Properly re-using btree state between application restarts

[markosski]

Would love some help or clarification on how to properly integrate the library within existing application ensuring state is properly preserved. Currently I noticed the following.

• Using with_config between program restarts seems to be creating a new root node as file size increases by about 4KB (new page?) and previously stored data is no longer accessible
• Using new_from_snapshot is also challenging because if application exits before creating a snapshot, program will no longer start due to mismatch of file size and expected size in header.

src/snapshot.rs:131:9:
assertion `left == right` failed
  left: 37376
 right: 8704

Using version 0.4.7

[acmshanyi]

Hey Marcin, so far, we rely on snapshot to preserve the state of a bf-tree for recovery. After an app creates a new bf-tree with SSD as the backend storage, it needs to explicitly call 'snapshot' on the created bf-tree to persist its state to SSD. Then the app can use 'new_from_snapshot' to recover the whole tree after restart.

Going forward, there are indeed opportunities to bring the whole recovery procedure to the background. All inputs and ideas are welcome :)