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This example shows deleting a row from a table already created and populated previously (seeSection 2.5.1.2, “NDB API Basic Insertion Example”). It performs the deletion using a singleNdbOperation within a transaction, and handles errors usingNdbError.

You can verify afterwards that the row was deleted by running the read example (Section 2.5.1.3, “NDB API Basic Reading Example”), or by executingSELECT * FROM basic in themysql client.

The source code for this example can also be found in the filestorage/ndb/ndbapi-examples/ndbapi_basic/ndbapi_basic_delete.cpp.

#include <iostream>#include <cstdlib>#include <string>#include <NdbApi.hpp>class BasicDelete{  public:    BasicDelete(const char * connectstring)      : m_connection(connectstring), m_ndb(&m_connection, "ndbapi_examples") {}    bool init();    bool do_delete(long long);  private:    Ndb_cluster_connection m_connection;    Ndb m_ndb;    inline bool on_error(const struct NdbError &error,                         const std::string &explanation)    {      // prints error in format:      // ERROR <NdbErrorCode>: <NdbError message>      //    explanation what went wrong on higher level (in the example code)      std::cout << "ERROR "<< error.code << ": " << error.message << std::endl;      std::cout << explanation << std::endl;      return false;    }};int main(int argc, char **argv){  if (argc != 3)  {    std::cout << "Usage: ndb_ndbapi_basic_delete <connectstring> <key: int>"              << std::endl;    return EXIT_FAILURE;  }  const char *connectstring = argv[1];  const long long key = std::strtoll(argv[2], nullptr, 10);  ndb_init();  {    BasicDelete example(connectstring);    if (!example.init()) return EXIT_FAILURE;    // Let's verify delete    if (example.do_delete(key))      std::cout << "Done, check your database:\n"                << "\t SELECT * FROM ndbapi_examples.basic;\n"                << "\t or run the example: ndb_ndbapi_basic_read"                << std::endl;    else return EXIT_FAILURE;  }  ndb_end(0);  return EXIT_SUCCESS;}bool BasicDelete::do_delete(long long key){  const NdbDictionary::Dictionary *dict = m_ndb.getDictionary();  const NdbDictionary::Table *table = dict->getTable("basic");  if (table == nullptr)    return on_error(dict->getNdbError(),                    "Failed to access 'ndbapi_examples.basic'");  // The delete operation will be performed within single transaction  NdbTransaction *transaction = m_ndb.startTransaction(table);  if(transaction == nullptr)    return on_error(m_ndb.getNdbError(), "Failed to start transaction");  NdbOperation *operation = transaction->getNdbOperation(table);  if(operation == nullptr)    return on_error(transaction->getNdbError(),                    "Failed to start delete operation");  operation->deleteTuple();  operation->equal("ATTR1", key);  if (transaction->execute(NdbTransaction::Commit) != 0)    return on_error(transaction->getNdbError(),        "Failed to execute transaction");  m_ndb.closeTransaction(transaction);  return true;}bool BasicDelete::init(){  if (m_connection.connect() != 0)  {    std::cout << "Cannot connect to cluster management server" << std::endl;    return false;  }  if (m_connection.wait_until_ready(30, 0) != 0)  {    std::cout << "Cluster was not ready within 30 secs" << std::endl;    return false;  }  if (m_ndb.init() != 0)    return on_error(m_ndb.getNdbError(), "Failed to initialize ndb object");  return true;}