[mapserver-users] MapServer v. 4.10.0 featureid problem

[Rahkonen Jukka]

-----Alkuperäinen viesti-----
Lähettäjä: mapserver-users-bounces at lists.osgeo.org puolesta: Brian Mixon

> Tom,

> Perhaps I should tell you why I'm after the (or any) unique AND
sequential id field for a service's features. I'm trying to page the
feature data in a UI and started designing my solution after having read
the WFS v 1.0.0 spec. I assumed (yes, I know what happens when one does
that (;>)) that I'd just use feature ids. 

> I should have asked what mechanism MapServer employs to allow me to do
something like this (the partial retrieval of features from a large
dataset on some service somewhere). I'm going to bring back a certain
number of features with each call to a WFS and as the user scrolls
through this data I will make subsequent calls to the same service and
ask for the next batch of features.

> Does this make sense and can you point me in the right direction for
getting MapServer to do this?

I fear that WFS itself does not support this well.  WFS does have a setting for maximum number of features returned by one request, but there is no way to ask for the following set of features starting from, let's say, feature number 100001. But if you take the WFS fid from sequential database field and sort that somehow then it should be possible to reach what you wand by addind a WFS filter like "AND fid>max_fid_from_last_request" to the next WFS request.  I can imagine that this could lead to most unuseful result if bounding box is also a part of a filter and user is panning around on the map between the requests (area unvisited before can have features with lower fid values).

-Jukka Rahkonen-