比较运算符 CompareFilter.CompareOp 比较运算符用于定义比较关系,可以有以下几类值供选择:
比较器 ByteArrayComparable 通过比较器可以实现多样化目标匹配效果,比较器有以下子类可以使用:
1.多重过滤器--FilterList(Shell不支持) FilterList代表一个过滤器链,它可以包含一组即将应用于目标数据集的过滤器,过滤器间具有“与” FilterList.Operator.MUST_PASS_ALL 和“或” FilterList.Operator.MUST_PASS_ONE 关系。
//结合过滤器,获取所有age在15到30之间的行
private static void scanFilter() throws IOException,
UnsupportedEncodingException {
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.rootdir", "hdfs://ncst:9000/hbase");
conf.set("hbase.zookeeper.quorum", "ncst");
HTable ht = new HTable(conf, "users");
// And
FilterList filterList = new FilterList(FilterList.Operator.MUST_PASS_ALL);
// >=15
SingleColumnValueFilter filter1 = new SingleColumnValueFilter("info".getBytes(), "age".getBytes(), CompareOp.GREATER_OR_EQUAL, "15".getBytes());
// =<30
SingleColumnValueFilter filter2 = new SingleColumnValueFilter("info".getBytes(), "age".getBytes(), CompareOp.LESS_OR_EQUAL, "30".getBytes());
filterList.addFilter(filter1);
filterList.addFilter(filter2);
Scan scan = new Scan();
// set Filter
scan.setFilter(filterList);
ResultScanner rs = ht.getScanner(scan);
for(Result result : rs){
for(Cell cell : result.rawCells()){
System.out.println(new String(CellUtil.cloneRow(cell))+"\t"
+new String(CellUtil.cloneFamily(cell))+"\t"
+new String(CellUtil.cloneQualifier(cell))+"\t"
+new String(CellUtil.cloneValue(cell),"UTF-8")+"\t"
+cell.getTimestamp());
}
}
ht.close();
}
2. 列值过滤器--SingleColumnValueFilter 用于测试列值相等(CompareOp.EQUAL ),不等(CompareOp.NOT_EQUAL),或单侧范围 (如CompareOp.GREATER)。构造函数: 2.1.比较的关键字是一个字符数组(Shell不支持?) SingleColumnValueFilter(byte[] family, byte[] qualifier, CompareFilter.CompareOp compareOp, byte[] value)
//SingleColumnValueFilter例子
private static void scanFilter01() throws IOException,
UnsupportedEncodingException {
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.rootdir", "hdfs://ncst:9000/hbase");
conf.set("hbase.zookeeper.quorum", "ncst");
HTable ht = new HTable(conf, "users");
SingleColumnValueFilter scvf = new SingleColumnValueFilter("info".getBytes(), "age".getBytes(), CompareOp.EQUAL, "18".getBytes());
Scan scan = new Scan();
scan.setFilter(scvf);
ResultScanner rs = ht.getScanner(scan);
for(Result result : rs){
for(Cell cell : result.rawCells()){
System.out.println(new String(CellUtil.cloneRow(cell))+"\t"
+new String(CellUtil.cloneFamily(cell))+"\t"
+new String(CellUtil.cloneQualifier(cell))+"\t"
+new String(CellUtil.cloneValue(cell),"UTF-8")+"\t"
+cell.getTimestamp());
}
}
ht.close();
}
2.2.比较的关键字是一个比较器ByteArrayComparable SingleColumnValueFilter(byte[] family, byte[] qualifier, CompareFilter.CompareOp compareOp, ByteArrayComparable comparator)
//SingleColumnValueFilter例子2 -- RegexStringComparator
private static void scanFilter02() throws IOException,
UnsupportedEncodingException {
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.rootdir", "hdfs://ncst:9000/hbase");
conf.set("hbase.zookeeper.quorum", "ncst");
HTable ht = new HTable(conf, "users");
