This release primarily fixes issues not successfully fixed in prior releases. It should be applied as soon as possible all users of major versions 9.3 and 9.4. Other users should apply at the next available downtime.
Crash Recovery Fixes:
Earlier update releases attempted to fix an issue in PostgreSQL 9.3 and 9.4 with "multixact wraparound", but failed to account for issues doing multixact cleanup during crash recovery. This could cause servers to be unable to restart after a crash. As such, all users of 9.3 and 9.4 should apply this update as soon as possible.
This release adds many new features which enhance PostgreSQL's flexibility, scalability and performance for many different types of database users, including improvements to JSON support, replication and index performance.