[Sqlalchemy-tickets] Issue #3444: sqlalchemy does not emit server_onupdate ON UPDATE clause with MySQL (zzzeek/sqlalchemy)

[Charles-Axel D. <iss...@bi...>]

New issue 3444: sqlalchemy does not emit server_onupdate ON UPDATE clause with MySQL
https://bitbucket.org/zzzeek/sqlalchemy/issue/3444/sqlalchemy-does-not-emit-server_onupdate

Charles-Axel Dein:

This seems similar to #3155 and #2631.

I have this simple script to reproduce the problem:

```
from sqlalchemy import create_engine
from sqlalchemy import func
from sqlalchemy.dialects.mysql import DATETIME
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.schema import Column
from sqlalchemy.types import Integer, DateTime

Base = declarative_base()


class Timestamp(Base):

    __tablename__ = 'timestamps'

    id = Column(Integer(), primary_key=True)
    created_at = Column(DateTime(), nullable=False,
                        server_default=func.current_timestamp())
    updated_at = Column(DateTime(), nullable=False,
                        server_default=func.current_timestamp(),
                        server_onupdate=func.current_timestamp())


if __name__ == '__main__':
    engine = create_engine('mysql://root:root@localhost/test', echo=True)
    Base.metadata.drop_all(engine)
    Base.metadata.create_all(engine)
```

The SQL that sqlalchemy generates does not have the `ON UPDATE` clause:

```
CREATE TABLE timestamps (
	id INTEGER NOT NULL AUTO_INCREMENT,
	created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
	updated_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
	PRIMARY KEY (id)
)
```

A `SHOW CREATE TABLE` query confirms that fact:

```
CREATE TABLE `timestamps` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `created_at` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `updated_at` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
```

I'm not 100% sure I'm not causing the problem or have fully understood the two similar tickets. I'll read about it and follow up on this thread if I find something.