MySQL :: MySQL NDB Cluster 8.0 :: 2.4 What is New in MySQL NDB Cluster 8.0

Compatibility enhancements. The following changes reduce longstanding nonessential differences in NDB behavior as compared to that of other MySQL storage engines:

Development in parallel with MySQL server. Beginning with this release, MySQL NDB Cluster is being developed in parallel with the standard MySQL 8.0 server under a new unified release model with the following features:
- NDB 8.0 is developed in, built from, and released with the MySQL 8.0 source code tree.
- The numbering scheme for NDB Cluster 8.0 releases follows the scheme for MySQL 8.0.
- Building the source with NDB support appends -cluster to the version string returned by mysql -V, as shown here:
```
$> mysql -V
mysql  Ver 8.0.41-cluster for Linux on x86_64 (Source distribution)
```
  NDB binaries continue to display both the MySQL Server version and the NDB engine version, like this:
```
$> ndb_mgm -V
MySQL distrib mysql-8.0.41 ndb-8.0.41, for Linux (x86_64)
```
  In MySQL Cluster NDB 8.0, these two version numbers are always the same.
To build the MySQL source with NDB Cluster support, use the CMake option -DWITH_NDB (NDB 8.0.31 and later; for earlier releases, use -DWITH_NDBCLUSTER instead).
Platform support notes. NDB 8.0 makes the following changes in platform support:
- NDBCLUSTER no longer supports 32-bit platforms. Beginning with NDB 8.0.21, the NDB build process checks the system architecture and aborts if it is not a 64-bit platform.
- It is now possible to build NDB from source for 64-bit ARM CPUs. Currently, this support is source-only, and we do not provide any precompiled binaries for this platform.
Database and table names. NDB 8.0 removes the previous 63-byte limit on identifiers for databases and tables. These identifiers can now use up to 64 bytes, as for such objects using other MySQL storage engines. See Section 2.7.11, “Previous NDB Cluster Issues Resolved in NDB Cluster 8.0”.
Generated names for foreign keys. NDB now uses the pattern tbl_name_fk_N for naming internally generated foreign keys. This is similar to the pattern used by InnoDB.

Schema and metadata distribution and synchronization. NDB 8.0 makes use of the MySQL data dictionary to distribute schema information to SQL nodes joining a cluster and to synchronize new schema changes between existing SQL nodes. The following list describes individual enhancements relating to this integration work:

Schema distribution enhancements. The NDB schema distribution coordinator, which handles schema operations and tracks their progress, has been extended in NDB 8.0 to ensure that resources used during a schema operation are released at its conclusion. Previously, some of this work was done by the schema distribution client; this has been changed due to the fact that the client did not always have all needed state information, which could lead to resource leaks when the client decided to abandon the schema operation prior to completion and without informing the coordinator.
To help fix this issue, schema operation timeout detection has been moved from the schema distribution client to the coordinator, providing the coordinator with an opportunity to clean up any resources used during the schema operation. The coordinator now checks ongoing schema operations for timeout at regular intervals, and marks participants that have not yet completed a given schema operation as failed when detecting timeout. It also provides suitable warnings whenever a schema operation timeout occurs. (It should be noted that, after such a timeout is detected, the schema operation itself continues.) Additional reporting is done by printing a list of active schema operations at regular intervals whenever one or more of these operations is ongoing.
As an additional part of this work, a new mysqld option --ndb-schema-dist-timeout makes it possible to set the length of time to wait until a schema operation is marked as having timed out.
Disk data file distribution. NDB Cluster 8.0.14, uses the MySQL data dictionary to make sure that disk data files and related constructs such as tablespaces and log file groups are correctly distributed between all connected SQL nodes.
Schema synchronization of tablespace objects. When a MySQL Server connects as an SQL node to an NDB cluster, it checks its data dictionary against the information found in the NDB dictionary.
Previously, the only NDB objects synchronized on connection of a new SQL node were databases and tables; MySQL NDB Cluster 8.0 also implements schema synchronization of disk data objects including tablespaces and log file groups. Among other benefits, this eliminates the possibility of a mismatch between the MySQL data dictionary and the NDB dictionary following a native backup and restore, in which tablespaces and log file groups were restored to the NDB dictionary, but not to the MySQL Server's data dictionary.
It is also no longer possible to issue a CREATE TABLE statement that refers to a nonexistent tablespace. Such a statement now fails with an error.
Database DDL synchronization enhancements. Work done for NDB 8.0 insures that synchronization of databases by newly joined (or rejoined) SQL nodes with those on existing SQL nodes now makes proper use of the data dictionary so that any database-level operations (CREATE DATABASE, ALTER DATABASE, or DROP DATABASE) that may have been missed by this SQL node are now correctly duplicated on it when it connects (or reconnects) to the cluster.
As part of the schema synchronization procedure performed when starting, an SQL node now compares all databases on the cluster's data nodes with those in its own data dictionary, and if any of these is found to be missing from the SQL node's data dictionary, the SQL Node installs it locally by executing a CREATE DATABASE statement. A database thus created uses the default MySQL Server database properties (such as those as determined by character_set_database and collation_database) that are in effect on this SQL node at the time the statement is executed.
NDB metadata change detection and synchronization. NDB 8.0 implements a new mechanism for detection of updates to metadata for data objects such as tables, tablespaces, and log file groups with the MySQL data dictionary. This is done using a thread, the NDB metadata change monitor thread, which runs in the background and checks periodically for inconsistencies between the NDB dictionary and the MySQL data dictionary.
The monitor performs metadata checks every 60 seconds by default. The polling interval can be adjusted by setting the value of the ndb_metadata_check_interval system variable; polling can be disabled altogether by setting the ndb_metadata_check system variable to OFF. The status variable Ndb_metadata_detected_count shows the number of times since mysqld was last started that inconsistencies have been detected.
NDB ensures that NDB database, table, log file group, and tablespace objects submitted by the metadata change monitor thread during operations following startup are automatically checked for mismatches and synchronized by the NDB binlog thread.
NDB 8.0 adds two status variables relating to automatic synchronization: Ndb_metadata_synced_count shows the number of objects synchronized automatically; Ndb_metadata_excluded_count indicates the number of objects for which synchronization has failed (prior to NDB 8.0.22, this variable was named Ndb_metadata_blacklist_size). In addition, you can see which objects have been synchronized by inspecting the cluster log.
Setting the ndb_metadata_sync system variable to true overrides any settings that have been made for ndb_metadata_check_interval and ndb_metadata_check, causing the change monitor thread to begin continuous metadata change detection.
In NDB 8.0.22 and later, setting ndb_metadata_sync to true clears the list of objects for which synchronization has failed previously, which means it is no longer necessary to discover individual tables or to re-trigger synchronization by reconnecting the SQL node to the cluster. In addition, setting this variable to false clears the list of objects waiting to be retried.
Beginning with NDB 8.0.21, more detailed information about the current state of automatic synchronization than can be obtained from log messages or status variables is provided by two new tables added to the MySQL Performance Schema. The tables are listed here:
- ndb_sync_pending_objects: Contains information about database objects for which mismatches have been detected between the NDB dictionary and the MySQL data dictionary (and which have not been excluded from automatic synchronization).
- ndb_sync_excluded_objects: Contains information about NDB database objects which have been excluded because they cannot be synchronized between the NDB dictionary and the MySQL data dictionary, and thus require manual intervention.
A row in one of these tables provides the database object's parent schema, name, and type. Types of objects include schemas, tablespaces, log file groups, and tables. (If the object is a log file group or tablespace, the parent schema is NULL.) In addition, the ndb_sync_excluded_objects table shows the reason for which the object has been excluded.
These tables are present only if NDBCLUSTER storage engine support is enabled. For more information about these tables, see Performance Schema NDB Cluster Tables.
Changes in NDB table extra metadata. The extra metadata property of an NDB table is used for storing serialized metadata from the MySQL data dictionary, rather than storing the binary representation of the table as in previous versions. (This was a .frm file, no longer used by the MySQL Server—see MySQL Data Dictionary.) As part of the work to support this change, the available size of the table's extra metadata has been increased. This means that NDB tables created in NDB Cluster 8.0 are not compatible with previous NDB Cluster releases. Tables created in previous releases can be used with NDB 8.0, but cannot be opened afterwards by an earlier version.
This metadata is accessible using the NDB API methods getExtraMetadata() and setExtraMetadata().
For more information, see Section 3.7, “Upgrading and Downgrading NDB Cluster”.
On-the-fly upgrades of tables using .frm files. A table created in NDB 7.6 and earlier contains metadata in the form of a compressed .frm file, which is no longer supported in MySQL 8.0. To facilitate online upgrades to NDB 8.0, NDB performs on-the-fly translation of this metadata and writes it into the MySQL Server's data dictionary, which enables the mysqld in NDB Cluster 8.0 to work with the table without preventing subsequent use of the table by a previous version of the NDB software.

Important

Once a table's structure has been modified in NDB 8.0, its metadata is stored using the data dictionary, and it can no longer be accessed by NDB 7.6 and earlier.

