[rrd-developers] New DEF: virtual def

[Alex van den Bogaerdt]

No, no code yet.

I was wondering about the resolution of the data inside a CDEF.
Doing functions with TIME, it will not be at the picture resolution,
it will be at the data resolution.

Try it: create a RRA with CDPs every two hours. Now use the TIME
function inside a CDEF and mask out every other half hour:

DEF:mydata=some.rrd:.....
CDEF:mask=TIME,3600,%,1800,LT,mydata,UNKN,IF

It won't work as intended, the resolution of the data is too low.

Perhaps we could use something like "VDEF" that carries no data in
it but can be used for time related stuff. It would have a resolution
of one calculation per pixel. I'm thinking of:

DEF=mydata=some.rrd....
VDEF:thetime=TIME
CDEF:mask=thetime,3600,%,1800,LT,mydata,UNKN,IF

Also, there would be no restriction to always use a DEF or CDEF in it
and the following is completely legal:

VDEF:constant=20

as opposed to

CDEF:constant=data,POP,20


Comments ?

Regards,
Alex

--
* To unsubscribe from the rrd-developers mailing list, send a message with the
  subject: unsubscribe to rrd-developers-request at list.ee.ethz.ch