Merge pull request #104 from openclimatefix/issue/read-forecast-read-latest

add function to get latest value from forecast table

Author: peterdudfield

nowcasting_datamodel/read/read.py

@@ -403,6 +403,46 @@ def get_forecast_values(
     return forecasts
 
 
+def get_forecast_values_latest(
+    session: Session,
+    gsp_id: int,
+    start_datetime: Optional[datetime] = None,
+) -> List[ForecastValueLatestSQL]:
+    """
+    Get forecast values
+
+    :param session: database session
+    :param gsp_id: gsp id, to filter query on
+    :param start_datetime: optional to filterer target_time by start_datetime
+        If None is given then all are returned.
+
+    return: List of forecasts values latest objects from database
+
+    """
+
+    # start main query
+    query = session.query(ForecastValueLatestSQL)
+
+    if start_datetime is not None:
+        query = query.filter(ForecastValueLatestSQL.target_time >= start_datetime)
+
+        # also filter on creation time, to speed up things
+        created_utc_filter = start_datetime - timedelta(days=1)
+        query = query.filter(ForecastValueLatestSQL.created_utc >= created_utc_filter)
+
+    # filter on gsp_id
+    if gsp_id is not None:
+        query = query.filter(ForecastValueLatestSQL.gsp_id == gsp_id)
+
+    # order by target time and created time desc
+    query = query.order_by(ForecastValueLatestSQL.target_time)
+
+    # get all results
+    forecast_values_latest = query.all()
+
+    return forecast_values_latest
+
+
 def get_latest_national_forecast(
     session: Session,
 ) -> ForecastSQL:

tests/read/test_read.py

@@ -26,6 +26,7 @@
     get_all_gsp_ids_latest_forecast,
     get_all_locations,
     get_forecast_values,
+    get_forecast_values_latest,
     get_latest_forecast,
     get_latest_forecast_created_utc,
     get_latest_input_data_last_updated,
@@ -144,6 +145,36 @@ def test_get_forecast_values_gsp_id(db_session, forecasts):
     assert forecast_values_read[0] == forecasts[0].forecast_values[0]
 
 
+def test_get_forecast_values_latest_gsp_id(db_session):
+
+    f1 = make_fake_forecasts(gsp_ids=[1, 2], session=db_session)
+    f1[0].historic = True
+    f1[0].forecast_values_latest = [
+        ForecastValueLatestSQL(
+            gsp_id=1,
+            expected_power_generation_megawatts=1,
+            target_time=datetime(2022, 1, 1, tzinfo=timezone.utc),
+        ),
+        ForecastValueLatestSQL(
+            gsp_id=1,
+            expected_power_generation_megawatts=1,
+            target_time=datetime(2022, 1, 1, 0, 30, tzinfo=timezone.utc),
+        ),
+    ]
+    db_session.add_all(f1)
+    assert len(db_session.query(ForecastValueLatestSQL).all()) == 2
+
+    forecast_values_read = get_forecast_values_latest(
+        session=db_session, gsp_id=f1[0].location.gsp_id
+    )
+    _ = ForecastValue.from_orm(forecast_values_read[0])
+
+    assert len(forecast_values_read) == 2
+    assert forecast_values_read[0].gsp_id == f1[0].location.gsp_id
+    assert forecast_values_read[0].target_time == f1[0].forecast_values_latest[0].target_time
+    assert forecast_values_read[0] == f1[0].forecast_values_latest[0]
+
+
 def test_get_latest_status(db_session):
     s1 = Status(message="Good", status="ok")
     s1 = s1.to_orm()