[mapserver-users] Image Speed Questions---Generic

[Ed McNierney]

Hmmm.  Since these pages are generated by a CGI program, I'd be
surprised to find a server caching them.  How does the server know that
the program isn't querying a database that just got updated?  If my page
was:

http://mybank.com/account.cgi?getbalance=345678980

and it reported my bank account balance, I would expect the server to
NOT cache the result.

On the other hand, your BROWSER could very well be doing this.
Depending on your browser version and brand preference, there are
various settings that will control whether the browser will re-query the
Web server for an identical URL.  Your browser may be set up to not
check again (at least during the current session) if the URL is the
same.

	- Ed

Ed McNierney
Chief Mapmaker
TopoZone.com
ed at topozone.com
(978) 251-4242


-----Original Message-----
From: Doug Nebert [mailto:ddnebert at fgdc.gov]
Sent: Tuesday, July 31, 2001 8:20 AM
To: Mapserver Users
Subject: Re: [mapserver-users] Image Speed Questions---Generic


Walt Lin wrote:
> 
> On the note of trivial rejection and tileindices, what about this
solution: store the extents of all the different shapefiles (perhaps one
per county on a national level) in a postgres table with an R-Tree
index.  When a request comes in, query Postgres for all the shapefiles
that intersect and load them using mapserver.  Of course, POSTGIS would
be optimal, storing everything in Postgres, but from what I've heard
this is really slow in practice.  Thoughts?
> 
> Walt

Actually a simpler technique is quite feasible: If you request a map
using the exact same URL (extents, layers, etc) then a caching 
webserver will provide the map from the cache instead of requesting
it. I have seen this work quite well on all sizes of datasets. By
having pre-set extents, such as counties, you can encourage this
behavior.

Doug.
-- 
Douglas D. Nebert
Geospatial Data Clearinghouse Coordinator 
FGDC/GSDI Secretariat	Phone: +1 703 648 4151	Fax: +1 703 648-5755	
Pager Messaging: 	http://clearinghouse3.fgdc.gov/dougmsg.html