On Mon, Mar 29, 2021 at 11:10 AM Campbell, Lance <lance@xxxxxxxxxxxx> wrote: > If you divide 451 by 21 you get 21.4 . I would have expected to see an average size greater than 24 MB. This implies to me that PostgreSQL is creating temp files that are smaller than 24 MB. > > What am I not understanding? work_mem limits the in-memory space used by sort and hash operations. It doesn't necessarily follow that the on-disk footprint is exactly (or even approximately) the same as the in-memory footprint for any given operation that barely can't fit in memory. The precise space overheads will vary based on lots of factors, most of which are implementation details. -- Peter Geoghegan
