4.5.0

Multi-process support

Database files cannot be shared between processes using these modes and processes using the
experimental-multiprocess feature of redb 4.3 or 4.4. Their locking is incompatible, and 4.5
can't detect the older processes.

• Add Builder::set_concurrency_mode(), which takes a ConcurrencyMode configuring how processes
  may share the database.
• ConcurrencyMode::ExclusiveWriter (the default) locks the whole file, as earlier versions do.
• ConcurrencyMode::SingleWriter allows one process to write, and any number of processes may open
  the database read-only.
• ConcurrencyMode::MultiWriter allows any number of processes to open the database for
  writing, one write transaction at a time, and any number may open it read-only.

New features

• Add Builder::open_read_only_with_backend() to open a read-only database from a storage backend.
• Add Builder::set_check_integrity_on_open(), which verifies the whole file on every open()
  instead of trusting the state recorded by a clean shutdown.
• Add ReadOnlyDatabase::close(), which releases the file and its locks without waiting for the
  read transactions opened from the database to be dropped.
• Add Database::close(), which closes the database as dropping it does, but returns any error
  rather than ignoring it.
• Add Database::try_begin_write(), which returns TransactionError::WouldBlock instead of
  waiting for an in-progress write transaction to finish.

Performance

• Operations on tables with &str or String keys are faster.

Deprecations

• Builder::create_file() is deprecated; use
  Builder::create_with_backend(FileBackend::new(file)?) instead.
• WriteTransaction::print_allocated_page_debug() is deprecated. It is an internal debugging aid,
  present only in debug builds.

Bug fixes

• open() reports a malformed allocator state as StorageError::Corrupted instead of panicking.
• Repair and check_integrity() verify the trees kept by persistent savepoints, which were not
  checked before.
• Fix cache_stats(), with the cache_metrics feature, panicking in debug builds or returning a
  write_misses() near u64::MAX in release builds when called while another thread is writing.
• Repair, check_integrity(), and commit() report some forms of file corruption as StorageError::Corrupted instead of panicking. This cannot occur in normal operation, and only effects database which were externally modified.