On Wed, Feb 14, 2018 at 12:17 PM, Rafia Sabih <rafia.sa...@enterprisedb.com>

> On Tue, Feb 13, 2018 at 6:21 PM, Jeevan Chalke <
> jeevan.cha...@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.

Off-list I have asked Rafia to provide me the perf machine access where she
is doing this bench-marking to see what's going wrong.
Thanks Rafia for the details.

What I have observed that, there are two sources, one with HEAD and other
with HEAD+PWA. However the configuration switches were different. Sources
with HEAD+PWA has CFLAGS="-ggdb3 -O0" CXXFLAGS="-ggdb3 -O0" flags in
addition with other sources. i.e. HEAD+PWA is configured with
debugging/optimization enabled which account for the slowness.

I have run EXPLAIN for these three queries on both the sources having
exactly same configuration switches and I don't find any slowness with PWA

Thus, it will be good if you re-run the benchmark by keeping configuration
switches same on both the sources and share the results.


> 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/

Jeevan Chalke
Technical Architect, Product Development
EnterpriseDB Corporation
The Enterprise PostgreSQL Company

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