Add parameter to skip layername in gdal:convertformat

[benoitblanc]

Description

In some use cases, user needs to export a whole source to an other format, using gdal:convertformat (ogr2ogr.py) but the processing only converts one layer at the moment.

For example, I want to export a whole schema from a database to a file :

INPUT: "PG:service='test' sslmode=disable" public.batiment
OUTPUT: /tmp/OUTPUT.gpkg

GDAL command is : ogr2ogr -f "GPKG" /tmp/OUTPUT.gpkg "PG:service='test' sslmode=disable" public.batiment. Only batiment table has been converted.

If I add a IGNORE_LAYERNAME parameter to True :

INPUT: "PG:service='test' sslmode=disable" public.batiment
IGNORE_LAYERNAME: True
OUTPUT: /tmp/OUTPUT.gpkg

GDAL command is : ogr2ogr -f "GPKG" /tmp/OUTPUT.gpkg "PG:service='test' sslmode=disable". Whole schema is converted.

IGNORE_LAYERNAME is a boolean parameter which default value is False so the default behavior of importing only one layer is kept.

This pull request superseds #39580

[nyalldawson]

Sounds like a useful feature!

I'm wondering, instead of "ignore layer name" if it would be more understandable to go with "convert all layers" or "convert entire dataset"?

In either case it needs some documentation in the short help string and also a unit test of the new parameter.

[github-actions]

@benoitblanc
This pull request has been tagged as requiring documentation.

A documentation ticket will be opened at https://github.com/qgis/QGIS-Documentation when this PR is merged.

Please update the description (not the comments) with helpful description and screenshot to help the work from documentors.
Also, any commit having [needs-doc] or [Needs Documentation] in will see its message pushed to the issue, so please be as verbose as you can.

Thank you!

[alexbruy]

Will this work with formats other than GPKG and how loading of the output layer will be handled in a such case?

[benoitblanc]

Yes this works with other formats than GPKG. I have added tests to convert one layer or all layers from a GPKG file to GML files. When all layers are converted, you can open the file in QGIS and chose layers you want to add in your project.

I think there might be other formats that supports FeatureCollection which can be used here such as KML or GeoJSON.

Edit: It doesn't work with GeoJSON because driver can not create layer.

ogr2ogr -f "GeoJSON" test.geojson points_lines.gpkg --debug ON
GPKG: GeoPackage v1.2.0
GDAL: GDALOpen(points_lines.gpkg, this=0x55cf645a1bf0) succeeds as GPKG.
GDAL: GDALDriver::Create(GeoJSON,test.geojson,0,0,0,Unknown,(nil))
GPKG: ResetStatement(SELECT m."fid", m."geom", m."id", m."id2" FROM "points" m)
GPKG: finalize 0x55cf645ccb48
GDALVectorTranslate: 9 features written in layer 'points'
ERROR 1: Layer 'lines' does not already exist in the output dataset, and cannot be created by the output driver.
ERROR 1: Terminating translation prematurely after failed
translation of layer lines (use -skipfailures to skip errors)
GDAL: GDALClose(test.geojson, this=0x55cf645d0c70)
GDAL: GDALClose(points_lines.gpkg, this=0x55cf645a1bf0)

[alexbruy]

Edit: It doesn't work with GeoJSON because driver can not create layer.

Then this should be mentioned in the docs (probably with the list of the supported formats) and maybe it is worth at least evaluate a possibility to check at runtime whether output format can be used and if this is possible then raise error.

[nyalldawson]

I'm happy with the current revision!

@alexbruy @DelazJ any objections to merge? any further changes desired?

[alexbruy]

@nyalldawson looks ok for me. While I think it would be good to have run-time check whether output format allows saving multiple layers or no, we can merge it now and add that check later if needed.

[DelazJ]

Looks OK to me. Thanks.

[github-actions]

@benoitblanc
A documentation ticket has been opened at qgis/QGIS-Documentation#7197
It is your responsibility to visit this ticket and add as much detail as possible for the documentation team to correctly document this change.
Thank you!

[agiudiceandrea]

Fixes #43701

[agiudiceandrea]

@benoitblanc @alexbruy

how loading of the output layer will be handled in a such case?

In fact, there is a issue here: when a multi layer GeoPackage (or other multilayer format, like GML, KML, Spatialite, SQLite) file is created by the algorithm and the "Open output file after running algorithm" is checked (as default), then only 1 layer is automatically added to the map instead of all the layer contained in the output multi layer GeoPackage file.

This could give the user the false impression that the conversion process has not happened correctly for all the layers contained in the source multi layer GeoPackage file.