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MySQL 5.7 Reference Manual  /  ...  /  What is New in MySQL NDB Cluster 7.5

20.1.4 What is New in MySQL NDB Cluster 7.5

In this section, we describe changes in the implementation of NDB Cluster in MySQL NDB Cluster 7.5 as compared to NDB 7.4 and earlier release series. NDB Cluster 7.5 is available as a General Availability release beginning with NDB 7.5.4, and is recommended for new deployments. NDB Cluster 7.4 a recent General Availability release still supported for new deployments. NDB Cluster 7.3, is a previous GA release, still supported in production for existing deployments. NDB Cluster 7.2 is also a previous GA release series which is still supported in production. NDB 7.1 and earlier releases series are no longer maintained or supported in production. We recommend that new deployments use NDB Cluster 7.4 or NDB Cluster 7.5, which is the latest GA release. For information about features added in NDB 7.4, see What is New in NDB Cluster 7.4; What is New in NDB Cluster 7.4 contains information about features added in NDB 7.3. For information about NDB Cluster 7.2 and previous NDB Cluster releases, see What is New in MySQL NDB Cluster 7.2.

Major changes and new features in NDB Cluster 7.5 which are likely to be of interest are shown in the following list:

  • ndbinfo Enhancements.  A number of changes are made in the ndbinfo database, chief of which is that it now provides detailed information about NDB Cluster node configuration parameters.

    The config_params table has been made read-only, and has been enhanced with additional columns providing information about each configuration parameter, including the parameter's type, default value, maximum and minimum values (where applicable), a brief description of the parameter, and whether the parameter is required. This table also provides each parameter with a unique param_number.

    A row in the config_values table shows the current value of a given parameter on the node having a specified ID. The parameter is identified by the value of the config_param column, which maps to the config_params table's param_number.

    Using this relationship you can write a join on these two tables to obtain the default, maximum, minimum, and current values for one or more NDB Cluster configuration parameters by name. An example SQL statement using such a join is shown here:

    SELECT  p.param_name AS Name,
            v.node_id AS Node,
            p.param_type AS Type,
            p.param_default AS 'Default',
            p.param_min AS Minimum,
            p.param_max AS Maximum,
            CASE p.param_mandatory WHEN 1 THEN 'Y' ELSE 'N' END AS 'Required',
            v.config_value AS Current
    FROM    config_params p
    JOIN    config_values v
    ON      p.param_number = v.config_param
    WHERE   p. param_name IN ('NodeId', 'HostName','DataMemory', 'IndexMemory');
    

    For more information about these changes, see Section 20.5.10.7, “The ndbinfo config_params Table”. See Section 20.5.10.8, “The ndbinfo config_values Table”, for further information and examples.

    In addition, the ndbinfo database no longer depends on the MyISAM storage engine. All ndbinfo tables and views now use NDB (shown as NDBINFO).

    Several new ndbinfo tables were introduced in NDB 7.5.4. These tables are listed here, with brief descriptions:

    • dict_obj_info provides the names and types of database objects in NDB, as well as information about parent obejcts where applicable

    • table_distribution_status provides NDB table distribution status information

    • table_fragments provides information about the distribution of NDB table fragments

    • table_info provides information about logging, checkpointing, storage, and other options in force for each NDB table

    • table_replicas provides information about fragment replicas

    See the descriptions of the individual tables for more information.

  • Default row and column format changes.  Starting with NDB 7.5.1, the default value for both the ROW_FORMAT option and the COLUMN_FORMAT option for CREATE TABLE can be set to DYNAMIC rather than FIXED, using a new MySQL server variable ndb_default_column_format is added as part of this change; set this to FIXED or DYNAMIC (or start mysqld with the equivalent option --ndb-default-column-format=FIXED) to force this value to be used for COLUMN_FORMAT and ROW_FORMAT. Prior to NDB 7.5.4, the default for this variable was DYNAMIC; in this and later versions, the default is FIXED, which provides backwards compatibility with prior releases (Bug #24487363).

    The row format and column format used by existing table columns are unaffected by this change. New columns added to such tables use the new defaults for these (possibly overridden by ndb_default_column_format), and existing columns are changed to use these as well, provided that the ALTER TABLE statement performing this operation specifies ALGORITHM=COPY.

    Note

    A copying ALTER TABLE cannot be done implicitly if mysqld is run with --ndb-allow-copying-alter-table=FALSE.

  • ndb_binlog_index No Longer Dependent On MyISAM.  As of NDB 7.5.2, the ndb_binlog_index table employed in NDB Cluster Replication now uses the InnoDB storage engine instead of MyISAM. When upgrading, you can run mysql_upgrade with --force --upgrade-system-tables to cause it to execute ALTER TABLE ... ENGINE=INNODB on this table. Use of MyISAM for this table remains supported for backward compatibility.

