IMAP search issue (dovecot fts or fts solr or none)

Used to have a pretty perfect and blazing fast dovecot IMAP server running for almost 10 years, I had never even enabled any plugin for it, but its IMAP search via Squirrelmail was similar in speed to grep on the commandline. Since I had it running on a RAID 10 SSD setup, it never even needed extra config. Apparently the *old* debian dovecot config was already doing full text indexing just fine! In fact, I've rarely seen faster search within email anywhere else. This server was not using any control panel, just lots of linux local users (no mysql, no virtual tables, just dovecot, postfix, nginx and webmail, all on the same machine).

Now I've migrated those IMAP users to ISPConfig Version: 3.1dev on an Ubuntu 16.04.2 LTS, with nginx, mariadb, dovecot 2.22.2 etc.
For some strange reason, however, search on this system in IMAP is ridiculously slow. On faster hardware than before. So something's not so good with the newer dovecot, in my opinion. What have they changed? And why? It worked fine for me before. This is not progression, but digression. A horrible slowdown in search performance.

So, to improve on that, I figured I could install solr and use it with dovecot, since dovecot says that is the preferred FTS now. Man is that another can of worms! The java install alone is like an entire bonus OS on top of ubuntu, of which I only need 1 tiny particle.

I have solr installed, wondering why this is needed for something as easy as searching in plain text maildirs. Wow, I didn't know grep could not be used for that in some smart way. Wouldn't even need indexing for that!
Can someone here point out how to even get the dovecot fts solr plugin module installed in this ISPC setup? Do I really have to recompile dovecot from source for that plugin alone? Geez. (No wonder linux for desktop is still wearing baby-shoes..)

Or, my preferred route:
Is there an existing method to have IMAP Maildirs searched using *grep* via webmail packages like rainloop and squirrelmail (my users use both)?

 

Also, I get this when I even try to enable FTS without solr:

Code:

# doveadm fts rescan -u admin
doveadm(admin): Error: fts not enabled for user's namespace INBOX

(and yes, user admin without domain exists. I've enabled users to login without domain..)

I don't even see any namespace config in /etc/dovecot/dovecot.conf
where I used to have:

Code:

namespace inbox {
  #prefix = INBOX. # the namespace prefix isn't added again to the mailbox names.
  inbox = yes
  # ...

  mailbox Trash {
    auto = subscribe
    special_use = \Trash
  }
  mailbox Drafts {
    auto = subscribe
    special_use = \Drafts
  }
  mailbox Sent {
    auto = subscribe
    special_use = \Sent
  }
  mailbox Spam {
    auto = create subscribe
    special_use = \Junk
  }

Why isn't ISPConfig using the /etc/dovecot/conf.d/* config files as ubuntu dictates to? Much easier to find stuff there..

 

FYI: I changed FTS to use Lucene. Here's a short howto: https://www.howtoforge.com/community/threads/dovecot-with-fts-lucene.76812/