com/blog/crunchy-data-joins-snowflake
• Neon joins Databricks https://neon.com/blog/neon-and-databricks

~~~

What did you like or not like? What should we discuss next time? Let us know via a YouTube comment, on social media, or by commenting on our Google doc!

~~~

Postgres FM is produced by:

• Michael Christofides, founder of pgMustard
• Nikolay Samokhvalov, founder of Postgres.ai

With credit to:

• Jessie Draws for the elephant artwork

Nik and Michael discuss a listener question about archiving a database.
 
Here are some links to things they mentioned: 

• Listener request to talk about archiving https://www.youtube.com/watch?v=KFRK8PiIvTg&lc=UgyiFrO37gEgUaVhRgN4AaABAg 
• Our episode on “Is pg_dump a backup tool?” https://postgres.fm/episodes/is-pg_dump-a-backup-tool 

~~~

What did you like or not like? What should we discuss next time? Let us know via a YouTube comment, on social media, or by commenting on our Google doc!

~~~

Postgres FM is produced by:

• Michael Christofides, founder of pgMustard
• Nikolay Samokhvalov, founder of Postgres.ai

With credit to:

• Jessie Draws for the elephant artwork

Nik and Michael discuss max_connections, especially in the context of increasing it to solve problems like migrations intermittently failing(!)
 
Here are some links to things they mentioned: 

• max_connections https://www.postgresql.org/docs/current/runtime-config-connection.html#GUC-MAX-CONNECTIONS
• Tweet about deployments vs connections issue https://x.com/brankopetric00/status/1991394329886077090
• Nik tweet in response https://x.com/samokhvalov/status/1991465573684027443
• Analyzing the Limits of Connection Scalability in Postgres (blog post by Andres Freund) https://www.citusdata.com/blog/2020/10/08/analyzing-connection-scalability/
• Exponential Backoff And Jitter (blog post by Marc Brooker) https://aws.amazon.com/blogs/architecture/exponential-backoff-and-jitter/

~~~

What did you like or not like? What should we discuss next time? Let us know via a YouTube comment, on social media, or by commenting on our Google doc!

~~~

Postgres FM is produced by:

• Michael Christofides, founder of pgMustard
• Nikolay Samokhvalov, founder of Postgres.ai

With credit to:

• Jessie Draws for the elephant artwork

Nik and Michael discuss the various changes to EXPLAIN that arrived in Postgres 18.
 
Here are some links to things they mentioned: 

• EXPLAIN (official docs) https://www.postgresql.org/docs/current/sql-explain.html
• Using EXPLAIN (official docs) https://www.postgresql.org/docs/current/using-explain.html 
• EXPLAIN glossary (pgMustard site) https://www.pgmustard.com/docs/explain
• Postgres 18 release notes https://www.postgresql.org/docs/release/18.0/
• Enable BUFFERS with EXPLAIN ANALYZE by default (commit) https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=c2a4078eb
• Our (first) BUFFERS by default episode https://postgres.fm/episodes/buffers-by-default 
• Show index search count in EXPLAIN ANALYZE (commit) https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=0fbceae841cb5a31b13d3f284ac8fdd19822eceb
• Our episode on Skip scan with Peter Geoghegan https://postgres.fm/episodes/skip-scan
• What do the new Index Searches lines in EXPLAIN mean? https://www.pgmustard.com/blog/what-do-index-searches-in-explain-mean
• pg_stat_plans presentation by Lukas Fittl https://www.youtube.com/watch?v=26coQV3f-wk
• Improve EXPLAIN's display of window functions (commit) https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=8b1b34254
• Show Parallel Bitmap Heap Scan worker stats in EXPLAIN ANALYZE (commit) https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=5a1e6df3b
• Add information about WAL buffers being full (commit) https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=320545bfc 

~~~

What did you like or not like? What should we discuss next time? Let us know via a YouTube comment, on social media, or by commenting on our Google doc!

~~~

Postgres FM is produced by:

• Michael Christofides, founder of pgMustard
• Nikolay Samokhvalov, founder of Postgres.ai

With credit to:

• Jessie Draws for the elephant artwork

Nik talks Michael through a recent benchmark he worked with Maxim Boguk on, to see how quickly they could provision a replica.
 
