Re: Damn slow query

Magnus Naeslund(f) wrote:
> Hello, i've got this query that's really slow...
> Figure this:
> 
> testdb=> select now() ; select gid from bs where gid not in ( select x
> from z2test ); select now();

"IN (subselect)" is notoriously slow (in fact it is an FAQ). Can you rewrite 
this as:

select b.gid from bs b where not exists (select 1 from z2test z where z.x = 
b.gid);

or possibly:

select b.gid from bs b left join z2test z on z.x = b.gid where z.x IS NULL;

HTH,

Joe