Transactions

Full ACID-compliant transaction support with distributed capabilities.

Overview

HeliosDB provides comprehensive transaction support including: - Full ACID compliance - Multiple isolation levels - Distributed transactions with 2PC - Savepoints and nested transactions - XA transaction support

Quick Start

-- Basic transaction
BEGIN;
  UPDATE accounts SET balance = balance - 100 WHERE id = 1;
  UPDATE accounts SET balance = balance + 100 WHERE id = 2;
COMMIT;

-- With savepoints
BEGIN;
  INSERT INTO orders (customer_id, total) VALUES (1, 500);
  SAVEPOINT before_items;
  INSERT INTO order_items (order_id, product_id) VALUES (1, 100);
  -- Rollback to savepoint if needed
  ROLLBACK TO SAVEPOINT before_items;
COMMIT;

-- Serializable isolation
BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE;
  -- Conflicts automatically detected
COMMIT;

Isolation Levels

Level	Description	Performance
READ UNCOMMITTED	Dirty reads allowed	Fastest
READ COMMITTED	Default, no dirty reads	Fast
REPEATABLE READ	Snapshot isolation	Good
SERIALIZABLE	Full serializability	Safe

Features

Feature	Description
Savepoints	Partial rollback within transaction
Distributed 2PC	Two-phase commit across nodes
XA Transactions	External transaction coordinator support
Deadlock Detection	Automatic deadlock resolution
Lock-Free MVCC	High concurrency without blocking

Related

• MVCC: /docs/features/mvcc/
• Deadlock Prevention: /docs/guides/user/DEADLOCK_PREVENTION_OPERATIONS_GUIDE.md

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Status: Production Ready Version: v7.0