number of layers in mapfile

[Stephen Woodbridge]

Eric Lemoine wrote:
> Hi
> 
> I've observed that mapserv image rendering performance decreases
> significantly with the number of layers. I currently have 500+ layers
> in my mapfile and I see a huge performance hit if I decrease this
> number to around 10. Is this expected? I use mapserver 4.10.
> 
> Thanks,
> 
> Sorry if this question has already been answered.
> 
> --
> Eric

Eric,

I think Ed McNierney did some performance tests on this issue (you might 
be able to find it in the archives).

Anyway the up shot is that you have to parse and allocate objects for 
all the layers, symbols, styles, etc that are defined in all the layers 
and this takes time.

There is also a performance hit if you are using projection definitions 
because parsing all the projection init definitions is very time 
consuming. Frank W. might have more info on this. I think some people 
have made stripped down projection files with only the projections that 
they are using, to speed this up for production use.

-Steve W