> Only an attribute name, not every expression
> - filter: you mention this as CQL but I expect an actual filter can be
> passed in
>
> Nope, I really meant a CQL formatted string, a Filter cannot be passed because
> it's not an Expression, and all filter function params are to be Expression
> objects instead.
> (at least this is my understanding).
>
Okay, I notice for that many of the relationship functions Dave Blasby has made
matching functions.
As an idea could we make a function called filter( String, Expression, … ) in
order to keep this above board and not make use of magic strings.
> What we do when we hit the next system that requires more extra params?
> A single open ended optional param gives us extensibility without having to
> count
> the nulls: say we add a new param for a third system, the first two would
> have to
> be null and the third valid, then a fourth one comes in and we have to leave
> three
> nulls before adding the fourth param and so on, it's messy.
>
The downside to an optional parameter is that we cannot describe the contents
very well
programatically. Still if that will help, is there any chance we can make it a
String so at least a user interface can prompt the user for something.
> This trouble is caused by function params being positional instead of being
> named.
>
Agreed, naming the parameters would be an easy way out:
So we end up with…
nearest( the_geom, point, filter( "greaterThan", category, 3 ) )
nearest( the_geom, point, filter( "greaterThan", category, 3 ), "10" )
nearest( the_geom, point, filter( "greaterThan", category, 3 ), "<->" )
nearest( the_geom, point, filter( "greaterThan", category, 3 ), "<#>" )
> It seems to me a filter function is cleaner than both of the above
> approaches, requires less effort to
> be implemented, and provides the same amount of functionality.
>
Yep - I like it. Just throwing other ideas at the wall to see if anything comes
of it.
Jody
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