//值比较的正则表达式 -- RegexStringComparator
//匹配info:age值以"4"结尾
RegexStringComparator comparator = new RegexStringComparator(".4");
//第四个参数不一样
SingleColumnValueFilter scvf = new SingleColumnValueFilter("info".getBytes(), "age".getBytes(), CompareOp.EQUAL, comparator);
Scan scan = new Scan();
scan.setFilter(scvf);
ResultScanner rs = ht.getScanner(scan);
for(Result result : rs){
for(Cell cell : result.rawCells()){
System.out.println(new String(CellUtil.cloneRow(cell))+"\t"
+new String(CellUtil.cloneFamily(cell))+"\t"
+new String(CellUtil.cloneQualifier(cell))+"\t"
+new String(CellUtil.cloneValue(cell),"UTF-8")+"\t"
+cell.getTimestamp());
}
}
ht.close();
}
hbase(main):032:0> scan 'users',{FILTER=>"SingleColumnValueFilter('info','age',=,'regexstring:.4')"}
ROW COLUMN+CELL
xiaoming01 column=address:contry, timestamp=1442000277200, value=\xE4\xB8\xAD\xE5\x9B\xBD
xiaoming01 column=address:country, timestamp=1442000228945, value=\xE4\xB8\xAD\xE5\x9B\xBD
xiaoming01 column=info:age, timestamp=1441998917568, value=24
xiaoming02 column=info:age, timestamp=1441998917594, value=24
xiaoming03 column=info:age, timestamp=1441998919607, value=24
3 row(s) in 0.0130 seconds
//SingleColumnValueFilter例子2 -- SubstringComparator
private static void scanFilter03() throws IOException,
UnsupportedEncodingException {
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.rootdir", "hdfs://ncst:9000/hbase");
conf.set("hbase.zookeeper.quorum", "ncst");
HTable ht = new HTable(conf, "users");
//检测一个子串是否存在于值中(大小写不敏感) -- SubstringComparator
//过滤age值中包含'4'的RowKey
SubstringComparator comparator = new SubstringComparator("4");
//第四个参数不一样
SingleColumnValueFilter scvf = new SingleColumnValueFilter("info".getBytes(), "age".getBytes(), CompareOp.EQUAL, comparator);
Scan scan = new Scan();
scan.setFilter(scvf);
ResultScanner rs = ht.getScanner(scan);
for(Result result : rs){
for(Cell cell : result.rawCells()){
System.out.println(new String(CellUtil.cloneRow(cell))+"\t"
+new String(CellUtil.cloneFamily(cell))+"\t"
+new String(CellUtil.cloneQualifier(cell))+"\t"
+new String(CellUtil.cloneValue(cell),"UTF-8")+"\t"
+cell.getTimestamp());
}
}
ht.close();
}
hbase(main):033:0> scan 'users',{FILTER=>"SingleColumnValueFilter('info','age',=,'substring:4')"}
ROW COLUMN+CELL
xiaoming01 column=address:contry, timestamp=1442000277200, value=\xE4\xB8\xAD\xE5\x9B\xBD
xiaoming01 column=address:country, timestamp=1442000228945, value=\xE4\xB8\xAD\xE5\x9B\xBD
xiaoming01 column=info:age, timestamp=1441998917568, value=24
xiaoming02 column=info:age, timestamp=1441998917594, value=24
xiaoming03 column=info:age, timestamp=1441998919607, value=24
3 row(s) in 0.0180 seconds
3.列名过滤器 由于HBase采用键值对保存内部数据,列名过滤器过滤一行的列名(ColumnFamily:Qualifiers)是否存在 , 对应前节所述列值的情况。
3.1.基于Columun Family列族过滤数据的FamilyFilter FamilyFilter(CompareFilter.CompareOp familyCompareOp, ByteArrayComparable familyComparator)
注意: 1.如果希望查找的是一个已知的列族,则使用 scan.addFamily(family); 比使用过滤器效率更高. 2.由于目前HBase对多列族支持不完善,所以该过滤器目前用途不大.
