import logging from logging.config import fileConfig from alembic import context from flask import current_app # 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") def get_engine(): try: # this works with Flask-SQLAlchemy<3 and Alchemical return current_app.extensions["migrate"].db.get_engine() except (TypeError, AttributeError): # this works with Flask-SQLAlchemy>=3 return current_app.extensions["migrate"].db.engine def get_engine_url(): try: return ( get_engine() .url.render_as_string(hide_password=False) .replace("%", "%%") ) except AttributeError: return str(get_engine().url).replace("%", "%%") # 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", get_engine_url()) target_db = current_app.extensions["migrate"].db # 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 get_metadata(): if hasattr(target_db, "metadatas"): return target_db.metadatas[None] return target_db.metadata 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=get_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.") conf_args = current_app.extensions["migrate"].configure_args if conf_args.get("process_revision_directives") is None: conf_args["process_revision_directives"] = process_revision_directives connectable = get_engine() with connectable.connect() as connection: context.configure( connection=connection, target_metadata=get_metadata(), **conf_args ) with context.begin_transaction(): context.run_migrations() if context.is_offline_mode(): run_migrations_offline() else: run_migrations_online()