MAPREDUCE服务 MRS-基于二级索引的查询:代码样例

时间：2023-11-13 09:56:23

MAPREDUCE服务 MRS

代码样例

下面代码片段在com.huawei.hadoop.hbase.example包的“HBaseSample”类的testScanDataByIndex方法中：

样例：使用二级索引查找数据

  public void testScanDataByIndex() {
    LOG.info("Entering testScanDataByIndex.");
    Table table = null;
    ResultScanner scanner = null;
    try {
      table = conn.getTable(tableName);
      
      // Create a filter for indexed column.
      Filter filter = new SingleColumnValueFilter(Bytes.toBytes("info"), Bytes.toBytes("name"),
          CompareOperator.EQUAL, "Li Gang".getBytes());
      Scan scan = new Scan();
      scan.setFilter(filter);
      scanner = table.getScanner(scan);
      LOG.info("Scan indexed data.");
      
      for (Result result : scanner) {
        for (Cell cell : result.rawCells()) {
           LOG.info("{}:{},{},{}", Bytes.toString(CellUtil.cloneRow(cell)),
              Bytes.toString(CellUtil.cloneFamily(cell)), Bytes.toString(CellUtil.cloneQualifier(cell)),
              Bytes.toString(CellUtil.cloneValue(cell)));
        }
      }
      LOG.info("Scan data by index successfully.");
    } catch (IOException e) {
      LOG.error("Scan data by index failed.");
    } finally {
      if (scanner != null) {
        // Close the scanner object.
        scanner.close();
      }
      try {
        if (table != null) {
          table.close();
        }
      } catch (IOException e) {
        LOG.error("Close table failed.");
      }
    }
    
    LOG.info("Exiting testScanDataByIndex.");
  }

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