From: Andrey V. Lepikhov <a.lepikhov@postgrespro.ru>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: etsuro.fujita@gmail.com
Cc: movead.li@highgo.ca
Cc: pgsql-hackers@lists.postgresql.org
Subject: Re: Asynchronous Append on postgres_fdw nodes.
Date: Mon, 15 Jun 2020 14:59:18 +0500
Message-ID: <3aa386ee-99d7-551f-85cf-c13b78947d4f@postgrespro.ru> (raw)
In-Reply-To: <20200615.172934.587211238374081803.horikyota.ntt@gmail.com>
References: <90cced83-9061-0cac-0012-84e5faac8c78@postgrespro.ru>
<20200610.120510.2075667454883130505.horikyota.ntt@gmail.com>
<dc214e8f-96bc-a6c0-19ba-0dffc2051b34@postgrespro.ru>
<20200615.172934.587211238374081803.horikyota.ntt@gmail.com>
On 6/15/20 1:29 PM, Kyotaro Horiguchi wrote:
> Thanks for testing, but..
>
> At Mon, 15 Jun 2020 08:51:23 +0500, "Andrey V. Lepikhov" <a.lepikhov@postgrespro.ru> wrote in
>> The patch has a problem with partitionwise aggregates.
>>
>> Asynchronous append do not allow the planner to use partial
>> aggregates. Example you can see in attachment. I can't understand why:
>> costs of partitionwise join are less.
>> Initial script and explains of the query with and without the patch
>> you can see in attachment.
>
> I had more or less the same plan with the second one without the patch
> (that is, vanilla master/HEAD, but used merge joins instead).
>
> I'm not sure what prevented join pushdown, but the difference between
> the two is whether the each partitionwise join is pushed down to
> remote or not, That is hardly seems related to the async execution
> patch.
>
> Could you tell me how did you get the first plan?
1. Use clear current vanilla master.
2. Start two instances with the script 'frgn2n.sh' from attachment.
There are I set GUCs:
enable_partitionwise_join = true
enable_partitionwise_aggregate = true
3. Execute query:
explain analyze SELECT sum(parts.b)
FROM parts, second
WHERE parts.a = second.a AND second.b < 100;
That's all.
--
Andrey Lepikhov
Postgres Professional
https://postgrespro.comAttachments:
[application/x-shellscript] frgn2n.sh (3.3K, ../3aa386ee-99d7-551f-85cf-c13b78947d4f@postgrespro.ru/2-frgn2n.sh)
download
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To: pgsql-hackers@postgresql.org
Cc: a.lepikhov@postgrespro.ru, horikyota.ntt@gmail.com, etsuro.fujita@gmail.com, movead.li@highgo.ca, pgsql-hackers@lists.postgresql.org
Subject: Re: Asynchronous Append on postgres_fdw nodes.
In-Reply-To: <3aa386ee-99d7-551f-85cf-c13b78947d4f@postgrespro.ru>
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