Legacy databases without Id fields: a lightweight proposal.
I plan to pluck information from a live Drupal site into a Web2Py
site, and I love Web2Py's compact database layer.
Drupal designs it's tables with an autoincrementing integer primary
key, which agrees with gluon.sql, but it names them differently, like
'nid' (node id), or 'uid' (user id), which gluon.sql won't accept.
Let's NOT get into another synthetic key vs. natural key debate. It's
an old argument with bright people on both sides who won't be
convinced (well, perhaps after we decide "What's the best editor?").
Personally, I applaud web2py's design decision to always require a
synthetic key (the implicit 'id' field). It keeps the DAL relativley
small and comprehensible. If I need natural keys, I'll use SQLAlchemy,
and the web2py site graciously show how to do this, and that may well
be what I end up doing.
I am considering patching sql.py for my own use when I want to access
existing tables that follow web2py's design, but not it's naming
convention. That is, they have 'id', but they name it something else.
Here are the proposed changes, all in gluon.sql:
1. Replace the string literal 'id' with an attribute of SQLTable like
self.id_field_name. (Careful not to replace locations where 'id' is a
field type rather than a field name.
2. Add a named arg to the table constructor: SqlTable(...,
id_field_name='id') which would change the value of that attribute.
3. Change SQLTable.__getattr__ to read:
def __getattr__(self, key):
if key=='id':
return dict.__getitem__(self, self.id_field_name)
return dict.__getitem__(self,key)
Seems like a good idea, but my head isn't in the code to fully know
what it would break. Does anybody see glaring red flags in this?
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