RE: speeding up planning with partitions

From: "Imai, Yoshikazu" <imai(dot)yoshikazu(at)jp(dot)fujitsu(dot)com>
To: 'Amit Langote' <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>
Cc: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Amit Langote <amitlangote09(at)gmail(dot)com>, "Pg Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: RE: speeding up planning with partitions
Date: 2019-01-30 03:11:17
Message-ID: 0F97FA9ABBDBE54F91744A9B37151A5125CE37@g01jpexmbkw24
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Amit-san,

On Tue, Jan 29, 2019 at 10:11 AM, Amit Langote wrote:
> On 2019/01/28 10:44, Imai, Yoshikazu wrote:
> > On Thu, Jan 24, 2019 at 6:10 AM, Imai, Yoshikazu wrote:
> >> updating partkey case:
> >>
> >> part-num master 0001 0002 0003 0004
> >> 1 8215.34 7924.99 7931.15 8407.40 8475.65
> >> 2 7137.49 7026.45 7128.84 7583.08 7593.73
> >> 4 5880.54 5896.47 6014.82 6405.33 6398.71
> >> 8 4222.96 4446.40 4518.54 4802.43 4785.82
> >> 16 2634.91 2891.51 2946.99 3085.81 3087.91
> >> 32 935.12 1125.28 1169.17 1199.44 1202.04
> >> 64 352.37 405.27 417.09 425.78 424.53
> >> 128 236.26 310.01 307.70 315.29 312.81
> >> 256 65.36 86.84 87.67 84.39 89.27
> >> 512 18.34 24.84 23.55 23.91 23.91
> >> 1024 4.83 6.93 6.51 6.45 6.49
> >
> > I also tested with non-partitioned table case.
> >
> > updating partkey case:
> >
> > part-num master 0001 0002 0003 0004
> > 0 10956.7 10370.5 10472.6 10571.0 10581.5
> > 1 8215.34 7924.99 7931.15 8407.40 8475.65
> > ...
> > 1024 4.83 6.93 6.51 6.45 6.49
> >
> >
> > In my performance results, it seems update performance degrades in
> non-partitioned case with v17-patch applied.
> > But it seems this degrades did not happen at v2-patch.
> >
> > On Thu, Aug 30, 2018 at 1:45 AM, Amit, Langote wrote:
> >> UPDATE:
> >>
> >> nparts master 0001 0002 0003
> >> ====== ====== ==== ==== ====
> >> 0 2856 2893 2862 2816
> >
> > Does this degradation only occur in my tests? Or if this result is correct,
> what may causes the degradation?
>
> I re-ran tests with v18 using the following setup [1]:
>
> create table ht (a int, b int) partition by hash (b); create table ht_0
> partition of ht for values with (modulus N, remainder 0); ...
> $ cat update-noprune.sql
> update ht set a = 0;
>
> pgbench -n -T 60 -f update-noprune,sql
>
> TPS:
>
> nparts master 0001 0002 0003 0004
> ====== ====== ==== ==== ==== ====
> 0 4408 4335 4423 4379 4314
> 1 3883 3873 3679 3856 4007
> 2 3495 3476 3477 3500 3627
>
> I can see some degradation for small number of partitions, but maybe it's
> just noise? At least, I don't yet have a systematic explanation for that
> happening.

Thanks for testing.

I also re-ran tests with v18 using settings almost same as I used before, but this time I run pgbench for 60 second which was 30 second in previous test.

TPS:

nparts master 0001 0002 0003 0004
====== ====== ==== ==== ==== ====
0 10794 11018 10761 10552 11066
1 7574 7625 7558 8071 8219
2 6745 6778 6746 7281 7344

I can see no degradation, so I also think that performance degradation in my previous test and your test was because of just noise.

Why I did these tests is that I wanted to confirm that even if we apply each patch one by one, there's no performance problem. Because patches are quite large, I just felt it might be difficult to commit these patches all at once and I thought committing patch one by one would be another option to commit these patches. I don't know there is the rule in the community how patches should be committed, and if there, my thoughts above may be bad.

Anyway, I'll restart code reviewing :)

--
Yoshikazu Imai

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