Python OGR SQL - Finding invalid geometry

Question

I previously asked this question@ regarding finding files that contain an invalid geometry using OGR.

The following SQL command was suggested to me, which seemed to work a treat: -sql "select * from filename WHERE not ST_IsValid(geometry)"

I am now trying to get this to work under python using the following code:

from osgeo import ogr

driver = ogr.GetDriverByName('MapInfo File') 
dataSource = driver.Open(file, 0)
layer = dataSource.GetLayer() 

result = dataSource.ExecuteSQL("select * from file WHERE ST_IsValid(geometry)")
featureCount = result.GetFeatureCount() 

print (featureCount)

Upon running the code however, I get the following error message: ERROR 1: Undefined function 'ST_IsValid' used.

Does anyone know how I go about checking ST_IsValid under python?

ST_IsValid is a SQLite/Spatialite function. I believe that by adding dialect SQLite it will work gdal.org/python/osgeo.ogr.DataSource-class.html#ExecuteSQL. — user30184
– user30184, Commented Feb 7, 2017 at 14:59

neuhausr · Accepted Answer · 2017-02-07 15:04:24Z

4

I don't think the plain vanilla OGR SQL includes spatial functions? You can specify pszDialect in the parameters for ExecuteSQL, for example to use SQLITE's spatial functions. http://www.gdal.org/ogr_sql_sqlite.html

answered Feb 7, 2017 at 15:04

neuhausr

2,29519 silver badges23 bronze badges

Excellent, using 'dataSource.ExecuteSQL("select * from HousingOptions WHERE ST_IsValid(geometry)", dialect = "SQLITE")' seems to have done the trick. I am getting some kind of logical output now. Thank you!

JamieTasker
– JamieTasker

2017-02-07 15:28:47 +00:00
Commented Feb 7, 2017 at 15:28

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