I'm not sure exactly what you're saying here. If the data in the in()
clause comes from a complex select, then just use the select in there, and
bypass the temporary table idea.
I'm not sure what a temporary database is, did you mean temporary table?
if so, then my above comment addresses that point.
On Wed, 10 Mar 2004, Marcus Andree S. Magalhaes wrote:
>
> Hmm... from the 'performance' point of view, since the data comes from
> a quite complex select statement, Isn't it better/quicker to have this
> select replaced by a select into and creating a temporary database?
>
>
>
> > The problem, as I understand it, is that 7.4 introduced massive
> > improvements in handling moderately large in() clauses, as long as they
> > can fit in sort_mem, and are provided by a subselect.
> >
> > So, creating a temp table with all the values in it and using in() on
> > the temp table may be a win:
> >
> > begin;
> > create temp table t_ids(id int);
> > insert into t_ids(id) values (123); <- repeat a few hundred times
> > select * from maintable where id in (select id from t_ids);
> > ...
>
>
>
>
