Re: Idempotence and "Replication Insensitivity" are equivalent ?

Jan Hidders ha scritto:

> Us? There's more than one of you? :-)

Plurale majestatis, like the Pope :)

>
> > Let's assume a Datetime field and this aggregate function:
> >
> > Central date = minDate + Half length of total time interval
> >
> > what would (E, S, A) be?
>
> You'd split that into computing (minDate, maxDate) and then do some
> post-processing. For (minDate, maxDate) you get:
> - E = (null, null)
> - S(d) = (d,d)
> - A((d1, d2), (d3, d4)) = (MIN(d1, d3), MAX(d2, d4))
> with MIN and MAX defined such that MIN(d, null) = MIN(null, d) = MAX(d,
> null) = MAX(null, d) = d.

I see. Interesting.

... but in case of a Median date, how would you proceed? Would it be all "postprocessing" ?

[ If so you, it would actually be redefining, in a certain sense, the aggregate function concept ;) ... ]

-P
>
> -- Jan Hidders
Received on Fri Sep 22 2006 - 11:41:42 CDT