You can inspect the index files with doveadm dump to check what is cached. Not sure how it went with mdbox storage driver.

According to `man doveadm-dump` it just seems to dump index files. I tried dumping the cache file but it complains that it can't auto detect the file type.

Try this:

[root@ketola .INBOX]# pwd

/vmail/sami@ketola.io/index/.INBOX

[root@ketola .INBOX]# doveadm dump . | grep -c hdr.message-id

11007

root@ht-mailstore01:/data/mail/hostmasterlog/mdbox/mailboxes/INBOX/dbox-Mails # doveadm dump . | grep -c hdr.MESSAGE-ID
4464736

In dovecot config I have `fts_enforced = yes` and after the search for Message-ID finishes and returns UID, I can do a FETCH .. ENVELOPE on it and it responds immediately.
I was under the impression that fts_enforced forces all searches, headers and body, to go to solr. Then all dovecot would have to do was to return the UID returned by solr.
Unless solr doesn't return UID and dovecot has to take the result from solr and lookup the UID, and with a full 1 GB cache file it always has to scan the whole index?

Nothing seems to be completely broken, I always receive a result, it's just that it takes 30 seconds when I really want it to be ~5 seconds at most.

I guess if we can't find a solution and 30 seconds becomes a real problem, we'll split the mailbox up by years. It should help with the size of the cache. It makes the searching code a little more complicated since it has to figure out the sent date before it can search, but it's doable.

.einar