什么是 OceanBase Client
OceanBase Client（简称 OBClient） 是一个基于 MariaDB 开发的客户端工具。您可以使用 OBClient 访问 OceanBase 数据库的集群。OBClient 采用 GPL 协议。
OBClient 依赖 libobclient。libobclient 是一个基于 MariaDB 的 mariadb-connector-c 开发的 OceanBase C API Lib 库。libobclient 允许 C/C++ 程序以一种较为底层的方式访问 OceanBase 数据库集群。libobclient 支持使用 OceanBase 数据库的最新数据模型。libobclient 采用 LGPL 协议。
如何获取 OBClient
按以下方式获取 OBClient：
通过 YUM 源获取 OBClient
# 添加 yum 源
sudo yum install -y yum-utils
sudo yum-config-manager \
--add-repo \
https://mirrors.aliyun.com/oceanbase/OceanBase.repo
# 安装 OBClient
sudo yum install obclient通过源码构建 OBClient
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
cd rpm
# 打包obclient的rpm包
sh obclient-build.sh
进入到libobclient的仓库
cd rpm
#打包libobclient的rpm 这里面主要是so和头文件
sh libobclient-build.sh
#安装，需要先安装libobclient的rpm，再安装obclient的rpm。使用限制
OBClient 暂时不支持部分 Oracle 类型的写入。例如 blob 和 raw 等。
操作指南
Statement
C API 详细信息，参考 MySQL C API 基础函数文档。代码示例如下：
/* connect to server with the CLIENT_MULTI_STATEMENTS option */
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);
exit(1);
}
/* execute multiple statements */
status = mysql_query(mysql,
"DROP TABLE IF EXISTS test_table;\
CREATE TABLE test_table(id INT);\
INSERT INTO test_table VALUES(10);\
UPDATE test_table SET id=20 WHERE id=10;\
SELECT * FROM test_table;\
DROP TABLE test_table");
if (status)
{
printf("Could not execute statement(s)");
mysql_close(mysql);
exit(0);
}
/* process each statement result */
do {
/* did current statement return data? */
result = mysql_store_result(mysql);
if (result)
{
/* yes; process rows and free the result set */
process_result_set(mysql, result);
mysql_free_result(result);
}
else /* no result set or error */
{
if (mysql_field_count(mysql) == 0)
{
printf("%lld rows affected\n",
mysql_affected_rows(mysql));
}
else /* some error occurred */
{
printf("Could not retrieve result set\n");
break;
}
}
/* more results? -1 = no, >0 = error, 0 = yes (keep looping) */
if ((status = mysql_next_result(mysql)) > 0)
printf("Could not execute statement\n");
} while (status == 0);
mysql_close(mysql);Prepared Statement
C API 详细信息，参考 MySQL C API 预置语句函数文档。代码示例如下：
MYSQL_STMT *stmt;
MYSQL_BIND ps_params[3]; /* input parameter buffers */
int int_data[3]; /* input/output values */
my_bool is_null[3]; /* output value nullability */
int status;
/* set up stored procedure */
status = mysql_query(mysql, "DROP PROCEDURE IF EXISTS p1");
test_error(mysql, status);
status = mysql_query(mysql,
"CREATE PROCEDURE p1("
" IN p_in INT, "
" OUT p_out INT, "
" INOUT p_inout INT) "
"BEGIN "
" SELECT p_in, p_out, p_inout; "
" SET p_in = 100, p_out = 200, p_inout = 300; "
" SELECT p_in, p_out, p_inout; "
"END");
test_error(mysql, status);
/* initialize and prepare CALL statement with parameter placeholders */
stmt = mysql_stmt_init(mysql);
if (!stmt)
{
printf("Could not initialize statement\n");
exit(1);
}
status = mysql_stmt_prepare(stmt, "CALL p1(?, ?, ?)", 16);
test_stmt_error(stmt, status);
/* initialize parameters: p_in, p_out, p_inout (all INT) */
memset(ps_params, 0, sizeof (ps_params));
