HBase权威指南阅读——第四章（一）

base过滤器的比较操作符：

LESS  <
LESS_OR_EQUAL <=
EQUAL =
NOT_EQUAL <>
GREATER_OR_EQUAL >=
GREATER >
NO_OP no operation

比较器：

BinaryComparator  按字节索引顺序比较指定字节数组，采用Bytes.compareTo(byte[])
BinaryPrefixComparator 跟前面相同，只是比较左端的数据是否相同
NullComparator 判断给定的是否为空
BitComparator 按位比较 a BitwiseOp class 做异或，与，并操作
RegexStringComparator 提供一个正则的比较器，仅支持 EQUAL 和非EQUAL

SubstringComparator 判断提供的子串是否出现在table的value中。

Hbase的过滤器分类

比较过滤器

1、Comparision Filters
     1.1  RowFilter

构造函数

public RowFilter(org.apache.hadoop.hbase.filter.CompareFilter.CompareOp rowCompareOp, org.apache.hadoop.hbase.filter.WritableByteArrayComparable rowComparator) {} 

选择比较rowkey来确定选择合适的行信息。

public class RowFilterExample {    public static void main(String[] args) throws IOException {      Configuration conf = HBaseConfiguration.create();        HBaseHelper helper = HBaseHelper.getHelper(conf);      helper.dropTable("testtable");      helper.createTable("testtable", "colfam1", "colfam2");      System.out.println("Adding rows to table...");      helper.fillTable("testtable", 1, 100, 100, "colfam1", "colfam2");        HTable table = new HTable(conf, "testtable");        // vv RowFilterExample      Scan scan = new Scan();      scan.addColumn(Bytes.toBytes("colfam1"), Bytes.toBytes("col-0"));        Filter filter1 = new RowFilter(CompareFilter.CompareOp.LESS_OR_EQUAL, // co RowFilterExample-1-Filter1 Create filter, while specifying the comparison operator and comparator. Here an exact match is needed.        new BinaryComparator(Bytes.toBytes("row-22")));      scan.setFilter(filter1);      ResultScanner scanner1 = table.getScanner(scan);      // ^^ RowFilterExample      System.out.println("Scanning table #1...");      // vv RowFilterExample      for (Result res : scanner1) {        System.out.println(res);      }      scanner1.close();        Filter filter2 = new RowFilter(CompareFilter.CompareOp.EQUAL, // co RowFilterExample-2-Filter2 Another filter, this time using a regular expression to match the row keys.        new RegexStringComparator(".*-.5"));      scan.setFilter(filter2);      ResultScanner scanner2 = table.getScanner(scan);      // ^^ RowFilterExample      System.out.println("Scanning table #2...");      // vv RowFilterExample      for (Result res : scanner2) {        System.out.println(res);      }      scanner2.close();        Filter filter3 = new RowFilter(CompareFilter.CompareOp.EQUAL, // co RowFilterExample-3-Filter3 The third filter uses a substring match approach.        new SubstringComparator("-5"));      scan.setFilter(filter3);      ResultScanner scanner3 = table.getScanner(scan);      // ^^ RowFilterExample      System.out.println("Scanning table #3...");      // vv RowFilterExample      for (Result res : scanner3) {        System.out.println(res);      }      scanner3.close();      // ^^ RowFilterExample    }  }  

1.2  FamilyFilter

构造函数

public FamilyFilter(CompareOp familyCompareOp, WritableByteArrayComparable familyComparator) {}  

