1.9 KiB
Operation Reference
This file provides documentation on Alembic migration directives.
The directives here are used within user-defined migration files,
within the upgrade() and downgrade()
functions, as well as any functions further invoked by those.
All directives exist as methods on a class called .Operations. When migration
scripts are run, this object is made available to the script via the
alembic.op datamember, which is a proxy to an
actual instance of .Operations. Currently, alembic.op is a
real Python module, populated with individual proxies for each method on
.Operations, so
symbols can be imported safely from the alembic.op
namespace.
The .Operations
system is also fully extensible. See operation_plugins for details on this.
A key design philosophy to the alembic.operations.toplevel methods is that to the
greatest degree possible, they internally generate the appropriate
SQLAlchemy metadata, typically involving ~sqlalchemy.schema.Table and ~sqlalchemy.schema.Constraint objects. This so that
migration instructions can be given in terms of just the string names
and/or flags involved. The exceptions to this rule include the ~.Operations.add_column and
~.Operations.create_table directives, which require
full ~sqlalchemy.schema.Column objects, though the table
metadata is still generated here.
The functions here all require that a .MigrationContext has been configured within the
env.py script first, which is typically via .EnvironmentContext.configure. Under normal
circumstances they are called from an actual migration script, which
itself would be invoked by the .EnvironmentContext.run_migrations method.
alembic.operations
Operations
BatchOperations