Re: Optimization for updating foreign tables in Postgres FDW

From: Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>
To: Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Stephen Frost <sfrost(at)snowman(dot)net>, Shigeru Hanada <shigeru(dot)hanada(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Optimization for updating foreign tables in Postgres FDW
Date: 2015-03-05 12:08:06
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On 2015/03/04 17:07, Etsuro Fujita wrote:
> On 2015/03/04 16:58, Albe Laurenz wrote:
>> Etsuro Fujita wrote:
>>> While updating the patch, I noticed that in the previous patch, there is
>>> a bug in pushing down parameterized UPDATE/DELETE queries; generic plans
>>> for such queries fail with a can't-happen error. I fixed the bug and
>>> tried to add the regression tests that execute the generic plans, but I
>>> couldn't because I can't figure out how to force generic plans. Is
>>> there any way to do that?
>> I don't know about a way to force it, but if you run the statement six
>> times, it will probably switch to a generic plan.
> Yeah, I was just thinking running the statement six times in the
> regression tests ...

Here is an updated version. In this version, the bug has been fixed,
but any regression tests for that hasn't been added, because I'm not
sure that the above way is a good idea and don't have any other ideas.

The EXPLAIN output has also been improved as discussed in [1].

On top of this, I'll try to extend the join push-down patch to support a
pushed-down update on a join, though I'm still digesting the series of

Comments welcome.

Best regards,
Etsuro Fujita


Attachment Content-Type Size
postgres_fdw-update-v5.patch text/x-patch 66.5 KB

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