Обсуждение: PostgreSQL performance deteriorates over time?

Hello all,

how fast PostgreSQL is supposed to be? Assume a table with
three columns (integer, char, char) and with 100 rows and
an index. Using libpq++ simple UPDATE has gone from under
one millisecond to over 20 milliseconds after a few days of
uptime (mostly idle)? VACUUM ANALYZE didn't help, but
restarting postmaster did. (All this with datasync turned
off with -o -F switches.) What am I doing wrong?

Some info: PostgreSQL 7.1.3, running on Linux 2.2.18 (or
somesuch) on 1GHz PentiumIII with 256MB RAM. PostgreSQL is
compiled from sources, gcc is redhat's 2.96-85. I'm a newbie
when it comes to databases, please tell me if I forgot some
vital information. Also if this is a FAQ or RTFM question,
please do tell where can I find it. I've already read
"3.7) How do I tune the database engine for better
performance?"
And, no I don't think tweaks other than datasync make any
difference, since my program is serialized (only one query
active at a time).

Thanks for any help.

    Taneli

Apparently bogus information in From: field ... <blush>

Please reply to the list, I'm subscribed. Or if you really
need to reply privately, use Ext-Taneli.Vahakangas@nokia.com

    Taneli

tvahakan@fw.cluster.net writes:
> Using libpq++ simple UPDATE has gone from under
> one millisecond to over 20 milliseconds after a few days of
> uptime (mostly idle)? VACUUM ANALYZE didn't help, but
> restarting postmaster did.

This seems *very* odd; restarting the postmaster should not make a
difference.  What exactly is the query you're using, what exactly
is the table and index schema, and what does EXPLAIN say is the
query plan (in both fast and slow states)?

            regards, tom lane