Path: csiph.com!usenet.pasdenom.info!news.albasani.net!newsfeed.freenet.ag!news2.euro.net!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.000 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'resulting': 0.04; 'cache': 0.07; 'objects,': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'subject:while': 0.09; 'python': 0.11; 'stored': 0.12; '(about': 0.16; "(i'm": 0.16; 'a()': 0.16; 'any.': 0.16; 'debugged': 0.16; 'operation.': 0.16; 'received:80.91.229.3': 0.16; 'received:dip0.t-ipconnect.de': 0.16; 'received:plane.gmane.org': 0.16; 'received:t-ipconnect.de': 0.16; 'subject:usage': 0.16; 'unneeded': 0.16; 'wrote:': 0.18; 'library': 0.18; 'module': 0.19; '>>>': 0.22; 'memory': 0.22; 'import': 0.22; 'minutes.': 0.22; 'header:User-Agent:1': 0.23; "haven't": 0.24; 'references': 0.26; 'pass': 0.26; 'least': 0.26; 'header:X-Complaints-To:1': 0.27; "i'm": 0.30; 'code': 0.31; 'getting': 0.31; 'pickle': 0.31; 'class': 0.32; 'another': 0.32; 'beginning': 0.33; 'objects': 0.35; 'but': 0.35; 'there': 0.35; 'false': 0.36; "didn't": 0.36; 'being': 0.38; 'sometimes': 0.38; 'saves': 0.38; 'to:addr:python-list': 0.38; 'that,': 0.38; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'new': 0.61; 'chance': 0.65; 'effectively': 0.66; 'default': 0.69; 'yourself': 0.78; 'thoroughly': 0.91 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Peter Otten <__peter__@web.de> Subject: Re: Memory usage steadily going up while pickling objects Date: Sat, 15 Jun 2013 08:37:49 +0200 Organization: None References: Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7Bit X-Gmane-NNTP-Posting-Host: p50848a16.dip0.t-ipconnect.de User-Agent: KNode/4.7.3 X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.python Message-ID: Lines: 40 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1371278248 news.xs4all.nl 15957 [2001:888:2000:d::a6]:45695 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:48255 Giorgos Tzampanakis wrote: > I have a program that saves lots (about 800k) objects into a shelve > database (I'm using sqlite3dbm for this since all the default python dbm > packages seem to be unreliable and effectively unusable, but this is > another discussion). > > The process takes about 10-15 minutes. During that time I see memory usage > steadily rising, sometimes resulting in a MemoryError. Now, there is a > chance that my code is keeping unneeded references to the stored objects, > but I have debugged it thoroughly and haven't found any. > > So I'm beginning to suspect that the pickle module might be keeping an > internal cache of objects being pickled. Is this true? Pickler/Unpickler objects use a cache to maintain object identity, but at least shelve in the standard library uses a new Pickler/Unpickler for each set/get operation. I don't have sqlite3dbm, but you can try the following: >>> import shelve >>> class A: pass ... >>> a = A() >>> s = shelve.open("tmp.shelve") >>> s["x"] = s["y"] = a >>> s["x"] is s["y"] False If you are getting True there must be a cache. One way to enable a cache yourself is writeback: >>> s = shelve.open("tmp.shelve", writeback=True) >>> s["x"] = s["y"] = a >>> s["x"] is s["y"] True You didn't do that, I guess?