Prashant Tekriwal MySQL Cluster 7.4.16 has been released
Jul 19, 2017; 01:13
MySQL Cluster 7.4.16 has been released
Dear MySQL Users,
MySQL Cluster is the distributed, shared-nothing variant of MySQL. This storage engine provides:
MySQL Cluster 7.4 makes significant advances in performance; operational efficiency (such as enhanced reporting and faster restarts and upgrades) and conflict detection and resolution for active-active replication between MySQL Clusters.
MySQL Cluster 7.4.16 has been released and can be downloaded from
where you will also find Quick Start guides to help you get your first MySQL Cluster database up and running.
Changes in MySQL NDB Cluster 7.4.16 (5.6.37-ndb-7.4.16) (2017-07-18)
MySQL NDB Cluster 7.4.16 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 http://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 (http://dev.mysql.com/doc/refman/5.6/en/mysql-cluster-what-is-new-7-4.html).
This release also incorporates all bugfixes and changes made in previous NDB Cluster releases, as well as all bugfixes and feature changes which were added in mainline MySQL 5.6 through MySQL 5.6.37 (see Changes in MySQL 5.6.37 (Not yet released, General Availability) (http://dev.mysql.com/doc/relnotes/mysql/5.6/en/news-5-6-37.html)).
* Functionality Added or Changed
* Bugs Fixed
Functionality Added or Changed
* NDB Replication: Added the --ndb-log-update-minimal option for logging by mysqld. This option causes only primary key values to be written in the before image, and only changed columns in the after image. (Bug #24438868)
* Added the --diff-default option for ndb_config. This option causes the program to print only those parameters having values that differ from their defaults. (Bug #85831, Bug #25844166)
* Added the --query-all option to ndb_config. This option acts much like the --query option except that --query-all (short form: -a) dumps configuration information for all attributes at one time. (Bug #60095, Bug #11766869)
* NDB Replication: Added a check to stop an NDB replication slave when configuration as a multi-threaded slave is detected (for example, if slave_parallel_workers is set to a nonzero value). (Bug #21074209)
* NDB Cluster APIs: The implementation method NdbDictionary::NdbTableImpl::getColumn(), used from many places in the NDB API where a column is referenced by name, has been made more efficient. This method used a linear search of an array of columns to find the correct column object, which could be inefficient for tables with many columns, and was detected as a significant use of CPU in customer applications. (Ideally, users should perform name-to-column object mapping, and then use column IDs or objects in method calls, but in practice this is not always done.) A less costly hash index implementation, used previously for the name lookup, is reinstated for tables having relatively many columns. (A linear search continues to be used for tables having fewer columns, where the difference in performance is neglible.) (Bug #24829435)
* MySQL NDB ClusterJ: The JTie and NDB JTie tests were skipped when the unit tests for ClusterJ were being run. (Bug #26088583)
* Backup .log files contained log entries for one or more extra fragments, due to an issue with filtering out changes logged by other nodes in the same node group. This resulted in a larger .log file and thus use of more resources than necessary; it could also cause problems when restoring, since backups from different nodes could interfere with one another while the log was being applied. (Bug #25891014)
* When making the final write to a redo log file, it is expected that the next log file is already opened for writes, but this was not always the case with a slow disk, leading to node failure. Now in such cases NDB waits for the next file to be opened properly before attempting to write to it. (Bug #25806659)
* Data node threads can be bound to a single CPU or a set of CPUs, a set of CPUs being represented internally by NDB as a SparseBitmask. When attempting to lock to a set of CPUs, CPU usage was excessive due to the fact that the routine performing the locks used the mt_thr_config.cpp::do_bind() method, which looks for bits that are set over the entire theoretical range of the SparseBitmask (2^32-2, or 4294967294). This is fixed by using SparseBitmask::getBitNo(), which can be used to iterate over only those bits that are actually set, instead. (Bug #25799506)
* A bulk update is executed by reading records and executing a transaction on the set of records, which is started while reading them. When transaction initialization failed, the transaction executor function was subsequently unaware that this had occurred, leading to SQL node failures. This issue is fixed by providing appropriate error handling when attempting to initialize the transaction. (Bug #25476474) References: See also: Bug #20092754.
* Setting NoOfFragmentLogParts such that there were more than 4 redo log parts per local data manager led to resource exhaustion and subsequent multiple data node failures. Since this is an invalid configuration, a check has been added to detect a configuration with more than 4 redo log parts per LDM, and reject it as invalid. (Bug #25333414)
* Execution of an online ALTER TABLE ... REORGANIZE PARTITION statement on an NDB table having a primary key whose length was greater than 80 bytes led to restarting of data nodes, causing the reorganization to fail. (Bug #25152165)
* Error 240 is raised when there is a mismatch between foreign key trigger columns and the values supplied to them during trigger execution, but had no error message indicating the source of the problem. (Bug #23141739) References: See also: Bug #23068914, Bug #85857.
