[QGIS-Developer] Warning: auto-transaction groups is broken for recent GDAL versions

[Even Rouault]

Le 17/12/2024 à 08:39, Alessandro Pasotti a écrit :
>
> Can/should we fix it upstream in GDAL?

GDAL vector drivers have never really thought about the possibility of a 
rollback after a OGRLayer::CreateField()/AlterFieldDefn()/DeleteField(). 
That's a change that must be done *per driver* that supports those 
operations and transactions. I'd suspect the expected behaviour woud be 
to update the layer definition to reflect that state it had before 
StartTransaction(). That probably requires to have some generic logic to 
memorize changes and undo them, but can't probably do just a simple 
"clone layer definition" and restore it, because it would invalidate 
field definitions that aren't affected.

Ideally we'd want the following to work:

my_field_defn = layer.GetFieldDefn(0)
layer.StartTransaction()
layer.CreateField(ogr.FieldDefn("foo"))
new_field_defn = layer.GetFieldDefn("foo")
layer.RollbackTransaction()  <-- new_field_defn should be put into a 
"ghost" list that is destroyed at layer de-instanciation
my_field_defn.GetName() <-- hopefully that object is still alive ...
new_field_defn.GetName() <-- shouldn't crash.

Eveb


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