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help / color / mirror / Atom feedFrom: Bruce Momjian <[email protected]>
To: [email protected] <[email protected]>
Cc: Alexander Pyhalov <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Tomas Vondra <[email protected]>
Cc: Julien Rouhaud <[email protected]>
Cc: Daniel Gustafsson <[email protected]>
Cc: Ilya Gladyshev <[email protected]>
Subject: Re: Partial aggregates pushdown
Date: Fri, 9 Jun 2023 12:44:03 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <OS3PR01MB66604E404B003A621B0C03A69552A@OS3PR01MB6660.jpnprd01.prod.outlook.com>
References: <OSZPR01MB6662875933E87F37C711B4FC95969@OSZPR01MB6662.jpnprd01.prod.outlook.com>
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<[email protected]>
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<[email protected]>
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<[email protected]>
<OS3PR01MB66604E404B003A621B0C03A69552A@OS3PR01MB6660.jpnprd01.prod.outlook.com>
On Tue, Jun 6, 2023 at 03:08:50AM +0000, [email protected] wrote:
> > I've seen this message. But introduction of new built-in function will break
> > requests to old servers only if this new function is used in the request (this
> > means that query changes). However, this patch changes the behavior of old
> > queries, which worked prior to update. This seems to be different to me.
>
> You are right.
> However, for now, partial aggregates pushdown is mainly used when using built-in sharding in PostgreSQL.
> I believe when using built-in sharding in PostgreSQL, the version of the primary node server and
> the version of the remote server will usually be the same.
> So I think it would be sufficient to include in the documentation a note about such problem
> and a workaround for them.
I agree that this feature is designed for built-in sharding, but it is
possible people could be using aggregates on partitions backed by
foreign tables without sharding. Adding a requirement for non-sharding
setups to need PG 17+ servers might be unreasonable.
Looking at previous release note incompatibilities, we don't normally
change non-administrative functions in a way that causes errors if run
on older servers. Based on Alexander's observations, I wonder if we
need to re-add the postgres_fdw option to control partial aggregate
pushdown, and default it to enabled.
If we ever add more function breakage we might need more postgres_fdw
options. Fortunately, such changes are rare.
Yuki, thank you for writing and updating this patch, and Alexander,
thank you for helping with this patch.
--
Bruce Momjian <[email protected]> https://momjian.us
EDB https://enterprisedb.com
Only you can decide what is important to you.
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Subject: Re: Partial aggregates pushdown
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