该程序说明了如何借助NdbRecord 接口在 NDB API 中使用二级索引。

此示例的源代码可以在文件中的 NDB Cluster 源树中找到 storage/ndb/ndbapi-examples/ndbapi_s_i_ndbrecord/main.cpp。

当在具有 2 个数据节点的集群上运行时，该程序的正确输出如下所示：

ATTR1 ATTR2
  0     0   (frag=0)
  1     1   (frag=1)
  2     2   (frag=1)
  3     3   (frag=0)
  4     4   (frag=1)
  5     5   (frag=1)
  6     6   (frag=0)
  7     7   (frag=0)
  8     8   (frag=1)
  9     9   (frag=0)
ATTR1 ATTR2
  0    10
  1     1
  2    12
Detected that deleted tuple doesn't exist!
  4    14
  5     5
  6    16
  7     7
  8    18
  9     9

程序清单如下所示：

//
//  ndbapi_simple_index_ndbrecord.cpp: Using secondary unique hash indexes
//  in NDB API, utilising the NdbRecord interface.
//
//  Correct output from this program is (from a two-node cluster):
//
// ATTR1 ATTR2
//   0     0   (frag=0)
//   1     1   (frag=1)
//   2     2   (frag=1)
//   3     3   (frag=0)
//   4     4   (frag=1)
//   5     5   (frag=1)
//   6     6   (frag=0)
//   7     7   (frag=0)
//   8     8   (frag=1)
//   9     9   (frag=0)
// ATTR1 ATTR2
//   0    10
//   1     1
//   2    12
// Detected that deleted tuple doesn't exist!
//   4    14
//   5     5
//   6    16
//   7     7
//   8    18
//   9     9

#include <mysql.h>
#include <NdbApi.hpp>

// Used for cout
#include <stdio.h>
#include <iostream>

#define PRINT_ERROR(code,msg) \
  std::cout << "Error in " << __FILE__ << ", line: " << __LINE__ \
            << ", code: " << code \
            << ", msg: " << msg << "." << std::endl
#define MYSQLERROR(mysql) { \
  PRINT_ERROR(mysql_errno(&mysql),mysql_error(&mysql)); \
  exit(1); }
#define APIERROR(error) { \
  PRINT_ERROR(error.code,error.message); \
  exit(1); }

/* C struct representing layout of data from table
 * api_s_i_ndbrecord in memory
 * This can make it easier to work with rows in the application,
 * but is not necessary - NdbRecord can map columns to any
 * pattern of offsets.
 * In this program, the same row offsets are used for columns
 * specified as part of a key, and as part of an attribute or
 * result.  This makes the example simpler, but is not
 * essential.
 */
struct MyTableRow
{
  unsigned int attr1;
  unsigned int attr2;
};

int main(int argc, char** argv)
{
  if (argc != 3)
    {
    std::cout << "Arguments are <socket mysqld> <connect_string cluster>.\n";
    exit(1);
  }
  char * mysqld_sock  = argv[1];
  const char *connection_string = argv[2];
  ndb_init();
  MYSQL mysql;

  /**************************************************************
   * Connect to mysql server and create table                   *
   **************************************************************/
  {
    if ( !mysql_init(&mysql) ) {
      std::cout << "mysql_init failed\n";
      exit(1);
    }
    if ( !mysql_real_connect(&mysql, "localhost", "root", "", "",
                             0, mysqld_sock, 0) )
      MYSQLERROR(mysql);

    mysql_query(&mysql, "CREATE DATABASE ndb_examples");
    if (mysql_query(&mysql, "USE ndb_examples") != 0)
      MYSQLERROR(mysql);

    mysql_query(&mysql, "DROP TABLE api_s_i_ndbrecord");
    if (mysql_query(&mysql,
                    "CREATE TABLE"
                    "  api_s_i_ndbrecord"
                    "    (ATTR1 INT UNSIGNED,"
                    "     ATTR2 INT UNSIGNED NOT NULL,"
                    "     PRIMARY KEY USING HASH (ATTR1),"
                    "     UNIQUE MYINDEXNAME USING HASH (ATTR2))"
                    "  ENGINE=NDB"))
      MYSQLERROR(mysql);
  }

  /**************************************************************
   * Connect to ndb cluster                                     *
   **************************************************************/

