fix: assign only run in a single run experiment as best_trial_id (#9051)

master/internal/api_experiment_intg_test.go

@@ -1112,7 +1112,7 @@ func TestSearchExperiments(t *testing.T) {
 	require.Nil(t, resp.Experiments[0].BestTrial)
 	require.Equal(t, int32(exp.ID), resp.Experiments[0].Experiment.Id)
 
-	require.Nil(t, resp.Experiments[1].BestTrial) // Still nil since no validations reported.
+	require.NotNil(t, resp.Experiments[1].BestTrial) // Now has a best trial, since it's the only one.
 	require.Equal(t, int32(noValidationsExp.ID), resp.Experiments[1].Experiment.Id)
 
 	// Validations returned properly.
@@ -1147,7 +1147,7 @@ func TestSearchExperiments(t *testing.T) {
 	require.Nil(t, resp.Experiments[0].BestTrial)
 	require.Equal(t, int32(exp.ID), resp.Experiments[0].Experiment.Id)
 
-	require.Nil(t, resp.Experiments[1].BestTrial)
+	require.NotNil(t, resp.Experiments[1].BestTrial)
 	require.Equal(t, int32(noValidationsExp.ID), resp.Experiments[1].Experiment.Id)
 
 	require.NotNil(t, resp.Experiments[2].BestTrial)
@@ -1169,6 +1169,18 @@ func TestSearchExperiments(t *testing.T) {
 	require.Equal(t, string(latestExpected), string(latestActual))
 
 	require.Equal(t, int32(5), resp.Experiments[2].BestTrial.Restarts)
+
+	// when single-trial experiment with no validation metrics completes
+	// ensure that the only trial is the best trial.
+	_, err = db.Bun().NewUpdate().Table("experiments").
+		Set("state = ?", model.CompletedState).
+		Where("id = ?", noValidationsExp.ID).
+		Exec(ctx)
+	require.NoError(t, err)
+	resp, err = api.SearchExperiments(ctx, req)
+	require.NoError(t, err)
+	require.NotNil(t, resp.Experiments[1].BestTrial)
+	require.Equal(t, int32(noValidationsExp.ID), resp.Experiments[1].Experiment.Id)
 }
 
 func TestSearchExperimentsFilters(t *testing.T) {

master/internal/db/postgres_trial.go

@@ -95,6 +95,22 @@ func AddTrial(ctx context.Context, trial *model.Trial, taskID model.TaskID) erro
 				return fmt.Errorf("inserting project hyperparameters: %w", err)
 			}
 		}
+
+		var isSingleTrial bool
+		err = tx.NewSelect().
+			ColumnExpr("config->'searcher'->>'name' = 'single'").
+			Table("experiments").
+			Where("id = ?", run.ExperimentID).
+			Scan(ctx, &isSingleTrial)
+		if err != nil {
+			return fmt.Errorf("getting experiment config while inserting trial: %w", err)
+		}
+		if isSingleTrial {
+			if _, err := tx.NewUpdate().Table("experiments").Set("best_trial_id = ?", run.ID).
+				Where("id = ?", run.ExperimentID).Exec(ctx); err != nil {
+				return fmt.Errorf("updating best trial id for single trial experiment: %w", err)
+			}
+		}
 		return nil
 	})
 	if err != nil {

master/static/migrations/20240724073853_handle-single-run-experiments-best-trial.tx.up.sql

@@ -0,0 +1,24 @@
+-- backfill existing single-trial experiments without best_trial_id
+WITH single_run_experiments AS (
+    SELECT 
+        id
+    FROM  
+        experiments e
+    WHERE
+        e.config->'searcher'->>'name' = 'single'
+),
+br_no_validation AS (
+    SELECT r.experiment_id, r.id, r.best_validation_id
+    FROM 
+        runs r 
+        INNER JOIN single_run_experiments sre 
+        ON r.experiment_id = sre.id
+    ORDER BY searcher_metric_value_signed)
+UPDATE 
+    experiments 
+SET 
+    best_trial_id = brnv.id 
+FROM 
+    br_no_validation brnv
+WHERE 
+    experiments.id = brnv.experiment_id;