Hi, On 2020-03-30 00:49:13 +0200, Peter J. Holzer wrote: > I noticed this with PostgreSQL 11.7 on Linux: > > I did a «vacuum full» on a table which had become quite bloated (size > before the vacuum: 392 GB, after: 291 GB). I expected the disk usage to > increase as the new table was written and then drop sharply after the > vacuum was finished. > > However, that didn't happen. While usage increased by about 300 GB > during the vacuum, it stayed the same afterwards (as reported by «df»). > > However, «du» reported about 400 GB less than «df». So apparently, files > had been unlinked but were still in use by some process. > > «lsof» confirmed this: There were some idle sessions which were keeping > the files open. As soon as I got those sessions to execute some request, > they closed the files, causing the disk space to be freed. > > I think I noticed that before when dropping tables, but didn't draw the > right conclusion at the time. > > So, if you are reorganizing large tables, keep an eye on idle sessions - > they may keep deleted files around for quite some time. I think this is partially related to https://postgr.es/m/20181003223725.elcu3t44fpd4lm56%40alap3.anarazel.de Greetings, Andres Freund
