Re: index and queries using '<' '>'

The system seems to think that a scan is cheap because the table is so
small. Have you ever ANALYZEd that table? Also, EXPLAIN ANALYZE gives a
much better idea of what is going on...

On Thu, Nov 18, 2004 at 03:55:12PM +0100, Marc Boucher wrote:
> I'm using PG 7.3.4
>
> I've a table with a column of type int8 where I store date-based values,
> and an index exists for it.
> The problem is that the index is almost never used with the '>' test.
>
> # explain SELECT date FROM album WHERE (date='1093989600');
>  Index Scan using date_album_key on album  (cost=0.00..86.31 rows=21 width=8)
>    Index Cond: (date = 1093989600::bigint)
>
> # explain SELECT date FROM album WHERE (date>'1093989600');
>  Seq Scan on album  (cost=0.00..907.91 rows=447 width=8)
>    Filter: (date > 1093989600::bigint)
>
> # explain SELECT date FROM album WHERE (date>'1099989600');
>  Index Scan using date_album_key on album  (cost=0.00..323.09 rows=84 width=8)
>    Index Cond: (date > 1099989600::bigint)
>
>
> It works when the query is supposed to generate low number of rows. The
> problem is that the execution time is much longer with a scan.
> How can I force the use of this index?
>
>
> --
> Marc
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster

--
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
> tool for doing 5% of the work and then sitting around waiting for someone
> else to do the other 95% so you can sue them.