Example: Common Functions and Batch Binding

The following is an example of the command for compiling ODBC application code in Windows:
```
gcc  odbctest.c -o odbctest -lodbc32
```
Run the following command:
```
./odbctest.exe
```
The following is an example of the command for compiling ODBC application code in Linux:
```
gcc odbctest.c -o odbctest -lodbc
```
Run the following command:
```
./odbctest
```
If sql.h or API cannot be found during compilation, manually connect to the header file and dynamic library of unixODBC.
```
gcc -I /home/omm/unixodbc/include -L /home/omm/unixodbc/lib odbctest.c -o odbctest -lodbc
```

Code for Common Functions

    
     
       
       
         // The example shows how to obtain data from GaussDB through ODBC.
// DBtest.c (compile with: libodbc.so)   
#ifdef WIN32
#include <windows.h>
#endif
#include <stdio.h> 
#include <stdlib.h> 
#include <sql.h> 
#include <sqlext.h> 
SQLHENV       V_OD_Env;        // Handle ODBC environment 
SQLHSTMT      V_OD_hstmt;      // Handle statement 
SQLHDBC       V_OD_hdbc;       // Handle connection     
char          typename[100];
SQLINTEGER    value = 100;
SQLINTEGER    V_OD_erg,V_OD_buffer,V_OD_err,V_OD_id;
int main(int argc,char *argv[]) 
{         
      // 1. Allocate an environment handle.
      V_OD_erg = SQLAllocHandle(SQL_HANDLE_ENV,SQL_NULL_HANDLE,&V_OD_Env);     
      if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))        
      {           
           printf("Error AllocHandle\n");           
           exit(0);        
      } 
      // 2. Set environment attributes (version information).
      SQLSetEnvAttr(V_OD_Env, SQL_ATTR_ODBC_VERSION, (void*)SQL_OV_ODBC3, 0);      
      // 3. Allocate a connection handle.
      V_OD_erg = SQLAllocHandle(SQL_HANDLE_DBC, V_OD_Env, &V_OD_hdbc);     
      if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))      
      {                     
           SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);          
           exit(0);       
      }
     // In this example, the username and password are stored in environment variables. Before running this example, set environment variables EXAMPLE_USERNAME_ENV and EXAMPLE_PASSWORD_ENV in the local environment (set the environment variable names based on the actual situation).
      char *userName;
      userName = getenv("EXAMPLE_USERNAME_ENV");
      char *password;
      password = getenv("EXAMPLE_PASSWORD_ENV");
      // 4. Set connection attributes.
      SQLSetConnectAttr(V_OD_hdbc, SQL_ATTR_AUTOCOMMIT, (SQLPOINTER *)SQL_AUTOCOMMIT_ON, 0);          
      // 5. Connect to the data source. userName and password indicate the username and password for connecting to the database, respectively.
     // If the username and password have been set in the odbc.ini file, you do not need to set userName or password here, retaining "" for them. However, you are advised not to do so because the username and password will be disclosed if the permission for odbc.ini is abused.
      V_OD_erg = SQLConnect(V_OD_hdbc, (SQLCHAR*) "gaussdb", SQL_NTS,  
                           (SQLCHAR*) userName, SQL_NTS,  (SQLCHAR*) password, SQL_NTS);        
      if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))      
      {           
          printf("Error SQLConnect %d\n",V_OD_erg);            
          SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);       
          exit(0);        
      }     
      printf("Connected !\n"); 
      // 6. Set statement attributes.
      SQLSetStmtAttr(V_OD_hstmt,SQL_ATTR_QUERY_TIMEOUT,(SQLPOINTER *)3,0);
       // 7. Allocate a statement handle.
      SQLAllocHandle(SQL_HANDLE_STMT, V_OD_hdbc, &V_OD_hstmt);       
      // 8. Run SQL statements.
      SQLExecDirect(V_OD_hstmt,"drop table IF EXISTS customer_t1",SQL_NTS);
      SQLExecDirect(V_OD_hstmt,"CREATE TABLE customer_t1(c_customer_sk INTEGER, c_customer_name VARCHAR(32));",SQL_NTS);
      SQLExecDirect(V_OD_hstmt,"insert into customer_t1 values(25,'li')",SQL_NTS);
      // 9. Prepare for execution.
      SQLPrepare(V_OD_hstmt,"insert into customer_t1 values(?)",SQL_NTS); 
      // 10. Bind parameters.
      SQLBindParameter(V_OD_hstmt,1,SQL_PARAM_INPUT,SQL_C_SLONG,SQL_INTEGER,0,0,
                       &value,0,NULL);
      // 11. Run prepared statements.
      SQLExecute(V_OD_hstmt);
      SQLExecDirect(V_OD_hstmt,"select c_customer_sk from customer_t1",SQL_NTS);
      // 12. Obtain attributes of a specific column in the result set.
      SQLColAttribute(V_OD_hstmt,1,SQL_DESC_TYPE,typename,100,NULL,NULL);                 
      printf("SQLColAtrribute %s\n",typename);
      // 13. Bind the result set.
      SQLBindCol(V_OD_hstmt,1,SQL_C_SLONG, (SQLPOINTER)&V_OD_buffer,150,
                (SQLLEN *)&V_OD_err);
      // 14. Obtain data in the result set by executing SQLFetch.
      V_OD_erg=SQLFetch(V_OD_hstmt);
      // 15. Obtain and return data by executing SQLGetData.
      while(V_OD_erg != SQL_NO_DATA)
      {
          SQLGetData(V_OD_hstmt,1,SQL_C_SLONG,(SQLPOINTER)&V_OD_id,0,NULL);
          printf("SQLGetData ----ID = %d\n",V_OD_id);
          V_OD_erg=SQLFetch(V_OD_hstmt);
      };
      printf("Done !\n");
      // 16. Disconnect data source connections and release handles.
      SQLFreeHandle(SQL_HANDLE_STMT,V_OD_hstmt);    
      SQLDisconnect(V_OD_hdbc);         
      SQLFreeHandle(SQL_HANDLE_DBC,V_OD_hdbc);       
      SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);  
      return(0);
 }

