Re: [PATCH] Provide rowcount for utility SELECTs

Tom Lane írta:
> Boszormenyi Zoltan <zb(at)cybertec(dot)at> writes:
>
>> attached is a small patch that makes it possible for clients
>> to receive row count for SELECT ... INTO ... and CREATE TABLE ... AS ...
>>
>
>
>> Comments?
>>
>
> This doesn't look tremendously well thought out to me.
>
> 1. As given, the patch changes the result not only for SELECT INTO but
> for any SELECT executed in PORTAL_MULTI_QUERY context (consider SELECTs
> added by rules for example). It seems like a pretty bad idea for the
> result of a statement to depend on context.
>
> 2. In the past we have regretted it when we made the same command tag
> sometimes have numbers attached and sometimes not (note the hack at
> the bottom of PortalRunMulti). It doesn't seem like terribly good
> design to do that here. On the other hand, always attaching a count
> to SELECT tags would greatly increase the risk of breaking clients.
>

Okay, how about introducing a new "SELECTINTO N" command tag, then?
It's also a protocol change, but at least it can fall into the very last
"else"
anywhere, hence have a high chance of being ignored and handled the same
way as other not rowcount-returning tags.

> I'm not at all convinced that this is so useful as to justify taking
> any compatibility risks for. People who really need that count can
> get it easily enough by breaking the command into a CREATE followed
> by INSERT/SELECT.
>

Yes, and every WITH RECURSIVE statement can also be broken up
manually as well. It's simply shorter and has a chance of being a little
more resource-effective:
- one parsing/planning phase instead of two on the server side
- one error checking in the app instead of two
- PostgreSQL already has the infrastructure to return the rowcount

Best regards,
Zoltán Böszörményi

--
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----------------------------------
Zoltán Böszörményi
Cybertec Schönig & Schönig GmbH
http://www.postgresql.at/