I've done the upgrade to 9.5. Memory bloat has reduced to a more manageable level. Most workers have an overhead of <20MB, with one outlier consuming 60MB.
— Theron
On Fri, Aug 26, 2016 at 5:41 AM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote:
Theron Luhn <theron@xxxxxxxx> writes:
> Okay, I got a semi-reproducible test case:
> https://gist.github.com/luhn/2b35a9b31255e3a6a2e6a06d1213df c9
> The one caveat is that the memory rise only happens when using a
> HashAggregate query plan (included in the gist), which I can't find a way
> to get Postgres to reliably use.
OK, I can reproduce some memory bloat in 9.3, but not in 9.5 and up.
I believe this was fixed by commit b419865a8, which reduced the overhead
of running a lot of instances of array_agg() concurrently in a HashAgg
plan. I think your options are to live with it or upgrade. Or I guess
you could turn off enable_hashagg when using array_agg() plus GROUP BY,
though you'd want to remember to undo that whenever you do upgrade.
regards, tom lane
