Using SQL to reduce overhead

djutils/dashboard/commands.py

@@ -1,6 +1,7 @@
 import datetime
 
 from django.conf import settings
+from django.db import connection
 
 from djutils import dashboard
 from djutils.dashboard.models import Panel, PanelData, PanelDataSet, PANEL_AGGREGATE_MINUTE
@@ -34,14 +35,29 @@ def remove_old_panel_data():
     if EXPIRATION_DAYS:
         cutoff = datetime.datetime.now() - datetime.timedelta(days=EXPIRATION_DAYS)
 
-        # try deleting these first so as not to load up the subsequent
-        # delete while collecting sub-objects
-        PanelDataSet.objects.filter(
-            panel_data__created_date__lte=cutoff,
-            panel_data__aggregate_type=PANEL_AGGREGATE_MINUTE,
-        ).delete()
-
-        PanelData.objects.filter(
-            created_date__lte=cutoff,
-            aggregate_type=PANEL_AGGREGATE_MINUTE,
-        ).delete()
+        cursor = connection.cursor()
+
+        data_set_table = PanelDataSet._meta.db_table
+        data_table = PanelData._meta.db_table
+
+        query = '''
+            DELETE FROM %s WHERE id IN (
+                SELECT dpd.id FROM %s AS dpd
+                INNER JOIN %s AS dp
+                    ON dpd.panel_data_id = dp.id
+                WHERE (
+                    dp.aggregate_type = %%s  AND 
+                    dp.created_date <= %%s
+                )
+            );
+        ''' % (data_set_table, data_set_table, data_table)
+
+        cursor.execute(query, [PANEL_AGGREGATE_MINUTE, cutoff])
+
+        query = '''
+            DELETE FROM %s WHERE
+                aggregate_type = %%s AND
+                created_date <= %%s;
+        ''' % (data_table)
+
+        cursor.execute(query, [PANEL_AGGREGATE_MINUTE, cutoff])