Re: aggregate functions, COUNT

Stephan Szabo <sszabo@megazone23.bigpanda.com> writes:
> I think you could use EXISTS for that,
> select EXISTS (<query>); should give a true/false on whether the 
> query returned any rows.  I'm not sure if it stops after one row
> or not, but if it doesn't you can add a limit 1 to the query.

Yes it does stop after one row; and furthermore, the planner knows to
generate a fast-start plan for it.  (Or at least it's supposed to
... hmm, this seems to be broken in current sources ...)  Anyway,
there's no need for LIMIT 1 inside an EXISTS, because the planner
assumes that automatically.
        regards, tom lane