ogrinspect multi_geom doesn't account for 25D types

[Michael Diener]

I would recommend changing the /contrib/gis/util/ogrinspect.py default to use "Multi" geometry because this will eliminate ERROR when trying to import a data set that could contain both linestring and multilinestring for example.

The reason is that gdal cannot always guess the correct geometry type for example in a Shapefile.

link to my GIT Branch ​https://github.com/mdiener21/django/blob/master/django/contrib/gis/utils/ogrinspect.py

# TODO: Autodetection of multigeometry types (see #7218).

[Michael Diener]

new ogrinspect.py code

[Michael Diener]

forgot the link to my GIT branch ​https://github.com/mdiener21/django/blob/master/django/contrib/gis/utils/ogrinspect.py

Pull Request was already sent off :)

[Tim Graham]

​PR

[Claude Paroz]

I'm not convinced to force multi geometries by default. If you obtain errors when importing data from a shapefile because of a missing multi field, you can always improve your model and force the multi geometries in a later time. And if you don't want to risk the potential errors, there is the multi_geom parameter you can set yourself.

Feel free to add more arguments if you think I missed the point.

[Michael Diener]

Hi the problem is this code if multi_geom and gtype.num in (1, 2, 3): LINE 213 gtype.num in (1,2,3) does NOT always return TRUE for multi_geom because GDAL does not always guess correct. Therefore if I set multi_geom to True it still fails because GDAL guesses wrong. Another solution is to simply remove the GDAL check ? any thoughts

[Michael Diener]

Replying to claudep:

I'm not convinced to force multi geometries by default. If you obtain errors when importing data from a shapefile because of a missing multi field, you can always improve your model and force the multi geometries in a later time. And if you don't want to risk the potential errors, there is the multi_geom parameter you can set yourself.

Feel free to add more arguments if you think I missed the point.

Please check out my comment :) cheers

[Claude Paroz]

Do you have an example of such a "deficient" layer? It would be nice to make a test case for this issue.

[Michael Diener]

Shapefile Example with both Linestrings and Multilinestrings

[Michael Diener]

Yes I do, the Shapefile origin is AutoCAD and this is where things get messy when converting to Shapefile then trying to import into PostGIS. I have attached the problem Shapefile of multilinestrings which is a false positive "linestring" according to GDAL and QGIS (which uses GDAL). The Shapefile is of course valid with no geometry errors or invalid geometries all is good. The problem is the Shapefile can store linestrings and multi-geom and still be valid. When trying to import such a Shapefile PostGIS will NOT allow you to have both you must choose and in this case you must always choose the multi-geom "MULTILINESTRING" geom type otherwise boom error on import.

[Claude Paroz]

Thanks, that's very useful. This demonstrates that the inspect code hasn't been updated after commit [c169f8cb174c9a885] to take 25D OGR types into account.

[Claude Paroz]

New PR: ​https://github.com/django/django/pull/4617

[Claude Paroz <claude@…>]

In d1df1fd2:

Fixed #24207 -- Added 25D-type geometry field support to ogrinspect

Thanks Michael Diener for the report and sample data, and Tim Graham
for the review.