On Sat, Nov 4, 2017 at 4:43 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Paul Ramsey <pramsey@cleverelephant.ca> writes:
>>> Whether I get a parallel aggregate seems entirely determined by the number
>>> of rows, not the cost of preparing those rows.
>
>> This is true, as far as I can tell and unfortunate. Feeding tables with
>> 100ks of rows, I get parallel plans, feeding 10ks of rows, never do, no
>> matter how costly the work going on within. That's true of changing costs
>> on the subquery select list, and on the aggregate transfn.
>
> This sounds like it might be the same issue being discussed in
>
> https://www.postgresql.org/message-id/flat/CAMkU=1ycXNipvhWuweUVpKuyu6SpNjF=yHWu4c4US5JgVGxtZQ@mail.gmail.com
>
I have rebased the patch being discussed on that thread.
Paul, you might want to once check with the recent patch [1] posted on
the thread mentioned by Tom.
[1] - https://www.postgresql.org/message-id/CAA4eK1%2B1H5Urm0_Wp-n5XszdLX1YXBqS_zW0f-vvWKwdh3eCJA%40mail.gmail.com
--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com
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