what happens when cyrus.squat is old?

[Gavin McCullagh]

Hi,

it seems that running squatter nightly on all mailboxes takes too long for
us.  I'm thinking of splitting the mailboxes over different nights or doing
the job over the weekend.

One question though, what happens when a cyrus.squat file is out of date
(ie the mailbox has been changed due to mails added/removed from the
mailbox).  Does it 

 - use the index for what it can and then look directly at the remaining
   emails?  
 - use the index and ignore the newer mails
 - ignore the index and look directly at all mails
 - something else

My tests suggest it's probably the first option, but I'd like to be sure.

Thanks,
Gavin