Re: [HACKERS] Partition-wise aggregation/grouping

On Tue, Feb 13, 2018 at 6:21 PM, Jeevan Chalke <
jeevan(dot)chalke(at)enterprisedb(dot)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
EnterpriseDB: http://www.enterprisedb.com/