Re: Gather Merge

From: Rushabh Lathia <rushabh(dot)lathia(at)gmail(dot)com>
To: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
Cc: Kuntal Ghosh <kuntalghosh(dot)2007(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Gather Merge
Date: 2017-02-01 13:32:30
Message-ID: CAGPqQf3f-mrZzdsjap_Bw=6V=Kk1DdSMUutvocUUy3qqrbq8cw@mail.gmail.com
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Due to recent below commit, patch not getting apply cleanly on
master branch.

commit d002f16c6ec38f76d1ee97367ba6af3000d441d0
Author: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Date: Mon Jan 30 17:15:42 2017 -0500

Add a regression test script dedicated to exercising system views.

Please find attached latest patch.

On Wed, Feb 1, 2017 at 5:55 PM, Rushabh Lathia <rushabh(dot)lathia(at)gmail(dot)com>
wrote:

> I am sorry for the delay, here is the latest re-based patch.
>
> my colleague Neha Sharma, reported one regression with the patch, where
> explain output for the Sort node under GatherMerge was always showing
> cost as zero:
>
> explain analyze select '' AS "xxx" from pgbench_accounts where filler
> like '%foo%' order by aid;
> QUERY
> PLAN
> ------------------------------------------------------------
> ------------------------------------------------------------
> ------------------------
> Gather Merge (cost=47169.81..70839.91 rows=197688 width=36) (actual
> time=406.297..653.572 rows=200000 loops=1)
> Workers Planned: 4
> Workers Launched: 4
> -> Sort (*cost=0.00..0.00 rows=0 width=0*) (actual
> time=368.945..391.124 rows=40000 loops=5)
> Sort Key: aid
> Sort Method: quicksort Memory: 3423kB
> -> Parallel Seq Scan on pgbench_accounts (cost=0.00..42316.60
> rows=49422 width=36) (actual time=296.612..338.873 rows=40000 loops=5)
> Filter: (filler ~~ '%foo%'::text)
> Rows Removed by Filter: 360000
> Planning time: 0.184 ms
> Execution time: 734.963 ms
>
> This patch also fix that issue.
>
>
>
>
> On Wed, Feb 1, 2017 at 11:27 AM, Michael Paquier <
> michael(dot)paquier(at)gmail(dot)com> wrote:
>
>> On Mon, Jan 23, 2017 at 6:51 PM, Kuntal Ghosh
>> <kuntalghosh(dot)2007(at)gmail(dot)com> wrote:
>> > On Wed, Jan 18, 2017 at 11:31 AM, Rushabh Lathia
>> > <rushabh(dot)lathia(at)gmail(dot)com> wrote:
>> >>
>> > The patch needs a rebase after the commit 69f4b9c85f168ae006929eec4.
>>
>> Is an update going to be provided? I have moved this patch to next CF
>> with "waiting on author" as status.
>> --
>> Michael
>>
>
>
>
> --
> Rushabh Lathia
>

--
Rushabh Lathia

Attachment Content-Type Size
gather-merge-v7.patch binary/octet-stream 52.8 KB

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