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
