MySQLInnoDB

MySQLInnoDB is the transactional storage engine used by MySQL. It is designed to provide reliable data processing with features such as atomic transactions, row-level locking, multi-version concurrency control (MVCC), and support for foreign keys. InnoDB is the default storage engine in many modern MySQL releases, reflecting its emphasis on reliability and performance for transactional workloads.

InnoDB organizes data in tables with a clustered index on the primary key, so the data is stored together with the primary key in the index. Secondary indexes store the primary key as part of their entries. Tables can be stored in a shared system tablespace or in per-table tablespaces, controlled by configuration such as innodb_file_per_table. The InnoDB buffer pool caches frequently accessed data and indexes to speed up operations.

Durability and crash recovery are central to InnoDB. It uses a redo log to reproduce committed changes after a crash and undo logs to roll back uncommitted transactions, enabling crash-safe reads and writes. Transactions commit atomically, ensuring data integrity even in the face of unexpected failures. InnoDB supports ACID properties across multiple statements and connections.

Concurrency and referential integrity are managed through row-level locking and MVCC, enabling many transactions to proceed in parallel without locking reads. The default isolation level is usually REPEATABLE READ, and InnoDB enforces foreign key constraints with optional cascading actions to maintain referential integrity.

Additional features include online DDL for non-disruptive schema changes, partitioning support, and encryption in newer MySQL versions. InnoDB can be tuned via configuration of the buffer pool, log file sizes, and other parameters, and integrates with backup and replication workflows. Originating from Innobase Oy and later acquired by Oracle, InnoDB remains the core transactional engine for MySQL.