Re: [HACKERS] Idea for speeding up uncorrelated subqueries

> Bruce Momjian <maillist@candle.pha.pa.us> writes:
> >> Bruce Momjian <maillist@candle.pha.pa.us> writes:
> >>>> Yes, the subqueries need work.  We don't even do index lookups into the
> >>>> inner plan, only sequential.  Already on TODO.
> >> 
> >> Huh?  I don't follow that at all...
> 
> > Suppose you have a subquery that returns 1000 rows.  There is no code so
> > lookups of the inner table are indexed:
> 
> >     select *
> >     from tab
> >     where col in (select col2 from tab2)
> 
> > In this case, a sequential scan of the subquery results are required.
> 
> Well, yes, the subquery is a sequential scan.  I guess what you are
> envisioning is rewriting this into some kind of nested-loop join?
> For simple cases that might be possible...

Yes, or mergejoin/hashjoin.

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