MySQL NDB Cluster 7.6.24 is a new release of NDB 7.6, based on
MySQL Server 5.7 and including features in version 7.6 of the
NDB
storage engine, as well as fixing
recently discovered bugs in previous NDB Cluster releases.
Obtaining NDB Cluster 7.6. NDB Cluster 7.6 source code and binaries can be obtained from https://dev.mysql.com/downloads/cluster/.
For an overview of changes made in NDB Cluster 7.6, see What is New in NDB Cluster 7.6.
This release also incorporates all bug fixes and changes made in previous NDB Cluster releases, as well as all bug fixes and feature changes which were added in mainline MySQL 5.7 through MySQL 5.7.40 (see Changes in MySQL 5.7.40 (2022-10-11, General Availability)).
-
NdbScanOperation
errors are returned asynchronously to the client, possibly while the client is engaged in other processing. A successful call toNdbTransaction::execute()
guarantees only that the scan request has been assembled and sent to the transaction coordinator without any errors; it does not wait for any sort ofCONF
orREF
signal to be returned from the data nodes. In this particular case, the expectedTAB_SCANREF
signal was returned asynchronously into the client space, possibly while the client was still performing other operations.We make this behavior more deterministic by not setting the
NdbTransaction
error code when aTAB_SCANREF
error is received. (Bug #34348706) The combination of batching with multiple in-flight operations per key, use of
IgnoreError
, and transient errors occurring on non-primary replicas led in some cases to inconsistencies withinDBTUP
resulting in replica misalignment and other issues. We now prevent this from happening by detecting when operations are failing on non-primary replicas, and forcingAbortOnError
handling (rollback) in such cases for the containing transaction. (Bug #34013385)When the rate of changes was high, event subscribers were slow to acknowledge receipt, or both, it was possible for the
SUMA
block to run out of space for buffering events. (Bug #30467140)-
ALTER TABLE ... COMMENT="NDB_TABLE=READ_BACKUP=1"
orALTER TABLE..COMMENT="NDB_TABLE=READ_BACKUP=0"
performs a non-copying (online)ALTER
operation on a table to add or remove itsREAD_BACKUP
property (see NDB_TABLE Options), which increments the index version of all indexes on the table. Existing statistics, stored using the previous index version, were orphaned and never deleted; this led to wasted memory and inefficient searches when collecting index statistics.We address these issues by cleaning up the index samples; we delete any samples whose sample version is greater than or less than the current sample version. In addition, when no existing statistics are found by index ID and version, and when indexes are dropped. In this last case, we relax the bounds for the delete operation and remove all entries corresponding to the index ID in question, as opposed to both index ID and index version.
This fix cleans up the sample table which stores the bulk of index statistics data. The head table, which consists of index metadata rather than actual statistics, still contains orphaned rows, but since these occupy an insignificant amount of memory, they do not adversely affect statistics search efficiency, and stale entries are cleaned up when index IDs and versions are reused.
See also NDB API Statistics Counters and Variables. (Bug #29611297)