Like with everything it depends...  Selection of features via a bounding box 
shouldn't be much, or really any, slower than drawing since it's basically the 
same mechanism for both. Attribute queries can be quite slow with shapefiles 
since MapServer doesn't do any attribute indexing. That's where the RDMS really 
adds value. There shouldn't be much of a difference with a bbox query, and in 
fact, a local shapefile will probably be faster, even on larger datasets as 
long as you've build an spatial index file.

Anyway, it's what you do with results afterwards that matters and that's 
probably specific to your application.  I've used query files to persist 
selected features over many map draws successfully on modest (50,000 feature) 
sized shapefiles.


From: Chris Jackson []
Sent: Tuesday, August 24, 2010 10:34 AM
To: Lime, Steve D (DNR)
Subject: Re: [mapserver-users] Feature select performance


The selection of layer data is done by a bounding box, though querying by 
parameter values is just as slow.  The mapfile is directly calling up the 
shapefile (I had just followed the P.Mapper examples of displaying/querying 
shapefiles directly).  So probably the answers to those questions lie under the 
hood of P.Mapper, which I assume is using the PHP mapscript.dll to do the work. 
 Is the direct query to shapefile approach v.efficient for larger datasets..?.  
Ignoring the app I am using what is a good approach to large feature datasets 
from a MapServer perspective?


On 24 August 2010 14:27, Lime, Steve D (DNR) 
<<>> wrote:
How is the selection done? How is the highlighting done? Those processes will 
really impact performance depending on how things are implemented.


 On Behalf Of Chris Jackson [<>]
Sent: Tuesday, August 24, 2010 3:19 AM
Subject: [mapserver-users] Feature select performance

Hi all

I have rigged up a webGIS app (P.Mapper framework) where one of the underlying 
datasets is a model grid (many thousand cells) in a shapefile.  The data 
displays nice and quick when just viewing, but if I allow the user to select 
say 5000 cells it is very (extremely) slow to redraw with the highlighted 
cells.  Doing the same task in a very old ArcGIS server web app was much 
quicker (admittedly the data was in SDE/MS SQL).  So my question is what is the 
best way to improve performance - would just transferring the shapefile to to 
say a MS SQL 2005 db with the MSSQLSPATIAL add-on be a good step or is there 
are better way to present the data in the Map file?
Many thanks

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