//基于列族过滤数据的FamilyFilter
private static void scanFilter04() throws IOException,
UnsupportedEncodingException {
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.rootdir", "hdfs://ncst:9000/hbase");
conf.set("hbase.zookeeper.quorum", "ncst");
HTable ht = new HTable(conf, "users");
//过滤 = 'address'的列族
//FamilyFilter familyFilter = new FamilyFilter(CompareOp.EQUAL, new BinaryComparator("address".getBytes()));
//过滤以'add'开头的列族
FamilyFilter familyFilter = new FamilyFilter(CompareOp.EQUAL, new BinaryPrefixComparator("add".getBytes()));
Scan scan = new Scan();
scan.setFilter(familyFilter);
ResultScanner rs = ht.getScanner(scan);
for(Result result : rs){
for(Cell cell : result.rawCells()){
System.out.println(new String(CellUtil.cloneRow(cell))+"\t"
+new String(CellUtil.cloneFamily(cell))+"\t"
+new String(CellUtil.cloneQualifier(cell))+"\t"
+new String(CellUtil.cloneValue(cell),"UTF-8")+"\t"
+cell.getTimestamp());
}
}
ht.close();
}
hbase(main):021:0> scan 'users',{FILTER=>"FamilyFilter(=,'binaryprefix:add')"}
ROW COLUMN+CELL
xiaoming column=address:city, timestamp=1441997498965, value=hangzhou
xiaoming column=address:contry, timestamp=1441997498911, value=china
xiaoming column=address:province, timestamp=1441997498939, value=zhejiang
xiaoming01 column=address:contry, timestamp=1442000277200, value=\xE4\xB8\xAD\xE5\x9B\xBD
xiaoming01 column=address:country, timestamp=1442000228945, value=\xE4\xB8\xAD\xE5\x9B\xBD
zhangyifei column=address:city, timestamp=1441997499108, value=jieyang
zhangyifei column=address:contry, timestamp=1441997499077, value=china
zhangyifei column=address:province, timestamp=1441997499093, value=guangdong
zhangyifei column=address:town, timestamp=1441997500711, value=xianqiao
3 row(s) in 0.0400 seconds
3.2.基于Qualifier列名过滤数据的QualifierFilter QualifierFilter(CompareFilter.CompareOp op, ByteArrayComparable qualifierComparator)
说明:该过滤器应该比FamilyFilter更常用!
//基于Qualifier(列名)过滤数据的QualifierFilter
private static void scanFilter05() throws IOException,
UnsupportedEncodingException {
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.rootdir", "hdfs://ncst:9000/hbase");
conf.set("hbase.zookeeper.quorum", "ncst");
HTable ht = new HTable(conf, "users");
//过滤列名 = 'age'所有RowKey
//QualifierFilter qualifierFilter = new QualifierFilter(CompareOp.EQUAL, new BinaryComparator("age".getBytes()));
//过滤列名 以'age'开头 所有RowKey(包含age)
//QualifierFilter qualifierFilter = new QualifierFilter(CompareOp.EQUAL, new BinaryPrefixComparator("age".getBytes()));
//过滤列名 包含'age' 所有RowKey(包含age)
//QualifierFilter qualifierFilter = new QualifierFilter(CompareOp.EQUAL, new SubstringComparator("age"));
//过滤列名 符合'.ge'正则表达式 所有RowKey
QualifierFilter qualifierFilter = new QualifierFilter(CompareOp.EQUAL, new RegexStringComparator(".ge"));
Scan scan = new Scan();
scan.setFilter(qualifierFilter);
ResultScanner rs = ht.getScanner(scan);
for(Result result : rs){
for(Cell cell : result.rawCells()){
System.out.println(new String(CellUtil.cloneRow(cell))+"\t"
+new String(CellUtil.cloneFamily(cell))+"\t"
+new String(CellUtil.cloneQualifier(cell))+"\t"
+new String(CellUtil.cloneValue(cell),"UTF-8")+"\t"
+cell.getTimestamp());
}
}
ht.close();
}
hbase(main):020:0> scan 'users',{FILTER=>"QualifierFilter(=,'regexstring:.ge')"}
ROW COLUMN+CELL
xiaoming column=info:age, timestamp=1441997971945, value=38
xiaoming01 column=info:age, timestamp=1441998917568, value=24
xiaoming02 column=info:age, timestamp=1441998917594, value=24
