hbase权威指南阅读随手笔记二之过滤器

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
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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。
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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
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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:
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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
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public QualifierFilter(CompareOp qualifierCompareOp, WritableByteArrayComparable qualifierComparator) { }
通过和列名比较,返回为真的数据,示例:
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// 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
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<pre name="code" class="java" style="color: rgb(88, 89, 93); font-size: 14px; line-height: 25px;">public ValueFilter(CompareOp valueCompareOp, WritableByteArrayComparable valueComparator) {}</pre>
通过和列名比较,返回为真的数据,示例:  
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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。
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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
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<pre name="code" class="java">SingleColumnValueFilter(byte[] family, byte[] qualifier, CompareOp compareOp, byte[] value)
SingleColumnValueFilter(byte[] family, byte[] qualifier, CompareOp compareOp, WritableByteArrayComparable comparator)</pre>
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
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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:
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// 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
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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。
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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
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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。
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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。
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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
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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:
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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
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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:
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TimestampsFilter(List<Long> timestamps)  
接受的参数的list参数,该Filter也可以和scan.setTimeRange混合使用。例如:

 

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// vv TimestampFilterExample  
    List<Long> ts = new ArrayList<Long>();  
    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.
 
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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:
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// 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
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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。
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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);  
 }  

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