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

Nik and Michael discuss user management in Postgres — how roles work, making administration easier, setting passwords, and avoiding them being logged.

Here are some links to things they mentioned:

• Roles https://www.postgresql.org/docs/current/user-manag.html
• Privileges https://www.postgresql.org/docs/current/ddl-priv.html
• ALTER DEFAULT PRIVILEGES https://www.postgresql.org/docs/current/sql-alterdefaultprivileges.html
• GRANT https://www.postgresql.org/docs/current/sql-grant.html
• REASSIGN OWNED https://www.postgresql.org/docs/current/sql-reassign-owned.html
• ALTER ROLE (including SET) https://www.postgresql.org/docs/current/sql-alterrole.html
• CREATE ROLE https://www.postgresql.org/docs/current/sql-createrole.html
• Have I Been Pwned https://haveibeenpwned.com
• Pwned Passwords API https://haveibeenpwned.com/API/v3#PwnedPasswords
• Crunchy Data PostgreSQL Security Technical Implementation Guide (STIG) https://www.crunchydata.com/blog/announcing-the-crunchy-data-postgresql-stig
• Our episode on auditing https://postgres.fm/episodes/auditing

~~~

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