On May 27 11:50, Tom Lane wrote: > Volkan YAZICI <[EMAIL PROTECTED]> writes: > > ISTM, there's a problem in the correlation of random() to outer JOINs. > > The random() functions are being evaluated more than once because the > subselect gets "flattened" into the outer query, so that you have > the equivalent of > > select random(), ... where t2.id = random() ...
Oops, sorry. I've just remembered this. > We've previously discussed preventing the planner from flattening if > there are any volatile functions in the sub-select's output list, but > I think that would probably do about as much harm as good. It can be quite informative to learn the pros and cons of this issue, but I couldn't find related discussion in archives. I'd be so appreciated if you can remember its subject or anything specifier for the thread. > > Furthermore, if you'd append an "OFFSET 0" to subselect, output becomes > > more stable but still has some inconsistencies. > > I didn't see any... That's all caused by a mis-interpretation of the output by me. Replacing "(random() * 100)::int % 17" with "1 + ((random() * 100)::int % 16)" solved my above question. Regards. ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly