DM-26600: Add ability to remove a dataset type

python/lsst/daf/butler/registry/_registry.py

@@ -497,6 +497,34 @@ def registerDatasetType(self, datasetType: DatasetType) -> bool:
         _, inserted = self._datasets.register(datasetType)
         return inserted
 
+    def removeDatasetType(self, name: str) -> None:
+        """Remove the named `DatasetType` from the registry.
+
+        .. warning::
+
+            Registry caches the dataset type definitions. This means that
+            deleting the dataset type definition may result in unexpected
+            behavior from other butler processes that are active that have
+            not seen the deletion.
+
+        Parameters
+        ----------
+        name : `str`
+            Name of the type to be removed.
+
+        Raises
+        ------
+        lsst.daf.butler.registry.OrphanedRecordError
+            Raised if an attempt is made to remove the dataset type definition
+            when there are already datasets associated with it.
+
+        Notes
+        -----
+        If the dataset type is not registered the method will return without
+        action.
+        """
+        self._datasets.remove(name, universe=self._dimensions.universe)
+
     def getDatasetType(self, name: str) -> DatasetType:
         """Get the `DatasetType`.
 

python/lsst/daf/butler/registry/datasets/byDimensions/_manager.py

@@ -21,7 +21,7 @@
     DimensionGraph,
     DimensionUniverse,
 )
-from lsst.daf.butler.registry import ConflictingDefinitionError
+from lsst.daf.butler.registry import ConflictingDefinitionError, OrphanedRecordError
 from lsst.daf.butler.registry.interfaces import (
     DatasetRecordStorage,
     DatasetRecordStorageManager,
@@ -115,6 +115,23 @@ def refresh(self, *, universe: DimensionUniverse) -> None:
         self._byName = byName
         self._byId = byId
 
+    def remove(self, name: str, *, universe: DimensionUniverse) -> None:
+        # Docstring inherited from DatasetRecordStorageManager.
+        compositeName, componentName = DatasetType.splitDatasetTypeName(name)
+        if componentName is not None:
+            raise ValueError(f"Cannot delete a dataset type of a component of a composite (given {name})")
+
+        # Delete the row
+        try:
+            self._db.delete(self._static.dataset_type, ["name"], {"name": name})
+        except sqlalchemy.exc.IntegrityError as e:
+            raise OrphanedRecordError(f"Dataset type {name} can not be removed."
+                                      " It is associated with datasets that must be removed first.") from e
+
+        # Now refresh everything -- removal is rare enough that this does
+        # not need to be fast.
+        self.refresh(universe=universe)
+
     def find(self, name: str) -> Optional[DatasetRecordStorage]:
         # Docstring inherited from DatasetRecordStorageManager.
         compositeName, componentName = DatasetType.splitDatasetTypeName(name)

python/lsst/daf/butler/registry/interfaces/_datasets.py

@@ -367,6 +367,19 @@ def register(self, datasetType: DatasetType) -> Tuple[DatasetRecordStorage, bool
         """
         raise NotImplementedError()
 
+    @abstractmethod
+    def remove(self, name: str, *, universe: DimensionUniverse) -> None:
+        """Remove the dataset type.
+
+        Parameters
+        ----------
+        name : `str`
+            Name of the dataset type.
+        universe : `DimensionUniverse`
+            Universe to use to trigger a refresh following removal.
+        """
+        raise NotImplementedError()
+
     @abstractmethod
     def __iter__(self) -> Iterator[DatasetType]:
         """Return an iterator over the the dataset types present in this layer.

tests/test_butler.py

@@ -64,7 +64,7 @@ def mock_s3(cls):
 from lsst.daf.butler import CollectionSearch, CollectionType
 from lsst.daf.butler import ButlerURI
 from lsst.daf.butler import script
-from lsst.daf.butler.registry import MissingCollectionError
+from lsst.daf.butler.registry import MissingCollectionError, OrphanedRecordError
 from lsst.daf.butler.core.repoRelocation import BUTLER_ROOT_TAG
 from lsst.daf.butler.core.s3utils import (setAwsEnvCredentials,
                                           unsetAwsEnvCredentials)
@@ -589,6 +589,27 @@ def testPruneCollections(self):
         ref1 = butler.put(metric, datasetType, {"instrument": "Cam1", "physical_filter": "Cam1-G"}, run=run1)
         ref2 = butler.put(metric, datasetType, {"instrument": "Cam1", "physical_filter": "Cam1-G"}, run=run2)
         ref3 = butler.put(metric, datasetType, {"instrument": "Cam1", "physical_filter": "Cam1-R1"}, run=run1)
+
+        # Add a new dataset type and delete it
+        tmpName = "prune_collections_disposable"
+        tmpDatasetType = self.addDatasetType(tmpName, dimensions, storageClass,
+                                             butler.registry)
+        tmpFromRegistry = butler.registry.getDatasetType(tmpName)
+        self.assertEqual(tmpDatasetType, tmpFromRegistry)
+        butler.registry.removeDatasetType(tmpName)
+        with self.assertRaises(KeyError):
+            butler.registry.getDatasetType(tmpName)
+        # Removing a second time is fine
+        butler.registry.removeDatasetType(tmpName)
+
+        # Component removal is not allowed
+        with self.assertRaises(ValueError):
+            butler.registry.removeDatasetType(DatasetType.nameWithComponent(tmpName, "component"))
+
+        # Try and fail to delete a datasetType that is associated with data
+        with self.assertRaises(OrphanedRecordError):
+            butler.registry.removeDatasetType(datasetType.name)
+
         # Try to delete a RUN collection without purge, or with purge and not
         # unstore.
         with self.assertRaises(TypeError):
@@ -683,6 +704,10 @@ def testPruneCollections(self):
         self.assertCountEqual(set(butler.registry.queryDatasets(..., collections=...)),
                               [])
 
+        # Now that the collections have been pruned we can remove the
+        # dataset type
+        butler.registry.removeDatasetType(datasetType.name)
+
     def testPickle(self):
         """Test pickle support.
         """