On 2020-07-13 16:11, Tomas Vondra wrote:
Why is running out of disk space worse experience than running out of
memory?
Sure, it'll take longer and ultimately the query fails (and if it fills
the device used by the WAL then it may also cause shutdown of the main
instance due to inability to write WAL). But that can be prevented by
moving the temp tablespace and/or setting the temp file limit, as
already mentioned.
With OOM, if the kernel OOM killer decides to act, it may easily bring
down the instance too, and there are much less options to prevent that.
Well, that's an interesting point. Depending on the OS setup, by
default an out of memory might actually be worse if the OOM killer
strikes in an unfortunate way. That didn't happen to me in my tests, so
the OS must have been configured differently by default.
So maybe a lesson here is that just like we have been teaching users to
adjust the OOM killer, we have to teach them now that setting the temp
file limit might become more important.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
