Load Experiment without runners and metrics in the case where search …

…space and optimization config are immutable (facebook#1656)

Summary:
Pull Request resolved: facebook#1656

`load_experiment` was previously failing when `skip_runners_and_metrics=True` for experiments with immutable search space and optimization config. See [Lena's comment](https://www.internalfb.com/diff/D46595953?dst_version_fbid=263061986396665&transaction_fbid=639853311380999) for more detail.

Differential Revision: D46595953

fbshipit-source-id: ac5370fa638cf6b7a52152374339132ccb6886a9

ax/storage/sqa_store/load.py

@@ -28,6 +28,7 @@
 from ax.utils.common.constants import Keys
 from ax.utils.common.typeutils import not_none
 from sqlalchemy.orm import defaultload, lazyload, noload
+from sqlalchemy.orm.exc import DetachedInstanceError
 
 
 # ---------------------------- Loading `Experiment`. ---------------------------
@@ -135,10 +136,13 @@ def _load_experiment(
         for sqa_metric in experiment_sqa.metrics:
             sqa_metric.metric_type = 0
 
-        for sqa_trial in experiment_sqa.trials:
-            for sqa_generator_run in sqa_trial.generator_runs:
-                for sqa_metric in sqa_generator_run.metrics:
-                    sqa_metric.metric_type = 0
+        try:
+            for sqa_trial in experiment_sqa.trials:
+                for sqa_generator_run in sqa_trial.generator_runs:
+                    for sqa_metric in sqa_generator_run.metrics:
+                        sqa_metric.metric_type = 0
+        except DetachedInstanceError:
+            pass
 
     return decoder.experiment_from_sqa(
         experiment_sqa=experiment_sqa,

ax/storage/sqa_store/tests/test_sqa_store.py

@@ -237,30 +237,40 @@ def testLoadExperimentSkipMetricsAndRunners(self) -> None:
             runner_registry=runner_registry,
         )
 
-        # Save the experiment to db using the updated registries.
-        save_experiment(experiment, config=sqa_config)
-
-        # At this point try to load the experiment back without specifying
-        # updated registries. Confirm that this attempt fails.
-        with self.assertRaises(SQADecodeError):
-            loaded_experiment = load_experiment(self.experiment.name)
-
-        # Now load it with the skip_runners_and_metrics argument set.
-        # The experiment should load (i.e. no exceptions raised)
-        loaded_experiment = load_experiment(
-            self.experiment.name, skip_runners_and_metrics=True
-        )
+        for immutable in [True, False]:
+            experiment = get_experiment_with_custom_runner_and_metric(
+                constrain_search_space=False
+            )
+            if immutable:
+                experiment._properties = {
+                    Keys.IMMUTABLE_SEARCH_SPACE_AND_OPT_CONF: True
+                }
+
+            # Save the experiment to db using the updated registries.
+            save_experiment(experiment, config=sqa_config)
+
+            # At this point try to load the experiment back without specifying
+            # updated registries. Confirm that this attempt fails.
+            with self.assertRaises(SQADecodeError):
+                loaded_experiment = load_experiment(experiment.name)
+
+            # Now load it with the skip_runners_and_metrics argument set.
+            # The experiment should load (i.e. no exceptions raised)
+            loaded_experiment = load_experiment(
+                experiment.name, skip_runners_and_metrics=True
+            )
 
-        # Validate that:
-        #   - the runner is not loaded
-        #   - the metric is loaded as a base Metric class (i.e. not CustomTestMetric)
-        self.assertIs(loaded_experiment.runner, None)
-        self.assertTrue("custom_test_metric" in loaded_experiment.metrics)
-        self.assertEqual(
-            loaded_experiment.metrics["custom_test_metric"].__class__, Metric
-        )
-        self.assertEqual(len(loaded_experiment.trials), 1)
-        self.assertIs(loaded_experiment.trials[0].runner, None)
+            # Validate that:
+            #   - the runner is not loaded
+            #   - the metric is loaded as a base Metric class, not CustomTestMetric
+            self.assertIs(loaded_experiment.runner, None)
+            self.assertTrue("custom_test_metric" in loaded_experiment.metrics)
+            self.assertEqual(
+                loaded_experiment.metrics["custom_test_metric"].__class__, Metric
+            )
+            self.assertEqual(len(loaded_experiment.trials), 1)
+            self.assertIs(loaded_experiment.trials[0].runner, None)
+            delete_experiment(exp_name=experiment.name)
 
     @patch(
         f"{Decoder.__module__}.Decoder.generator_run_from_sqa",