Re: BUG #1541: Unusually long INSERT times after fresh clean/CREATE TABLES

"John Engelhart" <johne@zang.com> writes:
> Since I'm developing an SQL based application, I routinely "start from
> scratch" with a script that deletes all the tables in my database and
> rebuilds them.  A problem started when I upgraded from 7.4.7 to 8.0.1 in
> that the first run after the clean takes an UNUSUALLY long time to complete,
> on the order of a few hundred inserts/sec.  A normal run takes ~30 seconds.
> A from scratch run takes ~15 minutes, with the next run completing in 30
> seconds with zero changes.

The 8.0 planner is intentionally sensitive to the current actual
physical sizes of tables.  It sounds like you've managed to get it to
plan something on the assumption that the tables are tiny and keep
using that plan after they aren't tiny any more.  The old planner had
the same kind of issue but it was far easier to hit, so "revert that
change" isn't an answer that I'm particularly interested in.

> Hopefully this is enough info to track down and recreate the problem

Not really.

            regards, tom lane