17.1 Introduction to InnoDB

InnoDB is a general-purpose storage engine that balances high reliability and high performance. In MySQL 8.4, InnoDB is the default MySQL storage engine. Unless you have configured a different default storage engine, issuing a CREATE TABLE statement without an ENGINE clause creates an InnoDB table.

Key Advantages of InnoDB

Its DML operations follow the ACID model, with transactions featuring commit, rollback, and crash-recovery capabilities to protect user data. See Section 17.2, “InnoDB and the ACID Model”.
Row-level locking and Oracle-style consistent reads increase multi-user concurrency and performance. See Section 17.7, “InnoDB Locking and Transaction Model”.
InnoDB tables arrange your data on disk to optimize queries based on primary keys. Each InnoDB table has a primary key index called the clustered index that organizes the data to minimize I/O for primary key lookups. See Section 17.6.2.1, “Clustered and Secondary Indexes”.
To maintain data integrity, InnoDB supports FOREIGN KEY constraints. With foreign keys, inserts, updates, and deletes are checked to ensure they do not result in inconsistencies across related tables. See Section 15.1.20.5, “FOREIGN KEY Constraints”.

Table 17.1 InnoDB Storage Engine Features

Feature	Support
B-tree indexes	Yes
Backup/point-in-time recovery (Implemented in the server, rather than in the storage engine.)	Yes
Cluster database support	No
Clustered indexes	Yes
Compressed data	Yes
Data caches	Yes
Encrypted data	Yes (Implemented in the server via encryption functions; In MySQL 5.7 and later, data-at-rest encryption is supported.)
Foreign key support	Yes
Full-text search indexes	Yes (Support for FULLTEXT indexes is available in MySQL 5.6 and later.)
Geospatial data type support	Yes
Geospatial indexing support	Yes (Support for geospatial indexing is available in MySQL 5.7 and later.)
Hash indexes	No (InnoDB utilizes hash indexes internally for its Adaptive Hash Index feature.)
Index caches	Yes
Locking granularity	Row
MVCC	Yes
Replication support (Implemented in the server, rather than in the storage engine.)	Yes
Storage limits	64TB
T-tree indexes	No
Transactions	Yes
Update statistics for data dictionary	Yes

To compare the features of InnoDB with other storage engines provided with MySQL, see the Storage Engine Features table in Chapter 18, Alternative Storage Engines.

InnoDB Enhancements and New Features

For information about InnoDB enhancements and new features, refer to:

The InnoDB enhancements list in Section 1.4, “What Is New in MySQL 8.4 since MySQL 8.0”.
The Release Notes.

Additional InnoDB Information and Resources

For InnoDB-related terms and definitions, see the MySQL Glossary.
For a forum dedicated to the InnoDB storage engine, see MySQL Forums::InnoDB.
InnoDB is published under the same GNU GPL License Version 2 (of June 1991) as MySQL. For more information on MySQL licensing, see http://www.mysql.com/company/legal/licensing/.