This enhancement also makes it possible to restore an NDB backup made using an earlier version to a cluster running NDB 8.0 (or later).
Metadata consistency check error logging. As part of work previously done in NDB 8.0, the metadata check performed as part of auto-synchronization between the representation of an NDB table in the NDB dictionary and its counterpart in the MySQL data dictionary includes the table's name, storage engine, and internal ID. Beginning with NDB 8.0.23, the range of properties checked is expanded to include properties of the following data objects:
- Columns
- Indexes
- Foreign keys
In addition, details of any mismatches in metadata properties are now written to the MySQL server error log. The formats used for the error log messages differ slightly depending on whether the discrepancy is found on the table level or on the level of a column, index, or foreign key. The format for a log error resulting from a table-level property mismatch is shown here, where property is the property name, ndb_value is the property value as stored in the NDB dictionary, and mysqld_value is the value of the property as stored in the MySQL data dictionary:
```
Diff in 'property' detected, 'ndb_value' != 'mysqld_value'
```
For mismatches in properties of columns, indexes, and foreign keys, the format is as follows, where obj_type is one of column, index, or foreign key, and obj_name is the name of the object:
```
Diff in obj_type 'obj_name.property' detected, 'ndb_value' != 'mysqld_value'
```
Metadata checks are performed during automatic synchronization of NDB tables when they are installed in the data dictionary of any mysqld acting as an SQL node in an NDB Cluster. If the mysqld is debug-compiled, checks are also made whenever a CREATE TABLE statement is executed, and whenever an NDB table is opened.

Synchronization of user privileges with NDB_STORED_USER. A new mechanism for sharing and synchronizing users, roles, and privileges between SQL nodes is available in NDB 8.0, using the NDB_STORED_USER privilege. Distributed privileges as implemented in NDB 7.6 and earlier (see Distributed Privileges Using Shared Grant Tables) are no longer supported.

Once a user account is created on an SQL node, the user and its privileges can be stored in NDB and thus shared between all SQL nodes in the cluster by issuing a GRANT statement such as this one:

GRANT NDB_STORED_USER ON *.* TO 'jon'@'localhost';

NDB_STORED_USER always has global scope and must be granted using ON *.*. System reserved accounts such as mysql.session@localhost or mysql.infoschema@localhost cannot be assigned this privilege.

Roles can also be shared between SQL nodes by issuing the appropriate GRANT NDB_STORED_USER statement. Assigning such a role to a user does not cause the user to be shared; the NDB_STORED_USER privilege must be granted to each user explicitly.

A user or role having NDB_STORED_USER, along with its privileges, is shared with all SQL nodes as soon as they join a given NDB Cluster. It is possible to make such changes from any connected SQL node, but recommended practice is to do so from a designated SQL node only, since the order of execution of statements affecting privileges from different SQL nodes cannot be guaranteed to be the same on all SQL nodes.

Prior to NDB 8.0.27, changes to the privileges of a user or role were synchronized immediately with all connected SQL nodes. Beginning with MySQL 8.0.27, an SQL node takes a global read lock when updating privileges, which keeps concurrent changes executed by multiple SQL nodes from causing a deadlock.

Implications for upgrades. Due to changes in the MySQL server's privilege system (see Grant Tables), privilege tables using the NDB storage engine do not function correctly in NDB 8.0. It is safe but not necessary to retain such privilege tables created in NDB 7.6 or earlier, but they are no longer used for access control. In NDB 8.0, a mysqld acting as an SQL node and detecting such tables in NDB writes a warning to the MySQL server log, and creates InnoDB shadow tables local to itself; such shadow tables are created on each MySQL server connected to the cluster. When performing an upgrade from NDB 7.6 or earlier, the privilege tables using NDB can be removed safely using ndb_drop_table once all MySQL servers acting as SQL nodes have been upgraded (see Section 3.7, “Upgrading and Downgrading NDB Cluster”).

The ndb_restore utility's --restore-privilege-tables option is deprecated but continues to be honored in NDB 8.0, and can still be used to restore distributed privilege tables present in a backup taken from a previous release of NDB Cluster to a cluster running NDB 8.0. These tables are handled as described in the preceding paragraph.

Shared users and grants are stored in the ndb_sql_metadata table, which ndb_restore by default does not restore in NDB 8.0; you can specify the --include-stored-grants option to cause it to do so.

See Section 6.13, “Privilege Synchronization and NDB_STORED_USER”, for more information.

INFORMATION_SCHEMA changes. The following changes are made in the display of information regarding Disk Data files in the Information Schema FILES table:

Tablespaces and log file groups are no longer represented in the FILES table. (These constructs are not actually files.)
Each data file is now represented by a single row in the FILES table. Each undo log file is also now represented in this table by one row only. (Previously, a row was displayed for each copy of each of these files on each data node.)

In addition, INFORMATION_SCHEMA tables are now populated with tablespace statistics for MySQL Cluster tables. (Bug #27167728)

Error information with ndb_perror. The deprecated --ndb option for perror has been removed. Instead, use ndb_perror to obtain error message information from NDB error codes. (Bug #81704, Bug #81705, Bug #23523926, Bug #23523957)

Condition pushdown enhancements. Previously, condition pushdown was limited to predicate terms referring to column values from the same table to which the condition was being pushed. In NDB 8.0, this restriction is removed such that column values from tables earlier in the query plan can also be referred to from pushed conditions. NDB 8.0 supports joins comparing column expressions, as well as comparisons between columns in the same table. Columns and column expressions to be compared must be of exactly the same type; this means they must also be of the same signedness, length, character set, precision, and scale, whenever these attributes apply. Conditions being pushed could not be part of pushed joins prior to NDB 8.0.27, when this restriction is lifted.

Pushing down larger parts of a condition allows more rows to be filtered out by the data nodes, thereby reducing the number of rows which mysqld must handle during join processing. Another benefit of these enhancements is that filtering can be performed in parallel in the LDM threads, rather than in a single mysqld process on an SQL node; this has the potential to improve query performance significantly.

Existing rules for type compatibility between column values being compared continue to apply (see Engine Condition Pushdown Optimization).

Pushdown of outer joins and semijoins. Work done in NDB 8.0.20 allows many outer joins and semijoins, and not only those using a primary key or unique key lookup, to be pushed down to the data nodes (see Engine Condition Pushdown Optimization).

Outer joins using scans which can now be pushed include those which meet the following conditions:

There are no unpushed conditions on the table
There are no unpushed conditions on other tables in the same join nest, or in upper join nests on which it depends
All other tables in the same join nest, or in upper join nests on which it depends, are also pushed

A semijoin that uses an index scan can now be pushed if it meets the conditions just noted for a pushed outer join, and it uses the firstMatch strategy (see Optimizing IN and EXISTS Subquery Predicates with Semijoin Transformations).

These additional improvements are made in NDB 8.0.21:

Antijoins produced by the MySQL Optimizer through the transformation of NOT EXISTS and NOT IN queries (see Optimizing IN and EXISTS Subquery Predicates with Semijoin Transformations) can be pushed down to the data nodes by NDB.
This can be done when there is no unpushed condition on the table, and the query fulfills any other conditions which must be met for an outer join to be pushed down.
NDB attempts to identify and evaluate a non-dependent scalar subquery before trying to retrieve any rows from the table to which it is attached. When it can do so, the value obtained is used as part of a pushed condition, instead of using the subquery which provided the value.

Beginning with NDB 8.0.27, conditions pushed as part of a pushed query can now refer to columns from ancestor tables within the same pushed query, subject to the following conditions:

Pushed conditions may include any of the comparison operators <, <=, >, >=, =, and <>.
Values being compared must be of the same type, including length, precision, and scale.
NULL handling is performed according to the comparison semantics specified by the ISO SQL standard; any comparison with NULL returns NULL.

Consider the table created using the statement shown here:

CREATE TABLE t (
    x INT PRIMARY KEY, 
    y INT
) ENGINE=NDB;

A query such as SELECT * FROM t AS m JOIN t AS n ON m.x >= n.y can now use the engine condition pushdown optimization to push down the condition column y.

When a join cannot be pushed, EXPLAIN should provide the reason or reasons.

See Engine Condition Pushdown Optimization, for more information.

The NDB API methods branch_col_eq_param(), branch_col_ne_param(), branch_col_lt_param(), branch_col_le_param(), branch_col_gt_param(), and branch_col_ge_param() were added in NDB 8.0.27 as part of this work. These NdbInterpretedCode can be used to compare column values with values of parameters.

In addition, NdbScanFilter::cmp_param(), also added in NDB 8.0.27, makes it possible to define comparisons between column values and parameter values for use in performing scans.

Increase in maximum row size. NDB 8.0 increases the maximum number of bytes that can be stored in an NDBCLUSTER table from 14000 to 30000 bytes.

A BLOB or TEXT column continues to use 264 bytes of this total, as before.

The maximum offset for a fixed-width column of an NDB table is 8188 bytes; this is also unchanged from previous releases.

See Section 2.7.5, “Limits Associated with Database Objects in NDB Cluster”, for more information.

ndb_mgm SHOW command and single user mode. In NDB 8.0, when the cluster in single user mode, the output of the management client SHOW command indicates which API or SQL node has exclusive access while this mode is in effect.

Online column renames. Columns of NDB tables can now be renamed online, using ALGORITHM=INPLACE. See Section 6.12, “Online Operations with ALTER TABLE in NDB Cluster”, for more information.

