Fix bug with ExperimentData.load (qiskit-community#423)

qiskit_experiments/framework/composite/composite_experiment_data.py

@@ -17,7 +17,7 @@
 from qiskit.result import marginal_counts
 from qiskit.exceptions import QiskitError
 from qiskit_experiments.framework.experiment_data import ExperimentData
-from qiskit_experiments.database_service import DbExperimentDataV1, DatabaseServiceV1
+from qiskit_experiments.database_service import DatabaseServiceV1
 
 
 class CompositeExperimentData(ExperimentData):
@@ -114,19 +114,16 @@ def save_metadata(self) -> None:
 
     @classmethod
     def load(cls, experiment_id: str, service: DatabaseServiceV1) -> "CompositeExperimentData":
-        expdata = DbExperimentDataV1.load(experiment_id, service)
-        components = []
+        expdata = ExperimentData.load(experiment_id, service)
+        expdata.__class__ = CompositeExperimentData
+        expdata._components = []
         for comp_id, comp_class in zip(
             expdata.metadata["component_ids"], expdata.metadata["component_classes"]
         ):
             load_class = globals()[comp_class]
             load_func = getattr(load_class, "load")
             loaded_comp = load_func(comp_id, service)
-            components.append(loaded_comp)
-
-        expdata.__class__ = CompositeExperimentData
-        expdata._experiment = None
-        expdata._components = components
+            expdata._components.append(loaded_comp)
 
         return expdata
 

qiskit_experiments/framework/experiment_data.py

@@ -17,6 +17,7 @@
 from datetime import datetime
 
 from qiskit_experiments.database_service import DbExperimentDataV1
+from qiskit_experiments.database_service.database_service import DatabaseServiceV1
 
 LOG = logging.getLogger(__name__)
 
@@ -62,6 +63,22 @@ def completion_times(self) -> Dict[str, datetime]:
 
         return job_times
 
+    @classmethod
+    def load(cls, experiment_id: str, service: DatabaseServiceV1) -> "ExperimentData":
+        """Load a saved experiment data from a database service.
+
+        Args:
+            experiment_id: Experiment ID.
+            service: the database service.
+
+        Returns:
+            The loaded experiment data.
+        """
+        expdata = DbExperimentDataV1.load(experiment_id, service)
+        expdata.__class__ = ExperimentData
+        expdata._experiment = None
+        return expdata
+
     def _copy_metadata(self, new_instance: Optional["ExperimentData"] = None) -> "ExperimentData":
         """Make a copy of the experiment metadata.
 

releasenotes/notes/fix-expdata-load-b7c6569bfbe67bec.yaml

@@ -0,0 +1,8 @@
+---
+fixes:
+  - |
+    Fixes bug where the 
+    :meth:`~qiskit_experiments.framework.ExperimentData.load` method of
+    :class:`~qiskit_experiments.framework.ExperimentData` would return a
+    :class:`~qiskit_experiments.database_service.DbExperimentDataV1` object
+    instead of a :class:`~qiskit_experiments.framework.ExperimentData` object.