Re: Support for RANGE ... PRECEDING windows in OVER

On Mon, Jul 1, 2013 at 3:28 PM, Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
> Robert Haas escribió:
>> On Sun, Jun 30, 2013 at 11:54 PM, ian link <ian@ilink.io> wrote:
>
>> > It seems pretty clear that assuming '+' and '-' are addition and subtraction
>> > is a bad idea. I don't think it would be too tricky to add support for new
>> > operator strategies. Andrew Gierth suggested calling these new strategies
>> > "offset -" and "offset +", which I think describes it pretty well. I
>> > assigned the operator itself to be "@+" and "@-" but that can obviously be
>> > changed. If this sounds like a good path to you guys, I will go ahead and
>> > implement the operators for the appropriate types. Please let me know if I
>> > am misunderstanding something - I am still figuring stuff out :)
>>
>> I don't think I understand the design you have in mind.  I'm actually
>> not clear that it would be all that bad to assume fixed operator
>> names, as we apparently do in a few places despite the existence of
>> operator classes.  But if that is bad, then I don't know how using @+
>> and @- instead helps anything.
>
> Yeah.
>
> Currently, all operator classes are tied to access methods.  Since
> nobody seems to have any great idea about creating an access method that
> requires addition and subtraction, would it make sense to have operator
> classes that exist solely to support keeping track of such operators for
> the various datatypes?

I suppose if we really wanted to do this, it would make more sense to
have a new kind of object, maybe CREATE TYPE INTERFACE, rather than
shoehorning it into the operator class machinery.  It seems like a
fairly heavyweight solution, however.

--
Robert Haas
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