I keep hearing about having uuid as primary keys into your database so I decided to give a try with sqlalchemy and python(of course).
So the plan is to have a table users that has the following fields
id - type UUID - 32
fname - varchar(50)
lname - varchar(50)
the code bellow builds the table for me.
1 from sqlalchemy import Table, Column, Integer, String, Sequence, MetaData, ForeignKey, CHAR
2 from sqlalchemy.orm import mapper, sessionmaker, scoped_session
3 from sqlalchemy import create_engine
4 import uuid
5
6 metadata = MetaData()
7
8 users = Table('users', metadata,
9 Column('id', CHAR(32), primary_key=True, autoincrement=True),
10 Column('fname', String(50)),
11 Column('lname', String(50))
12 )
13 # orm
14 class Users(object):
15 def __init__(self, fname, lname):
16 assert isinstance(fname, str), 'fname is not a string'
17 assert isinstance(lname, str), 'lname is not a string'
18 self.fname = fname
19 self.lname = lname
20
21
22
23 mapper(Users, users, version_id_col=users.c.id, version_id_generator = lambda version:uuid.uuid4().hex)
line of interest will be
4 - import the uuid module (standard with python 2.6 or higher)
23 - the version_id_col=users.c.id and version_id_generator = lambda version:uuid.uuid4().hex)
the explanation for it is http://www.sqlalchemy.org/docs/orm/mapper_config.html?highlight=uuid#sqlalchemy.orm.mapper
basically you map a temporary integer used my sqlaclhemy and then you transform it into the UUID with a 32 chars in hex.
the rest of the program
24
25 engine = create_engine('sqlite:///:memory:', echo=True)
26 Session = scoped_session(sessionmaker(bind=engine))
27 metadata.drop_all(engine)
28 metadata.create_all(engine)
29 # my test
30 session = Session()
31
32
33 u = Users('s', 'd');
34 u1 = Users('s1', 'd2');
35
36 session.add_all([u1, u])
37 session.commit()
38
39 session.query(Users).all()
if uuid are better then integers as primary keys I don't think so - at least with mysql taking
into consideration the following article http://www.mysqlperformanceblog.com/2007/03/13/to-uuid-or-not-to-uuid/
but they 'hide' your data from outside and seem to do the job.
