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Subject: Re: [HACKERS] PATCH: Batch/pipelining support for libpq
From: "Daniel Verite" <daniel@manitou-mail.org>
To: "Kyotaro HORIGUCHI" <horiguchi.kyotaro@lab.ntt.co.jp>
Cc: 
 vaishnaviprabakaran@gmail.com,michael.paquier@gmail.com,daniel@yesql.se,craig@2ndquadrant.com,andres@anarazel.de,david@pgmasters.net,VaishnaviP@fast.au.fujitsu.com,kommi.haribabu@gmail.com,tsunakawa.takay@jp.fujitsu.com,dmitigr@gmail.com,pgsql-hackers@postgresql.org,m.kniep@web.de,fujita.etsuro@lab.ntt.co.jp,iwata.aya@jp.fujitsu.com
In-Reply-To: <20180322.211148.187821341.horiguchi.kyotaro@lab.ntt.co.jp>
Date: Fri, 23 Mar 2018 14:18:09 +0100
Message-Id: <fa497dfa-348a-4fc7-89a2-e00e56544231@manitou-mail.org>
Precedence: bulk

	Kyotaro HORIGUCHI wrote:

> A disucssion on psql batch mode was held in another branch of
> this thread. How do we treat that?

There's a batch mode for pgbench in a patch posted in [1],
with \beginbatch and \endbatch commands, but nothing
for psql AFAICS.
psql is more complicated because currently it uses a=20
blocking PQexec() call at its core. Craig mentioned psql
integration in [2] and [3].
Also a script can have inter-query dependencies such as in
   insert into table(...) returning id \gset
   update othertable set col=3D :id where ...;
which is a problem in batch mode, as we don't want
to send the update before the right value for :id is
known. Whether we want to support these dependencies
and how needs discussion.
For instance we might not support them at all, or
create a synchronization command that collects
all results of queries sent so far, or do it implicitly
when a variable is injected into a query...
This looks like substantial work that might be best
done separately from the libpq patch.

[1]
https://www.postgresql.org/message-id/b4e34135-2bd9-4b8a-94ca-27d760da26d7@=
manitou-mail.org
[2]
https://www.postgresql.org/message-id/CAMsr+YGLhaDkjymLuNVQy4MrSKQoA=3DF1vO=
=3DaN8XQf30N=3DaQuVA@mail.gmail.com
[3]
https://www.postgresql.org/message-id/CAMsr+YE6BK4iAaQz=3DnY3xDnbLhnNZ_4tp-=
PTJqbNNpsZMgoo8Q@mail.gmail.com


Best regards,
--=20
Daniel V=E9rit=E9
PostgreSQL-powered mailer: http://www.manitou-mail.org
Twitter: @DanielVerite