Default value doesn't work in SQLAlchemy + PostgreSQL + aiopg + psycopg2 - postgresql

Question

I've found an unexpected behavior in SQLAlchemy. I'm using the following versions:
SQLAlchemy (0.9.8)
PostgreSQL (9.3.5)
psycopg2 (2.5.4)
aiopg (0.5.1)
This is the table definition for the example:
import asyncio
from aiopg.sa import create_engine
from sqlalchemy import (
MetaData,
Column,
Integer,
Table,
String,
)
metadata = MetaData()
users = Table('users', metadata,
Column('id_user', Integer, primary_key=True, nullable=False),
Column('name', String(20), unique=True),
Column('age', Integer, nullable=False, default=0),
)
Now if I try to execute a simple insert to the table just populating the id_user and name, the column age should be auto-generated right? Lets see...
#asyncio.coroutine
def go():
engine = yield from create_engine('postgresql://USER#localhost/DB')
data = {'id_user':1, 'name':'Jimmy' }
stmt = users.insert(values=data, inline=False)
with (yield from engine) as conn:
result = yield from conn.execute(stmt)
loop = asyncio.get_event_loop()
loop.run_until_complete(go())
This is the resulting statement with the corresponding error:
INSERT INTO users (id_user, name, age) VALUES (1, 'Jimmy', null);
psycopg2.IntegrityError: null value in column "age" violates not-null constraint
I didn't provide the age column, so where is that age = null value coming from? I was expecting something like this:
INSERT INTO users (id_user, name) VALUES (1, 'Jimmy');
Or if the default flag actually works should be:
INSERT INTO users (id_user, name, Age) VALUES (1, 'Jimmy', 0);
Could you put some light on this?

Answer 1

This issue has been confirmed has an aiopg bug. Seems like at the moment it's ignoring the default argument on data manipulation.
I've fixed the issue using server_default instead:
users = Table('users', metadata,
Column('id_user', Integer, primary_key=True, nullable=False),
Column('name', String(20), unique=True),
Column('age', Integer, nullable=False, server_default='0'))

Answer 2

I think you need to use inline=True in your insert. This turns off 'pre-execution'.
Docs are a bit cryptic on what exactly this 'pre-execution' entails, but they mentions default parameters:
:param inline:
if True, SQL defaults present on :class:`.Column` objects via
the ``default`` keyword will be compiled 'inline' into the statement
and not pre-executed. This means that their values will not
be available in the dictionary returned from
:meth:`.ResultProxy.last_updated_params`.
This piece of docstring is from Update class, but they have a shared behavior with Insert.
Besides, that's the only way they test it:
https://github.com/zzzeek/sqlalchemy/blob/rel_0_9/test/sql/test_insert.py#L385