from __future__ import with_statement import logging from logging.config import fileConfig from sqlalchemy import engine_from_config from sqlalchemy import pool from flask import current_app from alembic import context # this is the Alembic Config object, which provides # access to the values within the .ini file in use. config = context.config # Interpret the config file for Python logging. # This line sets up loggers basically. fileConfig(config.config_file_name) logger = logging.getLogger('alembic.env') # add your model's MetaData object here # for 'autogenerate' support # from myapp import mymodel # target_metadata = mymodel.Base.metadata config.set_main_option( 'sqlalchemy.url', str(current_app.extensions['migrate'].db.engine.url).replace('%', '%%')) target_metadata = current_app.extensions['migrate'].db.metadata # other values from the config, defined by the needs of env.py, # can be acquired: # my_important_option = config.get_main_option("my_important_option") # ... etc. def run_migrations_offline(): """Run migrations in 'offline' mode. This configures the context with just a URL and not an Engine, though an Engine is acceptable here as well. By skipping the Engine creation we don't even need a DBAPI to be available. Calls to context.execute() here emit the given string to the script output. """ url = config.get_main_option("sqlalchemy.url") context.configure( url=url, target_metadata=target_metadata, literal_binds=True ) with context.begin_transaction(): context.run_migrations() def run_migrations_online(): """Run migrations in 'online' mode. In this scenario we need to create an Engine and associate a connection with the context. """ # this callback is used to prevent an auto-migration from being generated # when there are no changes to the schema # reference: http://alembic.zzzcomputing.com/en/latest/cookbook.html def process_revision_directives(context, revision, directives): if getattr(config.cmd_opts, 'autogenerate', False): script = directives[0] if script.upgrade_ops.is_empty(): directives[:] = [] logger.info('No changes in schema detected.') connectable = engine_from_config( config.get_section(config.config_ini_section), prefix='sqlalchemy.', poolclass=pool.NullPool, ) with connectable.connect() as connection: context.configure( connection=connection, target_metadata=target_metadata, process_revision_directives=process_revision_directives, **current_app.extensions['migrate'].configure_args ) with context.begin_transaction(): context.run_migrations() if context.is_offline_mode(): run_migrations_offline() else: run_migrations_online()