On Tue, Jun 7, 2016 at 12:28 AM, Alvaro Herrera
<alvherre@2ndquadrant.com> wrote:
> Tom Lane wrote:
>> Alvaro Herrera <alvherre@2ndquadrant.com> writes:
>
>> > I can't imagine that the server is avoiding hash aggregation on a 1MB
>> > work_mem limit for data that's a few dozen of bytes. Is it really doing
>> > that?
>>
>> Yup:
>
> Aha. Thanks for testing.
>
>> Now that you mention it, this does seem a bit odd, although I remember
>> that there's a pretty substantial fudge factor in there when we have
>> no statistics (which we don't in this example). If I ANALYZE ctv_data
>> then it sticks to the hashagg plan all the way down to 64kB work_mem.
>
> Hmm, so we could solve the complaint by adding an ANALYZE. I'm open to
> that; other opinions?
We could just enforce work_mem to 64kB and then reset it.
--
Michael