New MySQL Features: Data Dictionary, InnoDB, JSON, and Optimizer Boosts

1. Data Dictionary

Added a transactional data dictionary to store database object information.

Previously, dictionary data was stored in metadata files and non‑transactional tables.

2. Account Permission Management

Added support for “roles”; each role maps to a set of permissions, and roles can be added or removed, with permissions being added or deleted as needed.

Roles can be assigned to or removed from user accounts.

3. InnoDB Improvements

Improved management of the auto‑increment counter, allowing the initial value to be set and preserving it across server restarts; ROLLBACK no longer reuses the counter value.

The InnoDB memcached plugin now supports retrieving multiple key/value pairs in a single query and range queries.

Added dynamic configuration option innodb_deadlock_detect to disable deadlock detection, which can significantly slow the database under high concurrency.

All InnoDB temporary tables are created in a shared temporary tablespace.

SELECT ... FOR SHARE and SELECT ... FOR UPDATE now support the NOWAIT and SKIP LOCKED options; NOWAIT returns immediately if the requested row is locked, while SKIP LOCKED removes locked rows from the result set.

4. JSON Enhancements

Added inline path operator ->> , equivalent to applying JSON_UNQUOTE() to the result of JSON_EXTRACT() .

Introduced two JSON aggregation functions: JSON_ARRAYAGG() and JSON_OBJECTAGG() .

Added utility function JSON_PRETTY() to format JSON for better readability.

When ordering by JSON values, the length of each sort key is now variable instead of a fixed 1K, improving buffer space usage and key comparison performance.

5. Optimizer Improvements

Supported hidden indexes, allowing the optimizer to ignore them while they remain maintained for testing; useful for safely removing indexes.

Supported descending indexes via the DESC attribute, enabling efficient reverse‑order scans.