Not quite given in an example, I guess I could add as a recipe but then people
will be using it which as you've noted isn't reliable in the general sense,
let's put together how to get the MigrationScript, which it looks like you
have, with then how to make the Operations object programmatically, which is at
https://alembic.sqlalchemy.org/en/latest/ops.html#alembic.operations.Operations,
then there's a method invoke() which is at
https://alembic.sqlalchemy.org/en/latest/ops.html#alembic.operations.Operations.invoke
, so we can use that to run the ops. We have to traverse them too where I'll
use a little bit of assumptions to make it succinct, seems to work for simple
operations, like this:
migrations = produce_migrations(mc, metadata)
operations = Operations(mc)
stack = [migrations.upgrade_ops]
while stack:
elem = stack.pop(0)
if hasattr(elem, "ops"):
stack.extend(elem.ops)
else:
# work around Alembic issue #753
if hasattr(elem, "column"):
elem.column = elem.column.copy()
operations.invoke(elem)
full example below
from alembic.migration import MigrationContext
from alembic.autogenerate import produce_migrations
from sqlalchemy.schema import SchemaItem
from sqlalchemy.types import TypeEngine
from sqlalchemy import create_engine, MetaData, Column, Integer, String, Table
import pprint
from alembic.operations import Operations
engine = create_engine("mysql://scott:tiger@localhost/test", echo=True)
with engine.connect() as conn:
m = MetaData()
m.reflect(conn)
m.drop_all(conn)
conn.execute(
"""
create table foo (
id integer not null primary key,
old_data varchar(50),
x integer
)"""
)
conn.execute(
"""
create table bar (
data varchar(50)
)"""
)
metadata = MetaData()
Table(
"foo",
metadata,
Column("id", Integer, primary_key=True),
Column("data", Integer),
Column("x", Integer, nullable=False),
)
Table("bat", metadata, Column("info", String(100)))
mc = MigrationContext.configure(engine.connect())
migrations = produce_migrations(mc, metadata)
operations = Operations(mc)
stack = [migrations.upgrade_ops]
while stack:
elem = stack.pop(0)
if hasattr(elem, "ops"):
stack.extend(elem.ops)
else:
# work around Alembic issue #753
if hasattr(elem, "column"):
elem.column = elem.column.copy()
operations.invoke(elem)
On Thu, Nov 5, 2020, at 2:14 AM, Jason Pascucci wrote:
> I couldn't lay my hands on an example of using
> MigrationContext(connect=<blah>) and running the results of
> produce_migrations(Base.metadata, mc).
>
> I got close, I think, evaling the results of render_python_code (which failed
> due to spaces, but I can wrap it into a def, I guess), but I think there's
> got to be a better way, I'm just not seeing it.
>
> (NB: I can guarantee that the migrations will always be simple alters to add
> only, &c, so not using the whole infrastructure lets it be consistent, and
> due to the nature of the project, I'd like to make it simple)
>
> Thanks
>
> JRP
>
>
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