Column default value persisted to the table

Question

I am currently using a Column that has the following signature:

Column(\'my_column\', DateTime, default=datetime.datetime.utcnow)

I am

Answer 1

There are multiple ways to have SQLAlchemy define how a value should be set on insert/update. You can view them in the documentation.

The way you're doing it right now (defining a default argument for the column) will only affect when SQLAlchemy is generating insert statements. In this case, it will call the callable function (in your case, the datetime.datetime.utcnow function) and use that value.

However, if you're going to be running straight SQL code, this function will never be run, since you'll be bypassing SQLAlchemy altogether.

What you probably want to do is use the Server Side Default ability of SQLAlchemy.

Try out this code instead:

from sqlalchemy.sql import func
...
Column('my_column', DateTime, server_default=func.current_timestamp())

SQLAlchemy should now generate a table that will cause the database to automatically insert the current date into the my_column column. The reason this works is that now the default is being used at the database side, so you shouldn't need SQLAlchemy anymore for the default.

Note: I think this will actually insert local time (as opposed to UTC). Hopefully, though, you can figure out the rest from here.