Class WriteAheadLog

Namespace

AiDotNet.RetrievalAugmentedGeneration.Graph

Assembly

AiDotNet.dll

Write-Ahead Log (WAL) for ensuring ACID properties and crash recovery.

public class WriteAheadLog : IDisposable

Inheritance

object

WriteAheadLog

Implements

IDisposable

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Remarks

A Write-Ahead Log records all changes before they're applied to the main data files. This ensures data integrity and enables recovery after crashes.

For Beginners: Think of WAL like a ship's log or diary.

Before making any change to your graph:

1. Write what you're about to do in the log (WAL)
2. Make sure the log is saved to disk
3. Then make the actual change

If the system crashes:

• The log shows what was happening
• You can replay the log to restore the graph
• No data is lost!

This is how databases ensure "durability" - the D in ACID.

Real-world analogy:

• Bank transaction: First log "transfer $100", then move the money
• If crash happens after logging but before transfer, replay the log on restart
• Money isn't lost!

Constructors

WriteAheadLog(string)

Initializes a new instance of the WriteAheadLog class.

public WriteAheadLog(string walFilePath)

Parameters

walFilePath string

Path to the WAL file.

Properties

CurrentTransactionId

Gets the current transaction ID.

public long CurrentTransactionId { get; }

Property Value

long

Methods

Dispose()

Disposes the WAL, ensuring all entries are flushed.

public void Dispose()

LogAddEdge<T>(GraphEdge<T>)

Logs an edge addition operation.

public long LogAddEdge<T>(GraphEdge<T> edge)

Parameters

edge GraphEdge<T>

The edge being added.

Returns

long

The transaction ID for this operation.

Type Parameters

T

The numeric type.

LogAddNode<T>(GraphNode<T>)

Logs a node addition operation.

public long LogAddNode<T>(GraphNode<T> node)

Parameters

node GraphNode<T>

The node being added.

Returns

long

The transaction ID for this operation.

Type Parameters

T

The numeric type.

LogCheckpoint()

Logs a checkpoint (all data successfully persisted to disk).

public long LogCheckpoint()

Returns

long

The transaction ID for this checkpoint.

LogRemoveEdge(string)

Logs an edge removal operation.

public long LogRemoveEdge(string edgeId)

Parameters

edgeId string

The ID of the edge being removed.

Returns

long

The transaction ID for this operation.

LogRemoveNode(string)

Logs a node removal operation.

public long LogRemoveNode(string nodeId)

Parameters

nodeId string

The ID of the node being removed.

Returns

long

The transaction ID for this operation.

ReadLog()

Reads all WAL entries from the log file.

public List<WALEntry> ReadLog()

Returns

List<WALEntry>

List of WAL entries in order.

Truncate()

Truncates the WAL after a successful checkpoint.

public void Truncate()

Remarks

This removes old entries that have been successfully applied, keeping the WAL file from growing indefinitely.