[mapserver-users] SUMM: CGI Map changes and question

[Robert Crossley]

Thanks for your replies.  This is an interesting experience participating in a list as a complete newbie.

Form the replies, I understand that Mapserver doesn't maintain knowledge of each users current state, so it means that any changes to a map template need to be made for 
each call.  No great problem.  Alternatively I could use the SaveMap call to save the current settings in a temporary Map file for use in that user-session.  At one point I thought I 
would have to generate the Map file dynamically prior to calling MapServer, so both of these options are much slicker.

I thought that other web servers like MapExtreme and ARCIMS spawned new instances for a user/ session and built on previous changes, but thus had the potential to bog 
down under load.  MapServer's stateless approach avoids this load, but does it have the disadvantage that it needs to redo operations like filters each time?

My app has about 1500 farmers who each want to look at only their farm.  There are 3 master tables of farm data: paddocks, harvested areas and labels, each with about ~
30,000 records.  Each record in these tables is tagged with the farm number.

I have been able to change mapfile data parameters using a URL OK, so I can allow each farmer to look at only their data by pre-processing the master table and splitting it into 
separate farm tables that have the farm number as part of the file name, and changing the data reference for the farm layer for each farmer at run-time.

Another option is to filter the master table in MapServer and change the filter string based on farm number.

While the first option is messy terms of the number of files, it is fast.  The filter option looks neater, but I am cautious that it will load the server substantially when a large number 
of farmers are using it as I gather that the filter has to be applied in each call.

Does anyone have any comments on the performance of filters  and the load it places on the server?  The 3 master shape files are about 9MB each versus  about < 10KB each 
for the shape files for each farm.

Thanks 

R


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Robert Crossley 
Robert Crossley & Associates
9 Short St
New Brighton NSW 2483
AUSTRALIA

P: 02 6680 1309
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