Re: Two proposed modifications to the PostgreSQL FDW

From: Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>
To: Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Chris Travers <chris(dot)travers(at)adjust(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Two proposed modifications to the PostgreSQL FDW
Date: 2018-08-29 11:38:56
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(2018/08/21 16:03), Amit Langote wrote:
> On 2018/08/20 23:43, Tom Lane wrote:
>> Chris Travers<chris(dot)travers(at)adjust(dot)com> writes:
>>> I am looking at trying to make two modifications to the PostgreSQL FDW and
>>> would like feedback on this before I do.
>>> 1. INSERTMETHOD=[insert|copy] option on foreign table.
>>> One significant limitation of the PostgreSQL FDW is that it does a prepared
>>> statement insert on each row written which imposes a per-row latency. This
>>> hits environments where there is significant latency or few latency
>>> guarantees particularly hard, for example, writing to a foreign table that
>>> might be physically located on another continent. The idea is that
>>> INSERTMETHOD would default to insert and therefore have no changes but
>>> where needed people could specify COPY which would stream the data out.
>>> Updates would still be unaffected.

>> A different thing we could think about is enabling COPY TO/FROM a
>> foreign table.
> Fwiw, the following commit did introduce COPY FROM support for foreign
> tables, although using a FDW INSERT interface, so not exactly optimized
> for bulk-loading yet.
> commit 3d956d9562aa4811b5eaaaf5314d361c61be2ae0
> Author: Robert Haas<rhaas(at)postgresql(dot)org>
> Date: Fri Apr 6 19:16:11 2018 -0400
> Allow insert and update tuple routing and COPY for foreign tables.

That's right. To improve the efficiency, I plan to work on COPY FROM/TO
a foreign table for PG12 (In [1], I proposed new FDW APIs for COPY FROM).

Sorry, I'm late to the party.

Best regards,
Etsuro Fujita


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