Question

I would like to use SQLAlchemy ORM not only for querying a database, but also to create the tables. So I connect to the empty schema of my database:

engine = create_engine(connection_string)
Base = declarative_base()

I have a few classes which looks similar to the following example:

class SomeClass(Base):
    __tablename__= 'SomeClass'
    id = Column(Integer, primary_key=True, auto_increment=True)
    name = Column(String(50))

    def __init__(self, name):
        self.name = name

To create the database I call:

Base.metadata.create_all(engine)

This works fine – the FIRST time. If I now drop the tables manually from the database OR calling Base.metadata.drop_all() and restart the script (hence call create_all again) I get an error that my tables already exists:

sqlalchemy.exc.OperationalError: (OperationalError) (1050, "Table 'someclass' already exists") 

I can clearly say, that this is not true. I am able to create a table with the same name using CREATE TABLE from my CLI tool AND also if I now stop the database daemon and start it again, I will be able to create the tables again using create_all.

So I guess this has something to do with the connection between SQLAlchemy and the database. Obviosly SQLAlchemy thinks the table still exists after I dropped it, which is not true. But if I try to query this none existing table it will tell me, that the table does not exist.

I googled around but wasn’t able to find an explanation for this behavior. I do not use SQLAlchemy too often, so maybe I’m simply not deep enough into it, to understand the problem.

Anyway I would be thankful to get a hint.

I’m using Python 2.7.3 and MySQL 5.1.47 and SQLAlchemy 0.8.0b2

PS: Using Postgres I’ve never suffered from such an issue.

Answer 1

I’ve fixed the issue by upgrading to MySQL 5.1.66. Note that I did not just upgrade the old instance, but unistalled it completely from my system and installing the new version from scratch. Thus I am still not able to tell if the issue was due to a misconfiguration of my old installation or just a bug.

However, now everything works fine.