Improved ndb_mgmd startup times. Start times for management nodes daemon have been significantly improved in NDB 8.0, in the following ways:

Due to replacing the list data structure formerly used by ndb_mgmd for handling node properties from configuration data with a hash table, overall startup times for the management server have been decreased by a factor of 6 or more.
In addition, in cases where data and SQL node host names not present in the management server's hosts file are used in the cluster configuration file, ndb_mgmd start times can be up to 20 times shorter than was previously the case.

NDB API enhancements. NdbScanFilter::cmp() and several comparison methods of NdbInterpretedCode can now be used to compare table column values with each other. The affected NdbInterpretedCode methods are listed here:

For all of the methods just listed, table column values to be compared much be of exactly matching types, including with respect to length, precision, signedness, scale, character set, and collation, as applicable.

See the descriptions of the individual API methods for more information.

Offline multithreaded index builds. It is now possible to specify a set of cores to be used for I/O threads performing offline multithreaded builds of ordered indexes, as opposed to normal I/O duties such as file I/O， compression， or decompression. “Offline” in this context refers to building of ordered indexes performed when the parent table is not being written to; such building takes place when an NDB cluster performs a node or system restart, or as part of restoring a cluster from backup using ndb_restore --rebuild-indexes.

In addition, the default behavior for offline index build work is modified to use all cores available to ndbmtd, rather limiting itself to the core reserved for the I/O thread. Doing so can improve restart and restore times and performance, availability, and the user experience.

This enhancement is implemented as follows:

The default value for BuildIndexThreads is changed from 0 to 128. This means that offline ordered index builds are now multithreaded by default.
The default value for TwoPassInitialNodeRestartCopy is changed from false to true. This means that an initial node restart first copies all data from a “live” node to one that is starting—without creating any indexes—builds ordered indexes offline, and then again synchronizes its data with the live node, that is, synchronizing twice and building indexes offline between the two synchronizations. This causes an initial node restart to behave more like the normal restart of a node, and reduces the time required for building indexes.
A new thread type (idxbld) is defined for the ThreadConfig configuration parameter, to allow locking of offline index build threads to specific CPUs.

In addition, NDB now distinguishes the thread types that are accessible to ThreadConfig by these two criteria:

Whether the thread is an execution thread. Threads of types main, ldm, recv, rep, tc, and send are execution threads; thread types io, watchdog, and idxbld are not.
Whether the allocation of the thread to a given task is permanent or temporary. Currently all thread types except idxbld are permanent.

For additional information, see the descriptions of the indicated parameters in the Manual. (Bug #25835748, Bug #26928111)

logbuffers table backup process information. 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)

ndbinfo.processes table on Windows. The process ID of the monitor process used on Windows platforms by RESTART to spawn and restart a mysqld is now shown in the processes table as an angel_pid.

String hashing improvements. Prior to NDB 8.0, all string hashing was based on first transforming the string into a normalized form, then MD5-hashing the resulting binary image. This could give rise to some performance problems, for the following reasons:

The normalized string is always space padded to its full length. For a VARCHAR, this often involved adding more spaces than there were characters in the original string.
The string libraries were not optimized for this space padding, which added considerable overhead in some use cases.
The padding semantics varied between character sets, some of which were not padded to their full length.
The transformed string could become quite large, even without space padding; some Unicode 9.0 collations can transform a single code point into 100 bytes or more of character data.
Subsequent MD5 hashing consisted mainly of padding with spaces, and was not particularly efficient, possibly causing additional performance penalties by flushing significant portions of the L1 cache.

A collation provides its own hash function, which hashes the string directly without first creating a normalized string. In addition, for a Unicode 9.0 collation, the hash is computed without padding. NDB now takes advantage of this built-in function whenever hashing a string identified as using a Unicode 9.0 collation.

Since, for other collations, there are existing databases which are hash partitioned on the transformed string, NDB continues to employ the previous method for hashing strings that use these, to maintain compatibility. (Bug #89590, Bug #89604, Bug #89609, Bug #27515000, Bug #27523758, Bug #27522732)

RESET MASTER changes. Because the MySQL Server now executes RESET MASTER with a global read lock, the behavior of this statement when used with NDB Cluster has changed in the following two respects:

It is no longer guaranteed to be synchronous; that is, it is now possible that a read coming immediately before RESET MASTER is issued may not be logged until after the binary log has been rotated.
It now behaves in exactly the same fashion, whether the statement is issued on the same SQL node that is writing the binary log, or on a different SQL node in the same cluster.

Note

SHOW BINLOG EVENTS, FLUSH LOGS, and most data definition statements continue, as they did in previous NDB versions, to operate in a synchronous fashion.

ndb_restore option usage. The --nodeid and --backupid options are now both required when invoking ndb_restore.

ndb_log_bin default. NDB 8.0 changes the default value of the ndb_log_bin system variable from TRUE to FALSE.

Dynamic transactional resource allocation. Allocation of resources in the transaction coordinator is now performed using dynamic memory pools. This means that resource allocation determined by data node configuration parameters such as MaxDMLOperationsPerTransaction, MaxNoOfConcurrentIndexOperations, MaxNoOfConcurrentOperations, MaxNoOfConcurrentScans, MaxNoOfConcurrentTransactions, MaxNoOfFiredTriggers, MaxNoOfLocalScans, and TransactionBufferMemory is now done in such a way that, if the load represented by each of these parameters is within the target load for all such resources, others of these resources can be limited so as not to exceed the total resources available.

As part of this work, several new data node parameters controlling transactional resources in DBTC, listed here, have been added:

See the descriptions of the parameters just listed for further information.

Backups using multiple LDMs per data node. NDB backups can now be performed in a parallel fashion on individual data nodes using multiple local data managers (LDMs). (Previously, backups were done in parallel across data nodes, but were always serial within data node processes.) No special syntax is required for the START BACKUP command in the ndb_mgm client to enable this feature, but all data nodes must be using multiple LDMs. This means that data nodes must be running ndbmtd (ndbd is single-threaded and thus always has only one LDM) and they must be configured to use multiple LDMs before taking the backup; you can do this by choosing an appropriate setting for one of the multi-threaded data node configuration parameters MaxNoOfExecutionThreads or ThreadConfig.

Backups using multiple LDMs create subdirectories, one per LDM, under the BACKUP/BACKUP-backup_id/ directory. ndb_restore now detects these subdirectories automatically, and if they exist, attempts to restore the backup in parallel; see Section 5.23.3, “Restoring from a backup taken in parallel”, for details. (Single-threaded backups are restored as in previous versions of NDB.) It is also possible to restore backups taken in parallel using an ndb_restore binary from a previous version of NDB Cluster by modifying the usual restore procedure; Section 5.23.3.2, “Restoring a parallel backup serially”, provides information on how to do this.

You can force the creation of single-threaded backups by setting the EnableMultithreadedBackup data node parameter to 0 for all data nodes in the [ndbd default] section of the cluster's global configuration file (config.ini).

Binary configuration file enhancements. NDB 8.0 uses a new format for the management server's binary configuration file. Previously, a maximum of 16381 sections could appear in the cluster configuration file; now the maximum number of sections is 4G. This is intended to support larger numbers of nodes in a cluster than was possible before this change.

Upgrades to the new format are relatively seamless, and should seldom if ever require manual intervention, as the management server continues to be able to read the old format without issue. A downgrade from NDB 8.0 to an older version of the NDB Cluster software requires manual removal of any binary configuration files or, alternatively, starting the older management server binary with the --initial option.

For more information, see Section 3.7, “Upgrading and Downgrading NDB Cluster”.

Increased number of data nodes. NDB 8.0 increases the maximum number of data nodes supported per cluster to 144 (previously, this was 48). Data nodes can now use node IDs in the range 1 to 144, inclusive.

Previously, the recommended node IDs for management nodes were 49 and 50. These are still supported for management nodes, but using them as such limits the maximum number of data nodes to 142; for this reason, it is now recommended that node IDs 145 and 146 are used for management nodes.

As part of this work, the format used for the data node sysfile has been updated to version 2. This file records information such as the last global checkpoint index, restart status, and node group membership of each node (see NDB Cluster Data Node File System Directory).

RedoOverCommitCounter and RedoOverCommitLimit changes. Due to ambiguities in the semantics for setting them to 0, the minimum value for each of the data node configuration parameters RedoOverCommitCounter and RedoOverCommitLimit has been increased to 1.

ndb_autoincrement_prefetch_sz changes. The default value of the ndb_autoincrement_prefetch_sz server system variable is increased to 512.

Changes in parameter maximums and defaults. NDB 8.0 makes the following changes in configuration parameter maximum and default values:

The maximum for DataMemory is increased to 16 terabytes.
The maximum for DiskPageBufferMemory is also increased to 16 terabytes.
The default value for StringMemory is increased to 25%.
The default for LcpScanProgressTimeout is increased to 180 seconds.

Disk Data checkpointing improvements. NDB Cluster 8.0 provides a number of new enhancements which help to reduce the latency of checkpoints of Disk Data tables and tablespaces when using non-volatile memory devices such as solid-state drives and the NVMe specification for such devices. These improvements include those in the following list:

Avoiding bursts of checkpoint disk writes
Speeding up checkpoints for disk data tablespaces when the redo log or the undo log becomes full
Balancing checkpoints to disk and in-memory checkpoints against one other, when necessary
Protecting disk devices from overload to help ensure low latency under high loads

As part of this work, two data node configuration parameters have been added. MaxDiskDataLatency places a ceiling on the degree of latency permitted for disk access and causes transactions taking longer than this length of time to be aborted. DiskDataUsingSameDisk makes it possible to take advantage of housing Disk Data tablespaces on separate disks by increasing the rate at which checkpoints of such tablespaces can be performed.

