Re: Fluctuating performance of updates on small table with trigger

On Wed, Jun 29, 2022 at 09:31:58PM +0200, Mikkel Lauritsen wrote:
> In short I'm running PostgreSQL 14.1 on Linux on a small test machine with

should try to upgrade to 14.4, for $reasons

> Is there any feasible way to find out what it is that causes Postgres to
> start doing slow updates? My guess would be a buffer filling up or something
> similar, but the regularity between runs paired with the irregular lengths
> of the fast and slow phases in each run doesn't really seem to fit with
> this.

Set log_checkpoints=on, log_autovacuum_min_duration=0, log_lock_waits=on, and
enable autoexplain with auto_explain.log_nested_statements=on.

Then see what's in the logs when that happens.

@hackers: the first two of those are enabled by default in 15dev, and this
inquiry seems to support that change.

--
Justin