Changes in MySQL NDB Cluster 7.5.3 (5.7.13-ndb-7.5.3) (2016-07-08, Release Candidate)

• Functionality Added or Changed

• Bugs Fixed

Functionality Added or Changed

• Important Change: It is now possible to set READ_BACKUP for an existing table online using an SQL statement such as ALTER TABLE ... ALGORITHM=INPLACE, COMMENT="NDB_TABLE=READ_BACKUP=1". See Setting NDB Comment Options, for further information about the READ_BACKUP option. (Bug #80858, Bug #23001617)

  References: See also: Bug #18435416.

• Added three new tables to the ndbinfo information database to provide running information about locks and lock attempts in an active MySQL NDB Cluster. These tables, with brief descriptions, are listed here:

  • cluster_locks: Current lock requests which are waiting for or holding locks; this information can be useful when investigating stalls and deadlocks. Analogous to cluster_operations.

  • locks_per_fragment: Counts of lock claim requests, and their outcomes per fragment, as well as total time spent waiting for locks successfully and unsuccessfully. Analogous to operations_per_fragment and memory_per_fragment.

  • server_locks: Subset of cluster transactions—those running on the local mysqld, showing a connection ID per transaction. Analogous to server_operations.

  For more information, see ndbinfo: The NDB Cluster Information Database. (WL #7656)

• The NDB storage engine now supports generated columns (see CREATE TABLE and Generated Columns) as well as indexes on stored generated columns.

  Indexes on virtual generated columns of NDB tables are not supported.

  ALTER TABLE statements that add stored generated columns to NDB tables cannot be performed online. (WL #8188, WL #9048)

Bugs Fixed

• NDB Cluster APIs: The scan lock takeover issued by NdbScanOperation::lockCurrentTuple() did not set the operation type for the takeover operation. (Bug #23314028)

• The ndbinfo cpustat_1sec and cpustat_20sec tables did not provide any history information. (Bug #23520271)

• During shutdown, the mysqld process could sometimes hang after logging NDB Util: Stop ... NDB Util: Wakeup. (Bug #23343739)

  References: See also: Bug #21098142.

• During expansion or reduction of a hash table, allocating a new overflow page in the DBACC kernel block caused the data node to fail when it was out of index memory. This could sometimes occur after a large table had increased or decreased very rapidly in size. (Bug #23304519)

  References: This issue is a regression of: Bug #13436216.

• When tracking time elapsed from sending a SCAN_FRAGREQ signal to receiving a corresponding SCAN_FRAGCONF, the assumption was made in the DBTC kernel block that a SCAN_FRAGCONF can occur only after sending a SCAN_FRAGREQ or SCAN_NEXTREQ signal, which is not always the case: It is actually possible that a local query handler can, immediately after sending a SCAN_FRAGCONF, send an additional SCAN_FRAGCONF signal upon reporting that the scan is closed. This problem is fixed by ensuring that the timer value is initialized each time before use. (Bug #81907, Bug #23605817, Bug #23306695)

• Table indexes were listed in the output of ndb_desc in a nondeterministic order that could vary between platforms. Now these indexes are ordered by ID in the output. (Bug #81763, Bug #23547742)

• Following a restart of the cluster, the first attempt to read from any of the ndbinfo cpustat, cpustat_50ms, cpustat_1sec, or cpustat_20sec tables generated a warning to the effect that columns were missing from the table. Subsequently, the thread_sleeping and spin_time columns were found to be missing from each of these tables. (Bug #81681, Bug #23514557)

  References: See also: Bug #23305078.

• Using a ThreadConfig parameter value with a trailing comma led to an assertion. (Bug #81588, Bug #23344374)