Can I "touch" a SQLAlchemy record to trigger "onupdate"?
<p>Here's a SQLAlchemy class:</p>

<pre><code>class MyGroup(Base):
    __tablename__ = 'my_group'
    group_id = Column(Integer, Sequence('my_seq'), primary_key=True)
    group_name = Column(String(200), nullable=False, index=True)
    date_created = Column(DateTime, default=func.now())
    date_updated = Column(DateTime, default=func.now(), onupdate=func.now())
</code></pre>

<p>Anytime I add a group_name or (for example) update the group_name, the <code>date_updated</code> field will get updated.  That's great.</p>

<p>But sometimes there are cases where I want to mark a group as "updated" even if the group record itself did not change (for example, if data in a different but related table is updated).  </p>

<p>I could do it manually:</p>

<pre><code>group = session.query(MyGroup).filter(MyGroup.group_name=='Some Group').one()
group.date_updated = datetime.datetime.utcnow()
session.commit()
</code></pre>

<p>but I'd really rather let the model do it in its own way, rather than recreate a Python process to manually update the date.  (For example, to avoid mistakes like where maybe the model uses <code>now()</code> while the manual function mistakenly uses <code>utcnow()</code>)</p>

<p>Is there a way with SQLAlchemy to "touch" a record (kind of like UNIX <code>touch</code>) that wouldn't alter any of the record's other values but would trigger the <code>onupdate=</code> function?</p>