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MySQL Cluster 7.5.2 has been released (part 2/2)

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-Sharding - Read & write scalability
  - Active-Active/Multi-Master geographic replication

  - 99.999% High Availability with no single point of failure
    and on-line maintenance
  - NoSQL and SQL APIs (including C++, Java, http, Memcached
    and JavaScript/Node.js)

MySQL Cluster 7.5.2 DMR, 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 Cluster NDB 7.5.2 (5.7.12-ndb-7.5.2) (2016-06-01,
Developer Milestone 3)

   MySQL Cluster NDB 7.5.2 is a new release of MySQL Cluster
   7.5, based on MySQL Server 5.7 and including features in
   version 7.5 of the NDB
   storage engine, as well as fixing recently discovered bugs in
   previous MySQL Cluster releases.

   Obtaining MySQL Cluster NDB 7.5.  MySQL Cluster NDB 7.5
   source code and binaries can be obtained from

   For an overview of changes made in MySQL Cluster NDB 7.5, see
   What is New in MySQL Cluster NDB 7.5
-new.html <http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-what-is-new.html>).

   This release also incorporates all bugfixes and changes made
   in previous MySQL Cluster releases, as well as all bugfixes
   and feature changes which were added in mainline MySQL 5.7
   through MySQL 5.7.12 (see Changes in MySQL 5.7.12
tml <http://dev.mysql.com/doc/relnotes/mysql/5.7/en/news-5-7-12.html>)).

   Bugs Fixed

     * Performance: A performance problem was found in an
       internal polling method do_poll() where the polling
       client did not check whether it had itself been woken up
       before completing the poll. Subsequent analysis showed
       that it is sufficient that only some clients in the
       polling queue receive data. do_poll() can then signal
       these clients and give up its polling rights, even if the
       maximum specified wait time (10 ms) has not expired.
       This change allows do_poll() to continue polling until
       either the maximum specified wait time has expired, or
       the polling client itself has been woken up (by receiving
       what it was waiting for). This avoids unnecessary thread
       switches between client threads and thus reduces the
       associated overhead by as much as 10% in the API client,
       resulting in a significant performance improvement when
       client threads perform their own polling. (Bug #81229,
       Bug #23202735)

     * Incompatible Change: When the data nodes are only
       partially connected to the API nodes, a node used for a
       pushdown join may get its request from a transaction
       coordinator on a different node, without (yet) being
       connected to the API node itself. In such cases, the
       NodeInfo object for the requesting API node contained no
       valid info about the software version of the API node,
       which caused the DBSPJ block to assume (incorrectly) when
       aborting to assume that the API node used NDB version
       7.2.4 or earlier, requiring the use of a backward
       compatability mode to be used during query abort which
       sent a node failure error instead of the real error
       causing the abort.
       Now, whenever this situation occurs, it is assumed that,
       if the NDB software version is not yet available, the API
       node version is greater than 7.2.4. (Bug #23049170)

     * Important Change: When started with the --initialize
ml#option_mysqld_initialize <http://dev.mysql.com/doc/refman/5.7/en/server-options.html#option_mysqld_initialize>) option, mysqld no longer
       enables the NDBCLUSTER
l <http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster.html>) storage engine plugin. This change was needed to
       prevent attempted initialization of system databases as
       distributed (rather than as specific to individual SQL
       nodes), which could result in a metadata lock deadlock.
       This fix also brings the behavior of --initialize in this
       regard into line with that of the discontinued
ml#option_mysqld_bootstrap <http://dev.mysql.com/doc/refman/5.7/en/server-options.html#option_mysqld_bootstrap>) option, which started a
       minimal mysqld instance without enabling NDB. (Bug

     * Microsoft Windows: ndb_mgmd failed to start on 32-bit
       Windows platforms, due to an issue with calling
       dynamically loaded functions; such issues were also
       likely to occur with other NDB programs using ndb_init().
       It was found that all of the functions used are already
       supported in targeted versions of Windows, so this
       problem is fixed by removing the dynamic loading of these
       functions and using the versions provided by the Windows
       header files instead. (Bug #80876, Bug #23014820)

     * Microsoft Windows: When building MySQL Cluster on Windows
       using more than one parallel build job it was sometimes
       possible for the build to fail because host_info.exe
       could not be be installed. To fix this problem, the
       install_mcc target is now always built prior to the
       host_info target. (Bug #80051, Bug #22566368)

