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) https://vondra.me/pdf/performance-cliffs-posette-2024.pdfIncrease the number of fast-path lock slots (committed for Postgres 18) https://www.postgresql.org/message-id/flat/E1ss4gX-000IvX-63%40gemulon.postgresql.org San Francisco Bay Area Postgres meet-up with Tomas on 8th April (online) https://www.meetup.com/postgresql-1/events/306484787Our episode on Extended Statistics https://postgres.fm/episodes/extended-statisticsLogging plan of the currently running query (proposed patch by Rafael Thofehrn Castro and Atsushi Torikoshi) https://commitfest.postgresql.org/patch/5330Our episode with Peter Geoghegan on Skip Scan https://postgres.fm/episodes/skip-scanIndex Prefetching patch that Tomas is collaborating with Peter Geoghegan on https://commitfest.postgresql.org/patch/4351A generalized join algorithm, G-Join (paper by Goetz Graefe) https://dl.gi.de/server/api/core/bitstreams/ce8e3fab-0bac-45fc-a6d4-66edaa52d574/content Smooth Scan: Robust Access Path Selection without Cardinality Estimation (paper by R. Borovica, S. Idreos, A. Ailamaki, M. Zukowski, C. Fraser) https://stratos.seas.harvard.edu/sites/g/files/omnuum4611/files/stratos/files/smoothscan.pdfJust-in-Time Compilation (JIT) https://www.postgresql.org/docs/current/jit.htmlNotes from a pgconf.dev unconference session in 2024 about JIT (discusses issues) https://wiki.postgresql.org/wiki/PGConf.dev_2024_Developer_Unconference#JIT_compilationImplementing an alternative JIT provider for PostgreSQL (by Xing Guo) https://higuoxing.com/archives/implementing-jit-provider-for-pgsqlTomas’ Office Hours https://vondra.me/posts/office-hours-experiment ~~~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 pgMustardNikolay Samokhvalov, founder of Postgres.aiWith special thanks to:Jessie Draws for the elephant artwork 

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) https://www.instacart.com/company/how-its-made/adopting-pgcat-a-nextgen-postgres-proxyPgDog discussion on Hacker News https://news.ycombinator.com/item?id=43364668Citus https://github.com/citusdata/citusSharding & IDs at Instagram (blog post) https://instagram-engineering.com/sharding-ids-at-instagram-1cf5a71e5a5cSharding pgvector (blog post by Lev) https://pgdog.dev/blog/sharding-pgvector~~~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 pgMustardNikolay Samokhvalov, founder of Postgres.aiWith special thanks to:Jessie Draws for the elephant artwork 

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) https://www.postgresql.org/docs/current/functions-admin.html#FUNCTIONS-ADMIN-BACKUP How to troubleshoot long Postgres startup (by Nikolay) https://gitlab.com/postgres-ai/postgresql-consulting/postgres-howtos/-/blob/main/0003_how_to_troubleshoot_long_startup.mdRestoring to a DB instance (RDS docs mentioning lazy loading) https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_RestoreFromSnapshot.html Amazon EBS fast snapshot restore https://docs.aws.amazon.com/ebs/latest/userguide/ebs-fast-snapshot-restore.htmlOur 100th episode “To 100TB, and beyond!” https://postgres.fm/episodes/to-100tb-and-beyond ~~~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 pgMustardNikolay Samokhvalov, founder of Postgres.aiWith credit to:Jessie Draws for the elephant artwork

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) https://pganalyze.com/blog/gin-index~~~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 pgMustardNikolay Samokhvalov, founder of Postgres.aiWith credit to:Jessie Draws for the elephant artwork

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 https://docs.telemetry.mozilla.org/concepts/sql_style“SQL vs NoSQL” episode with Franck Pachot https://postgres.fm/episodes/sql-vs-nosqlHA episode https://postgres.fm/episodes/high-availability ~~~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 pgMustardNikolay Samokhvalov, founder of Postgres.aiWith credit to:Jessie Draws for the elephant artwork

