Re: Optimizing DELETE

[Rod Taylor <rbt(at)rbt(dot)ca>]

On Tue, 2006-09-19 at 15:22 +0200, Ivan Voras wrote:
> I've just fired off a "DELETE FROM table" command (i.e. unfiltered 
> DELETE) on a trivially small table but with many foreign key references 
> (on similar-sized tables), and I'm waiting for it to finish. It's been 
> 10 minutes now, which seems very excessive for a table of 9000 rows on a 
> 3 GHz desktop machine.

I would guess that a few of those referenced tables are missing indexes
on the referenced column.

> 'top' says it's all spent in USER time, and there's a ~~500KB/s write 
> rate going on. Just before this DELETE, I've deleted data from a larger 
> table (50000 rows) using the same method and it finished in couple of 
> seconds - maybe it's a PostgreSQL bug?
> 
> My question is: assuming it's not a bug, how to optimize DELETEs? 
> Increasing work_mem maybe?
> 
> (I'm using PostgreSQL 8.1.4 on FreeBSD 6- amd64)
> 
> (I know about TRUNCATE; I need those foreign key references to cascade)
> 
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