Well the odd thing in my opinion is the fact that the explain shows the
same query plan in both installations while the data in the database is
_very_ different. On my mac, the installation was just for trying to
port dbmail to OS X. The database contains 6 messages making a total
size of 220 bytes for 1 user; no updates or changes. The production
environment contained over 150000 messages (5,3 Gb) for nearly 900
users and had updates on the table constantly. The database gets
vacuumed daily but the problem was found right after importing a dump -
in fact the problem already existed for a few days but after a
diskcrash we were forced to use a backup (pg_dump) it became _really_
apparent.
Philip Warner heeft op donderdag, 21 nov 2002 om 14:11
(Europe/Amsterdam) het volgende geschreven:
At 11:12 AM 21/11/2002 +0100, Roel Rozendaal - IC&S wrote:
We encountered this problem using version 7.2.3; i just checked on my
mac and version 7.2.1 has the same EXPLAIN output.
I'm still trying to understand this behaviour. Has the messageblks
table been vacuumed recently? In the case of the database on your mac,
it may be just a copy loaded from a dump, in which case vacuum is not
necesary...
[Reason is ask: One possible cause of this problem is a table *file*
that is very large and full of unused space. The optimizer does a very
bad job in this case].
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