我想在peewee(通過

MySQL)創建一個自定義UUID字段.

在python中,我使用UUID作為一個六角形字符串,例如：

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

但是我想將它存儲在數據庫中的BINARY(16)類型的列中以節省空間.

MySQL內置了HEX()和UNHEX()方法,可以在字符串和二進制文件之間來回轉換.

所以我的問題是如何告訴peewee生成使用內置函數的SQL？這是我想要的代碼的想法：

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)"?

請注意,我特別詢問如何讓peewee在自定義SQL中包裝或解包值.我意識到我可能完全在python中進行值轉換,但我正在尋找更通用的基于SQL的解決方案.

編輯：為了將來的參考,這里是我如何使它在python中進行轉換.它雖然沒有回答這個問題,所以任何想法都值得贊賞！

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

總結

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