Struct ConcurrentMvcc 

pub struct ConcurrentMvcc { /* private fields */ }

Manager for concurrent MVCC operations

Coordinates:

• Reader registration (lock-free)
• Writer locking (single-writer)
• Version store access
• Garbage collection

The MVCC header (writer_lock, current_ts, current_epoch) is stored in a memory-mapped file so that AtomicU32/AtomicU64 CAS operations work correctly across independent OS processes. Without mmap, each process would have its own copy of these atomics, making cross-process coordination impossible.

Implementations

impl ConcurrentMvcc

pub fn open<P: AsRef<Path>>(path: P) -> Result<Self>

Open or create MVCC manager with shared memory-mapped metadata

The metadata file (.mvcc_metadata) is mmap’d so that the writer_lock, current_ts, and reader slots are shared across all processes that open the same database. This enables true cross-process atomic coordination.

pub fn allocate_timestamp(&self) -> HlcTimestamp

Allocate next timestamp

pub fn current_timestamp(&self) -> HlcTimestamp

Get current timestamp without advancing

pub fn current_epoch(&self) -> u64

Get current epoch

pub fn register_reader(&self) -> Result<usize>

Register as active reader

Returns slot index on success. Must call unregister_reader() when done.

pub fn unregister_reader(&self, slot_idx: usize)

Unregister as reader

pub fn try_acquire_writer(&self) -> Result<WriterGuard<'_>>

Try to acquire writer lock

Returns WriterGuard on success, which releases lock on drop.

pub fn acquire_writer(&self, timeout: Duration) -> Result<WriterGuard<'_>>

Acquire writer lock with timeout

pub fn version_store(&self) -> &VersionStore

Get version store

pub fn min_active_snapshot(&self) -> u64

Calculate minimum visible snapshot across all readers

pub fn min_active_epoch(&self) -> u32

Calculate minimum active epoch across all readers

pub fn run_gc(&self) -> usize

Run garbage collection

Should be called periodically (e.g., every 1000 commits).

pub fn should_run_gc(&self) -> bool

Check if GC should run (based on commit count)

pub fn on_commit(&self)

Increment commit count and maybe run GC

pub fn cleanup_stale_readers(&self) -> usize

Clean up stale readers (from crashed processes)

pub fn advance_epoch(&self) -> u64

Advance epoch (called on recovery)

Trait Implementations

impl Drop for ConcurrentMvcc

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.

impl Send for ConcurrentMvcc

impl Sync for ConcurrentMvcc