[mapserver-dev] symbol lazy-loading

Stephen Woodbridge woodbri at swoodbridge.com
Sat Nov 21 10:43:13 EST 2009


I think for historical reasons maybe, but also for management reason, a 
lot of people have large repositories of image symbols, and a single 
symbolset file. I build mapfiles for a lot of people, and use a common 
repository, but in most cases only a few, less than 1%, are used in any 
one mapfile.

Part of the reason for this is that if you ship a mapfile to a client, 
you also need to send the symbolset, fontset, etc. and it is just easier 
and less error prone to tar up a standard directory of these support 
files. It is a pain when you ship something only to find that some file 
or another is missing and the product is broken when deployed remotely.

I think a lot of people would benefit from this.

On the other hand, as the symbology definitions are getting better and 
better in mapserver, I also find that I rely less and less on the older 
image symbols, but that just may be me.

-Steve W

thomas bonfort wrote:
> Pavel,
> On Wed, Nov 18, 2009 at 13:24, Pavel Iacovlev <iacovlev.pavel at gmail.com 
> <mailto:iacovlev.pavel at gmail.com>> wrote:
>     Good day all,
>     As I understood on render request mapserver loads all symbols into
>     memory thats is fine if you have under 64 symbols (default limit). 
>  recent versions of mapserver aren't limited to 64 symbols anymore.
>     I
>     have a topographical map to render that maybe will have around 200+
>     symbols and like 5-10 will be used per request. Maybe implementing
>     lazy-loading (only then needed) for symbols will improve the
>     performance ? and remove the cap at all. 
> lazy loading of symbols would definitely make sense for image symbols, 
> although only for people with a single symbolset for multiple instances, 
> as otherwise the case is rarer to have defined  a symbol but never use it.
> the other symbol types wouldn't see much benefit from lazy loading imho, 
> as this is only a parser operation that has to be done anyways.
>     Another question is if I have
>     100 image symbols all 100 images are loaded into memory on render
>     request ?
> yes, all the image files are loaded.
> regards,
> thomas
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