[MS4W-Users] slow access to PostGIS layer

[G. Allegri]

2012/6/28 Smith, Michael ERDC-RDE-CRREL-NH <Michael.Smith at erdc.dren.mil>

>  The biggest impact will be the total amount of data involved. The number
> of vertices you reported earlier seemed quite large for most scales. I'd
> consider doing some generalization for higher zoom levels.
>

I think I will do that. I didn't notice such an impact within our Linux
environments.
The timing is closely related to the number of vertices:

1 polygon (836 vertices):
0.108s
16 polygons (836 vertices each):
0.404s


1 polygon (19594 vertices):
0.627s
16 polygons (19594 vertices each)
7.672s
Delta time between msPostGISLayerNextShape 0.45s

As you can see, the delta is similar to calling the 16 smaller poligons,
which sum to 13376 vertices.

giovanni



>
>  Mike
>
>   --
> Michael Smith
>  US Army Corps
> Remote Sensing GIS/Center
>
>
>   From: "G. Allegri" <giohappy at gmail.com>
> Date: Thursday, June 28, 2012 9:45 AM
> To: Jeff McKenna <jmckenna at gatewaygeomatics.com>
> Cc: "ms4w-users at lists.maptools.org" <ms4w-users at lists.maptools.org>
> Subject: Re: [MS4W-Users] slow access to PostGIS layer
> Resent-From: Michael Smith <michael.smith at usace.army.mil>
>
>  The first important bottleneck is reprojection, obviously.
> Removing the reprojection from 23032 to 900913, the time is dropped from
> 7.2s to 4.6s.
>
>  I go on...
>
>  giovanni
>
> 2012/6/28 G. Allegri <giohappy at gmail.com>
>
>> I will go on testing.
>> In the meantime, the same exact shp2img command run on Linux gives much
>> better performances, and OGR outperforms POSTGIS again.
>>
>>  Windows
>> POSTGIS: 7.2s
>> OGR: 2.7s
>>
>>  Linux
>> POSTGIS: 2.5s
>> OGR: 1.0s
>>
>>  giovanni
>>
>> 2012/6/28 Jeff McKenna <jmckenna at gatewaygeomatics.com>
>>
>>> And how did another small polygon file do?  (it could be a problem with
>>> your one table)
>>>
>>> -jeff
>>>
>>>
>>> >     - load another small polygon shapefile into your PG, then try that
>>> with
>>> >     MapServer
>>> >
>>>
>>>
>>>  --
>>> Jeff McKenna
>>> MapServer Consulting and Training Services
>>> http://www.gatewaygeomatics.com/
>>>
>>>
>>>
>>> _______________________________________________
>>> MS4W-Users mailing list
>>> MS4W-Users at lists.maptools.org
>>> http://lists.maptools.org/mailman/listinfo/ms4w-users
>>>
>>
>>
>
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