Currently, we do not have any state associated with the index tree. Consider the following scenario:
1) Start node, put some data
2) start CREATE INDEX operation
3) Wait for a checkpoint and stop node before index create finished
4) Restart node
Since the checkpoint finished, the new index tree will be persisted to the disk, but not all data will be present in the index.
We should somehow store information about initializing index tree and mark it valid only after all data is indexed. The state should be persisted as well.