[Evolution] IMAPx and message body search

[Pete Biggs <pete biggs org uk>]

Evo 3.36.3

Has something changed recently with searches?  A while ago I turned on
indexing on my Dovecot IMAP server and, as expected, it massively
increased the speed of "Message contains" searches. Recently though the
searches have returned to being deathly slow - Dovecot is still
indexing the mail.

I ran debugging output on the IMAP exchange and it looks like it is
stepping through each message rather than asking Dovecot to do the
search (I searched for "printer"):

A00076 OK [READ-WRITE] Select completed (0.001 + 0.000 secs).'
[imapx:A] I/O: 'A00078 UID SEARCH UID 147137 BODY printer'
[imapx:A] I/O: '* SEARCH
A00078 OK Search completed (0.020 + 0.000 + 0.019 secs).'
[imapx:A] I/O: 'A00079 UID SEARCH UID 147318 BODY printer'
[imapx:A] I/O: '* SEARCH
A00079 OK Search completed (0.018 + 0.000 + 0.017 secs).'
[imapx:A] I/O: 'A00080 UID SEARCH UID 146691 BODY printer'
[imapx:A] I/O: '* SEARCH
A00080 OK Search completed (0.018 + 0.000 + 0.017 secs).'
[imapx:A] I/O: 'A00081 UID SEARCH UID 146000 BODY printer'
[imapx:A] I/O: '* SEARCH

there's about 150k messages in the folder and at 0.017s per message, it
will take 42 mins to complete.  The CAPABILITY response on that account
is:

[imapx:A] I/O: 'A00015 OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS
 ID ENABLE IDLE SORT SORT=DISPLAY THREAD=REFERENCES THREAD=REFS THREAD=ORDEREDSU
BJECT MULTIAPPEND URL-PARTIAL CATENATE UNSELECT CHILDREN NAMESPACE UIDPLUS LIST-
EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH ESORT SEARCHRES WITHIN CONTEXT=SE
ARCH LIST-STATUS SPECIAL-USE BINARY MOVE] Logged in'

Is this an Evolution problem or is it something up with Dovecot - i.e.
is it advertising the correct capabilities that Evolution uses for
offloading the search? Dovecot was upgraded to 2.3.10 from 2.3.9 back
in March (this is on a CentOS 7 system), but I think the problem
started after that.

P.