Unfortunately there's no RENAME CONSTRAINT directive, so dropping and
recreating is how it has to go.
Alembic and SQLAlchemy together do have the ability to return lists of
constraints and produce CREATE instructions for them. Recently I did
some of this related to foreign keys, and the same idea would apply to
indexes, unique constraints, CHECK constraints. Here's two ways to
do that to give you some ideas:
from alembic.operations.ops import CreateForeignKeyOp
from alembic.migration import MigrationContext
from alembic.operations import Operations
with engine.connect() as conn:
ctx = MigrationContext.configure(conn)
op = Operations(ctx)
m = MetaData(naming_convention={...})
t = Table(table_name, m, autoload_with=conn)
for fk in t.foreign_keys:
op.drop_constraint(
fk.name, table_name, type_="foreignkey")
# give fk the name we want
fk.name = "somename"
# or name it None to get the naming convention
# fk.name = None
create_fk = CreateForeignKeyOp.from_constraint(fk)
op.invoke(create_fk)
or using the inspector, more manual / explicit:
from sqlalchemy import inspect
with engine.connect() as conn:
ctx = MigrationContext.configure(conn)
op = Operations(ctx)
insp = inspect(conn)
for fk in insp.get_foreign_keys(table_name):
for fk in fks:
op.drop_constraint(
fk['name'], fk['source_table'], type_="foreignkey")
for fk in fks:
op.create_foreign_key(
fk['name'], fk['source_table'],
fk['referred_table'],
fk['constrained_columns'],
fk['referred_columns'],
onupdate=fk['options'].get('onupdate'),
ondelete=fk['options'].get('ondelete'),
deferrable=fk['options'].get('deferrable'),
initially=fk['options'].get('initially'),
)
On Tue, Aug 29, 2017 at 7:01 AM, <jens.troe...@gmail.com> wrote:
> Hello,
>
> I started out migrating my db schema forward using Alembic, and without any
> constraint naming convention. That caused constraints to be named using
> MySQL’s default naming. Alas, now I added a naming convention (see doc here)
> which is different than the db’s naming.
>
> So now I face a mix of current db-style constraint names, and new
> convention-stale constraint names. That’ll cause me a headache.
>
> What is the recommended way of renaming all existing constraint names? Is
> dropping/creating them the only way, or did I fail finding a
> “rename_constraint()” function in Alembic?
>
> Thanks!
> Jens
>
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