Django - 自定义 Filter
# Django <= 1.7
# 减少文本的长度，保存数据的时候压缩，读取的时候解压缩，如果发现压缩后更长，就用原文本直接存储
from django.db import models
class CompressedTextField(models.TextField):
""" model Fields for storing text in a compressed format (bz2 by default) """
__metaclass__ = models.SubfieldBase
# to_python 用于转化数据库中的字符到 Python 的变量
def to_python(self, value):
if not value:
return value
try:
return value.decode('base64').decode('bz2').decode('utf-8')
except Exception:
return value
# 用于将 Python 变量处理后保存到数据库
def get_prep_value(self, value):
if not value:
return value
try:
value.decode('base64')
return value
except Exception:
try:
tmp = value.encode('utf-8').encode('bz2').encode('base64')
except Exception:
return value
else:
if len(tmp) > len(value):
return value
return tmp
# Django >= 1.8
#coding:utf-8
from django.db import models
class CompressedTextField(models.TextField):
"""
model Fields for storing text in a compressed format (bz2 by default)
"""
#
def from_db_value(self, value, expression, connection, context):
if not value:
return value
try:
return value.decode('base64').decode('bz2').decode('utf-8')
except Exception:
return value
def to_python(self, value):
if not value:
return value
try:
return value.decode('base64').decode('bz2').decode('utf-8')
except Exception:
return value
def get_prep_value(self, value):
if not value:
return value
try:
value.decode('base64')
return value
except Exception:
try:
return value.encode('utf-8').encode('bz2').encode('base64')
except Exception:
return value