        

      

    
   

Code for Batch Processing

    
     
       
       
         /**********************************************************************
* Enable UseBatchProtocol in the data source and set the database parameter support_batch_bind to on.
*The CHECK_ERROR command is used to check and print error information.
*This example is used to interactively obtain the DSN, data volume to be processed, and volume of ignored data from users, and insert required data into the test_odbc_batch_insert table.
***********************************************************************/
#ifdef WIN32
#include <windows.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <sql.h>
#include <sqlext.h>
#include <string.h>
void Exec(SQLHDBC hdbc, SQLCHAR* sql)
{
    SQLRETURN retcode;                  // Return status
    SQLHSTMT hstmt = SQL_NULL_HSTMT;    // Statement handle
    SQLCHAR     loginfo[2048];
    // Allocate Statement Handle
    retcode = SQLAllocHandle(SQL_HANDLE_STMT, hdbc, &hstmt);
    
    if (!SQL_SUCCEEDED(retcode)) {
        printf("SQLAllocHandle(SQL_HANDLE_STMT) failed");
        return;
    }
    // Prepare Statement
    retcode = SQLPrepare(hstmt, (SQLCHAR*) sql, SQL_NTS);
    sprintf((char*)loginfo, "SQLPrepare log: %s", (char*)sql);
    
    if (!SQL_SUCCEEDED(retcode)) {
        printf("SQLPrepare(hstmt, (SQLCHAR*) sql, SQL_NTS) failed");
        return;
    }
    // Execute Statement
    retcode = SQLExecute(hstmt);
    sprintf((char*)loginfo, "SQLExecute stmt log: %s", (char*)sql);
    
    if (!SQL_SUCCEEDED(retcode)) {
        printf("SQLExecute(hstmt) failed");
        return;
    }
    // Free Handle
    retcode = SQLFreeHandle(SQL_HANDLE_STMT, hstmt);
    sprintf((char*)loginfo, "SQLFreeHandle stmt log: %s", (char*)sql);
    
