Connect C applications to OceanBase Database

This topic describes how to connect C applications to OceanBase Database.

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 OceanBase Connector/C

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, install LibOBClient first.

Compile a C application using source code

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.

   cd rpm
   

3. Execute the script and download the code of LibobClient.

   sh build.sh   # Compile the code. 
   cd libmariadb/rpm   # Access the package directory of LibobClient.
   

4. Compress the programs of LibobClient and OBClient in RPM packages.

   sh libobclient-build.sh    # Compress LibobClient in a package.
   cd ../../rpm      # Access the package directory of OBClient.
   sh obclient-build.sh    # Compress the program of OBClient in a package.
   

5. Install LibobClient.

   sudo rpm -ivh libobclient-xx.x86_64.rpm
   

6. Install OBClient.

   sudo rpm -ivh obclient-xx.x86_64.rpm
   

   Note

   Because OBClient depends on LibobClient, install LibobClient first.

Procedure

The basic methods for an application to interact with an OBServer by using OceanBase Connector/C include:

1. Call mysql_library_init() to initialize the MySQL library.

   mysql_library_init(0, NULL, NULL);
   

2. Call mysql_init() to initialize a connection handle.

   MYSQL *mysql = mysql_init(NULL);
   

3. Call mysql_real_connect() to connect to the OBServer.

   mysql_real_connect (mysql, host_name, user_name, password,
   db_name, port_num, socket_name, CLIENT_MULTI_STATEMENTS)
   

4. Call mysql_real_query() or mysql_query() to send an SQL statement to the OBServer.

   mysql_query(mysql,"sql_statement");
   

5. Call mysql_store_result() or mysql_use_result() to process the result.

   result=mysql_store_result(mysql);
   

6. Call mysql_free_result() to release the memory.

   mysql_free_result(result);
   

7. Call mysql_close() to disconnect from the OBServer.

   mysql_close(mysql);
   

8. Call mysql_library_end() to stop using LibobClient.

   mysql_library_end();
   

For more information about OceanBase Connector/C, see OceanBase Connector/C.