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Re: [PATCH] Provide rowcount for utility SELECTs

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Boszormenyi Zoltan <zb(at)cybertec(dot)at>, 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 03:30:24
Message-ID: 603c8f071002131930s24d7864fs2e38bb35e8b5bab5@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Sat, Feb 13, 2010 at 10:15 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> 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"?
>> >>
>> >
>> > Sorry, CTAS = CREATE TABLE AS SELECT.
>> >
>>
>> 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
> commit:
>
>    /*
>     * 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
> cleanup.

Thanks for taking the time to review this.  I think your adjustments are good.

...Robert

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