In addition, three new tables in the ndbinfo database provide information about Disk Data performance:

The diskstat table reports on writes to Disk Data tablespaces during the past second
The diskstats_1sec table reports on writes to Disk Data tablespaces for each of the last 20 seconds
The pgman_time_track_stats table reports on the latency of disk operations relating to Disk Data tablespaces

Memory allocation and TransactionMemory. A new TransactionMemory parameter simplifies allocation of data node memory for transactions as part of the work done to pool transactional and Local Data Manager (LDM) memory. This parameter is intended to replace several older transactional memory parameters which have been deprecated.

Transaction memory can now be set in any of the three ways listed here:

Several configuration parameters are incompatible with TransactionMemory. If any of these are set, TransactionMemory cannot be set (see Parameters incompatible with TransactionMemory), and the data node's transaction memory is determined as it was previous to NDB 8.0.

Note

Attempting to set TransactionMemory and any of these parameters concurrently in the config.ini file prevents the management server from starting.
If TransactionMemory is set, this value is used for determining transaction memory. TransactionMemory cannot be set if any of the incompatible parameters mentioned in the previous item have also been set.
If none of the incompatible parameters are set and TransactionMemory is also not set, transaction memory is set by NDB.

For more information, see the description of TransactionMemory, as well as Section 4.3.13, “Data Node Memory Management”.

Support for additional fragment replicas. NDB 8.0 increases the maximum number of fragment replicas supported in production from two to four. (Previously, it was possible to set NoOfReplicas to 3 or 4, but this was not officially supported or verified in testing.)

Restoring by slices. Beginning with NDB 8.0.20, it is possible to divide a backup into roughly equal portions (slices) and to restore these slices in parallel using two new options implemented for ndb_restore:

--num-slices determines the number of slices into which the backup should be divided.
--slice-id provides the ID of the slice to be restored by the current instance of ndb_restore.

This makes it possible to employ multiple instances of ndb_restore to restore subsets of the backup in parallel, potentially reducing the amount of time required to perform the restore operation.

For more information, see the description of the ndb_restore --num-slices option.

Read from any fragment replica enabled. Read from any fragment replica is enabled by default for all NDB tables. This means that the default value for the ndb_read_backup system variable is now ON, and that the value of the NDB_TABLE comment option READ_BACKUP is 1 when creating a new NDB table. Enabling read from any fragment replica significantly improves performance for reads from NDB tables, with minimal impact on writes.

For more information, see the description of the ndb_read_backup system variable, and Setting NDB Comment Options.

ndb_blob_tool enhancements. Beginning with NDB 8.0.20, the ndb_blob_tool utility can detect missing blob parts for which inline parts exist and replace these with placeholder blob parts (consisting of space characters) of the correct length. To check whether there are missing blob parts, use the --check-missing option with this program. To replace any missing blob parts with placeholders, use the --add-missing option.

For more information, see Section 5.6, “ndb_blob_tool — Check and Repair BLOB and TEXT columns of NDB Cluster Tables”.

ndbinfo versioning. NDB 8.0.20 and later supports versioning for ndbinfo tables, and maintains the current definitions for its tables internally. At startup, NDB compares its supported ndbinfo version with the version stored in the data dictionary. If the versions differ, NDB drops any old ndbinfo tables and recreates them using the current definitions.

Support for Fedora Linux. Beginning with NDB 8.0.20, Fedora Linux is a supported platform for NDB Cluster Community releases and can be installed using the RPMs supplied for this purpose by Oracle. These can be obtained from the NDB Cluster downloads page.

NDB programs—NDBT dependency removal. The dependency of a number of NDB utility programs on the NDBT library has been removed. This library is used internally for development, and is not required for normal use; its inclusion in these programs could lead to unwanted issues when testing.

Affected programs are listed here, along with the NDB versions in which the dependency was removed:

The principal effect of this change for users is that these programs no longer print NDBT_ProgramExit - status following completion of a run. Applications that depend upon such behavior should be updated to reflect the change when upgrading to the indicated versions.

Foreign keys and lettercasing. NDB stores the names of foreign keys using the case with which they were defined. Formerly, when the value of the lower_case_table_names system variable was set to 0, it performed case-sensitive comparisons of foreign key names as used in SELECT and other SQL statements with the names as stored. Beginning with NDB 8.0.20, such comparisons are now always performed in a case-insensitive fashion, regardless of the value of lower_case_table_names.

Multiple transporters. NDB 8.0.20 introduces support for multiple transporters to handle node-to-node communication between pairs of data nodes. This facilitates higher rates of update operations for each node group in the cluster, and helps avoid constraints imposed by system or other limitations on inter-node communications using a single socket.

By default, NDB now uses a number of transporters based on the number of local data management (LDM) threads or the number of transaction coordinator (TC) threads, whichever is greater. By default, the number of transporters is equal to half of this number. While the default should perform well for most workloads, it is possible to adjust the number of transporters employed by each node group by setting the NodeGroupTransporters data node configuration parameter (also introduced in NDB 8.0.20), up a maximum of the greater of the number of LDM threads or the number of TC threads. Setting it to 0 causes the number of transporters to be the same as the number of LDM threads.

ndb_restore: primary key schema changes. NDB 8.0.21 (and later) supports different primary key definitions for source and target tables when restoring an NDB native backup with ndb_restore when it is run with the --allow-pk-changes option. Both increasing and decreasing the number of columns making up the original primary key are supported.

When the primary key is extended with an additional column or columns, any columns added must be defined as NOT NULL, and no values in any such columns may be changed during the time that the backup is being taken. Because some applications set all column values in a row when updating it, whether or not all values are actually changed, this can cause a restore operation to fail even if no values in the column to be added to the primary key have changed. You can override this behavior using the --ignore-extended-pk-updates option also added in NDB 8.0.21; in this case, you must ensure that no such values are changed.

A column can be removed from the table's primary key whether or not this column remains part of the table.

For more information, see the description of the --allow-pk-changes option for ndb_restore.

Merging backups with ndb_restore. In some cases, it may be desirable to consolidate data originally stored in different instances of NDB Cluster (all using the same schema) into a single target NDB Cluster. This is now supported when using backups created in the ndb_mgm client (see Section 6.8.2, “Using The NDB Cluster Management Client to Create a Backup”) and restoring them with ndb_restore, using the --remap-column option added in NDB 8.0.21 along with --restore-data (and possibly additional compatible options as needed or desired). --remap-column can be employed to handle cases in which primary and unique key values are overlapping between source clusters, and it is necessary that they do not overlap in the target cluster, as well as to preserve other relationships between tables such as foreign keys.

--remap-column takes as its argument a string having the format db.tbl.col:fn:args, where db, tbl, and col are, respectively, the names of the database, table, and column, fn is the name of a remapping function, and args is one or more arguments to fn. There is no default value. Only offset is supported as the function name, with args as the integer offset to be applied to the value of the column when inserting it into the target table from the backup. This column must be one of INT or BIGINT; the allowed range of the offset value is the same as the signed version of that type (this allows the offset to be negative if desired).

The new option can be used multiple times in the same invocation of ndb_restore, so that you can remap to new values multiple columns of the same table, different tables, or both. The offset value does not have to be the same for all instances of the option.

In addition, two new options are provided for ndb_desc, also beginning in NDB 8.0.21:

--auto-inc (short form -a): Includes the next auto-increment value in the output, if the table has an AUTO_INCREMENT column.
--context (short form -x): Provides extra information about the table, including the schema, database name, table name, and internal ID.

For more information and examples, see the description of the --remap-column option.

Send thread improvements. As of NDB 8.0.20, each send thread now handles sends to a subset of transporters, and each block thread now assists only one send thread, resulting in more send threads, and thus better performance and data node scalability.

Adaptive spin control using SpinMethod. A simple interface for setting up adaptive CPU spin on platforms supporting it, using the SpinMethod data node parameter. This parameter (added in NDB 8.0.20, functional beginning with NDB 8.0.24) has four settings, one each for static spinning, cost-based adaptive spinning, latency-optimized adaptive spinning, and adaptive spinning optimized for database machines on which each thread has its own CPU. Each of these settings causes the data node to use a set of predetermined values for one or more spin parameters which enable adaptive spinning, set spin timing, and set spin overhead, as appropriate to a given scenario, thus obviating the need to set these directly for common use cases.

For fine-tuning spin behavior, it is also possible to set these and additional spin parameters directly, using the existing SchedulerSpinTimer data node configuration parameter as well as the following DUMP commands in the ndb_mgm client:

DUMP 104000 (SetSchedulerSpinTimerAll): Sets spin time for all threads
DUMP 104001 (SetSchedulerSpinTimerThread): Sets spin time for a specified thread
DUMP 104002 (SetAllowedSpinOverhead): Sets spin overhead as the number of units of CPU time allowed to gain 1 unit of latency
DUMP 104003 (SetSpintimePerCall): Sets the time for a call to spin
DUMP 104004 (EnableAdaptiveSpinning): Enables or disables adaptive spinning

NDB 8.0.20 also adds a new TCP configuration parameter TcpSpinTime which sets the time to spin for a given TCP connection.