通过和列簇比较得到，返回结果为真的数据，示例：

public class FamilyFilterExample {      public static void main(String[] args) throws IOException {      Configuration conf = HBaseConfiguration.create();        HBaseHelper helper = HBaseHelper.getHelper(conf);      helper.dropTable("testtable");      helper.createTable("testtable", "colfam1", "colfam2", "colfam3", "colfam4");      System.out.println("Adding rows to table...");      helper.fillTable("testtable", 1, 10, 2, "colfam1", "colfam2", "colfam3", "colfam4");        HTable table = new HTable(conf, "testtable");        // vv FamilyFilterExample      Filter filter1 = new FamilyFilter(CompareFilter.CompareOp.LESS, // co FamilyFilterExample-1-Filter Create filter, while specifying the comparison operator and comparator.        new BinaryComparator(Bytes.toBytes("colfam3")));        Scan scan = new Scan();      scan.setFilter(filter1);      ResultScanner scanner = table.getScanner(scan); // co FamilyFilterExample-2-Scan Scan over table while applying the filter.      // ^^ FamilyFilterExample      System.out.println("Scanning table... ");      // vv FamilyFilterExample      for (Result result : scanner) {        System.out.println(result);      }      scanner.close();        Get get1 = new Get(Bytes.toBytes("row-5"));      get1.setFilter(filter1);      Result result1 = table.get(get1); // co FamilyFilterExample-3-Get Get a row while applying the same filter.      System.out.println("Result of get(): " + result1);        Filter filter2 = new FamilyFilter(CompareFilter.CompareOp.EQUAL,        new BinaryComparator(Bytes.toBytes("colfam3")));      Get get2 = new Get(Bytes.toBytes("row-5")); // co FamilyFilterExample-4-Mismatch Create a filter on one column family while trying to retrieve another.      get2.addFamily(Bytes.toBytes("colfam1"));      get2.setFilter(filter2);      Result result2 = table.get(get2); // co FamilyFilterExample-5-Get2 Get the same row while applying the new filter, this will return "NONE".      System.out.println("Result of get(): " + result2);      // ^^ FamilyFilterExample    }  }  

     1.3 QualifierFilter

构造函数

public QualifierFilter(CompareOp qualifierCompareOp, WritableByteArrayComparable qualifierComparator) {  }  

通过和列名比较，返回为真的数据，示例：

// vv QualifierFilterExample     Filter filter = new QualifierFilter(CompareFilter.CompareOp.LESS_OR_EQUAL,       new BinaryComparator(Bytes.toBytes("col-2")));       Scan scan = new Scan();     scan.setFilter(filter);     ResultScanner scanner = table.getScanner(scan);     // ^^ QualifierFilterExample     System.out.println("Scanning table... ");     // vv QualifierFilterExample     for (Result result : scanner) {       System.out.println(result);     }     scanner.close();       Get get = new Get(Bytes.toBytes("row-5"));     get.setFilter(filter);     Result result = table.get(get);     System.out.println("Result of get(): " + result);

1.4 ValueFilter

构造函数

<pre name=< span="">"code" class="java" style="color: rgb(88, 89, 93); font-size: 14px; line-height: 25px;">public ValueFilter(CompareOp valueCompareOp, WritableByteArrayComparable valueComparator) {}     通过和列名比较，返回为真的数据，示例： 

Filter filter = new ValueFilter(CompareFilter.CompareOp.EQUAL, // co ValueFilterExample-1-Filter Create filter, while specifying the comparison operator and comparator.       new SubstringComparator(".4") );       Scan scan = new Scan();     scan.setFilter(filter); // co ValueFilterExample-2-SetFilter Set filter for the scan.     ResultScanner scanner = table.getScanner(scan);     // ^^ ValueFilterExample     System.out.println("Results of scan:");     // vv ValueFilterExample     for (Result result : scanner) {       for (KeyValue kv : result.raw()) {         System.out.println("KV: " + kv + ", Value: " + // co ValueFilterExample-3-Print1 Print out value to check that filter works.           Bytes.toString(kv.getValue()));       }     }     scanner.close();       Get get = new Get(Bytes.toBytes("row-5"));     get.setFilter(filter); // co ValueFilterExample-4-SetFilter2 Assign same filter to Get instance.     Result result = table.get(get);     // ^^ ValueFilterExample     System.out.println("Result of get: ");     // vv ValueFilterExample     for (KeyValue kv : result.raw()) {       System.out.println("KV: " + kv + ", Value: " +         Bytes.toString(kv.getValue()));     }  