Here are some links to things they mentioned:

• Ultra-fast replica creation with pgBackRest (blog post by Maxim Boguk and Nik) https://postgres.ai/blog/20251105-postgres-marathon-2-012-ultra-fast-replica-creation-pgbackrest
• Copying a database episode https://postgres.fm/episodes/copying-a-database
• Add snapshot backup support for PostgreSQL in wal-g (draft PR by Andrey Borodin) https://github.com/wal-g/wal-g/pull/2101
• Multi-threaded pg_basebackup discussion 1: https://www.postgresql.org/message-id/flat/CAEHH7R4%3D_GN%2BLSsj0YZOXZ13yc%3DGk9umJOLNopjS%3DimK0c1mWA%40mail.gmail.com
• Multi-threaded pg_basebackup discussion 2: https://www.postgresql.org/message-id/flat/
• io_method https://www.postgresql.org/docs/current/runtime-config-resource.html#GUC-IO-METHOD 
• pgBackRest https://github.com/pgbackrest/pgbackrest
• Add sequence synchronization for logical replication (commit) https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=5509055d6956745532e65ab218e15b99d87d66ce 
• Allow process priority to be set (pgBackRest feature added by David Steele) https://github.com/pgbackrest/pgbackrest/pull/2693 
• Hard limit on process-max (pgBackRest issue from 2019) https://github.com/pgbackrest/pgbackrest/issues/696 

~~~

What did you like or not like? What should we discuss next time? Let us know via a YouTube comment, on social media, or by commenting on our Google doc!

~~~

Postgres FM is produced by:

• Michael Christofides, founder of pgMustard
• Nikolay Samokhvalov, founder of Postgres.ai

With credit to:

• Jessie Draws for the elephant artwork

Nik and Michael discuss the concept of gapless sequences — when you might want one, why sequences in Postgres can have gaps, and an idea or two if you do want them.

And one quick clarification: changing the CACHE option in CREATE SEQUENCE can lead to even more gaps, the docs mention it explicitly.
 
Here are some links to things they mentioned:

• CREATE SEQUENCE https://www.postgresql.org/docs/current/sql-createsequence.html
• Sequence Manipulation Functions https://www.postgresql.org/docs/current/functions-sequence.html
• One, Two, Skip a Few (post by Pete Hamilton from Incident io) https://incident.io/blog/one-two-skip-a-few
• Postgres sequences can commit out-of-order (blog post by Anthony Accomazzo / Sequin) https://blog.sequinstream.com/postgres-sequences-can-commit-out-of-order
• Logical Replication of sequences (hackers thread) https://www.postgresql.org/message-id/flat/CAA4eK1LC%2BKJiAkSrpE_NwvNdidw9F2os7GERUeSxSKv71gXysQ%40mail.gmail.com
• Synchronization of sequences to subscriber (patch entry in commitfest) https://commitfest.postgresql.org/patch/5111/
• Get or Create (episode with Haki Benita) https://postgres.fm/episodes/get-or-create
• German tank problem https://en.wikipedia.org/wiki/German_tank_problem

~~~

What did you like or not like? What should we discuss next time? Let us know via a YouTube comment, on social media, or by commenting on our Google doc!

~~~

Postgres FM is produced by:

• Michael Christofides, founder of pgMustard
• Nikolay Samokhvalov, founder of Postgres.ai

With credit to:

• Jessie Draws for the elephant artwork

Nik and Michael discuss lightweight locks in Postgres — how they differ to (heavier) locks, some occasions they can be troublesome, and some resources for working out what to do if you hit issues.
 
Here are some links to things they mentioned:

• Wait Events of Type LWLock https://www.postgresql.org/docs/current/monitoring-stats.html#WAIT-EVENT-LWLOCK-TABLE
• Our episode on (heavier) locks https://postgres.fm/episodes/locks
• Nik’s new marathon posts https://postgres.ai/blog/tags/postgres-marathon
• Postgres LISTEN/NOTIFY does not scale (blog post by Recall ai) https://www.recall.ai/blog/postgres-listen-notify-does-not-scale
• Explicit Locking https://www.postgresql.org/docs/current/explicit-locking.html
• pg_stat_activity https://www.postgresql.org/docs/current/monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW
• Tuning with wait events for RDS for PostgreSQL https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/PostgreSQL.Tuning.html
• MultiXact member exhaustion incidents (blog post by Cosmo Wolfe / Metronome) https://metronome.com/blog/root-cause-analysis-postgresql-multixact-member-exhaustion-incidents-may-2025
• pg_index_pilot https://gitlab.com/postgres-ai/pg_index_pilot
• Myths and Truths about Synchronous Replication in PostgreSQL (talk by Alexander Kukushkin) https://www.youtube.com/watch?v=PFn9qRGzTMc
• Postgres Indexes, Partitioning and LWLock:LockManager Scalability (blog post by Jeremy Schneider) https://ardentperf.com /2024/03/03/postgres-indexes-partitioning-and-lwlocklockmanager-scalability

~~~

What did you like or not like? What should we discuss next time? Let us know via a YouTube comment, on social media, or by commenting on our Google doc!

~~~

Postgres FM is produced by:

• Michael Christofides, founder of pgMustard
• Nikolay Samokhvalov, founder of Postgres.ai

With credit to:

• Jessie Draws for the elephant artwork