🏦 Database Change: convert created utc to datetimez for viewers (#697)

* passed the test

* this works better

* Remove commented-out code.

* Remove commented-out code.

---------

Co-authored-by: Ben Rog-Wilhelm <zorba-github@pavlovian.net>

migrations/versions/2023_09_08_02_14_46_bcfaec0d682a_change_to_datetimez_table_viewers.py

@@ -0,0 +1,53 @@
+"""Change to datetimez table viewers
+
+Revision ID: bcfaec0d682a
+Revises: a2fce4808e1d
+Create Date: 2023-09-08 02:14:46.989072+00:00
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.sql.functions import now
+
+
+# revision identifiers, used by Alembic.
+revision = 'bcfaec0d682a'
+down_revision = 'a2fce4808e1d'
+branch_labels = None
+depends_on = None
+
+table_name = 'viewers'
+from_column = 'last_view_utc'
+to_column = 'last_view_datetimez'
+
+
+def upgrade():
+    op.add_column(table_name, sa.Column(to_column, sa.DateTime(timezone=True), nullable=True, server_default=now()))
+    op.execute(f"""
+        UPDATE {table_name} 
+        SET {to_column} = 
+            CASE 
+                WHEN {from_column} > 0 THEN 
+                    (timestamp 'epoch' + {from_column} * interval '1 second') at time zone 'utc' 
+                ELSE NULL 
+            END
+    """)
+    op.alter_column(table_name, to_column, nullable=False)
+    op.drop_column(table_name, from_column)
+
+
+def downgrade():
+    """
+    Downgrade will truncate the milliseconds.
+    """
+    op.add_column(table_name, sa.Column(from_column, sa.Integer(), server_default=sa.text('0'), nullable=True))
+    op.execute(f"""
+        UPDATE {table_name} 
+        SET {from_column} = 
+            COALESCE(
+                EXTRACT(EPOCH FROM {to_column})::integer,
+                0
+            )
+        """)
+    op.alter_column(table_name, from_column, nullable=False)
+    op.drop_column(table_name, to_column)