PODCAST

Postgres FM

Nikolay Samokhvalov and Michael Christofides

A weekly podcast about all things PostgreSQL

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All Episodes

38:51

Mean vs p99

Postgres FM ·

2025/06/13

Nikolay and Michael discuss looking at queries by mean time — when it makes sense, why ordering by a percentile (like p99) might be better, and the merits of approximating percentiles in pg_stat_statements using the standard deviation column. Here are some links to things they mentioned:Approximate the p99 of a query with pg_stat_statements (blog post by Michael) https://www.pgmustard.com/blog/approximate-the-p99-of-a-query-with-pgstatstatementspg_stat_statements

48:34

What to log

Postgres FM ·

2025/06/06

Nikolay and Michael discuss logging in Postgres — mostly what to log, and why changing quite a few settings can pay off big time in the long term. Here are some links to things they mentioned:What to log https://www.postgresql.org/docs/current/runtime-config-logging.html#RUNTIME-CONFIG-LOGGING-WHATOur episode about Auditing https://postgres.fm/episodes/auditing Our episode on auto_explain https://postgres.fm/episodes/auto_explain Here are the parameters they mentioned

47:33

How to move off RDS

Postgres FM ·

2025/05/30

Nikolay and Michael discuss moving off managed services — when and why you might want to, and some tips on how for very large databases. Here are some links to things they mentioned:Patroni https://github.com/patroni/patronipgBackRest https://github.com/pgbackrest/pgbackrestWAL-G https://github.com/wal-g/wal-gHetzner Cloud https://www.hetzner.com/cloudPostgres Extensions Day https://pgext.daypg_wait_sampling https://github.com/postgrespro/pg_wait_samplingpg_stat_kcache

38:53

Locks

Postgres FM ·

2025/05/23

Nikolay and Michael discuss heavyweight locks in Postgres — how to think about them, why you can't avoid them, and some tips for minimising issues. Here are some links to things they mentioned:Locking (docs) https://www.postgresql.org/docs/current/explicit-locking.htmlPostgres rocks, except when it blocks (blog post by Marco Slot) https://www.citusdata.com/blog/2018/02/15/when-postgresql-blocks/Lock Conflicts (tool by Hussein Nasser) https://pglocks.org/log_lock_waits (docs)

46:28

Top ten dangerous issues

Postgres FM ·

2025/05/09

Nikolay and Michael discuss ten dangerous Postgres related issues — ones that might be painful enough to get onto the CTO and even CEOs desk, and then what you can do proactively. The ten issues discussed are:Heavy lock contentionBloat control and index maintenance Lightweight lock contentionTransaction ID wraparound4-byte integer PKs hitting the limitReplication limitsHard limitsData lossPoor HA choice (split brain)Corruption of various kindsSome previous episodes they mentioned that

50:53

synchronous_commit

Postgres FM ·

2025/05/02

Nikolay and Michael discuss synchronous_commit — what it means on single node setups, for synchronous replication setups, and the pros and cons of the different options for each. Here are some links to things they mentioned:synchronous_commit https://www.postgresql.org/docs/current/runtime-config-wal.html#GUC-SYNCHRONOUS-COMMITsynchronous_commit history on pgPedia https://pgpedia.info/s/synchronous_commit.htmlPatroni’s maximum_lag_on_failover setting

35:37

Managed service support

Postgres FM ·

2025/04/25

Nikolay and Michael discuss managed service support — some tips on how to handle cases that aren't going well, tips for requesting features, whether to factor in support when choosing service provider, and whether to use one at all. Here are some links to things they mentioned:YugabyteDB’s new upgrade framework https://www.yugabyte.com/blog/postgresql-upgrade-frameworkEpisode on Blue-green deployments https://postgres.fm/episodes/blue-green-deploymentspg_createsubscriber

42:42

Time-series considerations

Postgres FM ·

2025/04/11

Nikolay and Michael discuss time-series considerations for Postgres — including when it matters, some tips for avoiding issues, performance considerations, and more. Here are some links to things they mentioned:Time series data https://en.wikipedia.org/wiki/Time_seriesTimescaleDB https://github.com/timescale/timescaledb13 Tips to Improve PostgreSQL Insert Performance https://www.timescale.com/blog/13-tips-to-improve-postgresql-insert-performanceWhy we're leaving the cloud (37 Signals /

38:08

Performance cliffs

Postgres FM ·

2025/04/04

Nikolay and Michael are joined by Tomas Vondra to discuss single query performance cliffs — what they are, why they happen, some things we can do to make them less likely or less severe, and some potential improvements to Postgres that could help. Here are some links to things they mentioned:Tomas Vondra https://postgres.fm/people/tomas-vondraWhere do performance cliffs come from? (Talk by Tomas) https://www.youtube.com/watch?v=UzdAelm-QSYWhere do performance cliffs come from? (Slides)

48:34

PgDog

Postgres FM ·

2025/03/28

Nikolay and Michael are joined by Lev Kokotov to discuss PgDog — including whether or when sharding is needed, the origin story (via PgCat), what's already supported, and what's coming next. Here are some links to things they mentioned:Lev Kokotov https://postgres.fm/people/lev-kokotovPgDog https://github.com/pgdogdev/pgdogPgCat https://github.com/postgresml/pgcatAdopting PgCat (Instacart blog post)

