On Fri, Feb 17, 2012 at 11:32 PM, Jay Levitt <jay.lev...@gmail.com> wrote:
> Alexander Korotkov wrote: > >> On Fri, Feb 17, 2012 at 11:00 PM, Jay Levitt <jay.lev...@gmail.com >> <mailto:jay.lev...@gmail.com>> wrote: >> >> At first I thought this posed a challenge for union; if I have these > points: > >> >> (1,2) >> (2,1) >> (1,NULL) >> >> what's the union? I think the answer is to treat NULL box coordinates >> like LL = -infinity, UR = infinity, or (equivalently, I think) to store >> a saw_nulls bit in addition to LL and UR. >> >> Similar problem appears at GiST indexing of ranges, because range can be >> empty. There additional "contain empty" flag was introduced. This "contain >> empty" flag indicates that underlying value can be empty. So, this flag is >> set when union with empty range or other range with this flag set. It's >> likely you need similar flag for each dimension. >> > > Ah, yes, exactly the same problem. So what led you to add a flag instead > of using the range NULL..NULL? I'm on the fence about choosing. At first, range bounds can't be NULL :) At second, if we have range (a;b)+"contain empty" in internal page, both facts: 1) All normal underlying ranges are contained in (a;b). 2) There can be empty underlying ranges. are useful for search. ------ With best regards, Alexander Korotkov.