    if (!SQL_SUCCEEDED(retcode)) {
        printf("SQLFreeHandle(SQL_HANDLE_STMT, hstmt) failed");
        return;
    }
}
int main () 
{
    SQLHENV  henv  = SQL_NULL_HENV;
    SQLHDBC  hdbc  = SQL_NULL_HDBC; 
    long     int      batchCount = 1000; // Amount of data that is bound in batches
    SQLLEN   rowsCount = 0;
    int      ignoreCount = 0; // Amount of data that is not imported to the database among the data that is bound in batches
    int      i = 0;
    SQLRETURN   retcode;
    SQLCHAR     dsn[1024] = {'\0'};
    SQLCHAR     loginfo[2048];
    do 
    {
        if (ignoreCount > batchCount)
        {
            printf("ignoreCount(%d) should be less than batchCount(%d)\n", ignoreCount, batchCount);
        }
    }while(ignoreCount > batchCount);
    retcode = SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &henv);
    
    if (!SQL_SUCCEEDED(retcode)) {
        printf("SQLAllocHandle failed");
        goto exit;
    }
    // Set ODBC version.
    retcode = SQLSetEnvAttr(henv, SQL_ATTR_ODBC_VERSION,
                                        (SQLPOINTER*)SQL_OV_ODBC3, 0);
    
    if (!SQL_SUCCEEDED(retcode)) {
        printf("SQLSetEnvAttr failed");
        goto exit;
    }
    // Allocate Connection
    retcode = SQLAllocHandle(SQL_HANDLE_DBC, henv, &hdbc);
    
    if (!SQL_SUCCEEDED(retcode)) {
        printf("SQLAllocHandle failed");
        goto exit;
    }
    // Set Login Timeout
    retcode = SQLSetConnectAttr(hdbc, SQL_LOGIN_TIMEOUT, (SQLPOINTER)5, 0);
    
    if (!SQL_SUCCEEDED(retcode)) {
        printf("SQLSetConnectAttr failed");
        goto exit;
    }
    // Set Auto Commit
    retcode = SQLSetConnectAttr(hdbc, SQL_ATTR_AUTOCOMMIT,
                                        (SQLPOINTER)(1), 0);
    
    if (!SQL_SUCCEEDED(retcode)) {
        printf("SQLSetConnectAttr failed");
        goto exit;
    }
    // Connect to DSN
    // Replace GaussDB with the name of the data source used by the user.
    sprintf(loginfo, "SQLConnect(DSN:%s)", dsn);
    retcode = SQLConnect(hdbc, (SQLCHAR*) "gaussdb", SQL_NTS,
                               (SQLCHAR*) NULL, 0, NULL, 0);
    
