I have an outdated database that creates default values ​​for multiple columns using various stored procedures. It would be more or less prohibitive to try to keep track of names and add queries to my code, not to mention the service nightmare.
I'd like to say sqlalchemy to ignore columns that I really don't like. Unfortunately not. Instead, it provides null values ​​that violate DB constraints.
Here is an example of what I mean:
import sqlalchemy as sa import logging from sqlalchemy.orm import sessionmaker from sqlalchemy.ext.declarative import declarative_base l = logging.getLogger('sqlalchemy.engine') l.setLevel(logging.INFO) l.addHandler(logging.StreamHandler()) engine = sa.create_engine('postgresql+psycopg2:// user@host :port/dbname') Session = sessionmaker(bind=engine) session = Session() temp_metadata = sa.MetaData(schema='pg_temp') TempBase = declarative_base(metadata=temp_metadata) with session.begin(subtransactions=True): session.execute(''' CREATE TABLE pg_temp.whatevs ( id serial , fnord text not null default 'fnord' , value text not null ); INSERT INTO pg_temp.whatevs (value) VALUES ('something cool'); ''') class Whatever(TempBase): __tablename__ = 'whatevs' id = sa.Column('id', sa.Integer, primary_key=True, autoincrement=True) fnord = sa.Column('fnord', sa.String) value = sa.Column('value', sa.String) w = Whatever(value='something cool') session.add(w)
These are barfs because:
INSERT INTO pg_temp.whatevs (fnord, value) VALUES (%(fnord)s, %(value)s) RETURNING pg_temp.whatevs.id {'fnord': None, 'value': 'something cool'} ROLLBACK Traceback (most recent call last): File "/home/wayne/.virtualenvs/myenv/lib64/python3.5/site-packages/sqlalchemy/engine/base.py", line 1139, in _execute_context context) File "/home/wayne/.virtualenvs/myenv/lib64/python3.5/site-packages/sqlalchemy/engine/default.py", line 450, in do_execute cursor.execute(statement, parameters) psycopg2.IntegrityError: null value in column "fnord" violates not-null constraint DETAIL: Failing row contains (2, null, something cool).
I was expecting it to just skip the fnord column since it will not be set.
Even if I do this:
w = Whatever() w.value = 'this breaks too'
or add:
def __init__(self, value): self.value = value
to Whatever class ... still no dice.
How can I tell sqlalchemy that “look, these other columns are beautiful, I know that I don’t provide values ​​- the database will take care of this for me. Everything is fine, just don’t worry about these columns”?
The only way I know is futz with class definition and false, saying that these columns do not exist ... but I really want them to come up with queries.