Re: Very slow queries on 8.1

What is the data type for "signum" ???



"David Rysdam" <drysdam@ll.mit.edu> wrote in message
news:437CA40A.8020507@ll.mit.edu...
> I'm porting an application from Sybase and I've noticed that similar
> application functions take 2 to 3 times longer on postgres than they used
> to on the same machine running under Sybase.  I've tried changing various
> "performance tuning" parameters, such as shared_buffers,
> effective_cache_size, etc but there's little or no effect.  I'm beginning
> to think there's a deeper root cause to the slowness.
>
> Right now, I'm working on a test case that involves a table with ~360k
> rows called "nb.sigs".  My sample query is:
>
> select * from nb.sigs where signum > 250000
>
> With no index, explain says this query costs 11341.  After CREATE INDEX on
> the signum field, along with an ANALYZE for nb.sigs, the query costs 3456
> and takes around 4 seconds to return the first row.  This seems extremely
> slow to me, but I can't figure out what I might be doing wrong.  Any
> ideas?
>
> (If necessary, I can write an entire script that creates and populates a
> table and then give my performance on that sample for someone else to
> check against.)
>
> ---------------------------(end of broadcast)---------------------------
> TIP 6: explain analyze is your friend
>