     * Microsoft Windows: Performing ANALYZE TABLE
l <http://dev.mysql.com/doc/refman/5.7/en/analyze-table.html>) on a table having one or more indexes caused ndbmtd to
       fail with an InvalidAttrInfo error due to signal
       corruption. This issue occurred consistently on Windows,
       but could also be encountered on other platforms. (Bug
       #77716, Bug #21441297)

     * Reserved send buffer for the loopback transporter,
       introduced in MySQL Cluster NDB 7.4.8 and used by API and
       management nodes for administrative signals, was
       calculated incorrectly. (Bug #23093656)
       References: This issue is a regression of: Bug #21664515.

     * During a node restart, re-creation of internal triggers
       used for verifying the referential integrity of foreign
       keys was not reliable, because it was possible that not
       all distributed TC and LDM instances agreed on all
       trigger identities. To fix this problem, an extra step is
       added to the node restart sequence, during which the
       trigger identities are determined by querying the current
       master node. (Bug #23068914)
       References: See also: Bug #23221573.

     * Following the forced shutdown of one of the 2 data nodes
       in a cluster where NoOfReplicas=2
d-definition.html#ndbparam-ndbd-noofreplicas <http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-ndbd-definition.html#ndbparam-ndbd-noofreplicas>), the other
       data node shut down as well, due to arbitration failure.
       (Bug #23006431)

     * Aborting a CREATE LOGFILE GROUP
oup.html <http://dev.mysql.com/doc/refman/5.7/en/create-logfile-group.html>) statement which had failed due to lack of
       shared global memory was not performed correctly, causing
       node failure. In addition, the transaction in which this
       occurred was not rolled back correctly, also causing any
       subsequent CREATE LOGFILE GROUP to fail. (Bug #22982618)

     * The ndbinfo.tc_time_track_stats
info-tc-time-track-stats.html <http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-ndbinfo-tc-time-track-stats.html>) table uses histogram
       buckets to give a sense of the distribution of latencies.
       The sizes of these bucket were also reported as HISTOGRAM
       BOUNDARY INFO messages during data node startup; this
       printout was redundant and so has been removed. (Bug

     * Online upgrades from previous versions of MySQL Cluster
       to MySQL Cluster NDB 7.5 were not possible due to missing
       entries in the matrix used to test upgrade compatibility
       between versions. (Bug #22024947)

     * A failure occurred in DBTUP in debug builds when
       variable-sized pages for a fragment totalled more than 4
       GB. (Bug #21313546)

     * Restoration of metadata with ndb_restore -m
grams-ndb-restore.html#option_ndb_restore_restore_meta <http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-programs-ndb-restore.html#option_ndb_restore_restore_meta>)
       occasionally failed with the error message Failed to
       create index... when creating a unique index. While
       disgnosing this problem, it was found that the internal
       error PREPARE_SEIZE_ERROR (a temporary error) was
       reported as an unknown error. Now in such cases,
       ndb_restore retries the creation of the unique index, and
       PREPARE_SEIZE_ERROR is reported as NDB Error 748 Busy
       during read of event table. (Bug #21178339)
       References: See also: Bug #22989944.

     * mysqld did not shut down cleanly when executing
       ndb_index_stat. (Bug #21098142)

     * The following improvements were made to the data node
       error logging mechanism:

          + Increased the message slot size 499 bytes to 999
            bytes to prevent log messages from overwriting one
            another or from being truncated.

          + Added a Trace file name field to the output. This
            field contains the trace file name (without any
            path) and trace file number for the thread causing
            the trace.

          + ndbmtd trace files are also now shown in the error
       (Bug #21082710)

     * DBDICT and GETTABINFOREQ queue debugging were enhanced as

          + Monitoring by a data node of the progress of
            GETTABINFOREQ signals can be enabled by setting
r-ndbd-definition.html#ndbparam-ndbd-dicttrace <http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-ndbd-definition.html#ndbparam-ndbd-dicttrace>) >=

          + Added the ApiVerbose
r-api-definition.html#ndbparam-api-apiverbose <http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-api-definition.html#ndbparam-api-apiverbose>)
            configuration parameter, which enables NDB API debug
            logging for an API node where it is set greater than
            or equal to 2.

