The replication issue affects some users of PostgreSQL binary replication, and can cause minor data loss between the master and the standby. While not all users are affected, it is difficult to predict when the bug will occur, so we urge all users of replication and continuous backup (PITR) to update immediately. Additionally, users who had replication running under PostgreSQL minor versions 9.3.0, 9.3.1, 9.2.5, 9.1.10, or 9.0.14 should plan to take a fresh base backup of each standby after update, in order to ensure no prior data corruption already exists.
This release also fixes two timing issues with VACUUM, which can cause old, overwritten or deleted rows to re-appear at a later date under some circumstances. Users with very high transaction rates, particularly those who experience "transaction ID wraparound" every few weeks or less, are the most at risk for this issue. Those users should set vacuum_freeze_table_age to 0, and run a database-wide VACUUM after the update. The second of the two VACUUM issues affects only 9.3, making it expecially important for 9.3 users to update.
43169be4f9