convert commentflag's created_utc to created_timestampz

created alembic migration like #597

migrations/versions/2023_07_09_21_52_50_7ae4658467d7_change_created_utc_to_timestampz_for_.py

@@ -0,0 +1,45 @@
+"""Change created_utc to timestampz for commentflags
+
+Revision ID: 7ae4658467d7
+Revises: ea282d7c711c
+Create Date: 2023-07-09 21:52:50.386177+00:00
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '7ae4658467d7'
+down_revision = 'ea282d7c711c'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.add_column('commentflags', sa.Column('created_timestampz', sa.DateTime(timezone=True), nullable=False, server_default=sa.text('NOW()')))
+    op.execute("""
+        UPDATE commentflags 
+        SET created_timestampz = 
+            CASE 
+                WHEN created_utc > 0 THEN 
+                    (timestamp 'epoch' + created_utc * interval '1 second') at time zone 'utc' 
+                ELSE NULL 
+            END
+    """)
+
+    op.drop_column('commentflags', 'created_utc')
+
+
+def downgrade():
+    op.add_column('commentflags', sa.Column('created_utc', sa.INTEGER(), server_default=sa.text('0'), nullable=True))
+    op.execute("""
+        UPDATE commentflags 
+        SET created_utc = 
+            COALESCE(
+                EXTRACT(EPOCH FROM created_timestampz)::integer,
+                0
+            )
+        """)
+    op.alter_column('commentflags', 'created_utc', nullable=False)
+    op.drop_column('commentflags', 'created_timestampz')