> So are we correct to rely on
> - 8 being slower than 7.x in general and

I think this is a highly unlikely claim ... *especially* if you are
comparing against 7.1.  The point about sync() being a no-op is real,
but offhand I think it would only come into play at checkpoints.  We
have never issued sync() during regular queries.

What seems more likely to me is that you have neglected to do any
performance tuning on the new installation.  Have you vacuumed/analyzed
all your tables?  Checked the postgresql.conf settings for sanity?

If you'd like to do an apples-to-apples comparison to prove whether
7.1's failure to sync() is relevant, then turn off fsync in the 8.0
configuration and see how much difference that makes.

If you can identify specific queries that are slower in 8.0 than 7.1,
I'd be interested to see the EXPLAIN ANALYZE details from each.
(Actually, I'm not sure 7.1 had EXPLAIN ANALYZE; you may have to
settle for EXPLAIN from it.)

                        regards, tom lane

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