[mapserver-users] Prevalence of the use of queryfiles...

[Paul Spencer]

Steve,

we use this feature in Fusion via mapscript to save the result of a  
spatial or attribute query and then via the CGI (via OpenLayers by  
merging new params queryfile=) to draw the query when rendering the  
map.  It is a *very* convenient and seemingly lightweight (at least in  
coding terms) mechanism to draw query results.   We don't need to  
modify the map file as a result of a query and we don't need to use  
mapscript to draw the map (since everything else is on the client for  
requesting the map).

We could change this to use another mechanism - when a fusion app  
starts, the requested mapfile is copied to a session so we can modify  
if necessary (add/remove layers, reorder etc).  This means that as a  
result of a query, we could add layers that point to temporary shape  
files that contain copies of selected features.  While this might give  
us a bit more control over presentation of the query results, it might  
also be problematic for selecting features like points with specific  
symbols coming from different layers etc ... I guess we would copy  
every layer that had a query result to new layer and modify the styles  
but that could get very complex to manage.

One of the requested features for Fusion (MapServer) is to modify the  
selection (add features, remove features).  We can do this in  
MapGuide.  Managing things in shapefiles would at least give us an  
option to implement this kind of thing, but it would be quite heavy  
handed I think.

Overall I would argue to keep it unless you know of a reasonably  
simple way to replicate this functionality with mapscript and not  
requiring mapscript to draw the map every time (which was what we did  
in Chameleon!).

Cheers

Paul

On 13-Mar-09, at 1:04 AM, Steve Lime wrote:

> Hi all: Consider this a survey of sorts. I'm wondering how many of  
> you make use of saving queries, either via the CGI or MapScript.  
> It's an old feature that isn't terribly useful and I'm trying to  
> understand the pain the community might incur if they go away in  
> 6.0. If you didn't know they existed or how you might use them then  
> it's safe to say you don't need 'em.
>
> Steve
> _______________________________________________
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> mapserver-users at lists.osgeo.org
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__________________________________________

    Paul Spencer
    Chief Technology Officer
    DM Solutions Group Inc
    http://research.dmsolutions.ca/