44:05

Snapshots

Postgres FM ·

2025/03/21

Nikolay talks Michael through using cloud snapshots — how they can be used to reduce RTO for huge Postgres setups, also to improve provisioning time, and some major catches to be aware of. Here are some links to things they mentioned:Snapshots on RDS https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_CreateSnapshot.htmlpgBackRest https://pgbackrest.orgWAL-G https://github.com/wal-g/wal-gpg_backup_start and pg_backup_stop (docs)

40:59

GIN Indexes

Postgres FM ·

2025/03/14

Nikolay and Michael discuss GIN indexes in Postgres — what they are, what they're used for, and some limitations to be aware of. Here are some links to things they mentioned:GIN Indexes https://www.postgresql.org/docs/current/gin.htmlGeneralized Search Trees for Database Systems (Hellerstein, Naughton, Pfeffer) https://dsf.berkeley.edu/papers/vldb95-gist.pdf RUM extension https://pgxn.org/dist/rum/1.1.0/Understanding Postgres GIN Indexes: The Good and the Bad (Lukas Fittl)

40:49

Best Practices

Postgres FM ·

2025/03/07

Nikolay and Michael use a recent "best practices" article as a prompt — giving a few tips each on the topics mentioned, like schema design, performance, backups, and more. Here are some links to things they mentioned:7 Crucial PostgreSQL Best Practices (recent blog post) https://speakdatascience.com/postgresql-best-practices“Don't do this” episode https://postgres.fm/episodes/dont-do-thisArticle discussion on Hacker News https://news.ycombinator.com/item?id=42992913Mozilla’s SQL Style Guide

32:41

Extended Statistics

Postgres FM ·

2025/02/28

Nikolay and Michael discuss the CREATE STATISTICS feature in Postgres — what it's for, how often it's used, and how to spot cases where it would help. Here are some links to things they mentioned:CREATE STATISTICS https://www.postgresql.org/docs/current/sql-createstatistics.htmlcitext https://www.postgresql.org/docs/current/citext.htmlStatistics Used by the Planner https://www.postgresql.org/docs/current/planner-stats.htmldefault_statistics_target

50:01

SQL vs NoSQL

Postgres FM ·

2025/02/14

Nikolay and Michael are joined by Franck Pachot to discuss SQL vs NoSQL — did Franck change teams by joining MongoDB, normalisation vs denormalisation, developer experience, NULLs, and more! Here are some links to things they mentioned:Franck Pachot https://postgres.fm/people/franck-pachotFranck's workshop at PGConf India https://pgconf.in/conferences/pgconfin2025/program/proposals/958 PostgreSQL Conference Germany https://2025.pgconf.de"Schema Later" Considered Harmful by Michael

51:46

Return of the BUFFERS

Postgres FM ·

2025/02/07

Nikolay and Michael return to the topic of BUFFERS for the third (and final?) time! They discuss the news that it'll be on by default with EXPLAIN ANALYZE in Postgres 18, and what effect that might have. Here are some links to things they mentioned:Our first BUFFERS episode https://postgres.fm/episodes/buffers-by-defaultOur second BUFFERS episode https://postgres.fm/episodes/buffers-ii-the-sequelBUFFERS enabled for EXPLAIN ANALYZE by default (commit for Postgres 18)

26:48

Reads causing writes

Postgres FM ·

2025/01/24

Nikolay and Michael discuss a couple of surprising ways read queries (selects) can cause writes (shared buffers dirtied) in Postgres. Here are some links to things they mentioned:Reads causing writes in Postgres (post by Alex Jesipow) https://jesipow.com/blog/postgres-reads-cause-writes/Exploring how SELECT queries can produce disk writes (post by Nikolay Sivko) https://blog.okmeter.io/postgresql-exploring-how-select-queries-can-produce-disk-writes-f36c8bee6b6f Hint Bits (wiki)

33:56

NOT VALID constraints

Postgres FM ·

2025/01/17

Nikolay and Michael discuss adding constraints in an online fashion, using NOT VALID and then VALIDATE CONSTRAINT. Here are some links to things they mentioned:ADD table_constraint NOT VALID https://www.postgresql.org/docs/current/sql-altertable.html#SQL-ALTERTABLE-DESC-ADD-TABLE-CONSTRAINTOur episode on zero-downtime migrations https://postgres.fm/episodes/zero-downtime-migrationsVALIDATE CONSTRAINT

36:26

pg_squeeze

Postgres FM ·

2025/01/10

Michael and Nikolay are joined by Antonín Houska to discuss pg_squeeze — what it is, how it started, some of its features, and hopes of getting the functionality into core. Here are some links to things they mentioned:Antonín Houska https://postgres.fm/people/antonin-houskapg_squeeze https://github.com/cybertec-postgresql/pg_squeezeCybertec https://www.cybertec-postgresql.compg_repack https://github.com/reorg/pg_repackIntroducing pg_squeeze (by Kaarel Moppel)

40:08

pg_duckdb

Postgres FM ·

2025/01/03

Michael and Nikolay are joined by Joe Sciarrino and Jelte Fennema-Nio to discuss pg_duckdb — what it is, how it started, what early users are using it for, and what they're working on next. Here are some links to things they mentioned:Joe Sciarrino https://postgres.fm/people/joe-sciarrinoJelte Fennema-Nio https://postgres.fm/people/jelte-fennema-niopg_duckdb https://github.com/duckdb/pg_duckdbHydra https://www.hydra.soMotherDuck https://motherduck.comThe problems and benefits of an elephant

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