kaxil commented on code in PR #47961:
URL: https://github.com/apache/airflow/pull/47961#discussion_r2003857280
##########
airflow/models/xcom.py:
##########
@@ -331,11 +331,44 @@ def serialize_value(
@staticmethod
def deserialize_value(result) -> Any:
- """Deserialize XCom value from str objects."""
+ """
+ Deserialize XCom value from a database result.
+
+ If deserialization fails, the raw value is returned, which must still
be a valid Python JSON-compatible
+ type (e.g., ``dict``, ``list``, ``str``, ``int``, ``float``, or
``bool``).
+
+ XCom values are stored as JSON in the database, and SQLAlchemy
automatically handles
+ serialization (``json.dumps``) and deserialization (``json.loads``).
However, we
+ use a custom encoder for serialization (``serialize_value``) and
deserialization to handle special
+ cases, such as encoding tuples via the Airflow Serialization module.
These must be decoded
+ using ``XComDecoder`` to restore original types.
+
+ Some XCom values, such as those set via the Task Execution API, bypass
``serialize_value``
+ and are stored directly in JSON format. Since these values are already
deserialized
+ by SQLAlchemy, they are returned as-is.
+
+ **Example: Handling a tuple**:
+
+ .. code-block:: python
+
+ original_value = (1, 2, 3)
+ serialized_value = XComModel.serialize_value(original_value)
+ print(serialized_value)
+ # '{"__classname__": "builtins.tuple", "__version__": 1,
"__data__": [1, 2, 3]}'
+
+ This serialized value is stored in the database. When deserialized,
the value is restored to the original tuple.
+
+ :param result: The XCom database row or object containing a ``value``
attribute.
+ :return: The deserialized Python object.
+ """
if result.value is None:
return None
- return json.loads(result.value, cls=XComDecoder)
+ try:
+ return json.loads(result.value, cls=XComDecoder)
+ except (ValueError, TypeError):
+ # Already deserialized (e.g., set via Task Execution API)
+ return result.value
Review Comment:
We shouldn't need orm_deserialize as we XComModel doesn't deserialise
objects in XCom backends -- so deserialise should be enough imo. That will
happen in the XCom class in Task SDK.
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