Re: Ranges for well-ordered types

On Jun 11, 2006, at 2:34 , Michael Glaesemann wrote:

>
> On Jun 11, 2006, at 0:54 , Ian Caulfield wrote:
>
>> I've done similar date range things by creating a composite type  
>> consisting of the lower and upper bounds, and then implementing a  
>> btree opclass where the comparator returns 0 if two ranges overlap  
>> - this allows a current btree index to enforce non-overlapping  
>> ranges, and allows indexed lookup of which range contains a  
>> particular value.
>
> As Tom already pointed out, this method leads to problems with  
> btree indexes. I haven't heavily tested my own implementation  
> (below), but it only returns 0 for equality, which is what btree  
> expects. All other possible relationships between two ranges have a  
> well-defined result of -1 or 1. I believe this should be enough to  
> prevent any transitivity issues with btree.

Of course, this method doesn't provide the non-overlapping  
constraint. That still needs to be handled by a constraint trigger.

Michael Glaesemann
grzm seespotcode net