[OpenLayers-Dev] [OpenLayers-Users] Work around for bug #541 ??

Christopher Schmidt crschmidt at metacarta.com
Mon Apr 2 16:50:22 EDT 2007

On Mon, Apr 02, 2007 at 04:31:30PM -0400, Stephen Woodbridge wrote:
> Christopher,
> I updated to trunk today, did a build.py full and I'm using the 
> OpenLayers.js - Thank you getting svn fixed up.
> I am still having serious performance problems.
> Step 1:
> http://imaptools.com/ld-test.html
> Click on Algers, DZ link this displays just fine and is very fast notice 
> the Features: 50, I have maxfeatures=50 set.


> Step 2:
> Click Zoom + This runs reasonably fast, BUT the Features: 100. This is 
> clearly wrong. maxfeatures=50 and there are less displayed because of 
> the zoom in. 

Agreed. The WFS layer should be clearing out its feature list when the
map is redrawn (when more data is requested from the server). Up until
now, the renderer was being cleared, but the features were still on the
list. I've opened #622 to fix this.

> 3) ALWAYS clear the current features set and requery, because in a 
> multiuser environment the features on the server might have been updated 
> and you want to get a fresh copy.

^^ This is the one we'll go with for now.

> Step 3:
> Click Zoom + again and it takes about 5 mins for the browser to process 
> the request. Features: 139

I'm not seeing this as being slow. 

> Step 4:
> Reload the page to start over.
> Click on Algers, DZ
> Click Zoom -, This takes about 5 mins to return with NO poi displayed. 
> The mapfile has MAXSCALE 50000 set for the WFS LAYER

Are you sure that this isn't your server? I saw several times while
testing yesterday that mapserver ended up just hanging out for 2-3
minutes and then never returning an image. If you zoom out from the
algers jump, no WFS is involved, just the Mapserver Untiled layer, and
it seems to me like your map is just slow :) Check the serverside on
this one, maybe?

> Step 5: after Step 4 returns, you can zoom out fast and zoom in until 
> you hit the WFS points and if you try to zoom out again you get the same 
> delay.

Interesting. It's possible that your computer is slower than mine such
that things are just really slow for you, but I don't really understand
anything difficult that would be happening at that stage. 

I'll work on getting the WFS to clear out its features, and we'll see if
that helps the rest of your performance issues, but, as I said, I'm not
entirely convinced, since I'm not seeing anything interesting that could
be causing this slow down, nor can I reproduce it in your application.

Christopher Schmidt

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