The ndb_top tool is also enhanced to provide spin time information per thread.

For additional information, see the description of the SpinMethod parameter, the listed DUMP commands, and Section 5.29, “ndb_top — View CPU usage information for NDB threads”.

Disk Data and cluster restarts. Beginning with NDB 8.0.21, an initial restart of the cluster forces the removal of all Disk Data objects such as tablespaces and log file groups, including any data files and undo log files associated with these objects.

See Section 6.11, “NDB Cluster Disk Data Tables”, for more information.

Disk Data extent allocation. Beginning with NDB 8.0.20, allocation of extents in data files is done in a round-robin fashion among all data files used by a given tablespace. This is expected to improve distribution of data in cases where multiple storage devices are used for Disk Data storage.

For more information, see Section 6.11.1, “NDB Cluster Disk Data Objects”.

--ndb-log-fail-terminate option. Beginning with NDB 8.0.21, you can cause the SQL node to terminate whenever it is unable to log all row events fully. This can be done by starting mysqld with the --ndb-log-fail-terminate option.

AllowUnresolvedHostNames parameter. By default, a management node refuses to start when it cannot resolve a host name present in the global configuration file, which can be problematic in some environments such as Kubernetes. Beginning with NDB 8.0.22, it is possible to override this behavior by setting AllowUnresolvedHostNames to true in the [tcp default] section of the cluster global configuration file (config.ini file). Doing so causes such errors to be treated as warnings instead, and to permit ndb_mgmd to continue starting

Blob write performance enhancements. NDB 8.0.22 implements a number of improvements which allow more efficient batching when modifying multiple blob columns in the same row, or when modifying multiple rows containing blob columns in the same statement, by reducing the number of round trips required between an SQL or other API node and the data nodes when applying these modifications. The performance of many INSERT, UPDATE, and DELETE statements can thus be improved. Examples of such statements are listed here, where table is an NDB table containing one or more Blob columns:

INSERT INTO table VALUES ROW(1, blob_value1, blob_value2, ...), that is, insertion of a row containing one or more Blob columns
INSERT INTO table VALUES ROW(1, blob_value1), ROW(2, blob_value2), ROW(3, blob_value3), ..., that is, insertion of multiple rows containing one or more Blob columns
UPDATE table SET blob_column1 = blob_value1, blob_column2 = blob_value2, ...
UPDATE table SET blob_column = blob_value WHERE primary_key_column in (value_list), where the primary key column is not a Blob type
DELETE FROM table WHERE primary_key_column = value, where the primary key column is not a Blob type
DELETE FROM table WHERE primary_key_column IN (value_list), where the primary key column is not a Blob type

Other SQL statements may benefit from these improvements as well. These include LOAD DATA INFILE and CREATE TABLE ... SELECT .... In addition, ALTER TABLE table ENGINE = NDB, where table uses a storage engine other than NDB prior to execution of the statement, may also execute more efficiently.

This enhancement applies to statements affecting columns of MySQL type BLOB, MEDIUMBLOB, LONGBLOB, TEXT, MEDIUMTEXT, and LONGTEXT. Statements which update TINYBLOB or TINYTEXT columns (or both types) only are not affected by this work, and no changes in their performance should be expected.

The performance of some SQL statements is not noticeably improved by this enhancement, due to the fact that they require scans of table Blob columns, which breaks up batching. Such statements include those of the types listed here:

SELECT FROM table [WHERE key_column IN (blob_value_list)], where rows are selected by matching on a primary key or unique key column which uses a Blob type
UPDATE table SET blob_column = blob_value WHERE condition, using a condition which does not depend on a unique value
DELETE FROM table WHERE condition to delete rows containing one or more Blob columns, using a condition which does not depend on a unique value
A copying ALTER TABLE statement on a table which already used the NDB storage engine prior to executing the statement, and whose rows contain one or more Blob columns before or after the statement is executed (or both)

To take advantage of this improvement to its fullest extent, you may wish to increase the values used for the --ndb-batch-size and --ndb-blob-write-batch-bytes options for mysqld, to minimize the number of round trips required to modify blobs. For replication, it is also recommended that you enable the slave_allow_batching system variable, which minimizes the number of round trips required by the replica cluster to apply epoch transactions.

Note

Beginning with NDB 8.0.30, you should also use ndb_replica_batch_size instead of --ndb-batch-size, and ndb_replica_blob_write_batch_bytes rather than --ndb-blob-write-batch-bytes. See the descriptions of these variables, as well as Section 7.5, “Preparing the NDB Cluster for Replication”, for more information.

Node.js update. Beginning with NDB 8.0.22, the NDB adapter for Node.js is built using version 12.18.3, and only that version (or a later version of Node.js) is now supported.

Encrypted backups. NDB 8.0.22 adds support for backup files encrypted using AES-256-CBC; this is intended to protect against recovery of data from backups that have been accessed by unauthorized parties. When encrypted, backup data is protected by a user-supplied password. The password can be any string consisting of up to 256 characters from the range of printable ASCII characters other than !, ', ", $, %, \, and ^. Retention of the password used to encrypt any given NDB Cluster backup must be performed by the user or application; NDB does not save the password. The password can be empty, although this is not recommended.

When taking an NDB Cluster backup, you can encrypt it by using ENCRYPT PASSWORD=password with the management client START BACKUP command. Users of the MGM API can also initiate an encrypted backup by calling ndb_mgm_start_backup4().

You can encrypt existing backup files using the ndbxfrm utility which is added to the NDB Cluster distribution in the 8.0.22 release; this program can also be employed for decrypting encrypted backup files. In addition, ndbxfrm can compress backup files and decompress compressed backup files using the same method that is employed by NDB Cluster for creating backups when the CompressedBackup configuration parameter is set to 1.

To restore from an encrypted backup, use ndb_restore with the options --decrypt and --backup-password. Both options are required, along with any others that would be needed to restore the same backup if it were not encrypted. ndb_print_backup_file and ndbxfrm can also read encrypted files using, respectively, -P password and --decrypt-password=password.

In all cases in which a password is supplied together with an option for encryption or decryption, the password must be quoted; you can use either single or double quotation marks to delimit the password.

Beginning with NDB 8.0.24, several NDB programs, listed here, also support input of the password from standard input, similarly to how this is done when logging in interactively with the mysql client using the --password option (without including the password on the command line):

For ndb_restore and ndb_print_backup_file, the --backup-password-from-stdin option enables input of the password in a secure fashion, similar to how it is done by the mysql client' --password option. For ndb_restore, use the option together with the --decrypt option; for ndb_print_backup_file, use the option in place of the -P option.
For ndb_mgm the option --backup-password-from-stdin, is supported together with --execute "START BACKUP [options]" for starting a cluster backup from the system shell.
Two ndbxfrm options, --encrypt-password-from-stdin and --decrypt-password-from-stdin, cause similar behavior when using that program to encrypt or to decrypt a backup file.

See the descriptions of the programs just listed for more information.

It is also possible, beginning with NDB 8.0.22, to enforce encryption of backups by setting RequireEncryptedBackup=1 in the [ndbd default] section of the cluster global configuration file. When this is done, the ndb_mgm client rejects any attempt to perform a backup that is not encrypted.

Beginning with NDB 8.0.24, you can cause ndb_mgm to use encryption whenever it creates a backup by starting it with --encrypt-backup. In this case, the user is prompted for a password when invoking START BACKUP if none is supplied.

IPv6 support. Beginning with NDB 8.0.22, IPv6 addressing is supported for connections to management and data nodes; this includes connections between management and data nodes with SQL nodes. When configuring a cluster, you can use numeric IPv6 addresses, host names which resolve to IPv6 addresses or both.

For IPv6 addressing to work, the operating platform and network on which the cluster is deployed must support IPv6. As when using IPv4 addressing, hostname resolution to IPv6 addresses must be provided by the operating platform.

A known issue on Linux platforms when running NDB 8.0.22 and later was that the operating system kernel was required to provide IPv6 support, even when no IPv6 addresses were in use. This issue is fixed in NDB 8.0.34 and later, where it is safe to disable IPv6 support in the Linux kernel if you do not intend to use IPv6 addressing (Bug #33324817, Bug #33870642).

IPv4 addressing continues to be supported by NDB. Using IPv4 and IPv6 addresses concurrently is not recommended, but can be made to work in the following cases:

When the management node is configured with IPv6 and data nodes are configured with IPv4 addresses in the config.ini file: This works if --bind-address is not used with mgmd, and data nodes are started with --ndb-connectstring set to the IPv4 address of the management nodes.
When the management node is configured with IPv4 and data nodes are configured with IPv6 addresses in config.ini: Similarly to the other case, this works if --bind-address is not passed to mgmd and data nodes are started with --ndb-connectstring set to the IPv6 address of the management node.

These cases work because ndb_mgmd does not bind to any IP address by default.

To perform an upgrade from a version of NDB that does not support IPv6 addressing to one that does, provided that the network supports IPv4 and IPv6, first perform the software upgrade; after this has been done, you can update IPv4 addresses used in the config.ini file with IPv6 addresses. After this, to cause the configuration changes to take effect and to make the cluster start using the IPv6 addresses, it is necessary to perform a system restart of the cluster.

