i upgraded my server from 11.4-1 ( note, this was the debian package before
) to 11.5-1.pgdg+1 which uses the postgresql apt repository package. after
this upgrade, i noticed a lot more system load and all 4 cores of my server
hit 100% usage by the database.
at ~11:10 i installed the new version, afterwards you see the cpu hit 100%
usage and than followed some desperate measures to get the database to
perform normal again, mostly reindex and vacuum full on the given database.
at 14:30 i wondered and installed the debian provided 11.5-1 package and
everything went back to 'normal' without any other changes. there was not a
single cause like a long running query. just everything went a lot slower
and used more cpu. there were no obvious differences in query planning.