Re: [HACKERS] Partition-wise aggregation/grouping

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От Rafia Sabih
Тема Re: [HACKERS] Partition-wise aggregation/grouping
Дата
Msg-id CAOGQiiPMAp0gQqJ3ZDHDpkbih1Wfi3ZZ4BXmbeThR4k=e=GNWg@mail.gmail.com
обсуждение исходный текст
Ответ на Re: [HACKERS] Partition-wise aggregation/grouping  (Jeevan Chalke <jeevan.chalke@enterprisedb.com>)
Ответы Re: [HACKERS] Partition-wise aggregation/grouping
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On Tue, Feb 13, 2018 at 6:21 PM, Jeevan Chalke <jeevan.chalke@enterprisedb.com> wrote:
 
I see that partition-wise aggregate plan too uses parallel index, am I missing something?
 
You're right, I missed that, oops. 

Q18 takes some 390 secs with patch and some 147 secs without it. 

This looks strange. This patch set does not touch parallel or seq scan as such. I am not sure why this is happening. All these three queries explain plan shows much higher execution time for parallel/seq scan.

Yeah strange it is.
However, do you see similar behaviour with patches applied, "enable_partition_wise_agg = on" and "enable_partition_wise_agg = off" ?

I tried that for query 18, with patch and  enable_partition_wise_agg = off, query completes in some 270 secs. You may find the explain analyse output for it in the attached file. I noticed that on head the query plan had parallel hash join however with patch and no partition-wise agg it is using nested loop joins. This might be the issue.
 
Also, does rest of the queries perform better with partition-wise aggregates?
 
As far as this setting goes, there wasn't any other query using partition-wise-agg, so, no.

BTW, just an FYI, this experiment is on scale factor 20.

--
Regards,
Rafia Sabih
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