feat: add support for pyarrow.ExtensionType

python/deltalake/schema.py

@@ -95,6 +95,8 @@ def dtype_to_delta_dtype(dtype: pa.DataType) -> pa.DataType:
                 return pa.timestamp("us", "UTC")
         elif type(dtype) is pa.FixedSizeBinaryType:
             return pa.binary()
+        elif isinstance(dtype, pa.ExtensionType):
+            return dtype.storage_type
         try:
             return dtype_map[dtype]
         except KeyError:

python/stubs/pyarrow/__init__.pyi

@@ -14,6 +14,7 @@ FixedSizeListType: Any
 LargeListViewType: Any
 ListViewType: Any
 FixedSizeBinaryType: Any
+ExtensionType: Any
 schema: Any
 map_: Any
 list_: Any

python/tests/test_schema.py

@@ -223,6 +223,26 @@ def test_delta_schema():
     assert schema_without_metadata == Schema.from_pyarrow(pa_schema)
 
 
+def _generate_test_type():
+    class UuidType(pa.ExtensionType):
+        def __init__(self):
+            pa.ExtensionType.__init__(self, pa.binary(16), "my_package.uuid")
+
+        def __arrow_ext_serialize__(self):
+            # since we don't have a parameterized type, we don't need extra
+            # metadata to be deserialized
+            return b""
+
+        @classmethod
+        def __arrow_ext_deserialize__(self, storage_type, serialized):
+            # return an instance of this subclass given the serialized
+            # metadata.
+            return UuidType()
+
+    pa.register_extension_type(UuidType())
+    return UuidType()
+
+
 def _generate_test_tuples():
     test_tuples = [
         (
@@ -515,6 +535,11 @@ def _generate_test_tuples():
             ),
             ArrowSchemaConversionMode.NORMAL,
         ),
+        (
+            pa.schema([("uuid", _generate_test_type())]),
+            pa.schema([("uuid", pa.binary(16))]),
+            ArrowSchemaConversionMode.NORMAL,
+        ),
     ]
 
     return test_tuples