Shape performance question - one larger file vs. several smaller

[Ed McNierney]

Dejan -

This will depend on your data.  A good way to think about things is what you
would like the optimal situation to be.  The best possible case for a map
request would be for exactly one shapefile to be opened, and for every shape
in that file to be drawn on the map.  That way you are not opening multiple
files (relatively expensive) nor are you skipping over features you don't
need (not as expensive, but not free).

Selecting features based on classification is also not expensive, but not
free.  But it's cheaper than opening multiple files (I suppose that might
not be true if you had a LOT of features but very few types).

How many different files/types do you have, and how many features (total) do
you have?  Do you have a particularly slow disk system?

By the way, provided you're using spatial indexes for your shapefiles, any
shapefile reorganization is unlikely to make a lot of difference.  It's
worth tuning a bit, but except in unusual cases it's not likely to make
things twice as fast or slow.

     - Ed

-- 
Ed McNierney
President and Chief Mapmaker
Maps a la carte, Inc. / TopoZone.com
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
Phone: (978) 251-4242
Fax: (978) 251-1396
ed at topozone.com

> From: Gambin Dejan <Dejan.Gambin at PULA.HR>
> Reply-To: Gambin Dejan <Dejan.Gambin at PULA.HR>
> Date: Mon, 22 Jan 2007 10:35:49 +0100
> To: <MAPSERVER-USERS at LISTS.UMN.EDU>
> Conversation: Shape performance question - one larger file vs. several smaller
> Subject: [UMN_MAPSERVER-USERS] Shape performance question - one larger file
> vs. several smaller
> 
> Hi,
> 
> I have several line shape files showing the borders of different types.
> I am wondering if it is better to merge them using ogr2ogr and tehn
> classifying them in map file, or use all the files as layers?
> 
> Does anybody know the difference in speed/performance?
> 
> By the way, I have one more question related to performance. Is it
> better to place all symbol definitions in symbol file or define them
> directly in map file?
> 
> thanks very much
> 
> regards, dejan