I am working with SQL Alchemy, and wish to update the tables schemes automatically, without using CLI (The structure of my code prevent it)
I don't need to store migrations files either.
I have been looking for Alembic, which seems to be the best tool to do this. However, I cannot find a proper process or explanation on how to do it without using CLIs.
The closest I have comes from this:
How to run a migration with Python Alembic by code?
However, the same error still appears, even with the solution.
I was thinking about using autogenerate.produce_migrations(alembic_context, metadata) to get the operations (That works fine), but how to execute those, then?
Thanks
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1 Answer
I finally found it. Below the code
from alembic import autogenerate, util
from alembic.config import Config
from alembic.runtime.environment import EnvironmentContext
from alembic.script import ScriptDirectory
config = Config()
config.set_main_option("script_location", <script location>)
alembic_script = ScriptDirectory.from_config(config)
environment = EnvironmentContext(config, alembic_script)
with metadata.bind.connect() as connection:
environment.configure(
connection=connection,
target_metadata=metadata,
fn=fn,
include_object=include_object
)
migrations = autogenerate.produce_migrations(context=environment.get_context(),
metadata=metadata)
alembic_script.generate_revision(util.rev_id(), "update table",
upgrades=autogenerate.render_python_code(migrations.upgrade_ops))
with environment.begin_transaction():
environment.run_migrations()
def fn(revision, context):
script = ScriptDirectory.from_config(context.config)
return script._upgrade_revs(script.get_heads(), revision)
def include_object(object, name, type_, reflected, compare_to):
if type_ == "table" and reflected and compare_to is None:
return False
else:
return True
Notes:
include_objectoption ensures that no table is deleted. It is then optionalreplace <'script location'> with the path of alembic. This directory must contain a direction "versions" and a file script.py.mako. Such data can be automatically generated by calling once the cli
alembic init <root path of data>Such code doesn't handle mutliple branches and downgrade: I assume it wouldn't be that complicate to handle those
All this code can be called in a function, with a single metadata input (That must be bounded to an engine).