Oceanbase C客户端实例

虽然在ObConnector的帮助下，Oceanbase已经能够被psql等通用SQL客户端访问，但在一些特定场合（例如调试）可能还是需要对查询有更强的控制，这时候依然需要用户自己编写C/Java客户端，下面以一个例子简要说明C客户端的编写方法。

#include <stdio.h>#include <stdlib.h>#include <string.h>#include "oceanbase.h"/////////////结果打印函数开始//////////////////////////const int MAX_DISPLAY_ROW_KEY_LEN = 48;char* get_display_row_key(const char* row_key, int64_t row_key_len){  const int aux_len = 2;  const int ending_len = 1;  static char dis_row_key[MAX_DISPLAY_ROW_KEY_LEN + aux_len + ending_len];  int64_t dis_row_key_len = row_key_len <= MAX_DISPLAY_ROW_KEY_LEN / 2 ?                            row_key_len : MAX_DISPLAY_ROW_KEY_LEN / 2;  int64_t dis_len = dis_row_key_len * 2;  dis_row_key[0] = '0';  dis_row_key[1] = 'x';  int i = 0;  for (i = 0; i < dis_row_key_len; i++)  {    snprintf(dis_row_key + i * 2 + aux_len, 3, "%02x", (unsigned char)row_key[i]);  }  dis_row_key[dis_len + aux_len] = '\0';  return dis_row_key;}char* rowkey2hex(const char* row_key, int64_t row_key_len){  static char* hex = NULL;  static int64_t hex_len = 0;  if (NULL == hex || hex_len <= row_key_len)  {    if (NULL != hex && hex_len <= row_key_len)    {      free(hex);      hex = NULL;    }    hex = (char*)malloc(row_key_len + 1);    if (NULL != hex)    {      hex_len = row_key_len + 1;    }  }  if (NULL != hex)  {    snprintf(hex, hex_len, "%.*x", row_key_len, row_key);  }  return hex;}char* trim_newline(char* s){  int s_len = strlen(s);  while (s_len > 0 && s[s_len - 1] == '\n')  {    s[s_len - 1] = '\0';    s_len--;  }  return s;}void pcell(OB_CELL* cell){  printf("%ld", cell->table_len);  printf("%.*s\t%s(%ld)\t%.*s\t",         (int)cell->table_len, cell->table,         rowkey2hex(cell->row_key, cell->row_key_len), cell->row_key_len,         (int)cell->column_len, cell->column);  switch (cell->v.type)  {    case OB_INT_TYPE:      printf("%ld", cell->v.v.v_int);      break;    case OB_VARCHAR_TYPE:      printf("%.*s", cell->v.v.v_varchar.len, cell->v.v.v_varchar.p);      break;    case OB_DATETIME_TYPE:      printf("\t%s(%d.%d)", trim_newline(ctime(&(cell->v.v.v_datetime.tv_sec))),          cell->v.v.v_datetime.tv_sec, cell->v.v.v_datetime.tv_usec);      break;  }  if (cell->is_null || cell->is_row_not_exist || cell->is_row_changed)  {    printf("(%s%s%s)\n",           cell->is_null ? "NULL " : "",           cell->is_row_not_exist ? "ROW NOT EXIST " : "",         cell->is_row_changed ? "NEW ROW" : "");  }  else  {    printf("\n");  }}void pcolumnname(OB_RES* res){  OB_CELL* cell = NULL;  cell = ob_fetch_cell(res);  if (NULL != cell)  {    printf("\t\t%.*s", cell->column_len, cell->column);  }  while ((cell = ob_fetch_cell(res)) != NULL && !cell->is_row_changed)  {    printf("\t%.*s", cell->column_len, cell->column);  }}void pres(OB_RES* res){  pcolumnname(res);  printf("\n");  ob_res_seek_to_begin_cell(res);  OB_ROW* row = NULL;  while ((row = ob_fetch_row(res)) != NULL)  {    int64_t i = 0;    printf("%s", get_display_row_key(row->cell[0].row_key, row->cell[0].row_key_len));    for (; i < row->cell_num; i++)    {      switch (row->cell[i].v.type)      {        case OB_INT_TYPE:          printf("\t%ld", row->cell[i].v.v.v_int);          break;        case OB_VARCHAR_TYPE:          printf("\t%.*s", row->cell[i].v.v.v_varchar.len, row->cell[i].v.v.v_varchar.p);          break;        case OB_DATETIME_TYPE:          printf("\t%s(%d.%d)", trim_newline(ctime(&(row->cell[i].v.v.v_datetime.tv_sec))),              row->cell[i].v.v.v_datetime.tv_sec, row->cell[i].v.v.v_datetime.tv_usec);          break;      }    }    printf("\n");  }}/////////////结果打印函数结束////////////////////////////// 上面是结果输出部分，主要是处理一些字符串和格式化问题，稍微看看即可。