    if (!SQL_SUCCEEDED(retcode)) {
        printf("SQLConnect failed");
        goto exit;
    }
    // init table info.
    Exec(hdbc, "drop table if exists test_odbc_batch_insert");
    Exec(hdbc, "create table test_odbc_batch_insert(id int primary key, col varchar2(50))");
   // The following code constructs the data to be inserted based on the data volume entered by users:
    {
        SQLRETURN retcode; 
        SQLHSTMT hstmtinesrt = SQL_NULL_HSTMT;
        SQLCHAR      *sql = NULL;
        SQLINTEGER   *ids  = NULL;
        SQLCHAR      *cols = NULL;
        SQLLEN       *bufLenIds = NULL;
        SQLLEN       *bufLenCols = NULL;
        SQLUSMALLINT *operptr = NULL;
        SQLUSMALLINT *statusptr = NULL;
        SQLULEN      process = 0;
        // Data is constructed by column. Each column is stored continuously.
        ids = (SQLINTEGER*)malloc(sizeof(ids[0]) * batchCount);
        cols = (SQLCHAR*)malloc(sizeof(cols[0]) * batchCount * 50);
       // Data size in each row for a column
        bufLenIds = (SQLLEN*)malloc(sizeof(bufLenIds[0]) * batchCount);
        bufLenCols = (SQLLEN*)malloc(sizeof(bufLenCols[0]) * batchCount);
       // Specifies whether this row needs to be processed. The value is SQL_PARAM_IGNORE or SQL_PARAM_PROCEED.
        operptr = (SQLUSMALLINT*)malloc(sizeof(operptr[0]) * batchCount);
        memset(operptr, 0, sizeof(operptr[0]) * batchCount);
       // Processing result of the row
       // Note: In the database, a statement belongs to one transaction. Therefore, data is processed as a unit. Either all data is inserted successfully or all data fails to be inserted.
        statusptr = (SQLUSMALLINT*)malloc(sizeof(statusptr[0]) * batchCount);
        memset(statusptr, 88, sizeof(statusptr[0]) * batchCount);
        if (NULL == ids || NULL == cols || NULL == bufLenCols || NULL == bufLenIds)
        {
            fprintf(stderr, "FAILED:\tmalloc data memory failed\n");
            goto exit;
        }
        for (i = 0; i < batchCount; i++)
        {
            ids[i] = i;
            sprintf(cols + 50 * i, "column test value %d", i);
            bufLenIds[i] = sizeof(ids[i]);
            bufLenCols[i] = strlen(cols + 50 * i);
            operptr[i] = (i < ignoreCount) ? SQL_PARAM_IGNORE : SQL_PARAM_PROCEED;
        }
        // Allocate Statement Handle
        retcode = SQLAllocHandle(SQL_HANDLE_STMT, hdbc, &hstmtinesrt);
        
        if (!SQL_SUCCEEDED(retcode)) {
            printf("SQLAllocHandle failed");
            goto exit;
        }
        // Prepare Statement
        sql = (SQLCHAR*)"insert into test_odbc_batch_insert values(?, ?)";
        retcode = SQLPrepare(hstmtinesrt, (SQLCHAR*) sql, SQL_NTS);
        sprintf((char*)loginfo, "SQLPrepare log: %s", (char*)sql);
        
        if (!SQL_SUCCEEDED(retcode)) {
            printf("SQLPrepare failed");
            goto exit;
        }
        retcode = SQLSetStmtAttr(hstmtinesrt, SQL_ATTR_PARAMSET_SIZE, (SQLPOINTER)batchCount, sizeof(batchCount));
        
        if (!SQL_SUCCEEDED(retcode)) {
            printf("SQLSetStmtAttr failed");
            goto exit;
        }
        retcode = SQLBindParameter(hstmtinesrt, 1, SQL_PARAM_INPUT, SQL_C_SLONG, SQL_INTEGER, sizeof(ids[0]), 0,&(ids[0]), 0, bufLenIds);
        
        if (!SQL_SUCCEEDED(retcode)) {
            printf("SQLBindParameter failed");
            goto exit;
        }
        retcode = SQLBindParameter(hstmtinesrt, 2, SQL_PARAM_INPUT, SQL_C_CHAR, SQL_CHAR, 50, 50, cols, 50, bufLenCols);
        
        if (!SQL_SUCCEEDED(retcode)) {
            printf("SQLBindParameter failed");
            goto exit;
        }
        retcode = SQLSetStmtAttr(hstmtinesrt, SQL_ATTR_PARAMS_PROCESSED_PTR, (SQLPOINTER)&process, sizeof(process));
        
        if (!SQL_SUCCEEDED(retcode)) {
            printf("SQLSetStmtAttr failed");
            goto exit;
        }
        retcode = SQLSetStmtAttr(hstmtinesrt, SQL_ATTR_PARAM_STATUS_PTR, (SQLPOINTER)statusptr, sizeof(statusptr[0]) * batchCount);
        