  Ndb_cluster_connection *cluster_connection=
    new Ndb_cluster_connection(connection_string); // Object representing the cluster

  if (cluster_connection->connect(5,3,1))
  {
    std::cout << "Connect to cluster management server failed.\n";
    exit(1);
  }

  if (cluster_connection->wait_until_ready(30,30))
  {
    std::cout << "Cluster was not ready within 30 secs.\n";
    exit(1);
  }

  Ndb* myNdb = new Ndb( cluster_connection,
                        "ndb_examples" );  // Object representing the database
  if (myNdb->init() == -1) {
    APIERROR(myNdb->getNdbError());
    exit(1);
  }

  NdbDictionary::Dictionary* myDict= myNdb->getDictionary();
  const NdbDictionary::Table *myTable= myDict->getTable("api_s_i_ndbrecord");
  if (myTable == NULL)
    APIERROR(myDict->getNdbError());
  const NdbDictionary::Index *myIndex= myDict->getIndex("MYINDEXNAME$unique","api_s_i_ndbrecord");
  if (myIndex == NULL)
    APIERROR(myDict->getNdbError());

  /* Create NdbRecord descriptors. */
  const NdbDictionary::Column *col1= myTable->getColumn("ATTR1");
  if (col1 == NULL)
    APIERROR(myDict->getNdbError());
  const NdbDictionary::Column *col2= myTable->getColumn("ATTR2");
  if (col2 == NULL)
    APIERROR(myDict->getNdbError());

  /* NdbRecord for primary key lookup. */
  NdbDictionary::RecordSpecification spec[2];
  spec[0].column= col1;
  spec[0].offset= offsetof(MyTableRow, attr1);
    // So that it goes nicely into the struct
  spec[0].nullbit_byte_offset= 0;
  spec[0].nullbit_bit_in_byte= 0;
  const NdbRecord *pk_record=
    myDict->createRecord(myTable, spec, 1, sizeof(spec[0]));
  if (pk_record == NULL)
    APIERROR(myDict->getNdbError());

  /* NdbRecord for all table attributes (insert/read). */
  spec[0].column= col1;
  spec[0].offset= offsetof(MyTableRow, attr1);
  spec[0].nullbit_byte_offset= 0;
  spec[0].nullbit_bit_in_byte= 0;
  spec[1].column= col2;
  spec[1].offset= offsetof(MyTableRow, attr2);
  spec[1].nullbit_byte_offset= 0;
  spec[1].nullbit_bit_in_byte= 0;
  const NdbRecord *attr_record=
    myDict->createRecord(myTable, spec, 2, sizeof(spec[0]));
  if (attr_record == NULL)
    APIERROR(myDict->getNdbError());

  /* NdbRecord for unique key lookup. */
  spec[0].column= col2;
  spec[0].offset= offsetof(MyTableRow, attr2);
  spec[0].nullbit_byte_offset= 0;
  spec[0].nullbit_bit_in_byte= 0;
  const NdbRecord *key_record=
    myDict->createRecord(myIndex, spec, 1, sizeof(spec[0]));
  if (key_record == NULL)
    APIERROR(myDict->getNdbError());

  MyTableRow row;

  /**************************************************************************
   * Using 5 transactions, insert 10 tuples in table: (0,0),(1,1),...,(9,9) *
   **************************************************************************/
  for (int i = 0; i < 5; i++) {
    NdbTransaction *myTransaction= myNdb->startTransaction();
    if (myTransaction == NULL) APIERROR(myNdb->getNdbError());

    /*
      We initialise the row data and pass to each insertTuple operation
      The data is copied in the call to insertTuple and so the original
      row object can be reused for the two operations.
    */
    row.attr1= row.attr2= i;

    const NdbOperation *myOperation=
      myTransaction->insertTuple(attr_record, (const char*)&row);
    if (myOperation == NULL)
      APIERROR(myTransaction->getNdbError());

    row.attr1= row.attr2= i+5;
    myOperation=
      myTransaction->insertTuple(attr_record, (const char*)&row);
    if (myOperation == NULL)
      APIERROR(myTransaction->getNdbError());

    if (myTransaction->execute( NdbTransaction::Commit ) == -1)
      APIERROR(myTransaction->getNdbError());

    myNdb->closeTransaction(myTransaction);
  }

  /*****************************************
   * Read and print all tuples using index *
   *****************************************/
  std::cout << "ATTR1 ATTR2" << std::endl;

  for (int i = 0; i < 10; i++) {
    NdbTransaction *myTransaction= myNdb->startTransaction();
    if (myTransaction == NULL)
      APIERROR(myNdb->getNdbError());

