Dear MySQL Users,

MySQL Cluster is the distributed, shared-nothing variant of MySQL.
This storage engine provides:
- In-Memory storage - Real-time performance (with optional
    checkpointing to disk)
  - Transparent Auto-Paritioning (Sharding) - Read & write scalability
  - Transactional consistency across partitioned and distributed datasets
  - Parallel cross partition queries such as joins
  - Active-Active/Multi-Master geographic replication
  - 99.9999% High Availability with on-line maintenance and no single point of
  - NoSQL and SQL APIs (including C++, Java, http, Memcached
    and JavaScript/Node.js)

MySQL Cluster 7.6.6 GA, 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.

The release notes are available from

MySQL Cluster enables users to meet the database challenges of next
generation web, cloud, and communications services with uncompromising
scalability, uptime and agility.

More details can be found at

Enjoy !

Changes in MySQL NDB Cluster 7.6.6 (5.7.22-ndb-7.6.6) (2018-05-31, General 

   MySQL NDB Cluster 7.6.6 is a new release of NDB 7.6, based on
   MySQL Server 5.7 and including features in version 7.6 of the
   NDB storage engine, as well as fixing recently discovered
   bugs in previous NDB Cluster releases.

   Obtaining NDB Cluster 7.6.  NDB Cluster 7.6 source code and
   binaries can be obtained from

   For an overview of changes made in NDB Cluster 7.6, see What
   is New in NDB Cluster 7.6

   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 5.7
   through MySQL 5.7.22 (see Changes in MySQL 5.7.22
   (2018-04-19, General Availability)

Functionality Added or Changed

     * When performing an NDB backup, the ndbinfo.logbuffers
       table now displays information regarding buffer usage by
       the backup process on each data node. This is implemented
       as rows reflecting two new log types in addition to REDO
       and DD-UNDO. One of these rows has the log type
       BACKUP-DATA, which shows the amount of data buffer used
       during backup to copy fragments to backup files. The
       other row has the log type BACKUP-LOG, which displays the
       amount of log buffer used during the backup to record
       changes made after the backup has started. One each of
       these log_type rows is shown in the logbuffers table for
       each data node in the cluster. Rows having these two log
       types are present in the table only while an NDB backup
       is currently in progress. (Bug #25822988)

     * Added the --logbuffer-size option for ndbd and ndbmtd,
       for use in debugging with a large number of log messages.
       This controls the size of the data node log buffer; the
       default (32K) is intended for normal operations.
       (Bug #89679, Bug #27550943)

     * The previously experimental shared memory (SHM)
       transporter is now supported in production. SHM works by
       transporting signals through writing them into memory,
       rather than on a socket. NDB already attempts to use SHM
       automatically between data nodes and API nodes sharing
       the same host. To enable explicit shared memory
       connections, set the UseShm SHM configuration parameter
       to true. When explicitly defining shared memory as the
       connection method, it is also necessary to identify the
       nodes at either end of the connection (NodeId1 and
       NodeId2 parameters), and to provide a shared memory key
       (ShmKey). In addition, to improve performance, it is also
       possible to set a spin time (ShmSpinTime) for the SHM
       Configuration of SHM is otherwise similar to that of the
       TCP transporter. NDB Cluster Shared-Memory Connections
       , provides additional information.

     * The SPJ kernel block now takes into account when it is
       evaluating a join request in which at least some of the
       tables are used in inner joins. This means that SPJ can
       eliminate requests for rows or ranges as soon as it
       becomes known that a preceding request did not return any
       results for a parent row. This saves both the data nodes
       and the SPJ block from having to handle requests and
       result rows which never take part in a result row from an
       inner join.
       When upgrading from NDB 7.6.5 or earlier, you should be
       aware that this optimization depends on both API client
       and data node functionality, and so is not available
       until all of these have been upgraded.

     * The poll receiver which NDB uses to read from sockets,
       execute messages from the sockets, and wake up other
       threads now offloads wakeup of other threads to a new
       thread that wakes up the other threads on request, and
       otherwise simply sleeps. This improves the scalability of
       a single cluster connection by keeping the receive thread
       from becoming overburdened by tasks including wakeup of
       other threads.