        if (!SQL_SUCCEEDED(retcode)) {
            printf("SQLSetStmtAttr failed");
            goto exit;
        }
        retcode = SQLSetStmtAttr(hstmtinesrt, SQL_ATTR_PARAM_OPERATION_PTR, (SQLPOINTER)operptr, sizeof(operptr[0]) * batchCount);
        
        if (!SQL_SUCCEEDED(retcode)) {
            printf("SQLSetStmtAttr failed");
            goto exit;
        }
        retcode = SQLExecute(hstmtinesrt);
        sprintf((char*)loginfo, "SQLExecute stmt log: %s", (char*)sql);
        
        if (!SQL_SUCCEEDED(retcode)) {
            printf("SQLExecute(hstmtinesrt) failed");
            goto exit;
            retcode = SQLRowCount(hstmtinesrt, &rowsCount);
            
            if (!SQL_SUCCEEDED(retcode)) {
                printf("SQLRowCount failed");
                goto exit;
            }
            if (rowsCount != (batchCount - ignoreCount))
            {
                sprintf(loginfo, "(batchCount - ignoreCount)(%d) != rowsCount(%d)", (batchCount - ignoreCount), rowsCount);
                
                if (!SQL_SUCCEEDED(retcode)) {
                    printf("SQLExecute failed");
                    goto exit;
                }
            }
            else
            {
                sprintf(loginfo, "(batchCount - ignoreCount)(%d) == rowsCount(%d)", (batchCount - ignoreCount), rowsCount);
                
                if (!SQL_SUCCEEDED(retcode)) {
                    printf("SQLExecute failed");
                    goto exit;
                }
            }
            // check row number returned
            if (rowsCount != process)
            {
                sprintf(loginfo, "process(%d) != rowsCount(%d)", process, rowsCount);
                
                if (!SQL_SUCCEEDED(retcode)) {
                    printf("SQLExecute failed");
                    goto exit;
                }
            }
            else
            {
                sprintf(loginfo, "process(%d) == rowsCount(%d)", process, rowsCount);
                
                if (!SQL_SUCCEEDED(retcode)) {
                    printf("SQLExecute failed");
                    goto exit;
                }
            }
            for (i = 0; i < batchCount; i++)
            {
                if (i < ignoreCount)
                {
                    if (statusptr[i] != SQL_PARAM_UNUSED)
                    {
                        sprintf(loginfo, "statusptr[%d](%d) != SQL_PARAM_UNUSED", i, statusptr[i]);
                        
                        if (!SQL_SUCCEEDED(retcode)) {
                            printf("SQLExecute failed");
                            goto exit;
                        }
                    }
                }
                else if (statusptr[i] != SQL_PARAM_SUCCESS)
                {
                    sprintf(loginfo, "statusptr[%d](%d) != SQL_PARAM_SUCCESS", i, statusptr[i]);
                    
                    if (!SQL_SUCCEEDED(retcode)) {
                        printf("SQLExecute failed");
                        goto exit;
                    }
                }
            }
            retcode = SQLFreeHandle(SQL_HANDLE_STMT, hstmtinesrt);
            sprintf((char*)loginfo, "SQLFreeHandle hstmtinesrt");
            
            if (!SQL_SUCCEEDED(retcode)) {
                printf("SQLFreeHandle failed");
                goto exit;
            }
        }
    }
exit:
    (void) printf ("\nComplete.\n");
    // Connection
    if (hdbc != SQL_NULL_HDBC) {
        SQLDisconnect(hdbc);
        SQLFreeHandle(SQL_HANDLE_DBC, hdbc);
    }
    // Environment
    if (henv != SQL_NULL_HENV)
        SQLFreeHandle(SQL_HANDLE_ENV, henv);
    return 0;
}

        

      

    
   

Connection Pool Scenario

A connection pool allows applications to reuse pre-established connections without re-establishing connections each time. Once a connection is created and put into the connection pool, applications can reuse the connection, avoiding repeated execution of the complete connection process.

The use of a connection pool can significantly improve performance, especially for middle-layer applications or applications requiring network connections that need to establish and close connections frequently.

