Dynamically create initial partitions

* First partition holds all events up to this very moment
* And second partition starts where first left off and runs
  .. through rest of current hour
* From there, dynamically generated partitions will cover
  one hour at a time

awx/main/migrations/0124_event_partitions.py

@@ -1,6 +1,9 @@
 # Generated by Django 2.2.8 on 2020-02-21 16:31
 
+from datetime import timedelta
+
 from django.db import migrations, models, connection
+from django.utils.timezone import now
 
 
 def migrate_event_data(apps, schema_editor):
@@ -59,13 +62,28 @@ def migrate_event_data(apps, schema_editor):
             )
 
             # .. as well as initial partition containing all existing events
+            current_time = now()  # only retrieve current time once to avoid a boundary error
+            end_timestamp = current_time.strftime('%Y-%m-%d %H:%M:%S.000000%z')
             cursor.execute(
-                f'CREATE TABLE {tblname}_part0 '
+                f'CREATE TABLE {tblname}_old_events '
                 f'PARTITION OF {tblname} '
-                f'FOR VALUES FROM (\'2000-01-01 00:00:00.000000+00\') to (\'2021-02-01 00:00:00.000000+00\');'
+                f'FOR VALUES FROM (\'1980-01-01 00:00:00.000000+00\') to (\'{end_timestamp}\');'
+            )
+
+            # First partition is a special case since it runs up through this moment
+            # Go ahead and create next partition, since it will also need to be a
+            # custom partition (that accounts for the remainder of the current hour)
+            partition_label = current_time.strftime('%Y%m%d_%H')
+            start_timestamp = end_timestamp
+            end_timestamp = (current_time + timedelta(hours=1)).strftime('%Y-%m-%d %H:00:00.000000%z')
+            cursor.execute(
+                f'CREATE TABLE {tblname}_{partition_label} '
+                f'PARTITION OF {tblname} '
+                f'FOR VALUES FROM (\'{start_timestamp}\') to (\'{end_timestamp}\');'
             )
 
             # copy over all job events into partitioned table
+            # TODO: https://github.com/ansible/awx/issues/9257
             cursor.execute(
                 f'INSERT INTO {tblname} '
                 f'SELECT {tblname}_old.*, main_unifiedjob.created '