    A benefit of this change is that it makes it possible to depend on transactional behavior and lock-free reads for this table, which can help alleviate concurrency issues during purge operations and log rotation, and improve the availability of this table.

  • ALTER TABLE Changes.  NDB Cluster formerly supported an alternative syntax for online ALTER TABLE. This is no longer supported in NDB Cluster 7.5, which makes exclusive use of ALGORITHM = DEFAULT|COPY|INPLACE for table DDL, as in the standard MySQL Server.

    Another change affecting the use of this statement is that ALTER TABLE ... ALGORITHM=INPLACE RENAME may now contain DDL operations in addition to the renaming.

  • ExecuteOnComputer Parameter Deprecated.  The ExecuteOnComputer configuration parameter for management nodes, data nodes, and API nodes has been deprecated and is now subject to removal in a future release of NDB Cluster. You should use the equivalent HostName parameter for all three types of nodes.

  • records-per-key Optimization.  The NDB handler now uses the records-per-key interface for index statistics implemented for the optimizer in MySQL 5.7.5. Some of the benefits from this change include those listed here:

    • The optimizer now chooses better execution plans in many cases where a less optimal join index or table join order would previously have been chosen

    • Row estimates shown by EXPLAIN are more accurate

    • Cardinality estimates shown by SHOW INDEX are improved

  • Connection Pool Node IDs.  NDB 7.5.0 adds the mysqld --ndb-cluster-connection-pool-nodeids option, which allows a set of node IDs to be set for the connection pool. This setting overrides --ndb-nodeid, which means that it also overrides both the --ndb-connectstring option and the NDB_CONNECTSTRING environment variable.

    Note

    You can set the size for the connection pool using the --ndb-cluster-connection-pool option for mysqld.

  • create_old_temporals Removed.  The create_old_temporals system variable was deprecated in NDB Cluster 7.4, and has now been removed.

  • ndb_mgm Client PROMPT Command.  NDB Cluster 7.5 adds a new command for setting the client's command-line prompt. The following example illustrates the use of the PROMPT command:

    ndb_mgm> PROMPT mgm#1:
    mgm#1: SHOW
    Cluster Configuration
    ---------------------
    [ndbd(NDB)]     4 node(s)
    id=5    @10.100.1.1  (mysql-5.7.18-ndb-7.5.7, Nodegroup: 0, *)
    id=6    @10.100.1.3  (mysql-5.7.18-ndb-7.5.7, Nodegroup: 0)
    id=7    @10.100.1.9  (mysql-5.7.18-ndb-7.5.7, Nodegroup: 1)
    id=8    @10.100.1.11  (mysql-5.7.18-ndb-7.5.7, Nodegroup: 1)
    
    [ndb_mgmd(MGM)] 1 node(s)
    id=50   @10.100.1.8  (mysql-5.7.18-ndb-7.5.7)
    
    [mysqld(API)]   2 node(s)
    id=100  @10.100.1.8  (5.7.18-ndb-7.5.7)
    id=101  @10.100.1.10  (5.7.18-ndb-7.5.7)
    
    mgm#1: PROMPT
    ndb_mgm> EXIT
    jon@valhaj:/usr/local/mysql/bin>
    

    For additional information and examples, see Section 20.5.2, “Commands in the NDB Cluster Management Client”.

  • Increased FIXED column storage per fragment.  NDB Cluster 7.5 and later supports a maximum of 128 TB per fragment of data in FIXED columns. In NDB Cluster 7.4 and earlier, this was 16 GB per fragment.

  • Deprecated Parameters Removed.  The following NDB Cluster data node configuration parameters were deprecated in previous releases of NDB Cluster, and were removed in NDB 7.5.0:

    • Id: deprecated in NDB 7.1.9; replaced by NodeId.

    • NoOfDiskPagesToDiskDuringRestartTUP, NoOfDiskPagesToDiskDuringRestartACC: both deprecated, had no effect; replaced in MySQL 5.1.6 by DiskCheckpointSpeedInRestart, which itself was later deprecated (in NDB 7.4.1) and is now also removed.

    • NoOfDiskPagesToDiskAfterRestartACC, NoOfDiskPagesToDiskAfterRestartTUP: both deprecated, had no effect; replaced in MySQL 5.1.6 by DiskCheckpointSpeed, which itself was later deprecated (in NDB 7.4.1) and is now also removed.

    • ReservedSendBufferMemory: deprecated in NDB 7.2.5; no longer had any effect.

    • MaxNoOfIndexes: archaic (pre-MySQL 4.1), had no effect; long since replaced by MaxNoOfOrderedIndexes or MaxNoOfUniqueHashIndexes.

    • Discless: archaic (pre-MySQL 4.1) synonym for and long since replaced by Diskless.

    The archaic and unused (and for this reason also previously undocumented) ByteOrder computer configuration parameter was also removed in NDB 7.5.0.

    The parameters just described are not supported in NDB 7.5. Attempting to use any of these parameters in an NDB Cluster configuration file now results in an error.