Auto-Installer deprecation and removal. The MySQL NDB Cluster Auto-Installer web-based installation tool (ndb_setup.py) is deprecated in NDB 8.0.22, and is removed in NDB 8.0.23 and later. It is no longer supported.

ndbmemcache deprecation and removal. ndbmemcache is no longer supported. ndbmemcache was deprecated in NDB 8.0.22, and removed in NDB 8.0.23.

ndbinfo backup_id table. NDB 8.0.24 adds a backup_id table to the ndbinfo information database. This is intended to serve as a replacement for obtaining this information by using ndb_select_all to dump the contents of the internal SYSTAB_0 table, which is error-prone and takes an excessively long time to perform.

This table has a single column and row containing the ID of the most recent backup of the cluster taken using the START BACKUP management client command. In the event that no backup of this cluster can be found, the table contains a single row whose column value is 0.

Table partitioning enhancements. NDB 8.0.23 introduces a new method for handling table partitions and fragments, which can determine the number of local data managers (LDMs) for a given data node independently of the number of redo log parts. This means that the number of LDMs can now be highly variable. NDB can employ this method when the ClassicFragmentation data node configuration parameter, also implemented in NDB 8.0.23, is set to false; when this is the case, the number of LDMs is no longer used to determine how many partitions to create for a table per data node, and the value of the PartitionsPerNode parameter (also introduced in NDB 8.0.23) determines this number instead, which is also used for calculating the number of fragments used for a table.

When ClassicFragmentation has its default value true, then the traditional method of using the number of LDMs is used to determine the number of fragments that a table should have.

For more information, see the descriptions of the new parameters referenced previously, in Multi-Threading Configuration Parameters (ndbmtd).

Terminology updates. To align with work begun in MySQL 8.0.21 and NDB 8.0.21, NDB 8.0.23 implements a number of changes in terminology, listed here:

The system variable ndb_slave_conflict_role is now deprecated. It is replaced by ndb_conflict_role.

Many NDB status variables are deprecated. These variables, and their replacements, are shown in the following table:

Table 2.1 Deprecated NDB status variables and their replacements

Deprecated variable	Replacement
`Ndb_api_adaptive_send_deferred_count_slave`	`Ndb_api_adaptive_send_deferred_count_replica`
`Ndb_api_adaptive_send_forced_count_slave`	`Ndb_api_adaptive_send_forced_count_replica`
`Ndb_api_adaptive_send_unforced_count_slave`	`Ndb_api_adaptive_send_unforced_count_replica`
`Ndb_api_bytes_received_count_slave`	`Ndb_api_bytes_received_count_replica`
`Ndb_api_bytes_sent_count_slave`	`Ndb_api_bytes_sent_count_replica`
`Ndb_api_pk_op_count_slave`	`Ndb_api_pk_op_count_replica`
`Ndb_api_pruned_scan_count_slave`	`Ndb_api_pruned_scan_count_replica`
`Ndb_api_range_scan_count_slave`	`Ndb_api_range_scan_count_replica`
`Ndb_api_read_row_count_slave`	`Ndb_api_read_row_count_replica`
`Ndb_api_scan_batch_count_slave`	`Ndb_api_scan_batch_count_replica`
`Ndb_api_table_scan_count_slave`	`Ndb_api_table_scan_count_replica`
`Ndb_api_trans_abort_count_slave`	`Ndb_api_trans_abort_count_replica`
`Ndb_api_trans_close_count_slave`	`Ndb_api_trans_close_count_replica`
`Ndb_api_trans_commit_count_slave`	`Ndb_api_trans_commit_count_replica`
`Ndb_api_trans_local_read_row_count_slave`	`Ndb_api_trans_local_read_row_count_replica`
`Ndb_api_trans_start_count_slave`	`Ndb_api_trans_start_count_replica`
`Ndb_api_uk_op_count_slave`	`Ndb_api_uk_op_count_replica`
`Ndb_api_wait_exec_complete_count_slave`	`Ndb_api_wait_exec_complete_count_replica`
`Ndb_api_wait_meta_request_count_slave`	`Ndb_api_wait_meta_request_count_replica`
`Ndb_api_wait_nanos_count_slave`	`Ndb_api_wait_nanos_count_replica`
`Ndb_api_wait_scan_result_count_slave`	`Ndb_api_wait_scan_result_count_replica`
`Ndb_slave_max_replicated_epoch`	`Ndb_replica_max_replicated_epoch`

The deprecated status variables continue to be shown in the output of SHOW STATUS, but applications should be updated as soon as possible not to rely upon them any longer, since their availability in future release series is not guaranteed.

The values ADD_TABLE_MASTER and ADD_TABLE_SLAVE previously shown in the tab_copy_status column of the ndbinfo ndbinfo.table_distribution_status table are deprecated. These are replaced by, respectively, the values ADD_TABLE_COORDINATOR and ADD_TABLE_PARTICIPANT.
The --help output of some NDB client and utility programs such as ndb_restore has been modified.

ThreadConfig enhancements. As of NDB 8.0.23, the configurability of the ThreadConfig parameter has been extended with two new thread types, listed here:

query: A query thread works (only) on READ COMMITTED queries. A query thread also acts as a recovery thread. The number of query threads must be 0, 1, 2, or 3 times the number of LDM threads. 0 (the default, unless using ThreadConfig, or AutomaticThreadConfig is enabled) causes LDMs to behave as they did prior to NDB 8.0.23.
recover: A recovery thread retrieves data from a local checkpoint. A recovery thread specified as such never acts as a query thread.

It is also possible to combine the existing main and rep threads in either of two ways:

Into a single thread by setting either one of these arguments to 0. When this is done, the resulting combined thread is shown with the name main_rep in the ndbinfo.threads table.
Together with the recv thread by setting both ldm and tc to 0, and setting recv to 1. In this case, the combined thread is named main_rep_recv.

In addition, the maximum numbers of a number of existing thread types have been increased. The new maximums, including those for query threads and recovery threads, are listed here:

LDM: 332
Query: 332
Recovery: 332
TC: 128
Receive: 64
Send: 64
Main: 2

Maximums for other thread types remain unchanged.

Also, as the result of work done relating to this task, NDB now employs mutexes to protect job buffers when using more than 32 block threads. While this can cause a slight decrease in performance (1 to 2 percent in most cases), it also significantly reduces the amount of memory required by very large configurations. For example, a setup with 64 threads which used 2 GB of job buffer memory prior to NDB 8.0.23 should require only about 1 GB instead in NDB 8.0.23 and later. In our testing this has resulted in an overall improvement on the order of 5 percent in the execution of very complex queries.

For further information, see the descriptions of the ThreadConfig parameter and the ndbinfo.threads table.

ThreadConfig thread count changes. As the result of work done in NDB 8.0.30, setting the value of ThreadConfig requires including main, rep, recv, and ldm in the ThreadConfig value string explicitly, in this and subsequent NDB Cluster releases. In addition, count=0 must be set explicitly for each thread type (of main, rep, or ldm) that is not to be used, and setting count=1 for replication threads (rep) requires also setting count=1 for main.

These changes can have a significant impact on upgrades of NDB clusters where this parameter is in use; see Section 3.7, “Upgrading and Downgrading NDB Cluster”, for more information.

ndbmtd Thread Auto-Configuration. Beginning with NDB 8.0.23, it is possible to employ automatic configuration of threads for multi-threaded data nodes using the ndbmtd configuration parameter AutomaticThreadConfig. When this parameter is set to 1, NDB sets up thread assignments automatically, based on the number of processors available to applications, for all thread supported thread types, including the new query and recover thread types described in the previous item. If the system does not limit the number of processors, you can do so if desired by setting NumCPUs (also added in NDB 8.0.23). Otherwise, automatic thread configuration accommodates up to 1024 CPUs.

Automatic thread configuration occurs regardless of any values set for ThreadConfig or MaxNoOfExecutionThreads in config.ini; this means that it is not necessary to set either of these parameters.

In addition, NDB 8.0.23 implements a number of new ndbinfo information database tables providing information about hardware and CPU availability, as well as CPU usage by NDB data nodes. These tables are listed here:

Some of these tables are not available on every platform supported by NDB Cluster; see the individual descriptions of them for more information.

Hierarchical views of NDB database objects. The dict_obj_tree table, added to the ndbinfo information database in NDB 8.0.24, can provide hierarchical and tree-like views of many NDB database objects, including the following:

Tables and associated indexes
Tablespaces and associated data files
Logfile groups and associated undo log files

For more information and examples, see Section 6.16.25, “The ndbinfo dict_obj_tree Table”.

Index statistics enhancements. NDB 8.0.24 implements the following improvements in calculation of index statistics:

Index statistics were previously collected from one fragment only; this is changed such that this extrapolation is extended to additional fragments.
The algorithm used for very small tables, such as those having very few rows where results are discarded, has been improved, so that estimates for such tables should be more accurate than previously.

As of NDB 8.0.27, the index statistics tables are created and updated automatically by default, IndexStatAutoCreate and IndexStatAutoUpdate both default to 1 (enabled) rather than 0 (disabled), and it is no longer necessary to run ANALYZE TABLE to update the statistics.

For additional information, see Section 6.15, “NDB API Statistics Counters and Variables”.