1.5 DependentColumnFilter

该过滤器有两个参数 —— 列族和列修饰。 尝试找到该列所在的每一行，并返回该行具有相同时间戳的全部键值对。如果某一行不包含指定的列，则该行的任何键值对都不返回。 该过滤器还可以有一个可选布尔参数 —— dropDependentColumn. 如果为true, 从属的列不返回。 该过滤器还可以有两个可选参数 —— 一个比较操作符和一个值比较器，用于列族和修饰的进一步检查。如果从属的列找到，其值还必须通过值检查，然后就是时间戳必须考虑。

package filters;    // cc DependentColumnFilterExample Example using a filter to include only specific column families  import org.apache.hadoop.conf.Configuration;  import org.apache.hadoop.hbase.HBaseConfiguration;  import org.apache.hadoop.hbase.KeyValue;  import org.apache.hadoop.hbase.client.Get;  import org.apache.hadoop.hbase.client.HTable;  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.BinaryPrefixComparator;  import org.apache.hadoop.hbase.filter.CompareFilter;  import org.apache.hadoop.hbase.filter.DependentColumnFilter;  import org.apache.hadoop.hbase.filter.Filter;  import org.apache.hadoop.hbase.filter.RegexStringComparator;  import org.apache.hadoop.hbase.filter.WritableByteArrayComparable;  import org.apache.hadoop.hbase.util.Bytes;  import util.HBaseHelper;    import java.io.IOException;    public class DependentColumnFilterExample {      private static HTable table = null;      // vv DependentColumnFilterExample    private static void filter(boolean drop,        CompareFilter.CompareOp operator,        WritableByteArrayComparable comparator)    throws IOException {      Filter filter;     if (comparator != null) {        filter = new DependentColumnFilter(Bytes.toBytes("colfam1"), // co DependentColumnFilterExample-1-CreateFilter Create the filter with various options.          Bytes.toBytes("col-5"), drop, operator, comparator);      } else {        filter = new DependentColumnFilter(Bytes.toBytes("colfam1"),          Bytes.toBytes("col-5"), drop);        }        Scan scan = new Scan();      scan.setFilter(filter);      ResultScanner scanner = table.getScanner(scan);      // ^^ DependentColumnFilterExample      System.out.println("Results of scan:");      // vv DependentColumnFilterExample      for (Result result : scanner) {        for (KeyValue kv : result.raw()) {          System.out.println("KV: " + kv + ", Value: " +            Bytes.toString(kv.getValue()));        }      }      scanner.close();        Get get = new Get(Bytes.toBytes("row-5"));      get.setFilter(filter);      Result result = table.get(get);      // ^^ DependentColumnFilterExample      System.out.println("Result of get: ");      // vv DependentColumnFilterExample      for (KeyValue kv : result.raw()) {        System.out.println("KV: " + kv + ", Value: " +          Bytes.toString(kv.getValue()));      }      // ^^ DependentColumnFilterExample      System.out.println("");      // vv DependentColumnFilterExample    }      public static void main(String[] args) throws IOException {      // ^^ DependentColumnFilterExample      Configuration conf = HBaseConfiguration.create();        HBaseHelper helper = HBaseHelper.getHelper(conf);      helper.dropTable("testtable");      helper.createTable("testtable", "colfam1", "colfam2");      System.out.println("Adding rows to table...");      helper.fillTable("testtable", 1, 10, 10, true, "colfam1", "colfam2");        table = new HTable(conf, "testtable");        // vv DependentColumnFilterExample      filter(true, CompareFilter.CompareOp.NO_OP, null);      filter(false, CompareFilter.CompareOp.NO_OP, null); // co DependentColumnFilterExample-2-Filter Call filter method with various options.      filter(true, CompareFilter.CompareOp.EQUAL,        new BinaryPrefixComparator(Bytes.toBytes("val-5")));      filter(false, CompareFilter.CompareOp.EQUAL,        new BinaryPrefixComparator(Bytes.toBytes("val-5")));      filter(true, CompareFilter.CompareOp.EQUAL,        new RegexStringComparator(".*\\.5"));      filter(false, CompareFilter.CompareOp.EQUAL,        new RegexStringComparator(".*\\.5"));    }    // ^^ DependentColumnFilterExample}  

2、Dedicated Filters
     2.1 SingleColumnValueFilter

选定列簇和某一列，然后与列的value相比，正确的返回全部的row，注意如果某一行不含有该列，同样返回，除非通过filterIfColumnMissing 设置成真。

构造函数

SingleColumnValueFilter(byte[] family, byte[] qualifier, CompareOp compareOp, byte[] value)   SingleColumnValueFilter(byte[] family, byte[] qualifier, CompareOp compareOp, WritableByteArrayComparable comparator)  第一个构造函数相当于构建了一个BinaryComparator的实例。其他的跟CompareFilter的参数含义一样。  