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 https://www.postgresql.org/docs/current/runtime-config-query.html#GUC-DEFAULT-STATISTICS-TARGETTomáš Vondra on Postgres TV https://www.youtube.com/watch?v=8la-OWfD3VIRecent commit to Postgres 18 for pg_upgrade https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=1fd1bd871012732e3c6c482667d2f2c56f1a9395Multivariate Statistics Examples https://www.postgresql.org/docs/current/multivariate-statistics-examples.htmlExtended statistics (README) https://github.com/postgres/postgres/blob/master/src/backend/statistics/READMEHow we used Postgres extended statistics to achieve a 3000x speedup (blog post by Jared Rulison) https://build.affinity.co/how-we-used-postgres-extended-statistics-to-achieve-a-3000x-speedup-ea93d3dcdc61~~~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 pgMustardNikolay Samokhvalov, founder of Postgres.aiWith credit to:Jessie Draws for the elephant artwork

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 Stonebraker and Álvaro Hernández https://www.enterprisedb.com/blog/schema-later-considered-harmfulComparison of JOINS by Michael Stonebraker and Álvaro Hernández https://www.enterprisedb.com/blog/comparison-joins-mongodb-vs-postgresql Franck’s post about why he joined MongoDB https://www.linkedin.com/pulse/2025-im-joining-mongodb-franck-pachot-e4shfEdgeDB https://www.edgedb.comNikolay’s tweet about a recent issue with NULLs https://x.com/samokhvalov/status/1889078097124999272PartiQL https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ql-reference.htmlFerretDB https://www.ferretdb.comDocumentDB https://github.com/microsoft/documentdb~~~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 pgMustardNikolay Samokhvalov, founder of Postgres.aiWith special thanks to:Jessie Draws for the elephant artwork 

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) https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=c2a4078ebad71999dd451ae7d4358be3c9290b07https://explain.depesz.com/historyLatency Numbers Every Programmer Should Know https://gist.github.com/jboner/2841832Twitter conversation about flushing caches https://x.com/prochazkafilip/status/1881655337499205736pg_buffercache_evict https://www.postgresql.org/docs/current/pgbuffercache.html#PGBUFFERCACHE-PG-BUFFERCACHE-EVICTHow to compare the quality of SQL query plans (blog post by Andrei Lepikhov) https://danolivo.substack.com/p/whose-optimisation-is-betterWe were added as PostgreSQL Contributors! https://www.postgresql.org/about/news/new-postgresql-contributors-3006~~~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 pgMustardNikolay Samokhvalov, founder of Postgres.aiWith special thanks to:Jessie Draws for the elephant artwork 

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) https://wiki.postgresql.org/wiki/Hint_Bitspg_stat_statements https://www.postgresql.org/docs/current/pgstatstatements.html pg_stat_kcache https://github.com/powa-team/pg_stat_kcache pg_wait_sampling https://github.com/postgrespro/pg_wait_sampling BUFFERS by default (episode 4!) https://postgres.fm/episodes/buffers-by-default Page layout (docs) https://www.postgresql.org/docs/current/storage-page-layout.html From Reddit (user merlinm), PD_ALL_VISIBLE may be a third case https://www.reddit.com/r/PostgreSQL/comments/1hjuyfn/comment/m3e6e7v/ Coroot https://coroot.com/ ~~~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 pgMustardNikolay Samokhvalov, founder of Postgres.aiWith special thanks to:Jessie Draws for the elephant artwork 

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 https://www.postgresql.org/docs/current/sql-altertable.html#SQL-ALTERTABLE-DESC-VALIDATE-CONSTRAINTALTER TABLE notes https://www.postgresql.org/docs/current/sql-altertable.html#SQL-ALTERTABLE-NOTESpgroll https://github.com/xataio/pgroll~~~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 pgMustardNikolay Samokhvalov, founder of Postgres.aiWith special thanks to:Jessie Draws for the elephant artwork