Bugs Fixed

     * Important Change; NDB Client Programs: ndb_top ignored
       short forms of command-line options, and did not in all
       cases handle misformed long options correctly. As part of
       the fix for these issues, the following changes have been
       made to command-line options used with ndb_top to bring
       them more into line with those used with other NDB
       Cluster and MySQL programs:

          + The --passwd option is removed, and replaced by
            --password (short form -p).

          + The short form -t for the --port option has been
            replaced by -P.

          + The short form -x for the --text option has been
            replaced by -t.
       (Bug #26907833)
       References: See also: Bug #88236, Bug #20733646.

     * NDB Cluster APIs: A previous fix for an issue, in which
       the failure of multiple data nodes during a partial
       restart could cause API nodes to fail, did not properly
       check the validity of the associated NdbReceiver object
       before proceeding. Now in such cases an invalid object
       triggers handling for invalid signals, rather than a node
       failure. (Bug #25902137)
       References: This issue is a regression of: Bug #25092498.

     * NDB Cluster APIs: Incorrect results, usually an empty
       result set, were returned when setBound() was used to
       specify a NULL bound. This issue appears to have been
       caused by a problem in gcc, limited to cases using the
       old version of this method (which does not employ
       NdbRecord), and is fixed by rewriting the problematic
       internal logic in the old implementation. (Bug #89468,
       Bug #27461752)

     * NDB Cluster APIs: Released NDB API objects are kept in
       one or more Ndb_free_list structures for later reuse.
       Each list also keeps track of all objects seized from it,
       and makes sure that these are eventually released back to
       it. In the event that the internal function
       NdbScanOperation::init() failed, it was possible for an
       NdbApiSignal already allocated by the NdbOperation to be
       leaked. Now in such cases, NdbScanOperation::release() is
       called to release any objects allocated by the failed
       NdbScanOperation before it is returned to the free list.
       This fix also handles a similar issue with
       NdbOperation::init(), where a failed call could also leak
       a signal. (Bug #89249, Bug #27389894)

     * NDB Client Programs: ndb_top did not support a number of
       options common to most NDB programs. The following
       options are now supported:

          + --defaults-file

          + --defaults-extra-file

          + --print-defaults

          + --no-defaults

          + --defaults-group-suffix
       In addition, ndb_top now supports a --socket option
       (short form -S) for specifying a socket file to use for
       the connection. (Bug #86614, Bug #26236298)

     * MySQL NDB ClusterJ: ClusterJ quit unexpectedly as there
       was no error handling in the scanIndex() function of the
       ClusterTransactionImpl class for a null returned to it
       internally by the scanIndex() method of the
       ndbTransaction class. (Bug #27297681, Bug #88989)

     * In some circumstances, when a transaction was aborted in
       the DBTC block, there remained links to trigger records
       from operation records which were not yet
       reference-counted, but when such an operation record was
       released the trigger reference count was still
       decremented. (Bug #27629680)

     * An NDB online backup consists of data, which is fuzzy,
       and a redo and undo log. To restore to a consistent state
       it is necessary to ensure that the log contains all of
       the changes spanning the capture of the fuzzy data
       portion and beyond to a consistent snapshot point. This
       is achieved by waiting for a GCI boundary to be passed
       after the capture of data is complete, but before
       stopping change logging and recording the stop GCI in the
       backup's metadata.
       At restore time, the log is replayed up to the stop GCI,
       restoring the system to the state it had at the
       consistent stop GCI. A problem arose when, under load, it
       was possible to select a GCI boundary which occurred too
       early and did not span all the data captured. This could
       lead to inconsistencies when restoring the backup; these
       could be be noticed as broken constraints or corrupted
       BLOB entries.
       Now the stop GCI is chosen is so that it spans the entire
       duration of the fuzzy data capture process, so that the
       backup log always contains all data within a given stop
       GCI. (Bug #27497461)
       References: See also: Bug #27566346.

