ZODB

简述

起因

公元2005年2月19日会课中, limodou提到用ZODB来完成知识存储的想法. 他挖坑,偶就先跳进去了.

学习笔记

《ZODB/ZEO Programming Guide》一共才25页, 花了3小时看完, 先写点不算翻译也不算感想的东西吧.

ZODB的安装

windows版本从[http://zope.org/Products/ZODB3.2]下载.
BSD下直接在ports/databases/zodb3中安装
ZODB主要包括了ZODB,ZEO,BTREE等几个重要都包, 他们可以独立于ZOPE运行的, 其实ZODB是ZOPE的地层, 整个ZOPE就架在ZODB上.

基本概念

ZODB虽然是OODB, 但是任何有一些和关系数据库类似的概念
ZODB的数据存储形式, 是多选的, 可以是普通文件(FileStorage), DB4和ZEO连接
Python类通过继承Persistent可以变为ZODB化的
ZODB是基于"事务"的
ZODB的逻辑结构是树状结构

例子

先来看一个例子, 这个例子是可以运行的, 源于《ZODB/ZEO Programming Guide》

   1 from ZODB import FileStorage, DB
   2 import ZODB
   3 from Persistence import Persistent
   4 from BTrees.OOBTree import OOBTree
   5 
   6 class User(Persistent):
   7     pass
   8 
   9 def test1():
  10     storage = FileStorage.FileStorage("test-filestorage.fs")
  11     db = DB(storage)
  12     conn = db.open()
  13     dbroot = conn.root()
  14     # Ensure that a 'userdb' key is present
  15     # in the root
  16     if not dbroot.has_key('userdb'):
  17         dbroot['userdb'] = OOBTree()
  18     userdb = dbroot['userdb']
  19     # Create new User instance
  20     newuser = User()
  21     # Add whatever attributes you want to track
  22     newuser.id = 'amk'
  23     newuser.first_name = 'Andrew'
  24     newuser.last_name = 'Kuchling'
  25     # Add object to the BTree, keyed on the ID
  26     userdb[newuser.id] = newuser
  27     # Commit the change
  28     get_transaction().commit()
  29     conn.close()
  30     storage.close()
  31 
  32 def test2():
  33     storage = FileStorage.FileStorage("test-filestorage.fs")
  34     db = DB(storage)
  35     conn = db.open()
  36     dbroot = conn.root()
  37     it = [dbroot]
  38     for t in it:
  39         for k, v in t.items():
  40             if isinstance(v, OOBTree):
  41                 print k, ':'
  42                 it.append(v)
  43             elif isinstance(v, User):
  44                 print 'Key:', k
  45                 print 'ID:', v.id
  46                 print 'first_name:', v.first_name
  47                 print 'last_name:', v.last_name
  48     
  49 if __name__ == "__main__":
  50     test1()
  51     test2()

test1向数据库写数据, test2从数据库读数据.

逐步分解

连接数据库, 这个例子中使用普通文本:

   1 from ZODB import FileStorage, DB
   2 storage = FileStorage.FileStorage('/tmp/test-filestorage.fs')
   3 db = DB(storage)
   4 conn = db.open()

建一个ZODB化的类User

   1 import ZODB
   2 from Persistence import Persistent
   3 
   4 class User(Persistent):
   5     pass

获取数据库的根, 若没有userdb添加一个userdb实例

   1 dbroot = conn.root()
   2 # Ensure that a 'userdb' key is present
   3 # in the root
   4 if not dbroot.has_key('userdb'):
   5    from BTrees.OOBTree import OOBTree
   6    dbroot[’userdb’] = OOBTree()
   7 userdb = dbroot[’userdb’]

dbroot和userdb都是OOBTree的实例

-  ⇤ ← Revision 5 as of 2005-02-20 08:03:27 → 
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Diff for "ZODB笔记"

ZODB

起因

学习笔记

ZODB的安装

基本概念

例子

逐步分解