OGR_SQL feature request: OGR_GEOM_LENGTH

[peifer]

It would be helpful to have an OGR_GEOM_LENGTH special field returning the length of line features (in analogy to OGR_GEOM_AREA, which returns a feature's area).

[rouault]

My feeling is that we should not go on adding those special fields that are more or less hacks. A better (but more complicated) approach would be to implement a subset of SQL/MM, so as to be able to use a standardized syntax like ST_Length(geom), ST_Area(geom), etc...

[rouault]

This is now possibly by using SQLite SQL dialect with Spatialite :  http://gdal.org/ogr/ogr_sql_sqlite.html