Tips on troubleshooting slow DELETE (suspect cascades)

Hi,

I have a slow (CPU bound) DELETE statement I'm attempting to debug and I
suspect that its actually the ON DELETE CASCADE on the foreign key thats
causing it. I suspect this because the dry-run mode of the same query (a
SELECT instead of DELETE) doesn't suffer the same fate. The statement is
effectively;

# Dry mode
SELECT prune_function(timestamp);
# Destructive mode
DELETE FROM foobar p USING prune_function(timestamp) AS e WHERE p.id =
e.prune_id

The logs seem to hold no information on the progress of the statement but
the CPU is pegged at 100% for hours. The SELECT equivalent runs in under a
minute.

What I need is a way to see into this statement as it executes to confirm
my suspicion - does anyone have any tips on that?

Cheers

Jim

--
Jim Vanns
Principal Production Engineer
Industrial Light & Magic, London