ps_params[0].buffer_type = MYSQL_TYPE_LONG;
ps_params[0].buffer = (char *) &int_data[0];
ps_params[0].length = 0;
ps_params[0].is_null = 0;
ps_params[1].buffer_type = MYSQL_TYPE_LONG;
ps_params[1].buffer = (char *) &int_data[1];
ps_params[1].length = 0;
ps_params[1].is_null = 0;
ps_params[2].buffer_type = MYSQL_TYPE_LONG;
ps_params[2].buffer = (char *) &int_data[2];
ps_params[2].length = 0;
ps_params[2].is_null = 0;
/* bind parameters */
status = mysql_stmt_bind_param(stmt, ps_params);
test_stmt_error(stmt, status);
/* assign values to parameters and execute statement */
int_data[0]= 10; /* p_in */
int_data[1]= 20; /* p_out */
int_data[2]= 30; /* p_inout */
status = mysql_stmt_execute(stmt);
test_stmt_error(stmt, status);
/* process results until there are no more */
do {
int i;
int num_fields; /* number of columns in result */
MYSQL_FIELD *fields; /* for result set metadata */
MYSQL_BIND *rs_bind; /* for output buffers */
/* the column count is > 0 if there is a result set */
/* 0 if the result is only the final status packet */
num_fields = mysql_stmt_field_count(stmt);
if (num_fields > 0)
{
/* there is a result set to fetch */
printf("Number of columns in result: %d\n", (int) num_fields);
/* what kind of result set is this? */
printf("Data: ");
if(mysql->server_status & SERVER_PS_OUT_PARAMS)
printf("this result set contains OUT/INOUT parameters\n");
else
printf("this result set is produced by the procedure\n");
MYSQL_RES *rs_metadata = mysql_stmt_result_metadata(stmt);
test_stmt_error(stmt, rs_metadata == NULL);
fields = mysql_fetch_fields(rs_metadata);
rs_bind = (MYSQL_BIND *) malloc(sizeof (MYSQL_BIND) * num_fields);
if (!rs_bind)
{
printf("Cannot allocate output buffers\n");
exit(1);
}
memset(rs_bind, 0, sizeof (MYSQL_BIND) * num_fields);
/* set up and bind result set output buffers */
for (i = 0; i < num_fields; ++i)
{
rs_bind[i].buffer_type = fields[i].type;
rs_bind[i].is_null = &is_null[i];
switch (fields[i].type)
{
case MYSQL_TYPE_LONG:
rs_bind[i].buffer = (char *) &(int_data[i]);
rs_bind[i].buffer_length = sizeof (int_data);
break;
default:
fprintf(stderr, "ERROR: unexpected type: %d.\n", fields[i].type);
exit(1);
}
}
status = mysql_stmt_bind_result(stmt, rs_bind);
test_stmt_error(stmt, status);
/* fetch and display result set rows */
while (1)
{
status = mysql_stmt_fetch(stmt);
if (status == 1 || status == MYSQL_NO_DATA)
break;
for (i = 0; i < num_fields; ++i)
{
switch (rs_bind[i].buffer_type)
{
case MYSQL_TYPE_LONG:
if (*rs_bind[i].is_null)
printf(" val[%d] = NULL;", i);
else
printf(" val[%d] = %ld;",
i, (long) *((int *) rs_bind[i].buffer));
break;
default:
printf(" unexpected type (%d)\n",
rs_bind[i].buffer_type);
}
}
printf("\n");
}
mysql_free_result(rs_metadata); /* free metadata */
free(rs_bind); /* free output buffers */
}
else
{
/* no columns = final status packet */
printf("End of procedure output\n");
}
/* more results? -1 = no, >0 = error, 0 = yes (keep looking) */
status = mysql_stmt_next_result(stmt);
if (status > 0)
test_stmt_error(stmt, status);
} while (status == 0);
mysql_stmt_close(stmt);