Re: "SELECT IN" Still Broken in 7.4b

On Wed, 20 Aug 2003, Rod Taylor wrote:

> On Wed, 2003-08-20 at 17:41, Stephan Szabo wrote:
> > On Wed, 20 Aug 2003, Rod Taylor wrote:
> >
> > > > Thanks, Stephan. I was really hoping that the IN(valuelist) was going to
> > > > be changed at the same time, because it really is unusable for anything
> > > > over a couple of thousand values.
> > >
> > > Changed to do what?
> >
> > One possibility might be to act as if the valuelist was a table and do the
> > IN as if it were that way, rather than treating it as a set of ORs. That
> > would be basically like doing the temporary table solution, but without
> > requiring the user to do it.
>
> Is the temp table version any faster? I realize it has a higher limit
> to the number of items you can have in the list.

Within the scope of the new hashed IN stuff I believe so in at least some
cases. I have a few million row table of integers where searching for
values IN (~10000 values) takes longer than creating the temp table,
copying into it and doing the in subquery. That's not a particularly
meaningful test case, but sending the psql output to /dev/null gives me:

create temp table/copy 10001 entries/select in subquery - .8 sec
select in (value list 9998 entries) - ~ 2min 19 sec
explain select in (value list) - ~ 4.8 sec