Re: Less than ideal error reporting in pg_stat_statements

On Fri, Sep 25, 2015 at 8:51 AM, Marti Raudsepp <marti(at)juffo(dot)org> wrote:
> I've also been seeing lots of log messages saying "LOG: out of
> memory" on a server that's hosting development databases. I put off
> debugging this until now because it didn't seem to have any adverse
> effects on the system.
>
> The file on my system is currently 5.1GB (!). I don't know how it got
> there -- under normal circumstances we don't have any enormous
> queries, but perhaps our application bugs during development triggered
> that.

It could be explained by legitimate errors during planning, for
example. The query text is still stored.

> So, as I understand it: if the system runs low on memory for an
> extended period, and/or the file grows beyond 1GB (MaxAlloc), garbage
> collection stops entirely, meaning it starts leaking disk space until
> a manual intervention.

I don't think that there is much more to discuss here: this is a bug.
I will try and write a patch to fix it shortly. It will be
non-trivial, and I'm quite busy right now, so it might take a while. A
short-term remediation is to call pg_stat_statements_reset() on
systems affected like this.

--
Peter Geoghegan