          + Added DUMP code 1229 which shows the current state
            of the GETTABINFOREQ queue. (See DUMP 1229
mp-command-1229.html <http://dev.mysql.com/doc/ndbapi/en/ndb-internals-dump-command-1229.html>).)
       See also The DBDICT Block
blocks-dbdict.html <http://dev.mysql.com/doc/ndbapi/en/ndb-internals-kernel-blocks-dbdict.html>). (Bug #20368450)
       References: See also: Bug #20368354.

     * When a write to the ndb_binlog_index table failed during
       a MySQL Server shutdown, mysqld killed the NDB binary
       logging thread. (Bug #81166, Bug #23142945)

     * Memory associated with table descriptions was not freed
       by the internal table information method
       NdbDictInterface::parseTableInfo(). (Bug #81141, Bug

     * Fixed a memory leak that occurred when an error was
       raised in ha_ndbcluster::get_metadata() or one of the
       functions which this method calls. (Bug #81045, Bug

     * An internal function used to validate connections failed
       to update the connection count when creating a new Ndb
       (http://dev.mysql.com/doc/ndbapi/en/ndb-ndb.html) object.
       This had the potential to create a new Ndb object for
       every operation validating the connection, which could
       have an impact on performance, particularly when
       performing schema operations. (Bug #80750, Bug #22932982)

     * A table scan on an NDB
l <http://dev.mysql.com/doc/refman/5.7/en/mysql-cluster.html>) table using neither an ordered index nor any Disk Data
       columns normally uses an ACC scan. If this happened while
       scanning an unique but unordered index which shrank (due
       to rows being deleted) after the scan started and then
       grew again (rows inserted), a single row that had been
       neither deleted nor inserted could be scanned twice. (Bug
       #80733, Bug #22926938)

     * Starting a backup in the ndb_mgm client after creating a
       large number of tables caused a forced shutdown of the
       cluster. (Bug #80640, Bug #228849958)

     * When an SQL node was started, and joined the schema
       distribution protocol, another SQL node, already waiting
       for a schema change to be distributed, timed out during
       that wait. This was because the code incorrectly assumed
       that the new SQL node would also acknowledge the schema
       distribution even though the new node joined too late to
       be a participant in it.
       As part of this fix, printouts of schema distribution
       progress now always print the more significant part of a
       bitmask before the less significant; formatting of
       bitmasks in such printouts has also been improved. (Bug
       #80554, Bug #22842538)

     * The ndb_print_file utility failed consistently on Solaris
       9 for SPARC. (Bug #80096, Bug #22579581)

     * The MySQL Cluster Auto-Installer failed to work in
       various ways on different platforms. (Bug #79853, Bug

     * The internal function ndbrequire(), which, like assert(),
       evaluates a given expression and terminates the process
       if the expression does not evaluate as true, now includes
       the failed expression in its output to the error logs.
       (Bug #77021, Bug #21128318)

     * Trying to drop a table during an ongoing backup failed
       with the error message Unknown table; now, it fails with
       Unable to alter table as backup is in progress. (Bug
       #47301, Bug #11755512)
       References: See also: Bug #44695, Bug #11753280.

     * Disk Data: The following improvements were made to
       logging during restarts by data nodes using MySQL Cluster
       Disk Data:

          + The total amount of undo log to be applied by the
            data node is now provided as the total number of
            pages present in the log. This is a worst case

          + Progress information is now provided at regular
            intervals (once for each 30000 records) as the undo
            log is applied. This information is supplied as the
            number of records and number of undo log pages
            applied so far during the current restart.
       (Bug #22513381)

     * Cluster API: Deletion of Ndb objects used a
       dispoportionately high amount of CPU. (Bug #22986823)

     * Cluster API: Executing a transaction with an
.html <http://dev.mysql.com/doc/ndbapi/en/ndb-ndbindexoperation.html>) based on an obsolete unique index caused the data
       node process to fail. Now the index is checked in such
       cases, and if it cannot be used the transaction fails
       with an appropriate error. (Bug #79494, Bug #22299443)

     * mysql_upgrade failed to upgrade the sys schema if a sys
       database directory existed but was empty. (Bug #81352,
       Bug #23249846, Bug #22875519)

On behalf of the MySQL RE Team,
Lars Tangvald