Database is slow, vacuum hangs

Hi-

This morning, my database suddenly got very slow. I had been testing an
import process, so I had loaded, deleted, and reloaded about 140MB of data
several times. After the last reload, I noticed that the database was very
slow. Queries that normally executed in seconds didn't return after several
minutes. I don't know if they ever would have returned results, as I
cancelled after about 5 minutes, so the database might have been completely
locked.

I decided to delete all of the data, do a vacuum, and then reload one more
time.

The deletes were slow, but worked, so the tables are all empty now. I
started the vacuum and let it run for 4 hours while I did other work & it
never came back. During this time, I noticed that two postmaster processes
were constantly running- each taking up almost exactly half of the CPU time.
There was no disk activity. After I canceled the vacuum, the two postmaster
processes remained and continued to use all of the CPU time. (they're still
there.)

postgres.log doesn't contain any new messages.

I guess the obvious next step is to restart postgres, but I don't want to
blow away any evidence.

Can anyone suggest tests I should do to learn what happened before trying a
restart?

I'm running PGSQL 7.1.3 on Debian Linux 2.4.14

Thanks-

-Nick

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Nick Fankhauser  nickf@ontko.com  Phone 1.765.935.4283  Fax 1.765.962.9788
Ray Ontko & Co.     Software Consulting Services     http://www.ontko.com/