该过滤器通过下面两个参数 filterIfMissing,latestVersionOnly

boolean getFilterIfMissing()  void setFilterIfMissing(boolean filterIfMissing)  boolean getLatestVersionOnly()  void setLatestVersionOnly(boolean latestVersionOnly)  

如果 filterIfColumnMissing 标志设为真，如果该行没有指定的列，那么该行的所有列将不发出。缺省值为假。
如果setLatestVersionOnly 标志设为假，将检查此前的版本。缺省值为真。实例如下：

// vv SingleColumnValueFilterExample    SingleColumnValueFilter filter = new SingleColumnValueFilter(      Bytes.toBytes("colfam1"),      Bytes.toBytes("col-5"),      CompareFilter.CompareOp.NOT_EQUAL,      new SubstringComparator("val-5"));    filter.setFilterIfMissing(true);      Scan scan = new Scan();    scan.setFilter(filter);    ResultScanner scanner = table.getScanner(scan);    // ^^ SingleColumnValueFilterExample    System.out.println("Results of scan:");    // vv SingleColumnValueFilterExample    for (Result result : scanner) {      for (KeyValue kv : result.raw()) {        System.out.println("KV: " + kv + ", Value: " +          Bytes.toString(kv.getValue()));      }    }    scanner.close();      Get get = new Get(Bytes.toBytes("row-6"));    get.setFilter(filter);    Result result = table.get(get);    System.out.println("Result of get: ");    for (KeyValue kv : result.raw()) {      System.out.println("KV: " + kv + ", Value: " +        Bytes.toString(kv.getValue()));    }  

    

     2.2 SingleColumnValueExcludeFilter

该过滤器同上面的过滤器正好相反，如果条件相符，将不会返回该列的内容。

     2.3 PrefixFilter

所有的row的实例匹配prefix的时候返回结果集合

Filter filter = new PrefixFilter(Bytes.toBytes("row1"));  Scan scan = new Scan();  scan.setFilter(filter);  ResultScanner scanner = table.getScanner(scan);  for(Result result: scanner){      for(KeyValue kv: result.raw()) {          System.out.println("KV:" + kv + ", Value:"  + Bytes.toString(kv.getValue()));      }  }  scanner.close();  Get get = new Get(Bytes.toBytes("row-5"));  get.setFilter(filter);  Result result = table.get(get);  for(KeyValue kv : result.raw()){      System.out.println("KV:" + kv + ", Value:"  + Bytes.toString(kv.getValue()));  }  

     2.4 PageFilter

页过滤，通过设置pagesize参数可以返回每一页page的数量。

客户端需要记住上一次访问的row的key值。

package hbaseTest;  import org.apache.hadoop.conf.Configuration;  import org.apache.hadoop.hbase.HBaseConfiguration;  import org.apache.hadoop.hbase.client.HTable;  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.Filter;  import org.apache.hadoop.hbase.filter.PageFilter;  import org.apache.hadoop.hbase.util.Bytes;  import java.io.IOException;  /**  * Hello world!  */  public class PageFilterExample {      public static void main(String[] args) throws IOException {          Configuration config = HBaseConfiguration.create();          config.set("hbase.zookeeper.quorum", "QT-H-0038");          String tableName = "testTable";          String cfName = "colfam1";          final byte[] POSTFIX = new byte[] { 0x00 };          HTable table = new HTable(config, tableName);          Filter filter = new PageFilter(15);          byte[] lastRow = null;          int totalRows = 0;          while (true) {              Scan scan = new Scan();              scan.setFilter(filter);              if(lastRow != null){                  //注意这里添加了POSTFIX操作，不然死循环了                  byte[] startRow = Bytes.add(lastRow,POSTFIX);                  scan.setStartRow(startRow);              }              ResultScanner scanner = table.getScanner(scan);              int localRows = 0;              Result result;              while((result = scanner.next()) != null){                  System.out.println(localRows++ + ":" + result);                  totalRows ++;                  lastRow = result.getRow();              }              scanner.close();              if(localRows == 0) break;          }          System.out.println("total rows:" + totalRows);      }  }  

