MBOX-Line: From bill.shannon at ymail.com  Fri May 22 18:00:49 2015
To: imap-protocol@u.washington.edu
From: Bill Shannon <bill.shannon@ymail.com>
Date: Fri Jun  8 12:34:55 2018
Subject: [Imap-protocol] COPYUID message order
In-Reply-To: <CABa8R6tpd-2GPoSTX0_d8wnROvQpm4_zmMxconJDPPud3NNdww@mail.gmail.com>
References: <555FBFD2.1030800@ymail.com>
	<CABa8R6tpd-2GPoSTX0_d8wnROvQpm4_zmMxconJDPPud3NNdww@mail.gmail.com>
Message-ID: <555FD141.1060300@ymail.com>

I *so* wish there were compatibility tests for servers, rather than "it didn't
break any clients so it must be good enough".  :-)

Ok, how about this.  If I sort the original message numbers, and sort the
returned source and destination UIDs, the result will be one-to-one, right?  The
first message number will correspond to the first source UID, which will
correspond to the first destination UID, right?  And all three sets will have
exactly the same cardinality?

Brandon Long wrote on 05/22/2015 05:17 PM:
> At least for Gmail, we always re-order the given set into sequence order
> (which is the same as uid order) before doing any operation.  So, the source
> UIDs in COPYUID are in the order in which they were copied.
>
> Since a COPY in Gmail is the equivalent of adding a label to a message, the
> message may already have that label, so it may already be in the recipient
> mailbox.  We always return the destination UIDs in the order which matches the
> source UID order, so in your example, source UID 1 is destination UID 2, and
> source UID 2 is destination UID 1.
>
> When APPEND'ing a duplicate message, we update the UID assigned to the
> original to be the newest UID in the mailbox (and that's returned with
> APPENDUID), since we found clients typically assumed that was the case and
> could get confused.
>
> We could have done this with COPY, I guess, but we didn't see any client
> issues in testing, so we left it this way since the performance is better.
>
> Brandon
>
> On Fri, May 22, 2015 at 4:46 PM, Bill Shannon <bill.shannon@ymail.com
> <mailto:bill.shannon@ymail.com>> wrote:
>
>     I'm unclear on the requirements around the COPY command and the COPYUID
>     response code.
>
>     Is there any guarantee that the order of messages in the COPY command is
>     the order they'll appear in the destination mailbox?  Or are they
>     allowed to appear in any arbitrary order in the destination mailbox?
>     (After any existing messages, of course.)
>
>     RFC 4315 says of the COPYUID response:
>
>           The source UID set is in the order the message(s) were copied; the
>           destination UID set corresponds to the source UID set and is in
>           the same order.
>
>     Exactly what order is that?  Is it the order in which the messages were
>     mentioned in the COPY command?  Is it the order they actually appear in
>     the destination mailbox (assuming it can be different)?  Or is it in
>     some other undefined order?
>
>     With Gmail I'm getting
>
>     A1 COPY 1:2 dest
>     A1 OK [COPYUID 123456 1:2 2,1]
>
>     and
>
>     A1 COPY 2,1 dest
>     A1 OK [COPYUID 123456 1:2 2,1]
>
>     The order of the source UIDs is unrelated to the order the messages
>     are mentioned in the COPY command and unrelated to the order they
>     appear in the destination mailbox.
>
>     If I don't know the UIDs of the source messages, is there any way to
>     determine which message was copied to which UID in the destination
>     mailbox?
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>

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