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Re: Arguments to foreign tables?

From: Jeff Davis <pgsql(at)j-davis(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Arguments to foreign tables?
Date: 2012-11-06 06:09:31
Message-ID: 1352182171.6292.29.camel@jdavis-laptop (view raw or flat)
Thread:
Lists: pgsql-hackers
On Sun, 2012-11-04 at 15:13 -0500, Tom Lane wrote:
> Jeff Davis <pgsql(at)j-davis(dot)com> writes:
> > Is there any fundamental or philosophical reason why a foreign table
> > can't accept arguments?
> 
> That isn't a table; it's some sort of function.  Now that we have
> LATERAL, there is no good reason to contort SQL's syntax and semantics
> in the direction you suggest.

Maybe I should rephrase this as a problem with SRFs: you don't get to
define the init/exec/end executor functions, and you don't get access to
the optimizer information.

It seems like foreign tables are a better mechanism (except for the
simple cases where you don't care about the details), and the only thing
an SRF can do that a foreign table can't is accept arguments. So, I
thought maybe it would make more sense to combine the mechanisms
somehow.

Take something as simple as generate_series: right now, it materializes
the entire thing if it's in the FROM clause, but it wouldn't need to if
it could use the foreign table mechanism.

Regards,
	Jeff Davis



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