因为hbase的row是字典序列排列的，因此上一次的lastrow需要添加额外的0表示新的开始。另外startKey的那一行是包含在scan里面的。

     2.5 KeyOnlyFilter

因为一些应用只想获取data数据，而不是真实的val，可以使用这个过滤器。该过滤器通过

KeyOnlyFilter(boolean lenAsVal)  

lenAsVal默认为假，表示不把val的长度作为val。否则 val的长度将作为val输出。

 final byte[] POSTFIX = new byte[] { 0x00 };          HTable table = new HTable(config, tableName);          Filter filter = new KeyOnlyFilter(false);          byte[] lastRow = null;          int totalRows = 0;          Scan scan = new Scan();          scan.setFilter(filter);          ResultScanner scanner = table.getScanner(scan);          for(Result result: scanner){              for(KeyValue kv: result.raw()){                  System.out.println(kv + ":" + Bytes.toString(kv.getValue()));              }          }  

2.6 FirstKeyOnlyFilter

在对hbase的表进行扫描的时候，如果指定了FirstKeyOnlyFilter过滤条件则仅仅会返回相同key的第一条kv。
当对hbase中的表进行count，sum操作等集合操作的时候，使用FirstKeyOnlyFilter会带来性能上的提升。

public class KeyOnlyFilterExample {      public static void main(String[] args) throws IOException {          Configuration config = HBaseConfiguration.create();          config.set("hbase.zookeeper.quorum", "QT-H-0038");            String tableName = "testTable";          String cfName = "colfam1";          final byte[] POSTFIX = new byte[] { 0x00 };          HTable table = new HTable(config, tableName);          Filter filter = new FirstKeyOnlyFilter();          byte[] lastRow = null;          int totalRows = 0;            Scan scan = new Scan();          scan.setFilter(filter);          ResultScanner scanner = table.getScanner(scan);          for(Result result: scanner){              for(KeyValue kv: result.raw()){                  System.out.println(kv + ":" + Bytes.toString(kv.getValue()));              }          }      }  }  

返回的结果是

row-5/colfam1:qual1/1354673733503/Put/vlen=4:row1  row1/colfam1:qual1/1354432930568/Put/vlen=4:val1  row2/colfam1:qual2/1354432930568/Put/vlen=4:val3  

如果注释掉过滤器的返回的结果是：

row-5/colfam1:qual1/1354673733503/Put/vlen=4:row1  row1/colfam1:qual1/1354432930568/Put/vlen=4:val1  row1/colfam1:qual2/1354435819120/Put/vlen=4:val2  row2/colfam1:qual2/1354432930568/Put/vlen=4:val3 

 2.7 InclusiveStopFilter

因为hbase的scan包含start-row不包含stop-row 如果使用这个过滤器我们可以包含stop-row

HTable table = new HTable(config, tableName);    Filter filter  = new InclusiveStopFilter(Bytes.toBytes("row1"));    Scan scan = new Scan();  scan.setFilter(filter);  scan.setStartRow(Bytes.toBytes("row-5"));  ResultScanner scanner = table.getScanner(scan);    for(Result result: scanner){      System.out.println(result);  }  

会看到row1包含在结果中了。

     2.8 TimestampsFilter

当访问某个Timestamp的新闻的时候，我们需要如下的代码：

TimestampsFilter(List timestamps)

接受的参数的list参数，该Filter也可以和scan.setTimeRange混合使用。例如：

// vv TimestampFilterExample      List ts = new ArrayList();      ts.add(new Long(5));    ts.add(new Long(10)); // co TimestampFilterExample-1-AddTS Add timestamps to the list.      ts.add(new Long(15));      Filter filter = new TimestampsFilter(ts);        Scan scan1 = new Scan();      scan1.setFilter(filter); // co TimestampFilterExample-2-AddFilter Add the filter to an otherwise default Scan instance.      ResultScanner scanner1 = table.getScanner(scan1);      // ^^ TimestampFilterExample      System.out.println("Results of scan #1:");      // vv TimestampFilterExample      for (Result result : scanner1) {        System.out.println(result);      }      scanner1.close();        Scan scan2 = new Scan();      scan2.setFilter(filter);      scan2.setTimeRange(8, 12); // co TimestampFilterExample-3-AddTSRange Also add a time range to verify how it affects the filter      ResultScanner scanner2 = table.getScanner(scan2);      // ^^ TimestampFilterExample      System.out.println("Results of scan #2:");      // vv TimestampFilterExample      for (Result result : scanner2) {        System.out.println(result);      }      scanner2.close();  

     2.9  ColumnCountGetFilter

这个在scan时，无用。

     2.10 ColumnPaginationFilter（下来用到的时候在仔细研究下）

 * A filter, based on the ColumnCountGetFilter, takes two arguments: limit and offset.
 * This filter can be used for row-based indexing, where references to other tables are stored across many columns,
 * in order to efficient lookups and paginated results for end users.

