It would be useful to have an API (or possibly a utility) that allows an LSM tree to finish it's merges.

The implementation is pretty simple, it requires that a handle to the relevant LSM tree is open, and we need a way to monitor whether there are merges happening - there is currently a statistic: LSM_ROWS_MERGED. If this becomes a general API we probably can't rely on a statistic, but a new member in the LSM_TREE structure could track the same progress.