Combining search criteria


I’m in the process of migrating ~550000 messages to my new MIAB installation. I’m at ~45000 now and I thought I’d try the search feature in roundcube to see how it’s keeping up.

First result: it works very nicely. That is when searching for individual terms.

Second result: I can’t make it work at all with combined search terms. For instance, I have a bunch of emails from somebody called John and some of them refer to “training” in the subject. Each of these terms by itself yields lots of results, but when I combine “john training” in the search field, I get nothing (yes, I have checked the “from” and “subject” boxes).

Now, I tried “john AND training”. I found the roundcube docs and on that basis tried “from:john subject:training”. No results. I have also activated “Entire message” searching, but in that case I got a “gateway timeout” message after a minute or so, while the process on the server kept working for almost five minutes.

I’m not sure where to look. I don’t know whether this is a general restriction (no combined search terms), or whether there is something I don’t know about roundcube, or whether it comes down to the dovecot-lucene plugin and its abilities and/or criteria syntax. Any hints?