 

Filter filter = new ColumnPaginationFilter(5, 15);       Scan scan = new Scan();     scan.setFilter(filter);     ResultScanner scanner = table.getScanner(scan);     // ^^ ColumnPaginationFilterExample     System.out.println("Results of scan:");     // vv ColumnPaginationFilterExample     for (Result result : scanner) {       System.out.println(result);     }     scanner.close();  

     2.11 ColumnPrefixFilter

跟prefxiFilter相似，只是改成了Column，实例如下：

// vv ColumnPaginationFilterExample        Filter filter = new ColumnPrefixFilter(Bytes.toBytes("qual2"));          Scan scan = new Scan();        scan.setFilter(filter);        ResultScanner scanner = table.getScanner(scan);        // ^^ ColumnPaginationFilterExample        System.out.println("Results of scan:");        // vv ColumnPaginationFilterExample        for (Result result : scanner) {            System.out.println(result);        }        scanner.close();  

值scan到与列值与前面匹配的数据。例如qual2匹配qual21。

 

     2.12 RandomRowFilter

随即的返回row的数据，构造函数为

RandomRowFilter(float chance)

chance取值为0到1.0，如果<0则为空，如果>1则包含所有的行。

3、Decorating Filters

装饰性过滤器

     3.1  SkipFilter

这个过滤器只作用到keyValueFilter上。KeyValueFilter会返回所有满足条件的row及对应的列。

而加上SkipFilter以后。会发现如果某一行的某一列不符合条件，则这一行全部不返回了。

public static void main(String[] args) throws IOException {     Configuration conf = HBaseConfiguration.create();       HBaseHelper helper = HBaseHelper.getHelper(conf);     helper.dropTable("testtable");     helper.createTable("testtable", "colfam1");     System.out.println("Adding rows to table...");     helper.fillTable("testtable", 1, 30, 5, 2, true, true, "colfam1");       HTable table = new HTable(conf, "testtable");       // vv SkipFilterExample     Filter filter1 = new ValueFilter(CompareFilter.CompareOp.NOT_EQUAL,       new BinaryComparator(Bytes.toBytes("val-0")));       Scan scan = new Scan();     scan.setFilter(filter1); // co SkipFilterExample-1-AddFilter1 Only add the ValueFilter to the first scan.     ResultScanner scanner1 = table.getScanner(scan);     // ^^ SkipFilterExample     System.out.println("Results of scan #1:");     int n = 0;     // vv SkipFilterExample     for (Result result : scanner1) {       for (KeyValue kv : result.raw()) {         System.out.println("KV: " + kv + ", Value: " +           Bytes.toString(kv.getValue()));         // ^^ SkipFilterExample         n++;         // vv SkipFilterExample       }     }     scanner1.close();       Filter filter2 = new SkipFilter(filter1);       scan.setFilter(filter2); // co SkipFilterExample-2-AddFilter2 Add the decorating skip filter for the second scan.     ResultScanner scanner2 = table.getScanner(scan);     // ^^ SkipFilterExample     System.out.println("Total KeyValue count for scan #1: " + n);     n = 0;     System.out.println("Results of scan #2:");     // vv SkipFilterExample     for (Result result : scanner2) {       for (KeyValue kv : result.raw()) {         System.out.println("KV: " + kv + ", Value: " +           Bytes.toString(kv.getValue()));         // ^^ SkipFilterExample         n++;         // vv SkipFilterExample       }     }     scanner2.close();     // ^^ SkipFilterExample     System.out.println("Total KeyValue count for scan #2: " + n);   }  

     3.2 WhileMatchFilters

相当于while执行，知道不match就break了返回了。