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MySQL NDB Cluster 7.4 Release Notes  /  Changes in MySQL NDB Cluster 7.4.15 (5.6.36-ndb-7.4.15) (2017-04-10, General Availability)

Changes in MySQL NDB Cluster 7.4.15 (5.6.36-ndb-7.4.15) (2017-04-10, General Availability)

MySQL NDB Cluster 7.4.15 is a new release of MySQL NDB Cluster 7.4, based on MySQL Server 5.6 and including features in version 7.4 of the NDB storage engine, as well as fixing recently discovered bugs in previous NDB Cluster releases.

Obtaining MySQL NDB Cluster 7.4.  MySQL NDB Cluster 7.4 source code and binaries can be obtained from https://dev.mysql.com/downloads/cluster/.

For an overview of changes made in MySQL NDB Cluster 7.4, see What is New in NDB Cluster 7.4.

This release also incorporates all bug fixes and changes made in previous NDB Cluster releases, as well as all bug fixes and feature changes which were added in mainline MySQL 5.6 through MySQL 5.6.36 (see Changes in MySQL 5.6.36 (2017-04-10, General Availability)).

Bugs Fixed

  • Partitioning: The output of EXPLAIN PARTITIONS displayed incorrect values in the partitions column when run on an explicitly partitioned NDB table having a large number of partitions.

    This was due to the fact that, when processing an EXPLAIN statement, mysqld calculates the partition ID for a hash value as (hash_value % number_of_partitions), which is correct only when the table is partitioned by HASH, since other partitioning types use different methods of mapping hash values to partition IDs. This fix replaces the partition ID calculation performed by mysqld with an internal NDB function which calculates the partition ID correctly, based on the table's partitioning type. (Bug #21068548)

    References: See also: Bug #25501895, Bug #14672885.

  • NDB Disk Data: Stale data from NDB Disk Data tables that had been dropped could potentially be included in backups due to the fact that disk scans were enabled for these. To prevent this possibility, disk scans are now disabled—as are other types of scans—when taking a backup. (Bug #84422, Bug #25353234)

  • NDB Disk Data: In some cases, setting dynamic in-memory columns of an NDB Disk Data table to NULL was not handled correctly. (Bug #79253, Bug #22195588)

  • CPU usage of the data node's main thread by the DBDIH master block as the end of a local checkpoint could approach 100% in certain cases where the database had a very large number of fragment replicas. This is fixed by reducing the frequency and range of fragment queue checking during an LCP. (Bug #25443080)

  • The ndb_print_backup_file utility failed when attempting to read from a backup file when the backup included a table having more than 500 columns. (Bug #25302901)

    References: See also: Bug #25182956.

  • Multiple data node failures during a partial restart of the cluster could cause API nodes to fail. This was due to expansion of an internal object ID map by one thread, thus changing its location in memory, while another thread was still accessing the old location, leading to a segmentation fault in the latter thread.

    The internal map() and unmap() functions in which this issue arose have now been made thread-safe. (Bug #25092498)

    References: See also: Bug #25306089.

  • There existed the possibility of a race condition between schema operations on the same database object originating from different SQL nodes; this could occur when one of the SQL nodes was late in releasing its metadata lock on the affected schema object or objects in such a fashion as to appear to the schema distribution coordinator that the lock release was acknowledged for the wrong schema change. This could result in incorrect application of the schema changes on some or all of the SQL nodes or a timeout with repeated waiting max ### sec for distributing... messages in the node logs due to failure of the distribution protocol. (Bug #85010, Bug #25557263)

    References: See also: Bug #24926009.

  • When a foreign key was added to or dropped from an NDB table using an ALTER TABLE statement, the parent table's metadata was not updated, which made it possible to execute invalid alter operations on the parent afterwards.

    Until you can upgrade to this release, you can work around this problem by running SHOW CREATE TABLE on the parent immediately after adding or dropping the foreign key; this statement causes the table's metadata to be reloaded. (Bug #82989, Bug #24666177)

  • Transactions on NDB tables with cascading foreign keys returned inconsistent results when the query cache was also enabled, due to the fact that mysqld was not aware of child table updates. This meant that results for a later SELECT from the child table were fetched from the query cache, which at that point contained stale data.

    This is fixed in such cases by adding all children of the parent table to an internal list to be checked by NDB for updates whenever the parent is updated, so that mysqld is now properly informed of any updated child tables that should be invalidated from the query cache. (Bug #81776, Bug #23553507)