Feature request #19895
Garbage-collection is not performed after deletion of vector layer from geopackage
|Pull Request or Patch supplied:||Yes||Resolution:|
|Easy fix?:||No||Copied to github as #:||27719|
With QGIS 3.3.0-master (d99d506e75), deleting a vector layer from a geopackage, through the "Browser" panel or the "DB Manager", is not followed by a proper garbage-collection (shrink/compact) of the geopackage.
I think a VACUUM sql command should be automatically executed after deleting a layer from a geopackage or a contextual menu option should be added in the "Browser" panel and in the "DB Manager" to let the user perform such operation.
GPKG Browser VACUUM menu item
Fixes #19895 - Garbage-collection is not performed after deletion of vector layer from geopackage
By design, VACUUM (being a potentially time-consuming operation)
was automatically performed only after deleting a raster
while when deleting a vector layer it was not executed.
This commit adds a menu item in the browser that allows
the user to perform this operation on the DB.
#1 Updated by Alessandro Pasotti about 3 years ago
- Status changed from Open to Feedback
- Assignee set to Alessandro Pasotti
I might be wrong but IIRC this was intentional, because a VACUUM can take a very long time on large layers, I think that a possible solution would be to add a "Run vacuum" option to the browser data item of a geopackage layer.
What do you think?
#2 Updated by Andrea Giudiceandrea about 3 years ago
It could be OK for me to add "Run vacuum" or "Compact geopackage" or something similar in the Browser panel for geopackages (along with "Add Connection"/"Remove connection" and "Create a New Layer or Table...") and eventually also in DB Manager (along with "Re-connect" and "Remove").
However, a VACUUM sql command is still executed automatically after a raster layer has been deleted from a geopackage, as you can see in https://github.com/qgis/QGIS/blob/master/src/providers/ogr/qgsgeopackagedataitems.cpp#L441-L450
#4 Updated by Andrea Giudiceandrea about 3 years ago
It seems that the VACUUM is only executed (in deleteGeoPackageRasterLayer) after a RASTER layers is deleted. I will confirm this when a new build of qgis-dev with your commit e62c4eb941c5b2e290675f8cab75758857c2a502 will be available on osgeo4w
For VECTOR layer I cannot trace down in the source code if and where VACUUM is executed. The fact is that the geopackage is not "vacuumed" after a vector layer is deleted.
#5 Updated by Alessandro Pasotti about 3 years ago
- Tracker changed from Bug report to Feature request
Yes, you are right of course, as I mentioned in my first reply IIRC it was not implemented on purpose and the idea was to add a menu item to do that.
Btw, that's technically a new feature, but it could also be considered a bug, so let's see if I can do it!
#6 Updated by Andrea Giudiceandrea about 3 years ago
Thank you Alessandro! I'm not so skilled to add such an options by myself (without the risk of breaking something).
I was writing this before reading your last comment, so now it may not be so useful anymore:
I confirm that VACUUM is executed after a RASTER layer is deleted, and that is not executed after a VECTOR layer is deleted.
As I can see in the source code (qgsgeopackagedataitems.ccp):
- for QgsGeoPackageRasterLayerItem, executeDeleteLayer() calls deleteGeoPackageRasterLayer() which executes all the sql commands in order to delete a RASTER layer and its references and executes the VACUUM sql command at the end;
- for QgsGeoPackageVectorLayerItem, executeDeleteLayer() calls deleteLayer() so relying on GDAL (GDALGeoPackageDataset::DeleteLayer) to execute all the sql commands required to delete a VECTOR layer and its references: DeleteLayer() does not executes a VACUUM sql command at the end.
So I think we could:
- add a "Run vacuum" or "Compact geopackage" options as previously said (which is anyway needed to allow users to easily shrink geopackages)
and one of the following
1) in QgsGeoPackageVectorLayerItem::executeDeleteLayer() or in a little deleteGeoPackageVectorLayer() (for symmetry)
2) (provided we add the "Run vacuum" option).
By the way - you probably know it already - I realised now that since GDAL 2.3.0 there are two new functions in GDALGeoPackageDataset: DeleteRasterLayer() and DeleteVectorOrRasterLayer() along with DeleteLayer().