xiaoming03 column=info:age, timestamp=1441998919607, value=24
zhangyifei column=info:age, timestamp=1442247255446, value=18
5 row(s) in 0.0460 seconds
3.3.基于列名前缀过滤数据的ColumnPrefixFilter(该功能用QualifierFilter也能实现) ColumnPrefixFilter(byte[] prefix) 注意:一个列名是可以出现在多个列族中的,该过滤器将返回所有列族中匹配的列。
//ColumnPrefixFilter例子
private static void scanFilter06() throws IOException,
UnsupportedEncodingException {
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.rootdir", "hdfs://ncst:9000/hbase");
conf.set("hbase.zookeeper.quorum", "ncst");
HTable ht = new HTable(conf, "users");
//匹配 以'ag'开头的所有的列
ColumnPrefixFilter columnPrefixFilter = new ColumnPrefixFilter("ag".getBytes());
Scan scan = new Scan();
scan.setFilter(columnPrefixFilter);
ResultScanner rs = ht.getScanner(scan);
for(Result result : rs){
for(Cell cell : result.rawCells()){
System.out.println(new String(CellUtil.cloneRow(cell))+"\t"
+new String(CellUtil.cloneFamily(cell))+"\t"
+new String(CellUtil.cloneQualifier(cell))+"\t"
+new String(CellUtil.cloneValue(cell),"UTF-8")+"\t"
+cell.getTimestamp());
}
}
ht.close();
}
hbase(main):018:0> scan 'users',{FILTER=>"ColumnPrefixFilter('ag')"}
ROW COLUMN+CELL
xiaoming column=info:age, timestamp=1441997971945, value=38
xiaoming01 column=info:age, timestamp=1441998917568, value=24
xiaoming02 column=info:age, timestamp=1441998917594, value=24
xiaoming03 column=info:age, timestamp=1441998919607, value=24
zhangyifei column=info:age, timestamp=1442247255446, value=18
5 row(s) in 0.0280 seconds
3.4.基于多个列名前缀过滤数据的MultipleColumnPrefixFilter MultipleColumnPrefixFilter 和 ColumnPrefixFilter 行为差不多,但可以指定多个前缀。
//MultipleColumnPrefixFilter例子
private static void scanFilter07() throws IOException,
UnsupportedEncodingException {
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.rootdir", "hdfs://ncst:9000/hbase");
conf.set("hbase.zookeeper.quorum", "ncst");
HTable ht = new HTable(conf, "users");
//匹配 以'a'或者'c'开头 所有的列{二维数组}
byte[][] prefixes =new byte[][]{"a".getBytes(), "c".getBytes()};
MultipleColumnPrefixFilter multipleColumnPrefixFilter = new MultipleColumnPrefixFilter(prefixes );
Scan scan = new Scan();
scan.setFilter(multipleColumnPrefixFilter);
ResultScanner rs = ht.getScanner(scan);
for(Result result : rs){
for(Cell cell : result.rawCells()){
System.out.println(new String(CellUtil.cloneRow(cell))+"\t"
+new String(CellUtil.cloneFamily(cell))+"\t"
+new String(CellUtil.cloneQualifier(cell))+"\t"
+new String(CellUtil.cloneValue(cell),"UTF-8")+"\t"
+cell.getTimestamp());
}
}
ht.close();
}
hbase(main):017:0> scan 'users',{FILTER=>"MultipleColumnPrefixFilter('a','c')"}
ROW COLUMN+CELL
xiaoming column=address:city, timestamp=1441997498965, value=hangzhou
xiaoming column=address:contry, timestamp=1441997498911, value=china
xiaoming column=info:age, timestamp=1441997971945, value=38
xiaoming column=info:company, timestamp=1441997498889, value=alibaba
xiaoming01 column=address:contry, timestamp=1442000277200, value=\xE4\xB8\xAD\xE5\x9B\xBD
xiaoming01 column=address:country, timestamp=1442000228945, value=\xE4\xB8\xAD\xE5\x9B\xBD
xiaoming01 column=info:age, timestamp=1441998917568, value=24
xiaoming02 column=info:age, timestamp=1441998917594, value=24
xiaoming03 column=info:age, timestamp=1441998919607, value=24
zhangyifei column=address:city, timestamp=1441997499108, value=jieyang
zhangyifei column=address:contry, timestamp=1441997499077, value=china
