v0.4.0

Breaking Changes

• get_multiple has been changed to accept an Iterator over borrowed byte slices.

• ExecutingTransaction::tree now returns a LockedTransactionTree, which
  holds a shared reference to the transaction now. Previously tree() required
  an exclusive reference to the transaction, preventing consumers of Nebari from
  using multiple threads to process more complicated transactions.

  This API is paired by a new addition: ExecutingTransaction::unlocked_tree.
  This API returns an UnlockedTransactionTree which can be sent across thread
  boundaries safely. It offers a lock() function to return a
  LockedTransactionTree when the tread is ready to operate on the tree.

• TransactionManager::push has been made private. This is a result of the
  previous breaking change. TransactionManager::new_transaction() is a new
  function that returns a ManagedTransaction. ManagedTransaction::commit()
  is the new way to commit a transaction in a transaction manager.

Fixed

• TransactionManager now enforces that transaction log entries are written
  sequentially. The ACID-compliance of Nebari was never broken when
  non-sequential log entries are written, but scanning the log file could fail
  to retrieve items as the scanning algorithm expects the file to be ordered
  sequentially.

Added

• ThreadPool::new(usize) allows creating a thread pool with a maximum number
  of threads set. ThreadPool::default() continues to use num_cpus::get to
  configure this value automatically.