[SQL] Simple delete takes hours

[Thomas Mueller]

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
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