zhangyifei column=info:age, timestamp=1442247255446, value=18
zhangyifei column=info:company, timestamp=1441997499039, value=alibaba
5 row(s) in 0.0430 seconds
3.5.基于列范围(不是行范围)过滤数据ColumnRangeFilter
构造函数: ColumnRangeFilter(byte[] minColumn, boolean minColumnInclusive, byte[] maxColumn, boolean maxColumnInclusive) 参数解释:
//ColumnRangeFilter例子
private static void scanFilter08() throws IOException,
UnsupportedEncodingException {
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.rootdir", "hdfs://ncst:9000/hbase");
conf.set("hbase.zookeeper.quorum", "ncst");
HTable ht = new HTable(conf, "users");
//匹配 以'a'开头到以'c'开头(不包含c) 所有的列
ColumnRangeFilter columnRangeFilter = new ColumnRangeFilter("a".getBytes(), true, "c".getBytes(), false);
Scan scan = new Scan();
scan.setFilter(columnRangeFilter);
ResultScanner rs = ht.getScanner(scan);
for(Result result : rs){
for(Cell cell : result.rawCells()){
System.out.println(new String(CellUtil.cloneRow(cell))+"\t"
+new String(CellUtil.cloneFamily(cell))+"\t"
+new String(CellUtil.cloneQualifier(cell))+"\t"
+new String(CellUtil.cloneValue(cell),"UTF-8")+"\t"
+cell.getTimestamp());
}
}
ht.close();
}
hbase(main):016:0> scan 'users',{FILTER=>"ColumnRangeFilter('a',true,'c',false)"}
ROW COLUMN+CELL
xiaoming column=info:age, timestamp=1441997971945, value=38
xiaoming column=info:birthday, timestamp=1441997498851, value=1987-06-17
xiaoming01 column=info:age, timestamp=1441998917568, value=24
xiaoming02 column=info:age, timestamp=1441998917594, value=24
xiaoming03 column=info:age, timestamp=1441998919607, value=24
zhangyifei column=info:age, timestamp=1442247255446, value=18
zhangyifei column=info:birthday, timestamp=1441997498990, value=1987-4-17
5 row(s) in 0.0340 seconds
4.RowKey 当需要根据行键特征查找一个范围的行数据时,使用Scan的startRow和stopRow会更高效,但是,startRow和stopRow只能匹配行键的开始字符,而不能匹配中间包含的字符。当需要针对行键进行更复杂的过滤时,可以使用RowFilter。 构造函数:RowFilter(CompareFilter.CompareOp rowCompareOp, ByteArrayComparable rowComparator)
//RowFilter例子
private static void scanFilter09() throws IOException,
UnsupportedEncodingException {
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.rootdir", "hdfs://ncst:9000/hbase");
conf.set("hbase.zookeeper.quorum", "ncst");
HTable ht = new HTable(conf, "users");
//匹配 行键包含'01' 所有的行
RowFilter rowFilter = new RowFilter(CompareOp.EQUAL, new SubstringComparator("01"));
Scan scan = new Scan();
scan.setFilter(rowFilter);
ResultScanner rs = ht.getScanner(scan);
for(Result result : rs){
for(Cell cell : result.rawCells()){
System.out.println(new String(CellUtil.cloneRow(cell))+"\t"
+new String(CellUtil.cloneFamily(cell))+"\t"
+new String(CellUtil.cloneQualifier(cell))+"\t"
+new String(CellUtil.cloneValue(cell),"UTF-8")+"\t"
+cell.getTimestamp());
}
}
ht.close();
}
hbase(main):013:0> scan 'users',{FILTER=>"RowFilter(=,'substring:01')"}
ROW COLUMN+CELL
xiaoming01 column=address:contry, timestamp=1442000277200, value=\xE4\xB8\xAD\xE5\x9B\xBD
xiaoming01 column=address:country, timestamp=1442000228945, value=\xE4\xB8\xAD\xE5\x9B\xBD
xiaoming01 column=info:age, timestamp=1441998917568, value=24
1 row(s) in 0.0190 seconds
5.PageFilter(Shell不支持?) 指定页面行数,返回对应行数的结果集。 需要注意的是,该过滤器并不能保证返回的结果行数小于等于指定的页面行数,因为过滤器是分别作用到各个region server的,它只能保证当前region返回的结果行数不超过指定页面行数。 构造函数:PageFilter(long pageSize)
//PageFilter例子
private static void scanFilter10() throws IOException,
UnsupportedEncodingException {
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.rootdir", "hdfs://ncst:9000/hbase");