* If the number of LDM blocks was not evenly divisible by the number of TC/SPJ blocks, SPJ requests were not equally distributed over the available SPJ instances. Now a round-robin distribution is used to distribute SPJ requests across all available SPJ instances more effectively. As part of this work, a number of unused member variables have been removed from the class Dbtc. (Bug #22627519)
* ALTER TABLE .. MAX_ROWS=0 can now be performed only by using a copying ALTER TABLE statement. Resetting MAX_ROWS to 0 can no longer be performed using ALGORITHM=INPLACE or the ONLINE keyword. (Bug #21960004)
* During a system restart, when a node failed due to having missed sending heartbeats, all other nodes reported only that another node had failed without any additional information. Now in such cases, the fact that heartbeats were missed and the ID of the node that failed to send heartbeats is reported in both the error log and the data node log. (Bug #21576576)
* The planned shutdown of an NDB Cluster having more than 10 data nodes was not always performed gracefully. (Bug #20607730)
* Due to a previous issue with unclear separation between the optimize and execute phases when a query involved a GROUP BY, the join-pushable evaluator was not sure whether its optimized query execution plan was in fact pushable. For this reason, such grouped joins were always considered not pushable. It has been determined that the separation issue has been resolved by work already done in MySQL 5.6, and so we now remove this limitation. (Bug #86623, Bug #26239591)
* When deleting all rows from a table immediately followed by DROP TABLE, it was possible that the shrinking of the DBACC hash index was not ready prior to the drop. This shrinking is a per-fragment operation that does not check the state of the table. When a table is dropped, DBACC releases resources, during which the description of the fragment size and page directory is not consistent; this could lead to reads of stale pages, and undefined behavior. Inserting a great many rows followed by dropping the table should also have had such effects due to expansion of the hash index. To fix this problem we make sure, when a fragment is about to be released, that there are no pending expansion or shrinkage operations on this fragment. (Bug #86449, Bug #26138592)
* The internal function execute_signals() in mt.cpp read three section pointers from the signal even when none was passed to it. This was mostly harmless, although unneeded. When the signal read was the last one on the last page in the job buffer, and the next page in memory was not mapped or otherwise accessible, ndbmtd failed with an error. To keep this from occurring, this function now only reads section pointers that are actually passed to it. (Bug #86354, Bug #26092639)
* The ndb_show_tables program --unqualified option did not work correctly when set to 0 (false); this should disable the option and so cause fully qualified table and index names to be printed in the output. (Bug #86017, Bug #25923164)
* When an NDB table with foreign key constraints is created, its indexes are created first, and then, during foreign key creation, these indexes are loaded into the NDB dictionary cache. When a CREATE TABLE statement failed due to an issue relating to foreign keys, the indexes already in the cache were not invalidated. This meant that any subsequent CREATE TABLE with any indexes having the same names as those in the failed statement produced inconsistent results. Now, in such cases, any indexes named in the failed CREATE TABLE are immediately invalidated from the cache. (Bug #85917, Bug #25882950)
* Attempting to execute ALTER TABLE ... ADD FOREIGN KEY when the key to be added had the name of an existing foreign key on the same table failed with the wrong error message. (Bug #85857, Bug #23068914)
* The node internal scheduler (in mt.cpp) collects statistics about its own progress and any outstanding work it is performing. One such statistic is the number of outstanding send bytes, collected in send_buffer::m_node_total_send_buffer_size. This information may later be used by the send thread scheduler, which uses it as a metric to tune its own send performance versus latency. In order to reduce lock contention on the internal send buffers, they are split into two thr_send_buffer parts, m_buffer and m_sending, each protected by its own mutex, and their combined size repesented by m_node_total_send_buffer_size. Investigation of the code revealed that there was no consistency as to which mutex was used to update m_node_total_send_buffer_size, with the result that there was no consurrency protection for this value. To avoid this, m_node_total_send_buffer_size is replaced with two values, m_buffered_size and m_sending_size, which keep separate track of the sizes of the two buffers. These counters are updated under the protection of two different mutexes protecting each buffer individually, and are now added together to obtain the total size. With concurrency control established, updates of the partial counts should now be correct, so that their combined value no longer accumulates errors over time. (Bug #85687, Bug #25800933)
* Dropped TRANS_AI signals that used the long signal format were not handled by the DBTC kernel block. (Bug #85606, Bug #25777337) References: See also: Bug #85519, Bug #27540805.
* To prevent a scan from returning more rows, bytes, or both than the client has reserved buffers for, the DBTUP kernel block reports the size of the TRANSID_AI it has sent to the client in the TUPKEYCONF signal it sends to the requesting DBLQH block. DBLQH is aware of the maximum batch size available for the result set, and terminates the scan batch if this has been exceeded. The DBSPJ block's FLUSH_AI attribute allows DBTUP to produce two TRANSID_AI results from the same row, one for the client, and one for DBSPJ, which is needed for key lookups on the joined tables. The size of both of these were added to the read length reported by the DBTUP block, which caused the controlling DBLQH block to believe that it had consumed more of the available maximum batch size than was actually the case, leading to premature termination of the scan batch which could have a negative impact on performance of SPJ scans. To correct this, only the actual read length part of an API request is now reported in such cases. (Bug #85408, Bug #25702850)
* When compiling the NDB kernel with gcc version 6.0.0 or later, it is now built using -flifetime-dse=1. (Bug #85381, Bug #25690926)
On Behalf of Oracle MySQL Release Engineering Team Prashant Tekriwal
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