In addition to the performance advantage, the connection pool architecture enables connections in the environment to be shared by multiple components in a single process. Therefore, different components in the same process can share connections in the connection pool without interfering with each other, further improving system efficiency and resource utilization.

In a connection pool, an open connection may be reused by multiple users. If an application script changes the database connection status, data leakage may occur. For security purposes, exercise caution when using a connection pool.

Configurations on Linux

Enable an connection pool in the odbcinst.ini configuration file. The reference configuration of the connection pool is as follows:

[ODBC]
Pooling=Yes # Enable an connection pool.
[GaussMPP]
CPTimeout=60 # Timeout for releasing a connection that is not reused in the connection pool. The default value is 0. To enable the connection pool, set this parameter to a value greater than 0.
CPTimeToLive=60 # Lifetime of the connection pool under the driver.
[GaussMPP2]
CPTimeout=0 # Disable the connection pool.

Configurations on Windows

On the Connection Pool tab, double-click GaussDB Unicode, and select Pool Connections to this driver (the default value is 60s). This parameter is the same as CPTimeout configured on Linux.

To configure the connection pool parameters in the application, you need to call SQLSetEnvAttr to set the connection pool parameters before creating the environment handle. The environment handle must be set to null. In this case, SQL_ATTR_CONNECTION_POOLING becomes a process-level attribute.
Currently, SQL_ATTR_CONNECTION_POOLING can be set to either of the following values on Windows:
- SQL_CP_OFF (Default): Disable a connection pool.
- SQL_CP_ONE_PER_DRIVER: Enable a connection pool. Each driver supports a connection pool, and all connections in the driver share the same connection pool.
When an application calls SQLConnect or SQLDriverConnect, the connection is extracted from the connection pool. If the connection times out or no connection matches the request in the pool, a new connection is opened. The connection pool is transparent to the application.
When an application calls SQLDisconnect, the connection is not released but put back to the connection pool for the next use.
Before SQLFreeHandle is called in the environment to release the environment handle, all environment attributes that are successfully set by an application persist.
If a connection of an application is inactive (not used) for a period of time, the connection is deleted from the pool. The size of the connection pool is limited only by the memory and server.

Code examples

Enabling a connection pool on Linux or Windows can significantly improve the performance of middle-layer applications that need to establish and close connections frequently. The reference configurations are as described above. The sample code is as follows:

#ifdef WIN32
#include <windows.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <sql.h>
#include <sqlext.h>
#include <string.h>
#include <sys/time.h>
#include <pthread.h>
#include <sqltypes.h>
#include <time.h>
SQLHENV env;
SQLHDBC conn;
struct timeval start, end;

#define CONN_COUNT 15000
#define CHECK_ERROR(retcode, str, handle, htype)                          \
    ({                                                                    \
        if (retcode != SQL_SUCCESS && retcode != SQL_SUCCESS_WITH_INFO) { \
            fprintf(stderr, "FAILED:\t");                                 \
            extract_error(str, handle, htype);                            \
            exit(-1);                                                     \
        } else {                                                          \
            printf("OK:\t%s\n", str);                                     \
        }                                                                 \
    })

void print_diag(char *msg, SQLSMALLINT htype, SQLHANDLE handle)
{
    char sqlstate[32];
    char message[1000];
    SQLINTEGER nativeerror;
    SQLSMALLINT textlen;
    SQLRETURN ret;

    if (msg) {
        printf("%s\n", msg);
    }

    ret = SQLGetDiagRec(htype, handle, 1, sqlstate, &nativeerror, message, 256, &textlen);

    if (ret != SQL_ERROR) {
        printf("%s=%s\n", (CHAR *)sqlstate, (CHAR *)message);
    }
}

void extract_error(char *fn, SQLHANDLE handle, SQLSMALLINT type)
{
    SQLINTEGER i = 0;
    SQLINTEGER NativeError;
    SQLCHAR SQLState[7];
    SQLCHAR MessageText[256];
    SQLSMALLINT TextLength;
    SQLRETURN ret;

