From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Pavel Biryukov <79166341370@yandex.ru>
Cc: PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
Cc: Andres Freund <andres@anarazel.de>
Subject: Re: posgres 12 bug (partitioned table)
Date: Tue, 11 Aug 2020 13:52:00 -0400
Message-ID: <18024.1597168320@sss.pgh.pa.us> (raw)
In-Reply-To: <CA+Tgmob1xt7b5gn0s_D2TvDsJ84+Ek9_q_+8W6Xqu5Q9D-M85w@mail.gmail.com>
References: <141051591267657@mail.yandex.ru>
<1251598.1591289850@sss.pgh.pa.us>
<CA+TgmoaN0kQa3nxToHtD8nRymSnUYaj4XL3zKq8Q_0AUJcQNPQ@mail.gmail.com>
<3398357.1597160032@sss.pgh.pa.us>
<1058041597161586@mail.yandex.ru>
<CA+Tgmob1xt7b5gn0s_D2TvDsJ84+Ek9_q_+8W6Xqu5Q9D-M85w@mail.gmail.com>
Robert Haas <robertmhaas@gmail.com> writes:
> On Tue, Aug 11, 2020 at 12:02 PM Pavel Biryukov <79166341370@yandex.ru> wrote:
>> I just want to point that Npgsql provider for .Net Core builds queries like that (RETURNING xmin) to keep track for concurrency.
>> This bug stops us from moving to partitioned tables in Postgres 12 with Npgsql.
> That's certainly a good reason to try to make it work. And we can make
> it work, if we're willing to assume that everything's a heap table.
> But at some point, that hopefully won't be true any more, and then
> this whole idea becomes pretty dubious. I think we shouldn't wait
> until it happens to start thinking about that problem.
For xmin in particular, you don't have to assume "everything's a heap".
What you have to assume is "everything uses MVCC", which seems a more
defensible position. It'll still fall down for foreign tables that are
partitions, though.
I echo Andres' nearby question about exactly why npgsql has such a
hard dependency on xmin. Maybe what we need is to try to abstract
that a little, and see if we could require all partition members
to support some unified concept of it.
regards, tom lane
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To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, robertmhaas@gmail.com, 79166341370@yandex.ru, pgsql-bugs@lists.postgresql.org, andres@anarazel.de
Subject: Re: posgres 12 bug (partitioned table)
In-Reply-To: <18024.1597168320@sss.pgh.pa.us>
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