PreloadDataStore added

Author: konstntokas

xcube/core/store/preload.py

@@ -75,11 +75,7 @@ def __repr__(self):
 
 
 class PreloadHandle(ABC):
-    """A handle for a preload job.
-
-    Instances of this class are returned by the
-    ``DataStore.preload_data()`` method.
-    """
+    """A handle for a preload job."""
 
     @abstractmethod
     def get_state(self, data_id: str) -> PreloadState:

xcube/core/store/store.py

@@ -487,7 +487,7 @@ def preload_data(
         self,
         *data_ids: str,
         **preload_params: Any,
-    ) -> PreloadHandle:
+    ) -> "PreloadDataStore":
         """Preload the given data items for faster access.
 
         Warning: This is an experimental and potentially unstable API
@@ -512,9 +512,10 @@ def preload_data(
             A handle for the preload process. The default implementation
             returns an empty preload handle.
         """
-        return NullPreloadHandle()
-
-    # noinspection PyMethodMayBeStatic
+        cache_store = new_data_store("file")
+        cache_store.preload_handle = NullPreloadHandle()
+        assert isinstance(cache_store, PreloadDataStore)
+        return cache_store
 
 
 class MutableDataStore(DataStore, DataWriter, ABC):
@@ -690,3 +691,22 @@ def deregister_data(self, data_id: str):
         Raises:
             DataStoreError: If an error occurs.
         """
+
+
+class PreloadDataStore(MutableDataStore):
+    """A preload data store is a multable data store which contains the preload handle.
+
+    Instances of this class are returned by the ``DataStore.preload_data()`` method.
+    """
+
+    @property
+    @abstractmethod
+    def preload_handle(self) -> PreloadHandle:
+        """This field must be defined and set in subclasses."""
+        pass
+
+    @preload_handle.setter
+    @abstractmethod
+    def preload_handle(self, value: PreloadHandle) -> None:
+        """Setter for preload_handle."""
+        pass

xcube/util/cache.py

@@ -439,9 +439,7 @@ def _compute_object_size(obj):
                 else (
                     3
                     if m in ("RGB", "YCbCr", "LAB", "HSV")
-                    else 1.0 / 8.0
-                    if m == "1"
-                    else 1
+                    else 1.0 / 8.0 if m == "1" else 1
                 )
             )
         )

xcube/util/dask.py

@@ -218,9 +218,7 @@ def new_cluster(
     cluster_account = (
         account
         if account is not None
-        else account_from_env_var
-        if account_from_env_var is not None
-        else "bc"
+        else account_from_env_var if account_from_env_var is not None else "bc"
     )
 
     if provider == "coiled":