    fprintf(stderr, "The driver reported the following error %s\n", fn);
    if (NULL == handle)
        return;
    do {
        ret = SQLGetDiagRec(type, handle, ++i, SQLState, &NativeError, MessageText, sizeof(MessageText), &TextLength);
        if (SQL_SUCCEEDED(ret)) {
            printf("[SQLState:%s]:[%ldth error]:[NativeError:%ld]: %s\n",
                SQLState,
                (long)i,
                (long)NativeError,
                MessageText);
        }
    } while (ret == SQL_SUCCESS);
}

void InitializeEnvironment()
{
    
    /* Enable a connection pool. Configure connection pool parameters on Windows before allocating an environment handle. */
    SQLSetEnvAttr(env, SQL_ATTR_CONNECTION_POOLING, (SQLINTEGER *)SQL_CP_ONE_PER_DRIVER, 0);

    /* Disable the connection pool on Windows. */
    // SQLSetEnvAttr(env, SQL_ATTR_CONNECTION_POOLING, (SQLINTEGER*)SQL_CP_OFF, 0);
    
    // Allocate an environment handle.
    SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &env);
    // Configure the ODBC version.
    SQLSetEnvAttr(env, SQL_ATTR_ODBC_VERSION, (SQLPOINTER)SQL_OV_ODBC3, 0);
    // Configure the timeout interval for establishing a connection.
    SQLSetConnectAttr(conn, SQL_LOGIN_TIMEOUT, (SQLPOINTER *)5, 0);
}

void test_connect()
{
    SQLRETURN ret;
    SQLCHAR str[1024];
    SQLSMALLINT strl;
    SQLCHAR dsn[1024];
    SQLUINTEGER uIntVal;

    SQLAllocHandle(SQL_HANDLE_DBC, env, &conn);

    /* Adjust the connection string based on the scenario. */
    char *config = "Driver=GaussMPP;DSN=gaussdb;";
    ret = SQLSetConnectAttr(conn, SQL_ATTR_AUTOCOMMIT, (SQLPOINTER)(1), 0);

    ret = SQLDriverConnect(conn, 0, (SQLCHAR *)config, SQL_NTS, (SQLCHAR *)NULL, SQL_NTS, 0, SQL_DRIVER_NOPROMPT);

    if (SQL_SUCCEEDED(ret)) {
        // printf("Connected\n");
    } else {
        print_diag("SQLDriverConnect failed.", SQL_HANDLE_DBC, conn);
        SQLFreeHandle(SQL_HANDLE_DBC, conn);
        SQLFreeHandle(SQL_HANDLE_ENV, env);
        exit(1);
    }

    /* Put the connection into the connection pool to reuse the connection. */
    if (conn != SQL_NULL_HDBC) {
        SQLDisconnect(conn);
        SQLFreeHandle(SQL_HANDLE_DBC, conn);
        conn = SQL_NULL_HDBC;
    }
}

int main()
{
    int count = 0;
    int timeuser;
    gettimeofday(&start, NULL);
    InitializeEnvironment();

    for (int i = 0; i < CONN_COUNT; i++) {
        test_connect();
        count++;
    }

    // Release an environment handle.
    SQLFreeHandle(SQL_HANDLE_ENV, env);
    printf("Connection count: %d\n", count);
    gettimeofday(&end, NULL);
    timeuser = 1000000 * (end.tv_sec - start.tv_sec) + end.tv_usec - start.tv_usec;
    printf("Connection time: %.3f s \n", (double)timeuser / 1000000);
    return 0;
}

The result varies with the environment. When the connection pool is enabled, the running result of this example is as follows:

Connection count: 15000
Connection time: 14.175 s

When the connection pool is disabled, the running result of this example is as follows:

Connection count: 15000
Connection time: 691.768 s

The application code on Windows is the same as that on Linux. The connection string needs to be configured based on the scenario.

Parent topic: Development Based on ODBC

Previous topic: Configuring a Data Source in the Windows OS

Next topic: Typical Application Scenarios and Configurations

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