Re: [HACKERS] Re: v7.1b4 bad performance

On Fri, Feb 23, 2001 at 01:09:37PM +0200, Hannu Krosing wrote:
> Dmitry Morozovsky wrote:
>
> > DM> I just done the experiment with increasing HZ to 1000 on my own machine
> > DM> (PII 374). Your test program reports 2 ms instead of 20. The other side
> > DM> of increasing HZ is surely more overhead to scheduler system. Anyway, it's
> > DM> a bit of data to dig into, I suppose ;-)
> > DM>
> > DM> Results for pgbench with 7.1b4: (BTW, machine is FreeBSD 4-stable on IBM
> > DM> DTLA IDE in ATA66 mode with tag queueing and soft updates turned on)
>
> Is this unmodified pgbench or has it Hiroshi tweaked behaviour of
> connecting each client to its own database, so that locking and such
> does not shade the possible benefits (was it about 15% ?) of delay>1
>
> also, IIRC Tom suggested running with at least -B 1024 if you can.

Just try this:
explain select * from <tablename> where <fieldname>=<any_value>
(Use for fieldname an indexed field).

If postgres is using an sequential scan in stead of an index scan. You have
to vacuum your database. This will REALLY remove deleted data from your indexes.

Hope it will work,

Dave Mertens
System Administrator ISM, Netherlands