Conversion between NULL and NOT NULL during restore operations. Beginning with NDB 8.0.26, ndb_restore can support restoring of NULL columns as NOT NULL and the reverse, using the options listed here:

To restore a NULL column as NOT NULL, use the --lossy-conversions option.
The column originally declared as NULL must not contain any NULL rows; if it does, ndb_restore exits with an error.
To restore a NOT NULL column as NULL, use the --promote-attributes option.

For more information, see the descriptions of the indicated ndb_restore options.

SQL-compliant NULL comparison mode for NdbScanFilter. Traditionally, when making comparisons involving NULL, NdbScanFilter treats NULL as equal to NULL (and thus considers NULL == NULL to be TRUE). This is not the same as specified by the SQL Standard, which requires that any comparison with NULL return NULL, including NULL == NULL.

Previously, it was not possible for an NDB API application to override this behavior; beginning with NDB 8.0.26, you can do so by calling NdbScanFilter::setSqlCmpSemantics() prior to creating a scan filter. (Thus, this method is always invoked as a class method and not as an instance method.) Doing so causes the next NdbScanFilter object to be created to employ SQL-compliant NULL comparison for all comparison operations performed over the lifetime of the instance. You must invoke the method for each NdbScanFilter object that should use SQL-compliant comparisons.

For more information, see NdbScanFilter::setSqlCmpSemantics().

Deprecation of NDB API .FRM file methods. MySQL 8.0 and NDB 8.0 no longer use .FRM files for storing table metadata. For this reason, the NDB API methods getFrmData(), getFrmLength(), and setFrm() are deprecated as of NDB 8.0.27, and subject to removal in a future release. For reading and writing table metadata, use getExtraMetadata() and setExtraMetadata() instead.

Preference for IPv4 or IPv6 addressing. NDB 8.0.26 adds the PreferIPVersion configuration parameter, which controls the addressing preference for DNS resolution. IPv4 (PreferIPVersion=4) is the default. Because configuration retrieval in NDB requires that this preference be the same for all TCP connections, you should set it only in the [tcp default] section of the cluster global configuration (config.ini) file.

See Section 4.3.10, “NDB Cluster TCP/IP Connections”, for more information.

Logging enhancements. Previously, analysis of NDB Cluster data node and management node logs could be hampered by the fact that different log messages used different formats, and that not all log messages included timestamps. Such issues were due in part to the fact that logging was performed by a number of different mechanisms, such as the functions printf, fprintf, ndbout, and ndbout_c, overloading of the << operator, and so on.

We fix these problems by standardizing on the EventLogger mechanism, which is already present in NDB, and which begins each log message with a timestamp in YYYY-MM-DD HH:MM:SS format.

See Section 6.3, “Event Reports Generated in NDB Cluster”, for more information about NDB Cluster event logs and the EventLogger log message format.

Copying ALTER TABLE improvements. Beginning with NDB 8.0.27, a copying ALTER TABLE on an NDB table compares the fragment commit counts for the source table before and after performing the copy. This allows the SQL node executing this statement to determine whether there has been any concurrent write activity to the table being altered; if so, the SQL node can then terminate the operation.

When concurrent writes are detected being made to the table being altered, the ALTER TABLE statement is rejected with the error Detected change to data in source table during copying ALTER TABLE. Alter aborted to avoid inconsistency (ER_TABLE_DEF_CHANGED). Stopping the alter operation, rather than allowing it to proceed with concurrent writes taking place, can help prevent silent data loss or corruption.

ndbinfo index_stats table. NDB 8.0.28 adds the index_stats table, which provides basic information about NDB index statistics. It is intended primarily for internal testing, but may be useful as a supplement to ndb_index_stat.

ndb_import --table option. Prior to NDB 8.0.28, ndb_import always imported the data read from a CSV file into a table whose name was derived from the name of the file being read. NDB 8.0.28 adds a --table option (short form: -t) for this program to specify the name of the target table directly, and override the previous behavior.

The default behavior for ndb_import remains to use the base name of the input file as the name of the target table.

ndb_import --missing-ai-column option. Beginning with NDB 8.0.29, ndb_import can import data from a CSV file that contains empty values for an AUTO_INCREMENT column, using the --missing-ai-column option introduced in that release. The option can be used with one or more tables containing such a column.

In order for this option to work, the AUTO_INCREMENT column in the CSV file must not contain any values. Otherwise, the import operation cannot proceed.

ndb_import and empty lines. ndb_import has always rejected any empty lines encountered in an incoming CSV file. NDB 8.0.30 adds support for importing empty lines into a single column, provided that it is possible to convert the empty value into a column value.

ndb_restore --with-apply-status option. Beginning with NDB 8.0.29, it is possible to restore the ndb_apply_status table from an NDB backup, using ndb_restore with the --with-apply-status option added in that release. To use this option, you must also use --restore-data when invoking ndb_restore.

--with-apply-status restores all rows of the ndb_apply_status table except for the row having server_id = 0; to restore this row, use --restore-epoch. For more information, see ndb_apply_status Table, as the description of the --with-apply-status option.

SQL access to tables with missing indexes. Prior to NDB 8.0.29, when a user query attempted to open an NDB table with a missing or broken index, the MySQL server raised NDB error 4243 (Index not found). This situation could arise when constraint violations or missing data make it impossible to restore an index on an NDB table, and ndb_restore --disable-indexes was used to restore the data without the index.

Beginning with NDB 8.0.29, an SQL query against an NDB table which has missing indexes succeeds if the query does not use any of the missing indexes. Otherwise, the query is rejected with ER_NOT_KEYFILE. In this case, you can use ALTER TABLE ... ALTER INDEX ... INVISIBLE to keep the MySQL Optimizer from trying to use the index, or drop the index (and then possibly re-create it) using the appropriate SQL statements.

NDB API List::clear() method. The NDB API Dictionary methods listEvents(), listIndexes(), and listObjects() each require a reference to a List object which is empty. Previously, reusing an existing List with any of these methods was problematic for this reason. NDB 8.0.29 makes this easier by implementing a clear() method which removes all data from the list.

As part of this work, the List class destructor now calls List::clear() before removing any elements or attributes from the list.

NDB dictionary tables in ndbinfo. NDB 8.0.29 introduces several new tables in the ndbinfo database providing information from NdbDictionary that previously required the use of ndb_desc, ndb_select_all, and other NDB utility programs.

Two of these tables are actually views. The hash_maps table provides information about hash maps used by NDB; the files table shows information regarding files used for storing data on disk (see Section 6.11, “NDB Cluster Disk Data Tables”).

The remaining six ndbinfo tables added in NDB 8.0.29 are base tables. These tables are not hidden and are not named using the prefix ndb$. These tables are listed here, with descriptions of the objects represented in each table:

blobs: Blob tables used to store the variable-size parts of BLOB and TEXT columns
dictionary_columns: Columns of NDB tables
dictionary_tables: NDB tables
events: Event subscriptions in the NDB API
foreign_keys: Foreign keys on NDB tables
index_columns: Indexes on NDB tables

NDB 8.0.29 also makes changes in the ndbinfo storage engine's implementation of primary keys to improve compatibility with NdbDictionary.

ndbcluster plugin and Performance Schema. As of NDB 8.0.29, ndbcluster plugin threads are shown in the Performance Schema threads and setup_threads tables, making it possible to obtain information about the performance of these threads. The three threads exposed in performance_schema tables are listed here:

ndb_binlog: Binary logging thread
ndb_index_stat: Index statistics thread
ndb_metadata: Metadata thread

See ndbcluster Plugin Threads, for more information and examples.

In NDB 8.0.30 and later, transaction batching memory usage is visible as memory/ndbcluster/Thd_ndb::batch_mem_root in the Performance Schema memory_summary_by_thread_by_event_name and setup_instruments tables. You can use this information to see how much memory is being used by transactions. For additional information, see Transaction Memory Usage.

Configurable blob inline size. Beginning with NDB 8.0.30, it is possible to set a blob column's inline size as part of CREATE TABLE or ALTER TABLE. The maximum inline size supported by NDB Cluster is 29980 bytes.

For additional information and examples, see NDB_COLUMN Options, as well as String Type Storage Requirements.

replica_allow_batching enabled by default. Replica write batching improves NDB Cluster Replication performance greatly, especially when replicating blob-type columns (TEXT, BLOB, and JSON), and so generally should be enabled whenever using replication with NDB Cluster. For this reason, beginning with NDB 8.0.30, the replica_allow_batching system variable is enabled by default, and setting it to OFF raises a warning.

Conflict resolution insert operation support. Prior to NDB 8.0.30, there were only two strategies available for resolving primary key conflicts for update and delete operations, implemented as the functions NDB$MAX() and NDB$MAX_DELETE_WIN(). Neither of these has any effect on write operations, other than that a write operation with the same primary key as a previous write is always rejected, and accepted and applied only if no operation having the same primary key already exists. NDB 8.0.30 introduces two new conflict resolution functions NDB$MAX_INS() and NDB$MAX_DEL_WIN_INS() that handle primary key conflicts between insert operations. These functions handle conflicting writes as follows:

If there is no conflicting write, apply this one (this is the same as NDB$MAX()).
Otherwise, apply “greatest timestamp wins” conflict resolution, as follows:
1. If the timestamp for the incoming write is greater than that of the conflicting write, apply the incoming operation.
2. If the timestamp for the incoming write is not greater, reject the incoming write operation.

