Matthew Wakeling <matthew@xxxxxxxxxxx> writes: > On Fri, 3 Apr 2009, Tom Lane wrote: >> Not unless you have sorted the inputs in some way that has more >> knowledge than the "equal" operator represents. Otherwise you can have >> elements drop out that might still be needed to match to a later >> left-hand element. > Of course. You certainly have to choose a sort order that works. Sorting > by the start field would be sufficient in this case. Uh, no, it wouldn't. Visually: L1 ------------------------- L2 ----------- L3 --------------------- R1 -------- At L2, you'd conclude that you're done matching R1. Intuitively, it seems like 1-D "overlaps" is a tractable enough operator that you should be able to make something merge-like work. But it's more complicated than I think you realize. regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
