Following an upgrade to MySQL NDB Cluster 7.2.7 or later, it was not possible to downgrade online again to any previous version, due to a change in that version in the default size (number of LDM threads used) for NDB table hash maps. The fix for this issue makes the size configurable, with the addition of the DefaultHashMapSize configuration parameter.

To retain compatibility with an older release that does not support large hash maps, you can set this parameter in the cluster' config.ini file to the value used in older releases (240) before performing an upgrade, so that the data nodes continue to use smaller hash maps that are compatible with the older release. You can also now employ this parameter in MySQL NDB Cluster 7.0 and MySQL NDB Cluster 7.1 to enable larger hash maps prior to upgrading to MySQL NDB Cluster 7.2. For more information, see the description of the DefaultHashMapSize parameter. (Bug #14800539)

References: See also: Bug #14645319.

Important Change; NDB Cluster APIs: When checking—as part of evaluating an if predicate—which error codes should be propagated to the application, any error code less than 6000 caused the current row to be skipped, even those codes that should have caused the query to be aborted. In addition, a scan that aborted due to an error from DBTUP when no rows had been sent to the API caused DBLQH to send a SCAN_FRAGCONF signal rather than a SCAN_FRAGREF signal to DBTC. This caused DBTC to time out waiting for a SCAN_FRAGREF signal that was never sent, and the scan was never closed.

As part of this fix, the default ErrorCode value used by NdbInterpretedCode::interpret_exit_nok() has been changed from 899 (Rowid already allocated) to 626 (Tuple did not exist). The old value continues to be supported for backward compatibility. User-defined values in the range 6000-6999 (inclusive) are also now supported. You should also keep in mind that the result of using any other ErrorCode value not mentioned here is not defined or guaranteed.

See also The NDB Communication Protocol, and NDB Kernel Blocks, for more information. (Bug #16176006)

NDB Cluster APIs: The Ndb::computeHash() API method performs a malloc() if no buffer is provided for it to use. However, it was assumed that the memory thus returned would always be suitably aligned, which is not always the case. Now when malloc() provides a buffer to this method, the buffer is aligned after it is allocated, and before it is used. (Bug #16484617)

When using tables having more than 64 fragments in a MySQL NDB Cluster where multiple TC threads were configured (on data nodes running ndbmtd, using ThreadConfig), AttrInfo and KeyInfo memory could be freed prematurely, before scans relying on these objects could be completed, leading to a crash of the data node. (Bug #16402744)

References: See also: Bug #13799800. This issue is a regression of: Bug #14143553.

When started with --initial and an invalid --config-file (-f) option, ndb_mgmd removed the old configuration cache before verifying the configuration file. Now in such cases, ndb_mgmd first checks for the file, and continues with removing the configuration cache only if the configuration file is found and is valid. (Bug #16299289)

Executing a DUMP 2304 command during a data node restart could cause the data node to crash with a Pointer too large error. (Bug #16284258)

Including a table as a part of a pushed join should be rejected if there are outer joined tables in between the table to be included and the tables with which it is joined with; however the check as performed for any such outer joined tables did so by checking the join type against the root of the pushed query, rather than the common ancestor of the tables being joined. (Bug #16199028)

References: See also: Bug #16198866.

Some queries were handled differently with ndb_join_pushdown enabled, due to the fact that outer join conditions were not always pruned correctly from joins before they were pushed down. (Bug #16198866)

References: See also: Bug #16199028.

Data nodes could fail during a system restart when the host ran short of memory, due to signals of the wrong types (ROUTE_ORD and TRANSID_AI_R) being sent to the DBSPJ kernel block. (Bug #16187976)

Attempting to perform additional operations such as ADD COLUMN as part of an ALTER [ONLINE | OFFLINE] TABLE ... RENAME ... statement is not supported, and now fails with an ER_NOT_SUPPORTED_YET error. (Bug #16021021)

The mysql.server script exited with an error if the status command was executed with multiple servers running. (Bug #15852074)

Due to a known issue in the MySQL Server, it is possible to drop the PERFORMANCE_SCHEMA database. (Bug #15831748) In addition, when executed on a MySQL Server acting as a MySQL NDB Cluster SQL node, DROP DATABASE caused this database to be dropped on all SQL nodes in the cluster. Now, when executing a distributed drop of a database, NDB does not delete tables that are local only. This prevents MySQL system databases from being dropped in such cases. (Bug #14798043)

References: See also: Bug #15831748.

When performing large numbers of DDL statements (100 or more) in succession, adding an index to a table sometimes caused mysqld to crash when it could not find the table in NDB. Now when this problem occurs, the DDL statement should fail with an appropriate error.

A workaround in such cases may be to create the table with the index as part of the initial CREATE TABLE, rather than adding the index in a subsequent ALTER TABLE statement. (Bug #14773491)

Executing OPTIMIZE TABLE on an NDB table containing TEXT or BLOB columns could sometimes cause mysqld to fail. (Bug #14725833)

Executing a DUMP 1000 command that contained extra or malformed arguments could lead to data node failures. (Bug #14537622)

Exhaustion of LongMessageBuffer memory under heavy load could cause data nodes running ndbmtd to fail. (Bug #14488185)

The ndb_mgm client HELP command did not show the complete syntax for the REPORT command.