MySQL

Notes: For a full list of changes go here. Upgrade from MySQL 5.7 to MySQL 8.0 is only supported using the in-place upgrade method. Downgrade from MySQL 8.0 to MySQL 5.7 (or from a MySQL 8.0 release to a previous MySQL 8.0 release) is not supported. The only supported alternative is to restore a backup taken before upgrading.

Bugs Fixed:

• NDB Cluster: EXPLAIN of a query executed with table access type eq_ref could also show a condition being pushed down, even when condition pushdown was not supported for the query. Now the access type is checked before NDB checks the condition for a possible pushdown optimization.
• This fix does not affect handling of tables which are part of a pushed join, for which NDB continues to support pushed conditions as before.
• InnoDB: Undo tablespaces remained unencrypted after enabling undo tablespace encryption at startup.
• InnoDB: Problematic macros introduced with undo tablespace DDL support in MySQL 8.0.14 were revised.
• InnoDB: Static thread local variables defined at the wrong scope were not released at thread exit.
• InnoDB: The performance_schema.data_locks LOCK_DATA column only showed the secondary index values of the locked record for a lock placed on a unique secondary index, which was not sufficient to ensure the uniqueness of identified records. The clustered index column values of the locked record are now appended.
• InnoDB: An incorrect count of transactions using a rollback segment for recovery of an XA transaction prevented an undo tablespace truncation operation from proceeding and left the purge thread busy checking for the undo tablespace to become empty.
• InnoDB: Invalid assertions were raised at startup after a failure to retrieve the space ID of a compressed file-per-table tablespace. The invalid assertion code was removed.
• InnoDB: Optimized InnoDB internal temporary tables did not support in-place UPDATE operations, which caused the number of delete-marked records to increase continuously. The large number of delete-marked records could cause longer than expected query execution times.
• InnoDB: The std::sort function in the Variance-Aware Transaction Scheduling (VATS) algorithm was replaced by the std::stable_sort function to preserve the original FIFO order for transactions of equal weight.
• InnoDB: Write-ahead did not work as expected due to an incorrectly initialized variable.