此问题与How to pack blobstorage with Plone and RelStorage
有关使用zodb数据库和RelStorage和sqlite作为后端，我试图删除未使用的Blob。当前db.pack不能从光盘中删除斑点。下面的最小工作示例演示了此行为：
import logging
import numpy as np
import os
import persistent
from persistent.list import PersistentList
import shutil
import time
from ZODB import config,blob
connectionString = """
%import relstorage
<zodb main>
<relstorage>
blob-dir ./blob
keep-history false
cache-local-mb 0
<sqlite3>
data-dir .
</sqlite3>
</relstorage>
</zodb>
"""
class Data(persistent.Persistent):
def __init__(self,data):
super().__init__()
self.children = PersistentList()
self.data = blob.Blob()
with self.data.open("w") as f:
np.save(f,data)
def main():
logging.basicConfig(level=logging.INFO)
# Initial cleanup
for f in os.listdir("."):
if f.endswith("sqlite3"):
os.remove(f)
if os.path.exists("blob"):
shutil.rmtree("blob",True)
# Initializing database
db = config.databaseFromString(connectionString)
with db.transaction() as conn:
root = Data(np.arange(10))
conn.root.Root = root
child = Data(np.arange(10))
root.children.append(child)
# Removing child reference from root
with db.transaction() as conn:
conn.root.Root.children.pop()
db.close()
print("blob directory:",[[os.path.join(rootDir,f) for f in files] for rootDir,_,files in os.walk("blob") if files])
db = config.databaseFromString(connectionString)
db.pack(time.time() + 1)
db.close()
print("blob directory:",files in os.walk("blob") if files])
if __name__ == "__main__":
main()
上面的示例执行以下操作：
- 删除当前目录中的所有先前数据库以及blob目录。
- 从头开始创建数据库/存储，添加两个对象（root和child），而child由root引用并执行事务。
- 从根到子之间删除链接并执行事务。
- 关闭数据库/存储
- 打开数据库/存储并在将来执行
db.pack一秒钟。
最小工作示例的输出如下：
INFO:ZODB.blob:(23376) Blob directory '<some path>/blob/' does not exist. Created new directory.
INFO:ZODB.blob:(23376) Blob temporary directory './blob/tmp' does not exist. Created new directory.
blob directory: [['blob/.layout'],['blob/3/.lock','blob/3/0.03da352c4c5d8877.blob'],['blob/6/.lock','blob/6/0.03da352c4c5d8877.blob']]
INFO:relstorage.storage.pack:pack: beginning pre-pack
INFO:relstorage.storage.pack:Analyzing transactions committed Thu Aug 27 11:48:17 2020 or before (TID 277592791412927078)
INFO:relstorage.adapters.packundo:pre_pack: filling the pack_object table
INFO:relstorage.adapters.packundo:pre_pack: Filled the pack_object table
INFO:relstorage.adapters.packundo:pre_pack: analyzing references from 7 object(s) (memory delta: 256.00 KB)
INFO:relstorage.adapters.packundo:pre_pack: objects analyzed: 7/7
INFO:relstorage.adapters.packundo:pre_pack: downloading pack_object and object_ref.
INFO:relstorage.adapters.packundo:pre_pack: traversing the object graph to find reachable objects.
INFO:relstorage.adapters.packundo:pre_pack: marking objects reachable: 4
INFO:relstorage.adapters.packundo:pre_pack: finished successfully
INFO:relstorage.storage.pack:pack: pre-pack complete
INFO:relstorage.adapters.packundo:pack: will remove 3 object(s)
INFO:relstorage.adapters.packundo:pack: cleaning up
INFO:relstorage.adapters.packundo:pack: finished successfully
blob directory: [['blob/.layout'],'blob/6/0.03da352c4c5d8877.blob']]
您可以看到db.pack确实删除了3个对象“ 将删除3个对象”，但是文件系统中的blob不变。
在RelStorage的单元测试中，它们似乎确实在测试是否从文件系统（see here）中删除了blob，但是在上面的脚本中，它不起作用。
我在做什么错？任何提示/链接/帮助表示赞赏。