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Re: [PATCH] Provide rowcount for utility SELECTs

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Boszormenyi Zoltan <zb(at)cybertec(dot)at>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, Hans-Juergen Schoenig <hs(at)cybertec(dot)at>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [PATCH] Provide rowcount for utility SELECTs
Date: 2010-02-14 03:15:26
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Boszormenyi Zoltan wrote:
> >>> Ah, I didn't even see that that section needed to be updated.  Good
> >>> catch.  I'd suggest the following wording:
> >>>
> >>> For a <command>SELECT</command> or <command>CREATE TABLE AS</command>
> >>> command, the tag is SELECT rows... [and the rest as you have it]
> >>>
> >>> We should probably also retitle that section from "Retrieving Result
> >>> Information for Other Commands" to "Retrieving Other Result
> >>> Information" and adjust the text of the opening sentence similarly.
> >>>
> >>> Also I think you need to update the docs for PQcmdtuples to mention
> >>> that it not works for SELECT and CTAS.
> >>>
> >>>       
> >> Ok, I will update libpq.sgml where this section resides.
> >> What's a CTA, btw? Do you mean CTE, a.k.a. "Common Table Expression"?
> >>     
> >
> >   
> Okay, new patch is attached. Please read the docs changes, and comment.

I have reviewed this patch and made some adjustments, attached.  The
major change is that our return of "0 0" in certain cases must remain,
though I have improved the C comment explaining it with a separate CVS

     * If a command completion tag was supplied, use it.  Otherwise use the
     * portal's commandTag as the default completion tag.
     * Exception: Clients expect INSERT/UPDATE/DELETE tags to have
     * counts, so fake them with zeros.  This can happen with DO INSTEAD
     * rules if there is no replacement query of the same type as the
     * original.  We print "0 0" here because technically there is no
     * query of the matching tag type, and printing a non-zero count for
     * a different query type seems wrong, e.g.  an INSERT that does
     * an UPDATE instead should not print "0 1" if one row
     * was updated.  See QueryRewrite(), step 3, for details.

I have removed the part of the patch that chagned "0 0";  it seems to
run fine without it.  The rest of my adjustments were minor.

One major part of the patch seems to be the collection of the
PORTAL_ONE_SELECT switch label into the label below it, which is a nice

  Bruce Momjian  <bruce(at)momjian(dot)us>

  + If your life is a hard drive, Christ can be your backup. +

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