Stephan Szabo <sszabo(at)megazone23(dot)bigpanda(dot)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