Re: Window function bug

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Jeff Davis <pgsql(at)j-davis(dot)com>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: Window function bug
Date: 2011-07-12 15:20:39
Message-ID: 12936.1310484039@sss.pgh.pa.us
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I wrote:
> ... so I guess the answer is that this code ought to avoid adding Vars that
> are only mentioned within aggregates.

The cleanest way to fix this would involve adding another flag parameter
to flatten_tlist and pull_var_clause. This is no problem to do in HEAD
or even 9.1, but I'm a bit worried about breaking third-party code if we
backpatch further than that. So far as I can see, the failure only
occurs if we have a plain (non-grouping) Agg node, which implies that
the user is trying to use windowing functions on a result set that's
guaranteed to contain exactly one aggregated row. That seems pretty
useless, so I'm thinking it's not worth back-patching a fix for.
Comments?

regards, tom lane

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