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From: Joe Conway <mail@joeconway.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Christopher Kings-Lynne <chris.kings-lynne@calorieking.com>
Cc: Hackers (PostgreSQL) <pgsql-hackers@postgresql.org>
Cc: Andrew Dunstan <andrew@dunslane.net>
Cc: Bernd Helmle <mailings@oopsware.de>
Cc: Peter Eisentraut <peter_e@gmx.net>
Cc: Susanne Ebrecht <susanne.ebrecht@credativ.de>
Subject: Re: Values list-of-targetlists patch for comments (was Re: [PATCHES]
Date: Sat, 29 Jul 2006 18:45:44 -0700
Message-ID: <44CC0F48.9020805@joeconway.com> (raw)
In-Reply-To: <21398.1154223324@sss.pgh.pa.us>
References: <44B69778.5050104@dunslane.net>
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	<44BC0432.3040509@joeconway.com>
	<44BC661F.80609@joeconway.com>
	<44BCD06C.3060409@calorieking.com>
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Tom Lane wrote:
> Joe Conway <mail@joeconway.com> writes:
>>One of the things I'm struggling with is lack of column aliases. Would 
>>it be reasonable to require something like this?

> Requiring column aliases is counter to spec ...

>>	SELECT ... FROM (VALUES ...) AS foo(col1 type1, col2 type2, ...)

> ... and this is even further away from it.

I figured as much, but thought I'd ask anyway :-). I did find something 
in the appendix to the spec after sending this:

Annex C
(informative)
Implementation-dependent elements

18) Subclause 7.3, “<table value constructor>”:
a) The column names of a <table value constructor> or a <contextually 
typed table value constructor>
are implementation-dependent.

> As for the names, just use "?column?", same as we do now in INSERT
> ... VALUES.  Anyone who wants to refer to those columns explicitly will
> need to assign aliases, but if they don't assign aliases, we don't have
> to do anything very intelligent.

OK, I just thought "?column?" was ugly and useless.

> As for the types, I believe that the spec pretty much dictates that we
> apply the same type resolution algorithm as for a UNION.  This is fairly
> expensive and we should avoid it in the case of INSERT ... VALUES, but
> for VALUES appearing anywhere else I think we have little choice.

Where do I find that algorithm -- somewhere in nodeAppend.c?

Thanks,

Joe




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