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MySQL NDB Cluster 7.6 Release Notes  /  Release Series Changelogs: MySQL NDB Cluster 7.6  /  Changes in MySQL NDB Cluster 7.6.7 (5.7.23-ndb-7.6.7) (2018-07-27, General Availability)

Changes in MySQL NDB Cluster 7.6.7 (5.7.23-ndb-7.6.7) (2018-07-27, General Availability)

Functionality Added or Changed

  • As part of ongoing work to improve handling of local checkpoints and minimize the occurrence of issues relating to Error 410 (REDO log overloaded) during LCPs, NDB now implements adaptive LCP control, which moderates LCP scan priority and LCP writes according to redo log usage.

    The following changes have been made with regard to NDB configuration parameters:

    • The default value of RecoveryWork is increased from 50 to 60 (60% of storage reserved for LCP files).

    • The new InsertRecoveryWork parameter controls the percentage of RecoveryWork that is reserved for insert operations. The default value is 40 (40% of RecoveryWork); the minimum and maximum are 0 and 70, respectively. Increasing this value allows for more writes during an LCP, while limiting the total size of the LCP. Decreasing InsertRecoveryWork limits the number of writes used during an LCP, but results in more space being used.

    Implementing LCP control provides several benefits to NDB deployments. Clusters should now survive heavy loads using default configurations much better than previously, and it should now be possible to run them reliably on systems where the available disk space is approximately 2.1 times the amount of memory allocated to the cluster (that is, the amount of DataMemory) or more. It is important to bear in mind that the figure just cited does not account for disk space used by tables on disk.

    During load testing into a single data node with decreasing redo log sizes, it was possible to successfully load a very large quantity of data into NDB with 16GB reserved for the redo log while using no more than 50% of the redo log at any point in time.

    See What is New in NDB Cluster 7.6, as well as the descriptions of the parameters mentioned previously, for more information. (Bug #90709, Bug #27942974, Bug #27942583)

    References: See also: Bug #27926532, Bug #27169282.

Bugs Fixed

  • ndbinfo Information Database: It was possible following a restart for (sometimes incomplete) fallback data to be used in populating the ndbinfo.processes table, which could lead to rows in this table with empty process_name values. Such fallback data is no longer used for this purpose. (Bug #27985339)

  • An NDB restore operation failed under the following conditions:

    • A data node was restarted

    • The local checkpoint for the fragment being restored used two .ctl files

    • The first of these .ctl files was the file in use

    • The LCP in question consisted of more than 2002 parts

    This happened because an array used in decompression of the .ctl file contained only 2002 elements, which led to memory being overwritten, since this data can contain up to 2048 parts. This issue is fixed by increasing the size of the array to accommodate 2048 elements. (Bug #28303209)

  • Local checkpoints did not always handle DROP TABLE operations correctly. (Bug #27926532)

    References: This issue is a regression of: Bug #26908347, Bug #26968613.

  • During the execution of CREATE TABLE ... IF NOT EXISTS, the internal open_table() function calls ha_ndbcluster::get_default_num_partitions() implicitly whenever open_table() finds out that the requested table already exists. In certain cases, get_default_num_partitions() was called without the associated thd_ndb object being initialized, leading to failure of the statement with MySQL error 157 Could not connect to storage engine. Now get_default_num_partitions() always checks for the existence of this thd_ndb object, and initializes it if necessary.