On Monday, July 22, 2024, Scott Ribe <
scott_ribe@elevated-dev.com> wrote:
> On Jul 22, 2024, at 7:00 AM, Holger Jakobs <holger@jakobs.com> wrote:
>
> Typically, queries which need a lot of memory (RAM) create temp files if work_mem isn't sufficient for some sorting or hash algorithms.
>
> Increasing work_mem will help, but small temp files don't create any trouble.
>
> You can set work_mem within each session, don't set it high globally.
I understand those things--my question is why, with work_mem set to 128MB, I would see tiny temp files (7452 is common, as is 102, and I've seen as small as 51).
You expect the smallest temporary file to be 128MB? I.e., if the memory used exceeds work_mem all of it gets put into the temp file at that point? Versus only the amount of data that exceeds work_mem getting pushed out to the temporary file. The overflow only design seems much more reasonable - why write to disk that which fits, and already exists, in memory.
David J.
