# -*- coding: utf-8 -*- ########################################################################### # Copyright (c), The AiiDA team. All rights reserved. # # This file is part of the AiiDA code. # # # # The code is hosted on GitHub at https://github.com/aiidateam/aiida-core # # For further information on the license, see the LICENSE.txt file # # For further information please visit http://www.aiida.net # ########################################################################### # pylint: disable=invalid-name,no-member """Prepare schema reset. Revision ID: 91b573400be5 Revises: 7b38a9e783e7 Create Date: 2019-07-25 14:58:39.866822 """ # Remove when https://github.com/PyCQA/pylint/issues/1931 is fixed # pylint: disable=no-name-in-module,import-error from alembic import op from sqlalchemy.sql import text # revision identifiers, used by Alembic. revision = '91b573400be5' down_revision = '7b38a9e783e7' branch_labels = None depends_on = None [docs]def upgrade(): """Migrations for the upgrade.""" conn = op.get_bind() # The following statement is trying to perform an UPSERT, i.e. an UPDATE of a given key or if it doesn't exist fall # back to an INSERT. This problem is notoriously difficult to solve as explained in great detail in this article: # https://www.depesz.com/2012/06/10/why-is-upsert-so-complicated/ Postgres 9.5 provides an offical UPSERT method # through the `ON CONFLICT` keyword, but since we also support 9.4 we cannot use it here. The snippet used below # taken from the provided link, is not safe for concurrent operations, but since our migrations always run in an # isolated way, we do not suffer from those problems and can safely use it. statement = text( """ INSERT INTO db_dbsetting (key, val, description) SELECT 'schema_generation', '"1"', 'Database schema generation' WHERE NOT EXISTS (SELECT * FROM db_dbsetting WHERE key = 'schema_generation'); """ ) conn.execute(statement) [docs]def downgrade(): """Migrations for the downgrade."""