Re: Counting records in a PL/pgsql cursor

From: "Magnus Hagander" <mha(at)sollentuna(dot)net>
To: "Richard Troy" <rtroy(at)ScienceTools(dot)com>, "Merlin Moncure" <mmoncure(at)gmail(dot)com>
Cc: "Martijn van Oosterhout" <kleptog(at)svana(dot)org>, <pgsql-general(at)postgresql(dot)org>
Subject: Re: Counting records in a PL/pgsql cursor
Date: 2006-11-03 14:33:27
Message-ID: 6BCB9D8A16AC4241919521715F4D8BCEA358A0@algol.sollentuna.se
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-general

> > > I can deal with materializing the resultset, but I want
> to get away
> > > from the loop-a-thousand-times-doing-plus-one...
> >
> > i dont think its possible. note that you can make a
> refcursor inside
> > your plpgsql function and pass it to an sql function which
> can do sql
> > cursor operations on it -- i think :-)..haven't tried it yet.
> >
> > merlin
>
> ...If you know your application well enough, you might get
> away with doing a select count() with the same where clause
> just before entering the cursor. It _could_ of course be
> wrong, though! OTOH, it would be much faster. If the only
> down-side is occasionally giving users an incorrect count,
> then perhaps call it a "row estimate", and let them marvel at
> how accurate the estimate is most of hte time!

Nope, the query is way too expensive to run it twice. (GIN scan over
well over half a million rows. It's faster to do the
get-as-cursor-then-loop-and-increment, I've measured that)

//Magnus

In response to

Responses

Browse pgsql-general by date

  From Date Subject
Next Message Richard Huxton 2006-11-03 14:35:07 Re: I know the bad way...what is the good way?
Previous Message Merlin Moncure 2006-11-03 14:18:51 Re: Counting records in a PL/pgsql cursor