Connect C applications to OceanBase Database

You can use OceanBase Connector/C to create connections between C-based applications and OceanBase Database. This topic describes the prerequisites and procedure of connecting to OceanBase Database by using OBCI.

Prerequisites

• Before you install OceanBase Connector/C, make sure that you have set up the basic database development environment that meets the following requirements:

  • The GNU Compiler Collection (GCC) version is 3.4.6 or later. Version 4.8.5 is recommended.

  • The CMake version is 2.8.12 or later.

• Contact OceanBase Technical Support to obtain the installation package of OceanBase Connector/C, also known as LibOBClient.

Install Linux

1. Install LibobClient.

   sudo rpm -ivh libobclient-xx.x86_64.rpm
   

2. Install OBClient.

   sudo rpm -ivh obclient-xx.x86_64.rpm
   

   Note

   OBClient depends on LibobClient. Therefore, you must install LibobClient first.

Use the source code to compile a C application

In the GitHub repository of OceanBase Connector/C, you can find the source code of the latest version.

1. Install the dependency tool.

   sudo yum install -y git cmake gcc make openssl-devel ncurses-devel rpm-build  gcc-c++ bison bison-devel zlib-devel gnutls-devel libxml2-devel openssl-devel \
   libevent-devel libaio-devel
   

2. Download the source code of obclient and libobclient (OceanBase Connector/C) from GitHub at:

   • obclient: https://github.com/oceanbase/obclient

   • libobclient: https://github.com/oceanbase/obconnector-c

3. Execute the compilation script to compile the source code. When you compile the code, the code of the submodule and OceanBase Connector/C is downloaded.

   sh build.sh   # Compile the code.
   

4. Package up libobclient into an RPM package, which contains the SO and header files.

   cd libmariadb/rpm   # Go to the package directory of libobclient.
   sh libobclient-build.sh    # Package up libobclient into an installation package.
   

5. Package up obclient into an RPM package.

   cd ../../rpm      # Go to the package directory of OBClient.
   sh obclient-build.sh    # Package up OBClient into an installation package.
   

6. Install LibobClient.

   sudo rpm -ivh libobclient-xx.x86_64.rpm
   

7. Install OBClient.

   sudo rpm -ivh obclient-xx.x86_64.rpm
   

   Note

   OBClient depends on LibobClient. Therefore, you must install LibobClient first.

Sample code

The following sample code shows how to connect a C application to OceanBase Database:

mysql_library_init(0, NULL, NULL);
MYSQL *mysql = mysql_init(NULL);

/* Use the CLIENT_MULTI_STATEMENTS option to connect to the server. */
if (mysql_real_connect (mysql, host_name, user_name, password,
    db_name, port_num, socket_name, CLIENT_MULTI_STATEMENTS) == NULL)
{
  printf("mysql_real_connect() failed\n");
  mysql_close(mysql);
  mysql_library_end();
  exit(1);
}

/* Execute multiple statements. */
status = mysql_query(mysql,
                     "DROP TABLE IF EXISTS tbl1;\
                      CREATE TABLE tbl1(id INT);\
                      INSERT INTO tbl1 VALUES(110);\
                      UPDATE tbl1 SET id=120 WHERE id=110;\
                      SELECT * FROM tbl1;\
                      DROP TABLE tbl1");
if (status)
{
  printf("Could not execute statement(s)");
  mysql_close(mysql);
  mysql_library_end();
  exit(0);
}

/* Process the result of each statement. */
do {
  /* Check whether the current statement returns data. */
  result = mysql_store_result(mysql);
  if (result)
  {
    /* If yes, process the rows and release the result set. */
    process_result_set(mysql, result);
    mysql_free_result(result);
  }
  else          /* No result set generated or an error occurred. */
  {
    if (mysql_field_count(mysql) == 0)
    {
      printf("%lld rows affected\n",
            mysql_affected_rows(mysql));
    }
    else  /* An error occurred. */
    {
      printf("Could not retrieve result set\n");
      break;
    }
  }
  /* Check whether more results are generated.  The value -1 indicates no. The value 0 indicates yes, which means the loop continues. A value greater than 0 indicates that an error occurred. */
  if ((status = mysql_next_result(mysql)) > 0)
    printf("Could not execute statement\n");
} while (status == 0);

mysql_close(mysql);
mysql_library_end();

For more information about how to use OceanBase Connector/C, see OceanBase Connector/C.