[Qgis-user] Selecting polygons on attribute - Trying OGR

[Zoltan Szecsei]

On 2012/07/24 16:41, Micha Silver wrote:
> On 07/24/2012 03:10 PM, Zoltan Szecsei wrote:
>> Hi,
>> I have a SHP file of some 1.1m polygons, of which I need to select 
>> about half of them, and save them as a separate SHP file.
>>
>> The trouble is when I select either via a Query, or via the TABLE 
>> using the select options below, it just falls asleep (100% CPU (ok, 
>> 12% as it must be single-threaded)).
>> After 45 minutes or so, I just kick it out and weep.
>>
>> My platform is Win 7 Prof 64 bit (also tried on 32 bit) and using 
>> 1.8.0 Lisboa.
>>
>> The selects I have tried are: "sq21code" = "C016*"   and also tried 
>> using "IN"
>>
>> Any ideas what I am doing wrong and what I should try next?
>>
>
> In addition to Andre's correction about the * wildcard, with 1M 
> polygons, you probably should move the shapefile into a database (i.e 
> spatialite, PostGIS)

That would be a bit sad (in terms of extra steps).
I'm trying with ogr on Linux, but haven't fiddled the correct syntax yet:

zls at gs0:~$ ogr2ogr -where " 21DigitKey LIKE 'C016%' "      zerf 
/mnt/geo_lvm0/SGO_cadastral/200909/WC/Erf.shp
ERROR 1: SQL Expression Parsing Error: syntax error
FAILURE: SetAttributeFilter( 21DigitKey LIKE 'C016%' ) failed.
zls at gs0:~$

>
>> Thanks & regards,
>> Zoltan
>>
>>
>>
>
>
> -- 
> Micha Silver
> GIS Consultant, Arava Development Co.
> http://www.surfaces.co.il


-- 

===========================================
Zoltan Szecsei PrGISc [PGP0031]
Geograph (Pty) Ltd.
P.O. Box 7, Muizenberg 7950, South Africa.

65 Main Road, Muizenberg 7945
Western Cape, South Africa.

34° 6'16.35"S 18°28'5.62"E

Tel: +27-21-7884897  Mobile: +27-83-6004028
Fax: +27-86-6115323     www.geograph.co.za
===========================================

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