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>

<pre></pre>

通过和列名比较，返回为真的数据，示例：

<pre></pre>

<pre></pre>

<pre></pre>

<pre></pre>

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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>

<pre></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。

<pre></pre>

<pre></pre>

<pre></pre>

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);

}

3.2 WhileMatchFilters

相当于while执行，知道不match就break了返回了。