Blockchain reset starts eariler than specified

[raze]

Hey guys, I'm not sure if this issue has been raised before or if I'm missing something but whenever I try to reset the blockchain to the day before, it starts ~a few weeks before the day that I specify. Is there a minimum timeframe for this action/is this normal?

It also appears that the reset blockchain feature has sped up a lot since upgrading, nice work

[jim618]

Hi Raze,

You are correct - it is to do with how the new blockchain store works.

Previously MultiBit stored every header for every block. This was a file about 16MB in size and was included in the download.

Now there is a file containing checkpoints every 2,000 blocks or so. This is only 12KB.
When you do a reset or an import it looks back through the checkpoints file and goes back to the last checkpoint which is a bit before the date it wants to reset to. Often it needs to go back an extra week or two.

The last checkpoint is set a month ago (when the installer is built) and there is another small store which contains every header for the last month. This 'tops up' the checkpoints to get to the present day. On a reset this small store is rebuilt so you often go back to the last checkpoint.

There are a few possible improvements that can be made:
+ automatically download a signed checkpoints file from multibit.org so that it is kept up to date
+ as the checkpoints and block store are only small it would be possible to have one per wallet and then each wallet could sync independently. I'm not sure this is worth the effort in doing though as the time is probably better spent on other things.