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Kirill Smelkov
ZODB
Commits
8626e034
Commit
8626e034
authored
Mar 24, 2005
by
Chris McDonough
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Add a test for transactions and refcounts.
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dafabb41
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8626e034
##############################################################################
#
# Copyright (c) 2005 Zope Corporation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
Transaction support for Blobs
=============================
We need a database with a blob supporting storage:
>>> from ZODB.MappingStorage import MappingStorage
>>> from ZODB.Blobs.BlobStorage import BlobStorage
>>> from ZODB.DB import DB
>>> from tempfile import mkdtemp
>>> base_storage = MappingStorage("test")
>>> blob_dir = mkdtemp()
>>> blob_storage = BlobStorage(blob_dir, base_storage)
>>> database = DB(blob_storage)
Putting a Blob into a Connection works like any other Persistent object:
>>> connection = database.open()
>>> root = connection.root()
>>> from ZODB.Blobs.Blob import Blob
>>> blob = Blob()
>>> blob.open('w').write('abc')
>>> root['myblob'] = blob
>>> import transaction
>>> transaction.commit()
Opening a blob gives us a filehandle. Getting data out of the
resulting filehandle is accomplished via the filehandle's read method:
>>> connection2 = database.open()
>>> root = connection2.root()
>>> blob2 = root['myblob']
>>> blob2._get_refcounts()
(0, 0)
>>>
>>> b1 = blob2.open("r")
>>> b1.read()
'abc'
>>> # we reach into the implementation here, dont try this at home
>>> b1.blob._get_refcounts()[0]
1
Let's make another filehandle for read only to blob2, this should bump
up its refcount by one, and each file handle has a reference to the
(same) underlying blob:
>>> b2 = blob2.open("r")
>>> b2.blob._get_refcounts()
(2, 0)
>>> b1.blob._get_refcounts()
(2, 0)
Let's close the first filehandle we got from the blob, this should decrease
its refcount by one:
>>> b1.close()
>>> b1.blob._get_refcounts()
(1, 0)
>>> b1.blob._get_refcounts()
(1, 0)
Let's abort this transaction, and ensure that the filehandles that we
opened are now closed and that the filehandle refcounts on the blob
object are cleared.
>>> transaction.abort()
>>> b1.blob._get_refcounts()
(0, 0)
>>> b2.blob._get_refcounts()
(0, 0)
>>> b2.read()
Traceback (most recent call last):
...
ValueError: I/O operation on closed file
While we are testing this, we don't need the storage directory and databases
anymore:
>>> import shutil
>>> shutil.rmtree(blob_dir)
>>> transaction.abort()
>>> database.close()
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