Question re: PostGIS and MapScript getExtent() function

[Steve Hall]

Hi All,

I'm using MapServer 4.6.0 with Oracle Spatial and PostGIS data sources via PHP/MapScript.  Part of my application code looks like this  pseudo-code :

    $map->setLayerFilter("ThematicData", "REQUEST_ID=121");
    $map->zoomToLayer("ThematicData");

Here i'm setting a specific FILTER expression for a layer, and then zooming to the extent of the (now filtered) layer.  I use the layerObj->getExtent() and then mapObj->setExtent() functions to achieve this behind the scenes.  This works great for Oracle, the query is fast and makes for nice, tidy code in my application without the need for Oracle specific SQL statements to derive the new extent.

However when I try this on PostGIS I just get a massive (useless) extent returned.  Digging into the code I can see that the msPOSTGISLayerGetExtent() function in mappostgis.c is effectively doing nothing although a lot of code is commented out.

Working on my local code I have re-enabled this code, fixed the compilation errors and changed it so that when a FILTER is applied to the layer this is used as part of the SQL call to PG.  It seems to work great (from PHP/MapScript) and performance is fine and is really useful for me meaning I don't need to calculate the extents for a map myself - MapServer can supply the information in a generic and abstract fashion.

Ideally I would like to get this code fed back into MapServer, but of course only if it's acceptable to you all.  So,  should I instead post this to mapserver-dev or can I pass on the new code to someone from here?

There may be good, historical, reasons why this wasn't ever implemented though so please let me know!

Many thanks,

Steve Hall
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