Why Mail on Mavericks keeps Writing changes to disc all the time?

Question

I have updated my MacBook Pro (early 2011) to Mavericks and now my IMAP Gmail account on Mail is having a huge endless "Writing changes to disc" on +/- sometimes with up to 50.000 messages, almost freezing my computer all the time! My Inbox, only has aprox 50 messages, I always move mesages to other folders!
Everything just worked fine on Mountain Lion and now my Mac is very slow because of this. Only if I close Mail than I have my Mac back... but I need to work with Mail open, so thats not an option.

Answer 1

I have the same problem.  Since installing Mavericks I have a major issue with Apple Mail drastically slowing my whole system down.  As others have mentioned, basically Mail takes over the computer and I find myself looking at spinning beach balls for minutes at a time.
From watching the Mail "Activity Window" (accessible from the "Window" menu item), I have discovered that several times a day it starts "Writing changes to disk" (see screenshot) for no apparent reason (it's not as if I have shifted any mailboxes); and that's the time when everything comes to a shuddering halt.  It takes a long time, about half an hour or so, to rewrite 27,000 messages (or some other ginormous number, it varies) to disk, and during that time I'm held up.   This problem never arose with Mountain Lion. 
Basically it seems to me that Mail has been messed up in Mavericks, and Apple needs to fix it.
It was suggested to me by the Apple "Support Advisor" that the fault may lie with Gmail, due to some changes Google have made.  But that sounds like it's a cop-out and anyway it's no excuse.  Here are two of the biggest companies in the world who are constantly talking with each other about many things.  If it's true (unlikely) Apple should be able to communicate with Gmail and get it sorted.