imapc fetch optimization

Timo Sirainen tss at
Mon May 4 15:45:42 UTC 2015

On 04 May 2015, at 16:59, Nagy, Attila <bra at> wrote:
> Hi,
> On 05/04/15 10:59, Timo Sirainen wrote:
>> On 28 Apr 2015, at 23:49, Nagy, Attila <bra at> wrote:
>>> Hi,
>>> imapc does a lot of UID FETCH $UID (BODY.PEEK[]), which is nice, because it works even with the dumbest IMAP server, altough it really kills performance, especially on high latency lines.
>>> I wonder: if IMAP servers can effectively handle boundless fetches (like a list with all wanted UIDs, or simply 1:* if all are needed), do you see this as a good addition to develop?
>> Set mail_prefetch_count = 10 or 100 or something and it'll do larger FETCHes. The higher the value, the more memory/disk space is used for storing the received mails.
> I'm aware of that, but it doesn't, or at least not always.
> For example Thunderbird issues this:
> 13 UID fetch 333574:333601,333630:333801 (UID RFC822.SIZE FLAGS BODY.PEEK[HEADER.FIELDS (From To Cc Bcc Subject Date Message-ID Priority X-Priority References Newsgroups In-Reply-To Content-Type Reply-To)])
> Dovecot does this to the IMAP backend
> 18 UID FETCH 333574 (BODY.PEEK[])

Oh, there were several bugs related to that. Fixed:

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