Important Change; NDB Replication: The slave_allow_batching system variable affects how efficiently the slave applies epoch transactions. When this variable is set to OFF, by default, every discrete replication event in the binary log is applied and executed separately, which generally leads to poor performance.

Beginning with this release, if slave batching is disabled (slave_allow_batching set to OFF), the MySQL server now reports a warning, with an admonition to enable it.

NDB Cluster APIs: The internal function NdbThread_SetThreadPrio() sets the thread priority (thread_prio) for a given thread type when applying the setting of the ThreadConfig configuration parameter. It was possible for this function in some cases to return an error when it had actually succeeded, which could have a an unfavorable impact on the performance of some NDB API applications. (Bug #34038630)

Path lengths were not always calculated correctly by the data nodes. (Bug #33993607)

The internal function NdbReceiver::unpackRecAttr(), which unpacks attribute values from a buffer from a GSN_TRANSID_AI signal, did not check to ensure that attribute sizes fit within the buffer. This could corrupt the buffer which could in turn lead to reading beyond the buffer and copying beyond destination buffers. (Bug #33941167)

Some NDB internal signals were not always checked properly. (Bug #33896428)