  • DBTC Scan Enhancements.  Scans have been improved by reducing the number of signals used for communication between the DBTC and DBDIH kernel blocks in NDB, enabling higher scalability of data nodes when used for scan operations by decreasing the use of CPU resources for scan operations, in some cases by an estimated five percent.

    Also as result of these changes response times should be greatly improved, which could help prevent issues with overload of the main threads. In addition, scans made in the BACKUP kernel block have also been improved and made more efficient than in previous releases.

  • JSON column support.  NDB 7.5.2 and later supports the JSON column type for NDB tables and the JSON functions found in the MySQL Server, subject to the limitation that an NDB table can have at most 3 JSON columns.

  • Read from any replica; specify number of hashmap partition fragments.  Previously, all reads were directed towards the primary replica except for simple reads. (A simple read is a reads that lock the row while reading it.) Beginning with NDB 7.5.2, it is possible to enabling reads from any replica. This is disabled by default but can be enabled for a given SQL node using the ndb_read_backup system variable added in this release.

    Previously, it was possible to define tables with only one type of partition mapping, with one primary partition on each LDM in each node, but in NDB 7.5.2 it becomes possible to be more flexible about the assignment of partitions by setting a partition balance (fragment count type). Possible balance schemes are one per node, one per node group, one per LDM per node, and one per LDM per node group.

    This setting can be controlled for individual tables by means of a PARTITION_BALANCE option (renamed from FRAGMENT_COUNT_TYPE in NDB 7.5.4) embedded in NDB_TABLE comments in CREATE TABLE or ALTER TABLE statements. Settings for table-level READ_BACKUP are also supported using this syntax. For more information and examples, see Section 14.1.18.9, “Setting NDB_TABLE Options in Table Comments”.

    In NDB API applications, a table's partition balance can also be get and set using methods supplied for this purpose; see Table::getPartitionBalance(), and Table::setPartitionBalance(), as well as Object::PartitionBalance, for more information about these.

    As part of this work, NDB 7.5.2 also introduces the ndb_data_node_neighbour system variable. This is intended for use, in transaction hinting, to provide a nearby data node to this SQL node.

    NDB 7.5.3 adds a further enhancement to READ_BACKUP: In this and later versions, it is possible to set READ_BACKUP for a given table online as part of ALTER TABLE ... ALGORITHM=INPLACE ....

  • ThreadConfig improvements.  A number of enhancements and feature additions are implemented in NDB 7.5.2 for the ThreadConfig multithreaded data node (ndbmtd) configuration parameter, including support for an increased number of platforms. These changes are described in the next few paragraphs.

    Non-exclusive CPU locking is now supported on FreeBSD and Windows, using cpubind and cpuset. Exclusive CPU locking is now supported on Solaris (only) using the cpubind_exclusive and cpuset_exclusive parameters which are introduced in this release.

    Thread prioritzation is now available, controlled by the new thread_prio parameter. thread_prio is supported on Linux, FreeBSD, Windows, and Solaris, and varies somewhat by platform. For more information, see the description of ThreadConfig.

    The realtime parameter is now supported on Windows platforms.

  • Partitions larger than 16 GB.  Due to an improvement in the hash index implementation used by NDB Cluster data nodes, partitions of NDB tables may now contain more than 16 GB of data for fixed columns, and the maximum partition size for fixed columns is now raised to 128 TB. The previous limitation was due to the fact that the DBACC block in the NDB kernel used only 32-bit references to the fixed-size part of a row in the DBTUP block, although 45-bit references to this data are used in DBTUP itself and elsewhere in the kernel outside DBACC; all such references in to the data handled in the DBACC block now use 45 bits instead.

  • Print SQL statements from ndb_restore.  NDB 7.5.4 adds the --print-sql-log option for the ndb_restore utility provided with the NDB Cluster distribution. This option enables SQL logging to stdout. Important: Every table to be restored using this option must have an explicitly defined primary key.

    See Section 20.4.21, “ndb_restore — Restore an NDB Cluster Backup”, for more information.

  • Organization of RPM packages.  Beginning with NDB 7.5.4, the naming and organization of RPM packages provided for NDB Cluster align more closely with those released for the MySQL server. The names of all NDB Cluster RPMs are now prefixed with mysql-cluster. Data nodes are now installed using the data-node package; management nodes are now installed from the management-server package; and SQL nodes require the server and common packages. MySQL and NDB client programs, including the mysql client and the ndb_mgm management client, are now included in the client RPM.

    For a detailed listing of NDB Cluster RPMs and other information, see Section 20.2.2.2, “Installing NDB Cluster from RPM”.

NDB Cluster 7.5 is also supported by MySQL Cluster Manager, which provides an advanced command-line interface that can simplify many complex NDB Cluster management tasks. See MySQL™ Cluster Manager 1.4.2 User Manual, for more information.


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