     * For NDB tables, when a foreign key was added or dropped
       as a part of a DDL statement, the foreign key metatdata
       for all parent tables referenced should be reloaded in
       the handler on all SQL nodes connected to the cluster,
       but this was done only on the mysqld on which the
       statement was executed. Due to this, any subsequent
       queries relying on foreign key metadata from the
       corresponding parent tables could return inconsistent
       results. (Bug #27439587)
       References: See also: Bug #82989, Bug #24666177.

     * ANALYZE TABLE used excessive amounts of CPU on large,
       low-cardinality tables. (Bug #27438963)

     * Queries using very large lists with IN were not handled
       correctly, which could lead to data node failures.
       (Bug #27397802)

     * A data node overload could in some situations lead to an
       unplanned shutdown of the data node, which led to all
       data nodes disconnecting from the management and nodes.
       This was due to a situation in which API_FAILREQ was not
       the last received signal prior to the node failure.
       As part of this fix, the transaction coordinator's
       handling of SCAN_TABREQ signals for an ApiConnectRecord
       in an incorrect state was also improved. (Bug #27381901)
       References: See also: Bug #47039, Bug #11755287.

     * In a two-node cluster, when the node having the lowest ID
       was started using --nostart, API clients could not
       connect, failing with Could not alloc node id at HOST
       port PORT_NO: No free node id found for mysqld(API).
       (Bug #27225212)

     * Changing MaxNoOfExecutionThreads without an initial
       system restart led to an unplanned data node shutdown.
       (Bug #27169282)
       References: This issue is a regression of: Bug #26908347,
       Bug #26968613.

     * Race conditions sometimes occurred during asynchronous
       disconnection and reconnection of the transporter while
       other threads concurrently inserted signal data into the
       send buffers, leading to an unplanned shutdown of the
       As part of the work fixing this issue, the internal
       templating function used by the Transporter Registry when
       it prepares a send is refactored to use
       likely-or-unlikely logic to speed up execution, and to
       remove a number of duplicate checks for NULL.
       (Bug #24444908, Bug #25128512)
       References: See also: Bug #20112700.

     * ndb_restore sometimes logged data file and log file
       progress values much greater than 100%. (Bug #20989106)

     * The internal function BitmaskImpl::setRange() set one bit
       fewer than specified. (Bug #90648, Bug #27931995)

     * It was not possible to create an NDB table using
       FOR_RA_BY_LDM_X_3, or FOR_RA_BY_LDM_X_4. (Bug #89811, Bug
       References: This issue is a regression of: Bug #81759,
       Bug #23544301.

     * Adding a [tcp] or [shm] section to the global
       configuration file for a cluster with multiple data nodes
       caused default TCP connections to be lost to the node
       using the single section. (Bug #89627, Bug #27532407)

     * As a result of the reuse of code intended for send
       threads when performing an assist send, all of the local
       release send buffers were released to the global pool,
       which caused the intended level of the local send buffer
       pool to be ignored. Now send threads and assisting worker
       threads follow their own policies for maintaining their
       local buffer pools. (Bug #89119, Bug #27349118)

     * When sending priority A signals, we now ensure that the
       number of pending signals is explicitly initialized.
       (Bug #88986, Bug #27294856)

     * In a MySQL Cluster with one MySQL Server configured to
       write a binary log failure occurred when creating and
       using an NDB table with non-stored generated columns. The
       problem arose only when the product was built with
       debugging support. (Bug #86084, Bug #25957586)

     * ndb_restore --print_data --hex did not print trailing 0s
       of LONGVARBINARY values. (Bug #65560, Bug #14198580)

     * When the internal function
       ha_ndbcluster::copy_fk_for_offline_alter() checked
       dependent objects on a table from which it was supposed
       to drop a foreign key, it did not perform any filtering
       for foreign keys, making it possible for it to attempt
       retrieval of an index or trigger instead, leading to a
       spurious Error 723 (No such table).

On Behalf of the MySQL/Oracle Release Engineering Team,
Hery Ramilison

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