Struct TransactionManager 

pub struct TransactionManager { /* private fields */ }

Manages transactions and MVCC versioning.

Implementations

impl TransactionManager

pub fn new() -> Self

Creates a new transaction manager.

pub fn begin(&self) -> TransactionId

Begins a new transaction with the default isolation level (Snapshot Isolation).

pub fn begin_with_isolation( &self, isolation_level: IsolationLevel, ) -> TransactionId

Begins a new transaction with the specified isolation level.

pub fn isolation_level( &self, transaction_id: TransactionId, ) -> Option<IsolationLevel>

Returns the isolation level of a transaction.

pub fn record_write( &self, transaction_id: TransactionId, entity: impl Into<EntityId>, ) -> Result<()>

Records a write operation for the transaction.

Errors

Returns an error if the transaction is not active.

pub fn record_read( &self, transaction_id: TransactionId, entity: impl Into<EntityId>, ) -> Result<()>

Records a read operation for the transaction (for serializable isolation).

Errors

Returns an error if the transaction is not active.

pub fn commit(&self, transaction_id: TransactionId) -> Result<EpochId>

Commits a transaction with conflict detection.

Conflict Detection

• All isolation levels: Write-write conflicts (two transactions writing to the same entity) are always detected and cause the second committer to abort.

• Serializable only: Read-write conflicts (SSI validation) are additionally checked. If transaction T1 read an entity that another transaction T2 wrote, and T2 committed after T1 started, T1 will abort. This prevents write skew.

Errors

Returns an error if:

• The transaction is not active
• There’s a write-write conflict with another committed transaction
• (Serializable only) There’s a read-write conflict (SSI violation)

pub fn abort(&self, transaction_id: TransactionId) -> Result<()>

Aborts a transaction.

Errors

Returns an error if the transaction is not active.

pub fn get_write_set( &self, transaction_id: TransactionId, ) -> Result<HashSet<EntityId>>

Returns the write set of a transaction.

This returns a copy of the entities written by this transaction, used for rollback to discard uncommitted versions.

pub fn reset_write_set( &self, transaction_id: TransactionId, write_set: HashSet<EntityId>, ) -> Result<()>

Replaces the write set of a transaction (used for savepoint rollback).

Errors

Returns an error if the transaction is not found.

pub fn abort_all_active(&self)

Aborts all active transactions.

Used during database shutdown.

pub fn state(&self, transaction_id: TransactionId) -> Option<TransactionState>

Returns the state of a transaction.

pub fn start_epoch(&self, transaction_id: TransactionId) -> Option<EpochId>

Returns the start epoch of a transaction.

pub fn current_epoch(&self) -> EpochId

Returns the current epoch.

pub fn min_active_epoch(&self) -> EpochId

Returns the minimum epoch that must be preserved for active transactions.

This is used for garbage collection - versions visible at this epoch must be preserved.

pub fn active_count(&self) -> usize

Returns the number of active transactions.

pub fn gc(&self) -> usize

Cleans up completed transactions that are no longer needed for conflict detection.

A committed transaction’s write set must be preserved until all transactions that started before its commit have completed. This ensures write-write conflict detection works correctly.

Returns the number of transactions cleaned up.

pub fn mark_committed(&self, transaction_id: TransactionId, epoch: EpochId)

Marks a transaction as committed at a specific epoch.

Used during recovery to restore transaction state.

pub fn last_assigned_transaction_id(&self) -> Option<TransactionId>

Returns the last assigned transaction ID.

Returns None if no transactions have been started yet.

Trait Implementations

impl Default for TransactionManager

fn default() -> Self

Returns the “default value” for a type.