Simple delete takes hours

Hi there,

I have a simple database:

CREATE TABLE pwd_description (
id SERIAL NOT NULL UNIQUE PRIMARY KEY,
name varchar(50) NOT NULL
);

CREATE TABLE pwd_name (
id SERIAL NOT NULL UNIQUE PRIMARY KEY,
description integer NOT NULL REFERENCES pwd_description(id),
name varchar(50) NOT NULL,
added timestamp DEFAULT now()
);

CREATE TABLE pwd_name_rev (
id SERIAL NOT NULL UNIQUE PRIMARY KEY,
description integer NOT NULL REFERENCES pwd_description(id),
rev_of integer NOT NULL REFERENCES pwd_name(id) ON DELETE
CASCADE,
name varchar(50) NOT NULL
);

The indexes shouldn't matter I think.

pwd_name_rev is filled by a stored procedure and a trigger (ON INSERT)
when something is inserted to pwd_name. Both tables contain about
4.500.000 emtries each.

I stopped 'delete from pwd_name where description=1' after about 8 hours
(!). The query should delete about 500.000 records.
Then I tried 'delete from pwd_name_rev where description=1' - this took
23 seconds (!).
Then I retried the delete on pwd_name but it's running for 6 hours now.

I use PostgreSQL 7.4.7 on Linux 2.6.10. The machine is a Celeron 2 GHz
with 512 MB RAM.

PostgreSQL should do a full table scan I think, get all records with
description=1 and remove them - I don't understand what's happening for
>8 hours.

Any help is appreciated.

Thomas