Tickets :: Comment on [#2341] Performance issue during recursive folder traversal

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Comment	> After upgrading to IMP 4.0.3 (from IMP 3.2.1), I noticed a severe > performance degradation. After some analysis, I noticed that IMP > send large amounts of LSUB queries to our IMAP server. Most of these > are unnecessary. > > > > This is a particular big problem with our support account. This > account has about 2000 folders that are placed in a 2-3 level folder > hierarchy with about 80 non-leaf nodes. > > > > IMP starts with listing all subscribed folders using > > 00000003 LSUB "" * > > Then, however, it starts to query every single folder, including the > leaf folders: > > 00000007 LSUB "" some/folder/% > > I.e. that results in about 2000 LSUB requests that put a high load on > both the IMAP server and the Apache/PHP installation. > > > > Since the imap-uw server that I was using didn't support the > HasNoChildren flag in the LSUB response, I decided try courier-imap. > However, the number of LSUB requests doesn't change: > > 00000007 LSUB "" INBOX.some.folder.% > > This server correctly returns the HasNoChildren flag on leaf nodes > > * LSUB (\HasNoChildren) "." "INBOX.some.folder" > > but IMP apparently doesn't utilize this information (in this > particular piece of code). > > > > I'd suppose that the problem is somewhere in the recursive folder > tree building code, probably somewhere around _getList - but that's > just my guess. > > > > IMP 3.2.1, OTOH, only used > > 00000003 LSUB "" * > > to get the complete list of folder and deducted everything else from > that information. > > > > I'd like to suggest that IMP either properly supports the > HasNoChildren flag or - preferably - caches the results of the > *-query and dispenses with subsequent calls of LSUB. > >
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