Check if user has signature WITHOUT "zmprov gsig"?

Hi

Is there an "easy" way to figure out which ones of my 13.000 users have signatures defined? Sure, I could call "zmprov gsig foo@bar.tld" for each and every account, but that takes forever (or maybe even a bit longer…).

I'd like to have a "call" (to LDAP, MySQL, one huge preliminary "zmprov") which, after some mungling, would show me that users 1, 2, 3, 8913 and 4711 have signatures. Then I could call "zmprov gsig" only for these few users.

Thanks,
Alexander

PS: ZCS NE 6.0.15

I have the output of "zmprov --ldap gaa -v" in a file and split it into per-user files (IOW: I've got "zmprov -l ga $mailbox" for each and every user).
Is it a safe bet to assume, that only those mailboxes have a signature defined, where "zimbraSignatureId:" is set?