For conflicting update and delete operations, NDB$MAX_INS() behaves as NDB$MAX() does, and NDB$MAX_DEL_WIN_INS() behaves in the same way as NDB$MAX_DELETE_WIN().

This enhancement provides support for configuring conflict detection when handling conflicting replicated write operations, so that a replicated INSERT with a higher timestamp column value is applied idempotently, while a replicated INSERT with a lower timestamp column value is rejected.

As with the other conflict resolution functions, rejected operations can optionally be logged in an exceptions table; rejected operations increment a counter (status variables Ndb_conflict_fn_max for “greatest timestamp wins” and Ndb_conflict_fn_old for “same timestamp wins”).

For more information, see the descriptions of the new conflict resolution functions, and as well as Section 7.12, “NDB Cluster Replication Conflict Resolution”.

Replication applier batch size control. Previously, the size of batches used when writing to a replica NDB Cluster was controlled by --ndb-batch-size, and the batch size used for writing blob data to the replica was determined by ndb-blob-write-batch-bytes. One problem with this arrangement was that the replica used the global values of these variables which meant that changing either of them for the replica also affected the value used by all other sessions. In addition, it was not possible to set different defaults for these values exclusive to the replica, which should preferably have a higher default value than other sessions.

NDB 8.0.30 adds two new system variables which are specific to the replica applier. ndb_replica_batch_size now controls the batch size used for the replica applier, and ndb_replica_blob_write_batch_bytes variable now determines the blob write batch size used to perform batch blob writes on the replica.

This change should improve the behavior of MySQL NDB Cluster Replication using default settings, and lets the user fine tune NDB replication performance without affecting user threads, such as those performing processing of SQL queries.

For more information, see the descriptions of the new variables. See also Section 7.5, “Preparing the NDB Cluster for Replication”.

Binary Log Transaction Compression. NDB 8.0.31 adds support for binary logs using compressed transactions with ZSTD compression. To enable this feature, set the ndb_log_transaction_compression system variable introduced in this release to ON. The level of compression used can be controlled using the ndb_log_transaction_compression_level_zstd system variable, which is also added in that release; the default compression level is 3.

Although the binlog_transaction_compression and binlog_transaction_compression_level_zstd server system variables have no effect on binary logging of NDB tables, starting mysqld with --binlog-transaction-compression=ON causes ndb_log_transaction_compression to be enabled automatically. You can disable it in a MySQL client session using SET @@global.ndb_log_transaction_compression=OFF after server startup has completed.

See the description of ndb_log_transaction_compression as well as Binary Log Transaction Compression, for more information.

NDB Replication: Multithreaded Applier. As of NDB 8.0.33, NDB Cluster replication supports the MySQL multithreaded applier (MTA) on replica servers (and nonzero values of replica_parallel_workers), which enables the application of binary log transactions in parallel on the replica and thereby increasing throughput. (For more information about the multithreaded applier in the MySQL server, see Replication Threads.)

Enabling this feature on the replica requires that the source be started with --ndb-log-transaction-dependency set to ON (this option is also implemented in NDB 8.0.33). It is also necessary on the source to set binlog_transaction_dependency_tracking to WRITESET. In addition, you must ensure that replica_parallel_workers has a value greater than 1 on the replica, and thus, that the replica uses multiple worker threads.

For additional information and requirements, see Section 7.11, “NDB Cluster Replication Using the Multithreaded Applier”.

Changes in build options. NDB 8.0.31 makes the following changes in CMake options used for building MySQL Cluster.

The WITH_NDBCLUSTER option is deprecated, and WITH_PLUGIN_NDBCLUSTER is removed.
To build MySQL Cluster from source, use the newly-added WITH_NDB option.
WITH_NDBCLUSTER_STORAGE_ENGINE continues to be supported, but is no longer needed for most builds.

See CMake Options for Compiling NDB Cluster, for more information.

File system encryption. Transparent Data Encryption (TDE) provides protection by encryption of NDB data at rest, that is, of all NDB table data and log files which are persisted to disk. This is intended to protect against recovering data after obtaining unauthorized access to NDB Cluster data files such as tablespace files or logs.

Encryption is implemented transparently by the NDB file system layer (NDBFS) on the data nodes; data is encrypted and decrypted as it is read from and written to the file, and NDBFS internal client blocks operate on files as normal.

NDBFS can transparently encrypt a file directly from a user provided password, but decoupling the encryption and decryption of individual files from the user provided password can be advantageous for reasons of efficiency, usability, security, and flexibility. See Section 6.14.2, “NDB File System Encryption Implementation”.

TDE uses two types of keys. A secret key is used to encrypt the actual data and log files stored on disk (including LCP, redo, undo, and tablespace files). A master key is then used to encrypt the secret key.

The EncryptedFileSystem data node configuration parameter, available beginning with NDB 8.0.29, when set to 1, enforces encryption on files storing table data. This includes LCP data files, redo log files, tablespace files, and undo log files.

It is also necessary to provide a password to each data node when starting or restarting it, using one of the options --filesystem-password or --filesystem-password-from-stdin. See Section 6.14.1, “NDB File System Encryption Setup and Usage”. This password uses the same format and is subject to the same constraints as the password used for an encrypted NDB backup (see the description of the ndb_restore --backup-password option for details).

Only tables using the NDB storage engine are subject to encryption by this feature; see Section 6.14.3, “NDB File System Encryption Limitations”. Other tables, such as those used for NDB schema distribution, replication, and binary logging, typically use InnoDB; see InnoDB Data-at-Rest Encryption. For information about encryption of binary log files, see Encrypting Binary Log Files and Relay Log Files.

Files generated or used by NDB processes, such as operating system logs, crash logs, and core dumps, are not encrypted. Files used by NDB but not containing any user table data are also not encrypted; these include LCP control files, schema files, and system files (see NDB Cluster Data Node File System). The management server configuration cache is also not encrypted.

In addition, NDB 8.0.31 adds a new utility ndb_secretsfile_reader for extracting key information from a secrets file (S0.sysfile).

This enhancement builds on work done in NDB 8.0.22 to implement encrypted NDB backups. For more information about encrypted backups, see the description of the RequireEncryptedBackup configuration parameter, as well as Section 6.8.2, “Using The NDB Cluster Management Client to Create a Backup”.

Removal of unneeded program options. A number of “junk” command-line options for NDB utility and other programs which had never been implemented were removed in NDB Cluster 8.0.31. The options and the programs from which they have been dropped are listed here:

--ndb-optimized-node-selection:
ndbd, ndbmtd, ndb_mgm, ndb_delete_all, ndb_desc, ndb_drop_index, ndb_drop_table, ndb_show_table, ndb_blob_tool, ndb_config, ndb_index_stat, ndb_move_data, ndbinfo_select_all, ndb_select_count
--character-sets-dir:
ndb_mgm, ndb_mgmd, ndb_config, ndb_delete_all, ndb_desc, ndb_drop_index, ndb_drop_table, ndb_show_table, ndb_blob_tool, ndb_config, ndb_index_stat, ndb_move_data, ndbinfo_select_all, ndb_select_count, ndb_waiter
--core-file:
ndb_mgm, ndb_mgmd, ndb_config, ndb_delete_all, ndb_desc, ndb_drop_index, ndb_drop_table, ndb_show_table, ndb_blob_tool, ndb_config, ndb_index_stat, ndb_move_data, ndbinfo_select_all, ndb_select_count, ndb_waiter
--connect-retries and --connect-retry-delay:
ndb_mgmd
--ndb-nodeid:
ndb_config

For more information, see the relevant program and option descriptions in Chapter 5, NDB Cluster Programs.

Reading Configuration Cache Files. Beginning with NDB 8.0.32, it is possible to read binary configuration cache files created by ndb_mgmd using the ndb_config option --config-binary-file introduced in that release. This can simplify the process of determining whether the settings in a given configuration file have been applied to the cluster, or of recovery of settings from the binary cache after the config.ini file has somehow been damaged or lost.

For more information and examples, see the description of this option in Section 5.7, “ndb_config — Extract NDB Cluster Configuration Information”.

ndbinfo transporter_details table. This ndbinfo table provides information about individual transporters used in an NDB cluster. Added in NDB 8.0.37, it is otherwise similar to the ndbinfo transporters table.

Several additional columns were added to this table in NDB 8.0.38. These are listed here:

sendbuffer_used_bytes
sendbuffer_max_used_bytes
sendbuffer_alloc_bytes
sendbuffer_max_alloc_bytes
type

See Section 6.16.64, “The ndbinfo transporter_details Table”, for more information.

Binary log transaction cache sizing. NDB 8.0.40 adds the ndb_log_cache_size server system variable, which makes it possible to set the size of the transaction cache used for writing the binary log. This enables use of a large cache for logging NDB transactions, and (using binlog_cache_size) a smaller cache for logging other transactions, thus making more efficient use of resources.

Ndb.cfg file deprecation. Use of an Ndb.cfg file for setting the connection string for an NDB process was not well documented or supported. As of NDB 8.0.40, use of this file is now formally deprecated; you should expect support for it to be removed in a future release of MySQL Cluster.

2.4 What is New in MySQL NDB Cluster 8.0

What is New in NDB Cluster 8.0