On Thu, 2021-02-04 at 10:03 +0000, Zwettler Markus (OIZ) wrote: > I have 2 identical systems A + B. > B being a clone of A. > > The table pg_catalog.pg_largeobject was identical on both systems: 300GB in total size; 100GB bloated. > > I did following on A: > ð vacuum full pg_catalog.pg_largeobject; > (using the default maintenance_work_mem of 64MB) > It took around 45 minutes and increased the diskspace by around 125% until the vacuum had been finished. > > I did following on B: > ð set maintenance_work_mem = '256MB'; > ð vacuum full pg_catalog.pg_largeobject; > This took around 5 minutes. I don't know if the diskspace ever increased. > > I was really surprised. > Is there any explanation on this behavior? > Is vacuum full heavily using on-disk sort areas if maintenance_work_mem is too low? > > Postgres Version 9.6 VACUUM (FULL) will re-create the indexes too, and "maintenance_work_mem" has an impact on index build speed. But I have no explanation for such a large difference. Yours, Laurenz Albe -- Cybertec | https://www.cybertec-postgresql.com
