Re: Long-running DELETE...WHERE...

Nice syntax. Could not find in doc. Do you have any ideas where I
could find it?

--- Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> jboes(at)nexcerpt(dot)com (Jeff Boes) writes:
> > My situation: table A has 200,000 rows. I've made up a temporary
> table
> > which holds the single-valued primary key for 80,000 rows which I
> want
> > to delete.
> > DELETE FROM a WHERE id IN (select ID from tmp LIMIT 800);
> > runs for several minutes.
>
> WHERE ... IN ... is notoriously inefficient. I'd try
>
> DELETE FROM aa WHERE id = tmp.id;
>
> which is not standard SQL but should be able to produce a decent
> plan.
>
> You might find that a VACUUM ANALYZE on both tables beforehand would
> be
> a good idea, too; never-vacuumed temp tables have some default
> statistics assumed that are a lot less than 80k rows.
>
> regards, tom lane
>
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