use min and max in query

Signed-off-by: F.N. Claessen <felix@seita.nl>

flexmeasures/data/services/timerange.py

@@ -2,37 +2,30 @@
 
 from datetime import datetime
 
+from sqlalchemy import func
+
 from flexmeasures.utils import time_utils
 
 
 def get_timerange(sensor_ids: list[int]) -> tuple[datetime, datetime]:
-    """Get the start and end of the least recent and most recent event, respectively."""
-    from flexmeasures.data.models.time_series import TimedBelief
+    """Get the start and end of the least recent and most recent event, respectively.
 
-    least_recent_query = (
-        TimedBelief.query.filter(TimedBelief.sensor_id.in_(sensor_ids))
-        .order_by(TimedBelief.event_start.asc())
-        .limit(1)
-    )
-    most_recent_query = (
-        TimedBelief.query.filter(TimedBelief.sensor_id.in_(sensor_ids))
-        .order_by(TimedBelief.event_start.desc())
-        .limit(1)
-    )
-    results = least_recent_query.union_all(most_recent_query).all()
-    try:
-        # try the most common case first (sensor has more than 1 data point)
-        least_recent, most_recent = results
-    except ValueError as e:
-        if not results:
-            # return now in case there is no data for any of the sensors
-            now = time_utils.server_now()
-            return now, now
-        elif len(results) == 1:
-            # return the start and end of the only data point found
-            least_recent = most_recent = results[0]
-        else:
-            # reraise this unlikely error
-            raise e
+    In case of no data, defaults to (now, now).
+    """
+    from flexmeasures.data.models.time_series import Sensor, TimedBelief
 
-    return least_recent.event_start, most_recent.event_end
+    least_recent_event_start_and_most_recent_event_end = (
+        TimedBelief.query.with_entities(
+            # least recent event start
+            func.min(TimedBelief.event_start),
+            # most recent event end
+            func.max(TimedBelief.event_start + Sensor.event_resolution),
+        )
+        .join(Sensor, TimedBelief.sensor_id == Sensor.id)
+        .filter(TimedBelief.sensor_id.in_(sensor_ids))
+    ).one_or_none()
+    if least_recent_event_start_and_most_recent_event_end == (None, None):
+        # return now in case there is no data for any of the sensors
+        now = time_utils.server_now()
+        return now, now
+    return least_recent_event_start_and_most_recent_event_end