[ python-Bugs-1607951 ] mailbox.Maildir re-reads directory too often

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Bugs item #1607951, was opened at 2006-12-03 12:28
Message generated for change (Comment added) made by akuchling
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Category: Python Library
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Matthias Klose (doko)
Assigned to: A.M. Kuchling (akuchling)
Summary: mailbox.Maildir re-reads directory too often

Initial Comment:
[forwarded from http://bugs.debian.org/401395]

Various functions in mailbox.Maildir call self._refresh, which always re-reads the cur and new directories with os.listdir.  _refresh should stat each of the two directories first to see if they changed.  This cuts processing time of a series of lookups down by a factor of the number of messages in the folder, a potentially large number.


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>Comment By: A.M. Kuchling (akuchling)
Date: 2006-12-13 08:38

Message:
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By stat()'ing the directories, do you mean checking the mtime?  I think
this isn't safe because of the limited resolution of mtime on filesystems;
ext3 seems to have a 1-second resolution for mtime, for example.  This
means that _refresh() might read a directory, and if some other process
adds or deletes a message in the same second, _refresh() couldn't detect
the change.  Is there some other property of directories that could be
used for a more reliable check?

The attached patch implements checking of mtime, but I don't recommend
applying it; it causes the test suite in test_mailbox.py to break all over
the place, because the process modifies mailboxes so quickly that the mtime
check doesn't notice the process's own changes.

I'll wait a bit for any alternative suggestion, and then close this bug as
"won't fix".


File Added: mailbox-mtime.patch

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