Zsort ?

Attila Csipa plists at PROMETHEUS.ORG.YU
Thu May 17 10:40:55 EDT 2007

On Thursday 17 May 2007 15:15, Stephen Woodbridge wrote:
> 1) have you thought about sorting objects in Z coordinate value? would
> you sort by bbox of the shape? min or max value? etc.

That could be an option as well, but needs to be thought through as Z values 
might be interpreted differently in different data formats (like 2.5D, 'm' 
values, etc). Min/max (or, rather, asc/desc, looking top-down or bottom-up) 
could also be regulated by a keyword (like ORDERASCENDING TRUE). Obviously 
there are a number of usually available and commonly used items like the bbox 
which could be hardcoded in the keyword (ORDERITEM [bbox|id|string] where 
string would be the column name, and the others predefined sort patterns).

> 2) a slight expansion of scope, if mapserver supported indexes, then you
> could simply apply a fetch from the index to do this and avoid building
> and sorting the data on every hit.

Indexes would make this easier, of course, but are not necessary (in fact, we 
should be able to do this sort regardless of the indexes being or not being 

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