    /* The optional OperationOptions parameter to NdbRecord methods
     * can be used to specify extra reads of columns which are not in
     * the NdbRecord specification, which need to be stored somewhere
     * other than specified in the NdbRecord specification, or
     * which cannot be specified as part of an NdbRecord (pseudo
     * columns)
     */
    Uint32 frag;
    NdbOperation::GetValueSpec getSpec[1];
    getSpec[0].column=NdbDictionary::Column::FRAGMENT;
    getSpec[0].appStorage=&frag;

    NdbOperation::OperationOptions options;
    options.optionsPresent = NdbOperation::OperationOptions::OO_GETVALUE;
    options.extraGetValues = &getSpec[0];
    options.numExtraGetValues = 1;

    /* We're going to read using the secondary unique hash index
     * Set the value of its column
     */
    row.attr2= i;

    MyTableRow resultRow;

    unsigned char mask[1]= { 0x01 };            // Only read ATTR1 into resultRow
    const NdbOperation *myOperation=
      myTransaction->readTuple(key_record, (const char*) &row,
                               attr_record, (char*) &resultRow,
                               NdbOperation::LM_Read, mask,
                               &options,
                               sizeof(NdbOperation::OperationOptions));
    if (myOperation == NULL)
      APIERROR(myTransaction->getNdbError());

    if (myTransaction->execute( NdbTransaction::Commit,
                                NdbOperation::AbortOnError ) != -1)
    {
      printf(" %2d    %2d   (frag=%u)\n", resultRow.attr1, i, frag);
    }

    myNdb->closeTransaction(myTransaction);
  }

  /*****************************************************************
   * Update the second attribute in half of the tuples (adding 10) *
   *****************************************************************/
  for (int i = 0; i < 10; i+=2) {
    NdbTransaction *myTransaction= myNdb->startTransaction();
    if (myTransaction == NULL)
      APIERROR(myNdb->getNdbError());

    /* Specify key column to lookup in secondary index */
    row.attr2= i;

    /* Specify new column value to set */
    MyTableRow newRowData;
    newRowData.attr2= i+10;
    unsigned char mask[1]= { 0x02 };            // Only update ATTR2

    const NdbOperation *myOperation=
      myTransaction->updateTuple(key_record, (const char*)&row,
                                 attr_record,(char*) &newRowData, mask);
    if (myOperation == NULL)
      APIERROR(myTransaction->getNdbError());

    if ( myTransaction->execute( NdbTransaction::Commit ) == -1 )
      APIERROR(myTransaction->getNdbError());

    myNdb->closeTransaction(myTransaction);
  }

  /*************************************************
   * Delete one tuple (the one with unique key 3) *
   *************************************************/
  {
    NdbTransaction *myTransaction= myNdb->startTransaction();
    if (myTransaction == NULL)
      APIERROR(myNdb->getNdbError());

    row.attr2= 3;
    const NdbOperation *myOperation=
      myTransaction->deleteTuple(key_record, (const char*) &row,
                                 attr_record);
    if (myOperation == NULL)
      APIERROR(myTransaction->getNdbError());

    if (myTransaction->execute(NdbTransaction::Commit) == -1)
      APIERROR(myTransaction->getNdbError());

    myNdb->closeTransaction(myTransaction);
  }

  /*****************************
   * Read and print all tuples *
   *****************************/
  {
    std::cout << "ATTR1 ATTR2" << std::endl;

    for (int i = 0; i < 10; i++) {
      NdbTransaction *myTransaction= myNdb->startTransaction();
      if (myTransaction == NULL)
        APIERROR(myNdb->getNdbError());

      row.attr1= i;

      /* Read using pk.  Note the same row space is used as
       * key and result storage space
       */
      const NdbOperation *myOperation=
        myTransaction->readTuple(pk_record, (const char*) &row,
                                 attr_record, (char*) &row);
      if (myOperation == NULL)
        APIERROR(myTransaction->getNdbError());

      if (myTransaction->execute( NdbTransaction::Commit,
                                  NdbOperation::AbortOnError ) == -1)
        if (i == 3) {
          std::cout << "Detected that deleted tuple doesn't exist!\n";
        } else {
          APIERROR(myTransaction->getNdbError());
        }

      if (i != 3)
        printf(" %2d    %2d\n", row.attr1, row.attr2);

      myNdb->closeTransaction(myTransaction);
    }
  }

  delete myNdb;
  delete cluster_connection;

  ndb_end(0);
  return 0;
}