Layer get distinct function...

[Steve Lime]

> I am also ok with adding the distinct capability though it will be
pretty
> expensive to execute for most OGR drivers.  I gather folks can still
> declare the list of values in the metadata to avoid this cost,
right?

> What about providers that might not get updated to support this
capability.
> What will happen then?

Yup. I was thinking that you'd look for the hardcoded list first and
then try
to generate one (based on something like ows_timeitem). If not
available then
throw an exception.

Steve

>>> Frank Warmerdam <warmerdam at POBOX.COM> 11/9/2004 1:34:03 PM >>>
Yewondwossen Assefa wrote:
> It can be costly in some cases but I can also see the immediate use
for
> me in the time support where the user sends a request like
Time=current
> (or Time=now).
>
>
> Steve Lime wrote:
>
>> Hi all: Tom's recent post about time and WMS reminded me of a
feature
>> that might be useful for WCS/WMS and other interfaces. The ability
to
>> get a list of distinct values for an attribute within a layer. At
the
>> moment with WCS for example you have to explicitly enter all
available
>> times in metadata. Works fine for a few but would get tedious
quickly. I
>> could also see this as being a way to extend templates to be more
>> dynamic (e.g. produce a select list) and data driven. It would be
very
>> helpful to be able to mine the data for that list. I'd like to
propose a
>> msLayerGetDistinct function that would return an array of all
unique
>> values for an attribute. What do folks think, other better ideas?

Steve,

I am also ok with adding the distinct capability though it will be
pretty
expensive to execute for most OGR drivers.  I gather folks can still
declare the list of values in the metadata to avoid this cost, right?

What about providers that might not get updated to support this
capability.
What will happen then?

Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam,
warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for
Rent