Plan flips

Nik and Michael discuss query plan flips in Postgres — what they are, some causes, mitigations, longer term solutions, and the recent outage at Clerk.

Here are some links to things they mentioned:

Recent postmortem from Clerk https://clerk.com/blog/2026-02-19-system-outage-postmortem
The real cost of random I/O (blog post by Tomas Vondra) https://vondra.me/posts/the-real-cost-of-random-io
autovacuum_analyze_scale_factor https://www.postgresql.org/docs/current/runtime-config-vacuum.html#GUC-AUTOVACUUM-ANALYZE-SCALE-FACTOR
default_statistics_target https://www.postgresql.org/docs/current/runtime-config-query.html#GUC-DEFAULT-STATISTICS-TARGET
pg_hint_plan https://github.com/ossc-db/pg_hint_plan
Aurora PostgreSQL query plan management https://docs.aws.amazon.comAmazonRDS/latest/AuroraUserGuide/AuroraPostgreSQL.Optimize.Start.html
pg_stat_plans https://github.com/pganalyze/pg_stat_plans
pg_plan_alternatives https://jnidzwetzki.github.io/2026/03/04/pg-plan-alternatives.html
Waiting for Postgres 19: Better Planner Hints with Path Generation Strategies https://pganalyze.com/blog/5mins-postgres-19-better-planner-hints

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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!

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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

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