Weird behavior with web2py DAL on table definition - database

Question

Hi getting behaviour I don't understand with web2py
In [50]: db = DAL('sqlite://deposit/sample.sqlite')
In [51]: db.define_table('customer',Field('name','string',required=True),
Field('nric','string',required=True),
Field('address','string'),
Field('phone','integer'),
primarykey=['name'])
Out[51]: <Table customer (name,nric,address,phone)>
works as expected.
I then do
In [53]: db.define_table('check',
Field('nric', db.customer.nric, required=True),
Field('clear','string'))
which gets me the message
AttributeError: 'DAL' object has no attribute 'customer.nric'
So thinking this may be an issue of not having committed customer to the database
so I do a db.commit() and then try again
In [56]: db.define_table('check',Field('nric', db.customer.nric, required=True), Field('clear','string'))
File "<string>", line unknown
SyntaxError: table already defined: check
Not sure why .. but anyway I try and drop the table
In [59]: db['check'].drop()
and get the following weird traceback
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
<ipython-input-59-998297b798f5> in <module>()
----> 1 db['check'].drop()
/home/tahnoon/.dropbox-cyn/Dropbox (TIS Group)/Cynopsis/Builds/Apollo/Code Src/web2py/gluon/dal.pyc in drop(self, mode)
9225
9226 def drop(self, mode=''):
-> 9227 return self._db._adapter.drop(self, mode)
9228
9229 def _listify(self, fields, update=False):
/home/tahnoon/.dropbox-cyn/Dropbox (TIS Group)/Cynopsis/Builds/Apollo/Code Src/web2py/gluon/dal.pyc in drop(self, table, mode)
1328 queries = self._drop(table, mode)
1329 for query in queries:
-> 1330 if table._dbt:
1331 self.log(query + '\n', table)
1332 self.execute(query)
/home/tahnoon/.dropbox-cyn/Dropbox (TIS Group)/Cynopsis/Builds/Apollo/Code Src/web2py/gluon/dal.pyc in __getitem__(self, key)
9108 return self._db(self._id == key).select(limitby=(0, 1), orderby_on_limitby=False).first()
9109 elif key:
-> 9110 return ogetattr(self, str(key))
9111
9112 def __call__(self, key=DEFAULT, **kwargs):
AttributeError: 'Table' object has no attribute '_dbt'
Checking tables shows
In [61]: db.tables()
Out[61]: ['customer']
Is this expected behaviour? If so how do I drop/create a table after a syntax error? thanks

Answer 1

Since db.customer is a keyed table (i.e., you have defined a primarykey attribute rather than relying on the default autoincrement integer ID field as the primary key), it can only be referenced by other keyed tables.
Also, when creating reference fields for keyed tables, use the following syntax:
Field('nric', 'reference customer.nric', required=True)
However, I don't think keyed tables are supported for SQLite (the docs say only DB2, MS-SQL, Ingres, and Informix are supported). Anyway, if you are creating a new table in SQLite, there is no reason to use a keyed table (that functionality was added primarily to enable access to legacy databases that lack autoincrement integer primary key fields).
Finally, dropping a table does not remove the model from the db DAL instance -- rather, that operation drops the table from the database itself. If you want to redefine a model within a shell session, you should use the "redefine" argument:
db.define_table(..., redefine=True)