我想在peewee(通过

MySQL)创建一个自定义UUID字段.

在python中,我使用UUID作为一个六角形字符串,例如：

uuid =’110e8400-e29b-11d4-a716-446655440000′

但是我想将它存储在数据库中的BINARY(16)类型的列中以节省空间.

MySQL内置了HEX()和UNHEX()方法,可以在字符串和二进制文件之间来回转换.

所以我的问题是如何告诉peewee生成使用内置函数的SQL？这是我想要的代码的想法：

class UUIDField(Field):

db_field='binary(16)'

def db_value(self, value):

if value is not None:

uuid = value.translate(None, '-') # remove dashes

# HERE: How do I let peewee know I want to generate

# a SQL string of the form "UNHEX(uuid)"?

def python_value(self, value):

if value is not None:

# HERE: How do I let peewee know I want to generate

# a SQL string of the form "HEX(value)"?

请注意,我特别询问如何让peewee在自定义SQL中包装或解包值.我意识到我可能完全在python中进行值转换,但我正在寻找更通用的基于SQL的解决方案.

编辑：为了将来的参考,这里是我如何使它在python中进行转换.它虽然没有回答这个问题,所以任何想法都值得赞赏！

import binascii

from peewee import *

db = MySQLDatabase(

'database',

fields={'binary(16)': 'BINARY(16)'} # map the field type

)

# this does the uuid conversion in python

class UUIDField(Field):

db_field='binary(16)'

def db_value(self, value):

if value is None: return None

value = value.translate(None, '-')

value = binascii.unhexlify(value)

return value

def python_value(self, value):

if value is None: return None

value = '{}-{}-{}-{}-{}'.format(

binascii.hexlify(value[0:4]),

binascii.hexlify(value[4:6]),

binascii.hexlify(value[6:8]),

binascii.hexlify(value[8:10]),

binascii.hexlify(value[10:16])

)

return value

from peewee import SelectQuery

# this does the uuid conversion in python

class UUIDField(Field):

db_field = 'binary(16)'

def db_value(self, value):

if value is None: return None

value = value.translate(None, '-')

query = SelectQuery(self.model_class, fn.UNHEX(value).alias('unhex'))

result = query.first()

value = result.unhex

return value

def python_value(self, value):

if value is None: return None

query = SelectQuery(self.model_class, fn.HEX(value).alias('hex'))

result = query.first()

value = '{}-{}-{}-{}-{}'.format(

result.hex[0:8],

result.hex[8:12],

result.hex[12:16],

result.hex[16:20],

result.hex[20:32]

)

return value