None

NdbIndexOperation, NdbScanOperation

NdbOperation represents a “generic” data operation. Its subclasses represent more specific types of operations. See NdbOperation::Type for a listing of operation types and their corresponding NdbOperation subclasses.

The following table lists the public methods of this class and the purpose or use of each method:

This class has no public constructor. To create an instance of NdbOperation, you must use NdbTransaction::getNdbOperation().

The NdbOperation class defines three public types, shown in the following table:

This type is used to determine whether failed operations should force a transaction to be aborted. It is used as an argument to the execute() method—see NdbTransaction::execute(), for more information.

Possible values are shown, along with descriptions, in the following table:

This method defines the NdbOperation as a DELETE operation. When the NdbTransaction::execute() method is invoked, the operation deletes a tuple from the table.

virtual int deleteTuple
    (
      void
    )

None.

Returns 0 on success, -1 on failure.

This method defines a search condition with an equality. The condition is true if the attribute has the given value. To set search conditions on multiple attributes, use several calls to equal(); in such cases all of them must be satisfied for the tuple to be selected.

If the attribute is of a fixed size, its value must include all bytes. In particular a Char value must be native-space padded. If the attribute is of variable size, its value must start with 1 or 2 little-endian length bytes (2 if its type is Long*).

When using insertTuple(), you may also define the search key with setValue(). See NdbOperation::setValue().

There are 10 versions of equal(), each having slightly different parameters. All of these are shown here:

int  equal
    (
      const char* name,
      const char* value
    )

int  equal
    (
      const char* name,
      Int32       value
    )

int  equal
    (
      const char* name,
      Uint32      value
    )

int  equal
    (
      const char* name,
      Int64       value
    )

int  equal
    (
      const char* name,
      Uint64      value
    )

int  equal
    (
      Uint32      id,
      const char* value
    )

int  equal
    (
      Uint32 id,
      Int32  value
    )

int  equal
    (
      Uint32 id,
      Uint32 value
    )

int  equal
    (
      Uint32 id,
      Int64  value
    )

int  equal
    (
      Uint32 id,
      Uint64 value
    )

This method requires two parameters:

Returns -1 in the event of an error.

This method is used in place of getValue() or setValue() for blob attributes. It creates a blob handle (NdbBlob object). A second call with the same argument returns the previously created handle. The handle is linked to the operation and is maintained automatically.

This method has two forms, depending on whether it is called with the name or the ID of the blob attribute:

virtual NdbBlob* getBlobHandle
    (
      const char* name
    )

or

virtual NdbBlob* getBlobHandle
    (
      Uint32 id
    )

This method takes a single parameter, which can be either one of the following:

Regardless of parameter type used, this method return a pointer to an instance of NdbBlob.

Returns a pointer to the current operation's lock handle. When used with NdbRecord, the lock handle must first be requested with the OO_LOCKHANDLE operation option. For other operations, this method can be used alone. In any case, the NdbLockHandle object returned by this method cannot be used until the operation has been executed.

const NdbLockHandle* getLockHandle
    (
      void
    ) const

or

const NdbLockHandle* getLockHandle
    (
      void
    )

None.

Pointer to an NdbLockHandle that can be used by the NdbTransaction methods unlock() and releaseLockHandle().

This method gets the operation's lock mode.

LockMode getLockMode
    (
      void
    ) const

None.

A LockMode value. See NdbOperation::LockMode.

This method gets the most recent error (an NdbError object).

const NdbError& getNdbError
    (
      void
    ) const

None.

An NdbError object.

This method retrieves the method number in which the latest error occurred.

int getNdbErrorLine
    (
      void
    ) const

None.

The method number (an integer).

This method is used to retrieve the table object associated with the operation.

const NdbDictionary::Table* getTable
    (
      void
    ) const

None.

A pointer to an instance of Table.

This method retrieves the name of the table used for the operation.

const char* getTableName
    (
      void
    ) const

None.

The name of the table.

Gets the NdbTransaction object for this operation.

virtual NdbTransaction* getNdbTransaction
    (
      void
    ) const

None.

A pointer to an NdbTransaction object.

This method is used to retrieve the access type for this operation.

Type getType
    (
      void
    ) const

None.

A Type value.

This method prepares for the retrieval of an attribute value. The NDB API allocates memory for an NdbRecAttr object that is later used to obtain the attribute value. This can be done by using one of the many NdbRecAttr accessor methods, the exact method to be used depending on the attribute's data type. (This includes the generic NdbRecAttr::aRef() method, which retrieves the data as char*, regardless of its actual type. You should be aware that this is not type-safe, and requires an explicit cast from the user.)

This method does not fetch the attribute value from the database; the NdbRecAttr object returned by this method is not readable or printable before calling NdbTransaction::execute().

If a specific attribute has not changed, the corresponding NdbRecAttr has the state UNDEFINED. This can be checked by using NdbRecAttr::isNULL(), which in such cases returns -1.

See NdbTransaction::execute(), and NdbRecAttr::isNULL().

There are three versions of this method, each having different parameters:

NdbRecAttr* getValue
    (
      const char* name,
      char*       value = 0
    )

NdbRecAttr* getValue
    (
      Uint32 id,
      char*  value = 0
    )

NdbRecAttr* getValue
    (
      const NdbDictionary::Column* col,
      char*                        value = 0
    )

All three forms of this method have two parameters, the second parameter being optional (defaults to 0). They differ only with regard to the type of the first parameter, which can be any one of the following:

In all three cases, the second parameter is a character buffer in which a non-NULL attribute value is returned. In the event that the attribute is NULL, is it stored only in the NdbRecAttr object returned by this method.

