Module version_chain 

Unified MVCC Version Chain Interface

This module defines the canonical interface for MVCC version chains across SochDB. Multiple implementations exist for different subsystems, but they share these traits.

Implementations

Implementation	Location	Use Case
VersionChain	sochdb_core::epoch_gc	Epoch-based GC with VecDeque
VersionChain	sochdb_storage::mvcc_snapshot	Snapshot-based visibility
VersionChain	sochdb_storage::version_store	Generic key-value MVCC
VersionChain	sochdb_storage::durable_storage	Binary-search optimized

Visibility Semantics

All implementations follow these MVCC visibility rules:

1. Read Committed: A version is visible if its creating transaction has committed before the reader’s start timestamp.

2. Snapshot Isolation: A version is visible if:

   • It was committed before the reader’s snapshot timestamp
   • It was not deleted, or deleted after the snapshot timestamp

3. Serializable (SSI): Adds read-write conflict detection on top of SI.

Structs

VersionMeta

Version metadata

VisibilityContext

Version visibility context

Traits

MvccVersionChain

Trait for MVCC version chain implementations

MvccVersionChainMut

Trait for mutable version chain operations

WriteConflictDetection

Trait for detecting write conflicts

Type Aliases

Timestamp

Logical timestamp type

TxnId

Transaction identifier type