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2.3.13.2. NdbIndexScanOperation Methods

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2.3.13.2.1. NdbIndexScanOperation::get_range_no()
2.3.13.2.2. NdbIndexScanOperation::getSorted()
2.3.13.2.3. NdbIndexScanOperation::getDescending()
2.3.13.2.4. NdbIndexScanOperation::readTuples()
2.3.13.2.5. NdbIndexScanOperation::setBound
2.3.13.2.6. NdbIndexScanOperation::reset_bounds()
2.3.13.2.7. NdbIndexScanOperation::end_of_bound()

Abstract

This section lists and describes the public methods of the NdbIndexScanOperation class.

2.3.13.2.1. NdbIndexScanOperation::get_range_no()

Description.  This method returns the range number for the current row.

Signature.  

int get_range_no
    (
      void
    )

Parameters.  None.

Return value.  The range number (an integer).

2.3.13.2.2. NdbIndexScanOperation::getSorted()

Description.  This method is used to check whether the scan is sorted.

Signature.  

bool getSorted
    (
      void
    ) const

Parameters.  None.

Return value.  true if the scan is sorted, otherwise false.

2.3.13.2.3. NdbIndexScanOperation::getDescending()

Description.  This method is used to check whether the scan is descending.

Signature.  

bool getDescending
    (
      void
    ) const

Parameters.  None.

Return value.  This method returns true if the scan is sorted in descending order; otherwise, it returns false.

2.3.13.2.4. NdbIndexScanOperation::readTuples()

Description.  This method is used to read tuples, using an ordered index.

Signature.  

virtual int readTuples
    (
      LockMode mode = LM_Read,
      Uint32   flags = 0,
      Uint32   parallel = 0,
      Uint32   batch = 0

    )

Parameters.  The readTuples() method takes 3 parameters, as listed here:

  • The lock mode used for the scan. This is a LockMode value; see Section 2.3.15.1.3, “The NdbOperation::LockMode Type” for more information, including permitted values.

  • One or more scan flags; multiple flags are OR'ed together as they are when used with NdbScanOperation::readTuples(). See Section 2.3.18.1, “The NdbScanOperation::ScanFlag Type” for possible values.

  • The number of fragments to scan in parallel; use 0 to specify the maximum automatically.

  • The batch parameter specifies how many records will be returned to the client from the server by the next NdbScanOperation::nextResult(true) method call. Use 0 to specify the maximum automatically.

    Note

    This parameter was ignored prior to MySQL 5.1.12, and the maximum was used.(Bug#20252)

Return value.  An integer: 0 indicates success; -1 indicates failure.

2.3.13.2.5. NdbIndexScanOperation::setBound

Description.  This method defines a bound on an index key used in a range scan. In MySQL Cluster NDB 6.2.3 and later, it is also sets bounds for index scans defined using NdbRecord.

“Old” API usage (prior to introduction of NdbRecord).  Each index key can have a lower bound, upper bound, or both. Setting the key equal to a value defines both upper and lower bounds. Bounds can be defined in any order. Conflicting definitions gives rise to an error.

Bounds must be set on initial sequences of index keys, and all but possibly the last bound must be nonstrict. This means, for example, that “a >= 2 AND b > 3” is permissible, but “a > 2 AND b >= 3” is not.

The scan may currently return tuples for which the bounds are not satisfied. For example, a <= 2 && b <= 3 not only scans the index up to (a=2, b=3), but also returns any (a=1, b=4) as well.

When setting bounds based on equality, it is better to use BoundEQ instead of the equivalent pair BoundLE and BoundGE. This is especially true when the table partition key is a prefix of the index key.

NULL is considered less than any non-NULL value and equal to another NULL value. To perform comparisons with NULL, use setBound() with a null pointer (0).

An index also stores all-NULL keys as well, and performing an index scan with an empty bound set returns all tuples from the table.

Signature (“Old” API).  

int setBound
    (
      const char* name,
      int         type,
      const void* value
    )

or 

int setBound
    (
      Uint32      id,
      int         type,
      const void* value
    )

Parameters (“Old” API).  This method takes 3 parameters:

As used with NdbRecord (MySQL Cluster NDB 6.2.3 and later).  This method is called to add a range to an IndexScan operation which has been defined with a call to NdbTransaction::scanIndex(). To add more than one range, the index scan operation must have been defined with the SF_MultiRange flag set. (See Section 2.3.18.1, “The NdbScanOperation::ScanFlag Type”.)

Note

Where multiple numbered ranges are defined with multiple calls to setBound(), and the scan is ordered, the range number for each range must be larger than the range number for the previously defined range.

Signature (when used with NdbRecord).  MySQL Cluster NDB 6.2.3 and later: 

int setBound
    (
      const NdbRecord* keyRecord,
      const IndexBound& bound
    )

Parameters.  As used with NdbRecord in MySQL Cluster NDB 6.2.3 and later, this method takes 2 parameters:

Starting with MySQL Cluster NDB 6.3.24 and NDB 7.0.4, an additional version of this method is available, which can be used when the application knows that rows in-range will be found only within a particular partition. This is the same as that shown previously, except for the addition of a PartitionSpecification. Doing so limits the scan to a single partition, improving system efficiency.

Signature (when specifying a partition).  

int setBound
    (
      const NdbRecord* keyRecord,
      const IndexBound& bound,
      const Ndb::PartitionSpec* partInfo,
      Uint32 sizeOfPartInfo = 0
    )

Parameters (when specifying a partition).  Beginning with MySQL Cluster NDB 6.3.24 and MySQL Cluster NDB 7.0.4, this method can be invoked with the following 4 parameters:

Note

keyRecord and bound are defined and used in the same way as with the 2-parameter version of this method.

  • partInfo: This is a pointer to an Ndb::PartitionSpec, which provides extra information making it possible to scan a reduced set of partitions. See Section 2.3.33, “The PartitionSpec Structure”, for more information.

  • sizeOfPartInfo: The length of the partition specification.

Return value.  Returns 0 on success, -1 on failure.

2.3.13.2.6. NdbIndexScanOperation::reset_bounds()

Description.  Reset the bounds, and put the operation into the list that will be sent on the next NdbTransaction::execute() call.

Signature.  

int reset_bounds
    (
      bool forceSend = false
    )

Parameters.  Set forceSend to true in order to force the operation to be sent immediately.

Return value.  0 on success, -1 on failure.

2.3.13.2.7. NdbIndexScanOperation::end_of_bound()

Description.  This method is used to mark the end of a bound; used when batching index reads (that is, when employing multiple ranges).

Signature.  

int end_of_bound
    (
      Uint32 range_no
    )

Parameters.  The number of the range on which the bound occurs.

Return value.  0 indicates success; -1 indicates failure.