Re: speeding up planning with partitions

From: Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>
To: "Imai, Yoshikazu" <imai(dot)yoshikazu(at)jp(dot)fujitsu(dot)com>
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: 2019-01-29 10:11:15
Message-ID: 70d7a3c7-0ab0-f814-09dd-da21034d5611@lab.ntt.co.jp
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Imai-san,

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,
Amit

[1] I changed the compile flags in build scripts to drop
-DCATCACHE_FORCE_RELEASE, which would cause many syscache misses in my
test runs

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