Re: (ITS#8475) Feature request: MDB low durability transactions

[bentrask@comcast.net]

On 08/07/2016 09:29 PM, Howard Chu wrote:
> Knowing whether or not the root pages are pristine still doesn't tell
> you anything about whether the data pages are intact. The only way to
> make any of these schemes work is to avoid overwriting/reusing any data
> pages for the last N transactions. I.e., reverting to append-only
> behavior. So the underlying question (which we have wrestled with
> internally for quite some time) which you haven't asked or answered -
> how many of these non-durable transactions will you support at any given
> time?

The idea was that the two "floating" roots would reuse pages the way MDB 
does now. The 3rd durable root would have its pages preserved 
separately. I can see why this would cause up to a ~2X storage increase 
as the two sets diverged, but I don't see why it would need to grow 
unbounded. Apologies for this stupid question.