[mapserver-users] Re: WMS and tiles cutting off

Fri Apr 30 09:37:44 EDT 2010

Adam,

It sounds like you have boiled the issue down to too much of a time lag between the time the query is executed and the image appears in the client.

Is it taking a long time for MapServer to draw the image, or is it the delivery of the image to the requesting machine and subsequent placement in the client?

If it is taking MapServer a long time, maybe there are some more data optimizations that you can do.  Is there a better way to structure your data, can you do any pre-processing?  Is it all in the same SRS, got attribute and spatial indexes?  I have used the SQL IN for some apps with reasonable performance, but in the last 6 months or so, there were some posts on this list comparing the use of IN to a layer (or class?) filter.  The latter solution was significantly faster.

If it is taking a long time to get to the client, then that is likely an infrastructure issue on either end.

If you want some more help digging in more deeply, post some more stats and mapfile snippets.

David.

From: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of Adam Eskreis
Sent: Thursday, April 29, 2010 4:24 PM
To: Lime, Steve D (DNR)
Cc: mapserver-users at lists.osgeo.org
Subject: Re: [mapserver-users] Re: WMS and tiles cutting off

I tried doing ratio:1 unfortunately it doesn't seem like enough of a performance increase.  Separate layers for each category is an option, however, there are over a hundred categories, and any combination of categories can be on at any given time, so this could prove to have performance issues of it's own.  However, I thank you guys Steve and Kaipi for your advice.  I think I am just going to go back to my old method, which was using php mapscript to generate the tiles, then each time the user selected new categories, purge the cache and remake the mapfile.  It's not the ideal solution but it seems to be the only one.

Thanks again,

-Adam
On Thu, Apr 29, 2010 at 3:50 PM, Lime, Steve D (DNR) <Steve.Lime at state.mn.us<mailto:Steve.Lime at state.mn.us>> wrote:
Note that by default I believe openlayers will request an image that is *much* larger than what is visible. Setting the layers (OL) ratio:1 makes it the same size as the view port and that can speed up rendering considerably.

Alternatively you could create a separate set of tiles for each category I suppose and switch OL layers as necessary...

Steve

________________________________________
From: mapserver-users-bounces at lists.osgeo.org<mailto:mapserver-users-bounces at lists.osgeo.org> [mapserver-users-bounces at lists.osgeo.org<mailto:mapserver-users-bounces at lists.osgeo.org>] On Behalf Of Adam Eskreis [aeskreis at gmail.com<mailto:aeskreis at gmail.com>]
Sent: Thursday, April 29, 2010 2:25 PM
To: mapserver-users at lists.osgeo.org<mailto:mapserver-users at lists.osgeo.org>
Subject: Re: [mapserver-users] Re: WMS and tiles cutting off
Ok, I just gave an untiled layer a try, unfortunately though, due to the large amount of symbols being displayed on the screen, there is about a 2 second delay every time the map is panned.  My client will most certainly find this unacceptable.  I have tried using smaller images, but I cannot sacrifice any more quality.  I believe my database query to be as optimized as it can be (has about 50 ms runtime, I honestly don't think I can get it any lower than that).

If these are the only options, is there something else besides WMS that you all would recommend using to solve this issue?

Thanks,
-Adam
On Thu, Apr 29, 2010 at 2:54 PM, Lime, Steve D (DNR) <Steve.Lime at state.mn.us<mailto:Steve.Lime at state.mn.us><mailto:Steve.Lime at state.mn.us<mailto:Steve.Lime at state.mn.us>>> wrote:
So use two layers. One for the background, use tilecache for that. Then use an untiled wms/mapserver layer for the overlayed points. - Steve
________________________________________
From: mapserver-users-bounces at lists.osgeo.org<mailto:mapserver-users-bounces at lists.osgeo.org><mailto:mapserver-users-bounces at lists.osgeo.org<mailto:mapserver-users-bounces at lists.osgeo.org>> [mapserver-users-bounces at lists.osgeo.org<mailto:mapserver-users-bounces at lists.osgeo.org><mailto:mapserver-users-bounces at lists.osgeo.org<mailto:mapserver-users-bounces at lists.osgeo.org>>] On Behalf Of Adam Eskreis [aeskreis at gmail.com<mailto:aeskreis at gmail.com><mailto:aeskreis at gmail.com<mailto:aeskreis at gmail.com>>]
Sent: Thursday, April 29, 2010 1:24 PM
To: mapserver-users at lists.osgeo.org<mailto:mapserver-users at lists.osgeo.org><mailto:mapserver-users at lists.osgeo.org<mailto:mapserver-users at lists.osgeo.org>>
Subject: Re: [mapserver-users] Re: WMS and tiles cutting off

I have thought about using tilecache with metatiling, however there is a caveat about this map that i forgot to mention in my main post, and it has to do with that "categories" parameter.  Basically, each point/symbol on the map has an associated category in the database backend.  I am using mapserver/WMS parameters to change the categories which are called.  Each time the user selects a category, only the points in that category are shown.  My query in the mapfile looks something like thi:

SELECT point_geom,gid,symbol,angle FROM mapdata WHERE category IN(%CATEGORIES%)";

And each time the user changes the categories, I use openlayers to merge new parameters, and input the new category values that should be used.  Is tilecache still useable if I have a system like this set up?

Thanks,
-Adam

On Thu, Apr 29, 2010 at 6:14 AM, kaipi <mapcollect at gmx.net<mailto:mapcollect at gmx.net><mailto:mapcollect at gmx.net<mailto:mapcollect at gmx.net>><mailto:mapcollect at gmx.net<mailto:mapcollect at gmx.net><mailto:mapcollect at gmx.net<mailto:mapcollect at gmx.net>>>> wrote:

Hi,

you can use  http://tilecache.org/ Tilecache   with the option metatiling
enabled. With metatiling enabled Tilecache will fetch larger tiles (eg.
4096x4096) from Mapserver and will cut them into smaller tiles (eg.
256x256). It will also increase performance because Mapserver does not need
to render tiles when they are already in cache.

kaipi
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