If no value is specified in the getValue() method call, or if 0 is passed as the value, then the NdbRecAttr object provides memory management for storing the received data. If the maximum size of the received data is above a small fixed size, malloc() is used to store it: For small sizes, a small, fixed internal buffer (32 bytes in extent) is provided. This storage is managed by the NdbRecAttr instance; it is freed when the operation is released, such as at transaction close time; any data written here that you wish to preserve should be copied elsewhere before this freeing of memory takes place.

If you pass a non-zero pointer for value, then it is assumed that this points to an portion of memory which is large enough to hold the maximum value of the column; any returned data is written to that location. The pointer should be at least 32-bit aligned.

Index columns cannot be used in place of table columns with this method. In cases where a table column is not available, you can use the attribute name, obtained with getName(), for this purpose instead.

A pointer to an NdbRecAttr object to hold the value of the attribute, or a NULL pointer, indicating an error.

NdbOperation

This structure is used to specify an extra value to obtain as part of an NdbRecord operation.

The elements making up this structure are shown in the following table:

Blob reads cannot be specified using GetValueSpec.

This method defines the NdbOperation to be an INSERT operation. When the NdbTransaction::execute() method is called, this operation adds a new tuple to the table.

virtual int insertTuple
    (
      void
    )

None.

Returns 0 on success, -1 on failure.

This type describes the lock mode used when performing a read operation.

Possible values for this type are shown, along with descriptions, in the following table:

There is also support for dirty reads (LM_Dirty), but this is normally for internal purposes only, and should not be used for applications deployed in a production setting.

NdbOperation

These options are passed to the NdbRecord-based primary key and scan takeover operation methods defined in the NdbTransaction and NdbScanOperation classes.

Most NdbTransaction::*Tuple() methods (see Section 2.3.25, “The NdbTransaction Class”) take a supplementary sizeOfOptions parameter. This is optional, and is intended to permit the interface implementation to remain backward compatible with older un-recompiled clients that may pass an older (smaller) version of the OperationOptions structure. This effect is achieved by passing sizeof(OperationOptions) into this parameter.

Each option type is marked as present by setting the corresponding bit in optionsPresent. (Only the option types marked in optionsPresent need have sensible data.) All data is copied out of the OperationOptions structure (and any subtended structures) at operation definition time. If no options are required, then NULL may be passed instead.

The elements making up this structure are shown in the following table:

This method defines the NdbOperation as a READ operation. When the NdbTransaction::execute() method is invoked, the operation reads a tuple.

virtual int readTuple
    (
      LockMode mode
    )

mode specifies the locking mode used by the read operation. See NdbOperation::LockMode, for possible values.

Returns 0 on success, -1 on failure.

This method defines an attribute to be set or updated.

There are a number of NdbOperation::setValue() methods that take a certain type as input (pass by value rather than passing a pointer). It is the responsibility of the application programmer to use the correct types.

The NDB API does check that the application sends a correct length to the interface as given in the length parameter. A char* value can contain any data type or any type of array. If the length is not provided, or if it is set to zero, then the API assumes that the pointer is correct, and does not check it.

To set a NULL value, use the following construct:

setValue("ATTR_NAME", (char*)NULL);

When you use insertTuple(), the NDB API automatically detects that it is supposed to use equal() instead.

In addition, it is not necessary when using insertTuple() to use setValue() on key attributes before other attributes.

There are 14 versions of NdbOperation::setValue(), each with slightly different parameters, as listed here:

int setValue
    (
      const char* name,
      const char* value
)

int setValue
    (
      const char* name,
      Int32       value
    )

int setValue
    (
      const char* name,
      Uint32      value
    )

int setValue
    (
      const char* name,
      Int64       value
    )

int setValue
    (
      const char* name,
      Uint64      value
    )

int setValue
    (
      const char* name,
      float       value
    )

int setValue
    (
      const char* name,
      double      value
    )

int setValue
    (
      Uint32      id,
      const char* value
    )

int setValue
    (
      Uint32 id,
      Int32  value
    )

int setValue
    (
      Uint32 id,
      Uint32 value
    )

int setValue
    (
      Uint32 id,
      Int64  value
    )

int setValue
    (
      Uint32 id,
      Uint64 value
    )

int setValue
    (
      Uint32 id,
      float  value
    )

int setValue
    (
      Uint32 id,
      double value
    )

This method requires the following two parameters:

Returns -1 in the event of failure.

NdbOperation

This structure is used to specify an extra value to set as part of an NdbRecord operation.

The elements making up this structure are shown in the following table:

Type is used to describe the operation access type. Each access type is supported by NdbOperation or one of its subclasses, as shown in the following table:

Possible values are shown, along with descriptions, in the following table:

This method defines the NdbOperation as an UPDATE operation. When the NdbTransaction::execute() method is invoked, the operation updates a tuple found in the table.

virtual int updateTuple
    (
      void
    )

None.

Returns 0 on success, -1 on failure.

This method defines the NdbOperation as a WRITE operation. When the NdbTransaction::execute() method is invoked, the operation writes a tuple to the table. If the tuple already exists, it is updated; otherwise an insert takes place.

virtual int writeTuple
    (
      void
    )

None.

Returns 0 on success, -1 on failure.