Fix bug in DbExperimentData._retrieve_data

qiskit_experiments/database_service/db_experiment_data.py

@@ -343,16 +343,21 @@ def _add_single_data(self, data: Dict[str, any]) -> None:
     def _retrieve_data(self):
         """Retrieve job data if missing experiment data."""
         # Get job results if missing experiment data.
-        if (not self._data) and self._provider:
+        if (not self._data) and self._backend:
             with self._jobs.lock:
-                for jid in self._jobs:
-                    if self._jobs[jid] is None:
+                for jid, job in self._jobs.items():
+                    if job is None:
                         try:
-                            self._jobs[jid] = self._provider.retrieve_job(jid)
+                            job = self._backend.retrieve_job(jid)
+                            self._jobs[jid] = job
                         except Exception:  # pylint: disable=broad-except
-                            pass
-                    if self._jobs[jid] is not None:
-                        self._add_result_data(self._jobs[jid].result())
+                            LOG.warning(
+                                "Unable to retrive data from job %s on backend %s",
+                                jid,
+                                self._backend,
+                            )
+                    if job is not None:
+                        self._add_result_data(job.result())
 
     def data(self, index: Optional[Union[int, slice, str]] = None) -> Union[Dict, List[Dict]]:
         """Return the experiment data at the specified index.

qiskit_experiments/database_service/utils.py

@@ -178,6 +178,10 @@ def _init_container(self, init_values):
         """Initialize the container."""
         pass
 
+    def __iter__(self):
+        with self._lock:
+            return iter(self._container)
+
     def __getitem__(self, key):
         with self._lock:
             return self._container[key]

releasenotes/notes/fix-retrieve-data-c93c8406ff4f2e7e.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixed bug in :class:`~qiskit_experiments.framework.ExperimentData` where
+    trying to load saved job data from a backend using
+    ``ExperimentData(backend=backend, job_ids=job_ids)`` resulted in an error.