MySQL NDB Cluster 7.5 Release Notes
Packaging: 
        Expected NDB header files were in the devel
        RPM package instead of libndbclient-devel.
       (Bug #84580, Bug #26448330)
MySQL NDB ClusterJ: 
        When a table containing a BLOB or
        a TEXT field was being queried
        with ClusterJ for a record that did not exist, an exception
        (“The method is not valid in current blob
        state”) was thrown.
       (Bug #28536926)
MySQL NDB ClusterJ: 
        A NullPointerException was thrown when a full
        table scan was performed with ClusterJ on tables containing
        either a BLOB or a TEXT field. It was because the proper object
        initializations were omitted, and they have now been added by
        this fix.
       (Bug #28199372, Bug #91242)
        When the SUMA kernel block receives a
        SUB_STOP_REQ signal, it executes the signal
        then replies with SUB_STOP_CONF. (After this
        response is relayed back to the API, the API is open to send
        more SUB_STOP_REQ signals.) After sending the
        SUB_STOP_CONF, SUMA drops the subscription if
        no subscribers are present, which involves sending multiple
        DROP_TRIG_IMPL_REQ messages to
        DBTUP. LocalProxy can handle up to 21 of
        these requests in parallel; any more than this are queued in the
        Short Time Queue. When execution of a
        DROP_TRIG_IMPL_REQ was delayed, there was a
        chance for the queue to become overloaded, leading to a data
        node shutdown with Error in short time
        queue.
      
        This issue is fixed by delaying the execution of the
        SUB_STOP_REQ signal if
        DBTUP is already handling
        DROP_TRIG_IMPL_REQ signals at full capacity,
        rather than queueing up the
        DROP_TRIG_IMPL_REQ signals.
       (Bug #26574003)
Having a large number of deferred triggers could sometimes lead to job buffer exhaustion. This could occur due to the fact that a single trigger can execute many operations—for example, a foreign key parent trigger may perform operations on multiple matching child table rows—and that a row operation on a base table can execute multiple triggers. In such cases, row operations are executed in batches. When execution of many triggers was deferred—meaning that all deferred triggers are executed at pre-commit—the resulting concurrent execution of a great many trigger operations could cause the data node job buffer or send buffer to be exhausted, leading to failure of the node.
This issue is fixed by limiting the number of concurrent trigger operations as well as the number of trigger fire requests outstanding per transaction.
        For immediate triggers, limiting of concurrent trigger
        operations may increase the number of triggers waiting to be
        executed, exhausting the trigger record pool and resulting in
        the error Too many concurrently fired triggers
        (increase MaxNoOfFiredTriggers. This can be avoided
        by increasing
        MaxNoOfFiredTriggers,
        reducing the user transaction batch size, or both.
       (Bug #22529864)
References: See also: Bug #18229003, Bug #27310330.
        When moving an OperationRec from the serial
        to the parallel queue, Dbacc::startNext()
        failed to update the
        Operationrec::OP_ACC_LOCK_MODE flag which is
        required to reflect the accumulated
        OP_LOCK_MODE of all previous operations in
        the parallel queue. This inconsistency in the ACC lock queues
        caused the scan lock takeover mechanism to fail, as it
        incorrectly concluded that a lock to take over was not held. The
        same failure caused an assert when aborting an operation that
        was a member of such an inconsistent parallel lock queue.
       (Bug #92100, Bug #28530928)
        DBTUP sent the error Tuple
        corruption detected when a read operation attempted
        to read the value of a tuple inserted within the same
        transaction.
       (Bug #92009, Bug #28500861)
References: See also: Bug #28893633.
False constraint violation errors could occur when executing updates on self-referential foreign keys. (Bug #91965, Bug #28486390)
References: See also: Bug #90644, Bug #27930382.
        An NDB internal trigger definition could be
        dropped while pending instances of the trigger remained to be
        executed, by attempting to look up the definition for a trigger
        which had already been released. This caused unpredictable and
        thus unsafe behavior possibly leading to data node failure. The
        root cause of the issue lay in an invalid assumption in the code
        relating to determining whether a given trigger had been
        released; the issue is fixed by ensuring that the behavior of
        NDB, when a trigger definition is determined
        to have been released, is consistent, and that it meets
        expectations.
       (Bug #91894, Bug #28451957)
        In certain cases, a cascade update trigger was fired repeatedly
        on the same record, which eventually consumed all available
        concurrent operations, leading to Error 233 Out of
        operation records in transaction coordinator (increase
        MaxNoOfConcurrentOperations). If
        MaxNoOfConcurrentOperations
        was set to a value sufficiently high to avoid this, the issue
        manifested as data nodes consuming very large amounts of CPU,
        very likely eventually leading to a timeout.
       (Bug #91472, Bug #28262259)
        Inserting a row into an NDB table
        having a self-referencing foreign key that referenced a unique
        index on the table other than the primary key failed with
        ER_NO_REFERENCED_ROW_2. This was
        due to the fact that NDB checked foreign key
        constraints before the unique index was updated, so that the
        constraint check was unable to use the index for locating the
        row. Now, in such cases, NDB waits until all
        unique index values have been updated before checking foreign
        key constraints on the inserted row.
       (Bug #90644, Bug #27930382)
References: See also: Bug #91965, Bug #28486390.