Alembic attempts to recreate all tables in the Base class on every migration - sqlalchemy

Question

In my env.py I have set my target_metadata to Base.metadata which I import from models.py. I have a fresh database with a schema named basic that I want to use to create the tables and setup my models.py like this:
from datetime import datetime
from sqlalchemy import Column, DateTime, Integer, MetaData, String
from sqlalchemy.orm import declarative_base
Base = declarative_base(metadata=MetaData(schema='basic'))
class User(Base):
__tablename__ = 'user'
id = Column(Integer, primary_key=True)
name = Column(String, nullable=False)
created_on = Column(DateTime, default=datetime.utcnow)
I run alembic revision --autogenerate -m"Create user model" and run alembic upgrade heads. Everything works as expected and I have table user in my database under the schema basic.
Now I want to add a table country. I add it to my models.py which now looks like this:
from datetime import datetime
from sqlalchemy import Column, DateTime, Integer, MetaData, String
from sqlalchemy.orm import declarative_base
Base = declarative_base(metadata=MetaData(schema='basic'))
class User(Base):
__tablename__ = 'user'
id = Column(Integer, primary_key=True)
name = Column(String, nullable=False)
created_on = Column(DateTime, default=datetime.utcnow)
class Country(Base):
__tablename__ = 'country'
id = Column(Integer, primary_key=True)
country = Column(String, nullable=False)
created_on = Column(DateTime, default=datetime.utcnow)
I run alembic revision --autogenerate -m"Create country model" which creates a new versions file that looks like this:
"""Create country model
Revision ID: 0eef32919b0d
Revises: 2da4668d1069
Create Date: 2023-01-19 15:39:08.778274
"""
from alembic import op
import sqlalchemy as sa
# revision identifiers, used by Alembic.
revision = '0eef32919b0d'
down_revision = '2da4668d1069'
branch_labels = None
depends_on = None
def upgrade() -> None:
# ### commands auto generated by Alembic - please adjust! ###
op.create_table('country',
sa.Column('id', sa.Integer(), nullable=False),
sa.Column('country', sa.String(), nullable=False),
sa.Column('created_on', sa.DateTime(), nullable=True),
sa.PrimaryKeyConstraint('id'),
schema='basic'
)
op.create_table('user',
sa.Column('id', sa.Integer(), nullable=False),
sa.Column('name', sa.String(), nullable=False),
sa.Column('created_on', sa.DateTime(), nullable=True),
sa.PrimaryKeyConstraint('id'),
schema='basic'
)
# ### end Alembic commands ###
def downgrade() -> None:
# ### commands auto generated by Alembic - please adjust! ###
op.drop_table('user', schema='basic')
op.drop_table('country', schema='basic')
# ### end Alembic commands ###
Why does it also try to create the table user again? Running this will give an error that the object basic.user already exists. How can I fix this so that it looks at the current state of the db and only wants to create the table country?
Setting the option include_schemas=True (which is suggested in this thread: Alembic - sqlalchemy does not detect existing tables) helps but then includes all schemas and I only want it to be aware of this single schema.

Answer 1

I only want it to be aware of this single schema.
Then you also need to use include_name=, like so:
def run_migrations_online():
# …
def include_name(name, type_, parent_names):
if type_ == "schema":
# note this will not include the default schema
return name in ["basic"]
else:
return True
with connectable.connect() as connection:
context.configure(
connection=connection, target_metadata=target_metadata,
include_schemas=True,
include_name=include_name
)