重点请关注下面的核心逻辑int main(int argc, char **argv){  /// select nick,auc_cnt_max_cnt,prov from test_seller_wm_4   /// where /*+ rowkey, issue_id:6,cat_id:8,selr_user_id:8 */ issue_id = '201145' and cat_id=16   /// and nick='lovinlovin3' and prov='shanghai3' limit 2 offset 0;/*  char* table = "collect_item";  char* column1 = "item_collector_count";  char* column2 = "item_collect_count";  char* rowkey1 = "AAAAAAAAA";  char* rowkey2 = "AAAAAAAAF";*/  char* table = "test_seller_wm_4";  char* column1 = "nick";  char* column2 = "prov";  char* column3 = "auc_cnt_max_cnt";  char rowkey1[44];  char rowkey2[44];  OB_ERR_CODE err = OB_ERR_SUCCESS;  memset(rowkey1, 0x00, 44);  memset(rowkey2, 0x00, 44);    memcpy(&rowkey1[0], "201145", 6);  rowkey1[8+6-1] = 16;    memcpy(&rowkey2[0], "201145", 6);  rowkey2[8+6-1] = 16;  memset(&rowkey2[14], 0xff, 8);      OB* ob = ob_api_init();  if (NULL == ob)  {    fprintf(stderr, "ob_init error: %s\n", ob_error());    return 1;  }  ob_api_debug_log(ob, "DEBUG", NULL);  if (argc > 2)  {    fprintf(stderr, "connection param used: %s:%s\n", argv[1], argv[2]);    char *rs_ip = argv[1];    int rs_port = atoi(argv[2]);    // 连接OceanBase    err = ob_connect(ob, rs_ip, rs_port, NULL, NULL);  }  else  {    // 连接OceanBase    err = ob_connect(ob, "172.24.131.234", 5433, NULL, NULL);  }  if (OB_ERR_SUCCESS != err)  {    fprintf(stderr, "ob_connect error: %s\n", ob_error());  }  else  {    // 获得OB_SCAN结构体    OB_SCAN* scan_st = ob_acquire_scan_st(ob);    if (NULL == scan_st)    {      fprintf(stderr, "ob_acquire_scan_st error: %s\n", ob_error());    }    else    {      memset(rowkey1, 0x00, 22);      memset(rowkey2, 0xff, 22);      ob_scan(scan_st, table, rowkey1, 22, 1, rowkey2, 22, 1);      ob_scan_column(scan_st, "nick", 1);      ob_scan_column(scan_st, "prov", 1);      //ob_scan_complex_column(scan_st, "1=1", "_expr0", 0);      //ob_scan_complex_column(scan_st, "2 < 1", "_expr1", 0);      ob_scan_complex_column(scan_st, "nick='lovinlovin'", "_expr0", 0);      ob_scan_complex_column(scan_st, "`prov`='shanghai'", "_expr1", 0);      //ob_scan_complex_column(scan_st, "3+4", "_expr2", 0);            //ob_scan_complex_column(scan_st, "nick='songyi0209'", "_expr1", 0);            //ob_scan_set_where(scan_st, "nick='lovinlovin' and prov='shanghai'");      //ob_scan_set_where(scan_st, "_expr0 or nick='songyi0209'");      if (argc > 3)      {      }      else      {        //ob_scan_set_where(scan_st, "`_expr0` = `_expr0` and `prov`='beijing'");        fprintf(stderr, "++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++\n");        //ob_scan_set_where(scan_st, "_expr2 < 10 and (_expr1 or _expr0)");        ob_scan_set_where(scan_st, "_expr1 and _expr0");      }      //ob_scan_set_where(scan_st, "_expr0 = _expr1");      //ob_scan_set_where(scan_st, "nick='lovinlovin'");      //ob_scan_column(scan_st, column2, 1);      //ob_scan_column(scan_st, column3, 1);      ob_scan_set_limit(scan_st,0, 20);      if (OB_ERR_SUCCESS != ob_errno())      {        fprintf(stderr, "ob_scan error: %s\n", ob_error());      }      else      {        OB_RES* res_st = ob_exec_scan(ob, scan_st);        if (NULL == res_st)        {          fprintf(stderr, "ob_exec_scan error(%d): %s\n", ob_errno(), ob_error());        }        else        {          printf("scan succ: row_num=%ld\n", ob_fetch_row_num(res_st));          pres(res_st);#if 0          OB_CELL* cell = NULL;          while ((cell = ob_fetch_cell(res_st)) != NULL)          {            pcell(cell);          }#endif                  }        ob_release_res_st(ob, res_st);      }    ob_release_scan_st(ob, scan_st);    }  }  ob_api_destroy(ob);  return 0;}

执行方式：

./scan_client  rs_ip   rs_port

简要说明：

主要函数包括：

ob_api_init,ob_connect,ob_acquire_scan_st,ob_scan,ob_scan_column,ob_scan_complex_column,ob_scan_set_where,ob_scan_set_limit,ob_exec_scan,ob_fetch_cell,ob_release_scan_st,ob_api_destroy

其中ob_scan,ob_scan_column,ob_scan_complex_column,ob_scan_set_where,ob_scan_set_limit,ob_exec_scan这几个函数是与scan相关的（oceanbase还支持get，支持单个或者多个cell的获取，而不是scan这种按行获取）

Oceanbase C客户端 API手册下载：

http://ishare.iask.sina.com.cn/f/22948741.html

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