[Dovecot] FTS/squat search indexes built when?

I know that a given search index doesn't get built the first time until you do an actual search on it from an IMAP client. I don't much care about that; I'm the only user, and I don't create new folders too often. At worst, I could create a script to go search every folder once.

But what I'm not clear about: Does it then get updated on every delivery by LDA? Or does the index also need to get updated when I do a search, assuming there's been at least one message delivered since the last search?

Jay Levitt