Re: plpgsql arrays

Matthew Wakeling <matthew(at)flymine(dot)org> 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