Hadoop期末复习贴-Hbase过滤器

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• 行过滤器RowFilter

  为什么会产生过滤器，因为在之前get和scan的时候，没有办法得到我们想的数据，虽然get和scan中都有addColumn，但是比起下面Filter，也没谁了。

  过滤器分两步

  • 创建过滤器

    Filter filter = new RowFilter(op,Object)

    op是运算符，Object是比较对象

  • 设置过滤器

    get/scan.setFilter(filter)

  下面来看看行过滤器的代码

  package Filter;
  
  import org.apache.hadoop.conf.*;
  import org.apache.hadoop.hbase.*;
  import org.apache.hadoop.hbase.client.*;
  import org.apache.hadoop.hbase.client.Result;
  import org.apache.hadoop.hbase.client.ResultScanner;
  import org.apache.hadoop.hbase.client.Scan;
  import org.apache.hadoop.hbase.filter.BinaryComparator;
  import org.apache.hadoop.hbase.filter.Filter;
  import org.apache.hadoop.hbase.util.Bytes;
  
  public class RowFilter {
      public static void main(String[] args) throws Exception {
          query("new_table");
      }
  
      public static void printResult(Result result) throws Exception {
          System.out.println("row:" +
                  new String(result.getRow(), "utf-8"));
          for (Cell cell : result.listCells()) {
              String family = Bytes.toString(CellUtil.cloneFamily(cell));
              String qualifier = Bytes.toString(CellUtil.cloneQualifier(cell));
              String value = Bytes.toString(CellUtil.clonevalue(cell));
              System.out.println(family + ":" + qualifier + " " + value);
          }
      }
  
      public static void query(String tName) throws Exception {
          
          Configuration configuration = new Configuration();
          Connection connection = ConnectionFactory.createConnection();
          TableName tableName = TableName.valueOf(tName);
          Table table = connection.getTable(tableName);
  
  
          
          Scan scan = new Scan();
          scan.addColumn(Bytes.toBytes("info"), Bytes.toBytes("name"));
          Filter filter = new org.apache.hadoop.hbase.filter.RowFilter(CompareOperator.EQUAL,
                  new BinaryComparator(Bytes.toBytes("1001")));
          scan.setFilter(filter);
          ResultScanner scanner = table.getScanner(scan);
          for (Result result : scanner) {
              printResult(result);
          }
          Scan scan1 = new Scan();
          scan1.addColumn(Bytes.toBytes("school_info"), Bytes.toBytes("college"));
          Filter filter1 = new org.apache.hadoop.hbase.filter.RowFilter(CompareOperator.GREATER_OR_EQUAL,
                  new BinaryComparator(Bytes.toBytes("2020")));
          scan1.setFilter(filter1);
          ResultScanner results = table.getScanner(scan1);
  
          Scan scan2 = new Scan();
          scan2.addColumn(Bytes.toBytes("basic_info"), Bytes.toBytes("name"));
          Filter filter2 = new org.apache.hadoop.hbase.filter.RowFilter(CompareOperator.LESS_OR_EQUAL,
                  new BinaryComparator(Bytes.toBytes("2018")));
  
  
          scanner.close();
  
      }
  }
  

  CompareOperator op
  op有如下多种场景

• 多种过滤器

  先上來王炸

  1. Get和Scan的不同：Get是通过指定的RowKey来返回一行数据,而Scan是通过特定的条件来返回一批数据。然后两者生成的对象中都有.setFilter方法，即两者都可以和Filter配合使用。
  2. Get结果产生：Result = table.get(get)
     Scan结果产生：ResultScanner = table.getScan(scan)
  3. 固二者最后print的方式也不用，前者直接printResult函数，而后者用有多条Result类型数据，则要循环输出(Result res: ResultScanner…)。
  • 列族过滤器FamilyFilter

           //设置一个列族过滤器，只输出2018行的school_info列族
            Filter filter = new FamilyFilter(CompareOperator.EQUAL,
                    new BinaryComparator(Bytes.toBytes("school_info")));
            Get get = new Get(Bytes.toBytes("2018"));
            get.setFilter(filter);
            Result result = table.get(get);
            printResult(result);
    

  • 列名过滤器QualifierFilter

    		//Scan 设置一个列名过滤器,获取所有列名为name的值
            Scan scan = new Scan();
            Filter filter1 = new QualifierFilter(CompareOperator.EQUAL,
                    new BinaryComparator(Bytes.toBytes("name")));
            scan.setFilter(filter1);
    
    
            //Get 获取行键为2018，列名为name的值
            Get get1 = new Get(Bytes.toBytes("2018"));
            Filter filter2 = new QualifierFilter(CompareOperator.EQUAL,
                    new BinaryComparator(Bytes.toBytes("name")));
            get1.setFilter(filter2);
            Result result1 = table.get(get1);
            printResult(result1);
            
    

  • 值过滤器
    1. 值过滤器ValueFilter，可以帮助用户筛选某个特定值的单元格
    2. 特殊注意，SubstringComparator(是String类型)

    public static void ValueFilterQuery(Table table) throws Exception {
            
            Filter filter3 = new ValueFilter(CompareOperator.EQUAL,
                    new SubstringComparator("Ha"));
            Scan scan = new Scan();
            scan.setFilter(filter3);
            ResultScanner results = table.getScanner(scan);
            //printResult(results);
            for (Result re : results) {
                printResult(re);
            }
        }
    
    

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