Comment 155 for bug 119899

(In reply to WADA from comment #135)

> Very good news for many bugs!
> But one bad... No performane impact by (a)?
> (Huge Mbox like [Gmail]/All Mail is very popular, and I saw a bug report by
> user on slowness with 136MB Junk.msf in the past...)

The changes that I am thinking of only expand the size of the mbox for custom headers added by the user. Although there is a performance impact in that case, it applies only to a small minority of users who add a particular custom header. By adding the header, they are saying that it is important to them, so adding it to the database is necessary for them to be able to use it effectively.