From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jeff Janes <jeff.janes@gmail.com>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: postgres_fdw and column casting shippability
Date: Mon, 15 May 2017 18:22:48 -0400
Message-ID: <22431.1494886968@sss.pgh.pa.us> (raw)
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Jeff Janes <jeff.janes@gmail.com> writes:
> I've tried versions 9.6.3 and 10dev, and neither do what I expected. It
> doesn't seem to be a planning problem where it thinks the fast plan is
> slower, it just doesn't seem to consider the faster plans as being options
> at all. Is there some setting to make it realize the cast is shippable?
AFAICS, postgres_fdw doesn't have any knowledge of CoerceViaIO parse
nodes, so it's never going to consider this type of brute-force cast
as shippable. Normal casts would presumably be shippable if the
underlying function is considered safe.
Looks like a round-tuit-shortage issue rather than anything fundamental.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, jeff.janes@gmail.com
Subject: Re: postgres_fdw and column casting shippability
In-Reply-To: <22431.1494886968@sss.pgh.pa.us>
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