[Users] [Bug 3462] New:=?UTF-8?Q?=20Speed=20up=20folder=20scanning=20with=20=C2=ABLSUB=20?="" "*" »

noreply at thewildbeast.co.uk noreply at thewildbeast.co.uk
Sun Jul 5 21:57:50 CEST 2015


            Bug ID: 3462
           Summary: Speed up folder scanning with «LSUB "" "*"»
    Classification: Unclassified
           Product: Claws Mail
           Version: 3.11.1
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P3
         Component: Folders/IMAP
          Assignee: users at lists.claws-mail.org
          Reporter: tore at fud.no

When scanning the folder tree, CM will recursively search for subscribed
folders using multiple LSUB commands using the "%" wildcard, like so:

1 LSUB "" "%"
* LSUB () "/" "Foo"
* LSUB () "/" "Bar"
1 OK LSUB completed
2 LSUB "" "Foo/%"
* [...]
3 LSUB "" "Bar/%"
* [...]

...and so on for every level of every branch of the hierarchy. With large
hierarchies, this means a lot of LSUB commands will be issued, which makes the
folder tree scanning slow - especially if the IMAP server takes a few seconds
to respond to each LSUB command. (My employer's Zimbra server uses 2-3

I suggest that this multi-command recursive method be replaced by a single

LSUB "" "*"

This makes the server return the entire list of subscribed folders in one go.
If CM had used this approach, the entire folder scanning procedure would have
taken 2-3 seconds, rather than the current 2-3 seconds multiplied by the number
of nodes in the folder hierarchy. With a large folder hierarchy, that's a huge

Note: It might well be that the folder scanning procedure when in the show all
folders mode (i.e., including non-subscribed ones) would also benefit from a
similar change, only that it would apply to the LIST command rather than LSUB.
I haven't checked that, though.

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