Sqlalchemy中Unique Key引起的问题

用MetaData创建表的时候, 报错:

sqlalchemy.exc.OperationalError: (OperationalError) (1071, 'Specified key was to

o long; max key length is 767 bytes') '/nCREATE TABLE user (/n/tid INTEGER NOT N

ULL AUTO_INCREMENT, /n/tnickname VARCHAR(40), /n/temail VARCHAR(256), /n/tpasswd

 VARCHAR(256), /n/tavatar VARCHAR(256), /n/tcreated DATETIME, /n/tlocation VARCH

AR(256), /n/tpoint INTEGER, /n/tlocked BOOL, /n/tPRIMARY KEY (id), /n/t UNIQUE (

nickname), /n/t UNIQUE (email)/n)/n/n' {}

原因是出在这个 UNIQUE (email)上了.

Mysql里有个key length limitation.

原来的代码是:

#table table

user_table = Table('user', metadata,

Column('id', Integer, primary_key=True),

Column('nickname', String(40), unique=True),

Column('email', String(256), unique=True),

Column('passwd', String(256)),

Column('avatar', String(256), default='d.jpg'),

Column('created', DateTime, default=datetime.now()),

Column('location', String(256)),

Column('point', Integer),

Column('locked', Boolean, default=False)

)

解决方法:

email长度改短. 不需要那么长...

参看: 

http://www.xaprb.com/blog/2006/04/17/max-key-length-in-mysql/