conf.set("hbase.zookeeper.quorum", "ncst");
HTable ht = new HTable(conf, "users");
//从RowKey为 "xiaoming" 开始,取3行(包含xiaoming)
PageFilter pageFilter = new PageFilter(3L);
Scan scan = new Scan();
scan.setStartRow("xiaoming".getBytes());
scan.setFilter(pageFilter);
ResultScanner rs = ht.getScanner(scan);
for(Result result : rs){
for(Cell cell : result.rawCells()){
System.out.println(new String(CellUtil.cloneRow(cell))+"\t"
+new String(CellUtil.cloneFamily(cell))+"\t"
+new String(CellUtil.cloneQualifier(cell))+"\t"
+new String(CellUtil.cloneValue(cell),"UTF-8")+"\t"
+cell.getTimestamp());
}
}
ht.close();
}
注意:由于该过滤器并不能保证返回的结果行数小于等于指定的页面行数,所以更好的返回指定行数的办法是ResultScanner.next(int nbRows),即:
//上面Demo的改动版
private static void scanFilter11() throws IOException,
UnsupportedEncodingException {
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.rootdir", "hdfs://ncst:9000/hbase");
conf.set("hbase.zookeeper.quorum", "ncst");
HTable ht = new HTable(conf, "users");
//从RowKey为 "xiaoming" 开始,取3行(包含xiaoming)
//PageFilter pageFilter = new PageFilter(3L);
Scan scan = new Scan();
scan.setStartRow("xiaoming".getBytes());
//scan.setFilter(pageFilter);
ResultScanner rs = ht.getScanner(scan);
//指定返回3行数据
for(Result result : rs.next(3)){
for(Cell cell : result.rawCells()){
System.out.println(new String(CellUtil.cloneRow(cell))+"\t"
+new String(CellUtil.cloneFamily(cell))+"\t"
+new String(CellUtil.cloneQualifier(cell))+"\t"
+new String(CellUtil.cloneValue(cell),"UTF-8")+"\t"
+cell.getTimestamp());
}
}
ht.close();
}
6.SkipFilter(Shell不支持) 根据整行中的每个列来做过滤,只要存在一列不满足条件,整行都被过滤掉。 构造函数:SkipFilter(Filter filter)
例如,如果一行中的所有列代表的是不同物品的重量,则真实场景下这些数值都必须大于零,我们希望将那些包含任意列值为0的行都过滤掉。在这个情况下,我们结合ValueFilter和SkipFilter共同实现该目的: scan.setFilter(new SkipFilter(new ValueFilter(CompareOp.NOT_EQUAL,new BinaryComparator(Bytes.toBytes(0))));
//SkipFilter例子
private static void scanFilter12() throws IOException,
UnsupportedEncodingException {
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.rootdir", "hdfs://ncst:9000/hbase");
conf.set("hbase.zookeeper.quorum", "ncst");
HTable ht = new HTable(conf, "users");
//跳过列值中包含"24"的所有列
SkipFilter skipFilter = new SkipFilter(new ValueFilter(CompareOp.NOT_EQUAL, new BinaryComparator("24".getBytes())));
Scan scan = new Scan();
scan.setFilter(skipFilter);
ResultScanner rs = ht.getScanner(scan);
for(Result result : rs){
for(Cell cell : result.rawCells()){
System.out.println(new String(CellUtil.cloneRow(cell))+"\t"
+new String(CellUtil.cloneFamily(cell))+"\t"
+new String(CellUtil.cloneQualifier(cell))+"\t"
+new String(CellUtil.cloneValue(cell),"UTF-8")+"\t"
+cell.getTimestamp());
}
}
ht.close();
}
7.Utility--FirstKeyOnlyFilter 该过滤器仅仅返回每一行中第一个cell的值,可以用于高效的执行行数统计操作。估计实战意义不大。 构造函数:public FirstKeyOnlyFilter()
//FirstKeyOnlyFilter例子
private static void scanFilter12() throws IOException,
UnsupportedEncodingException {
Configuration conf = HBaseConfiguration.create();
conf.set("hbase.rootdir", "hdfs://ncst:9000/hbase");
conf.set("hbase.zookeeper.quorum", "ncst");
HTable ht = new HTable(conf, "users");
//返回每一行中的第一个cell的值
FirstKeyOnlyFilter firstKeyOnlyFilter = new FirstKeyOnlyFilter();
Scan scan = new Scan();
scan.setFilter(firstKeyOnlyFilter);
ResultScanner rs = ht.getScanner(scan);
int i = 0;
for(Result result : rs){
for(Cell cell : result.rawCells()){
System.out.println(new String(CellUtil.cloneRow(cell))+"\t"
+new String(CellUtil.cloneFamily(cell))+"\t"
+new String(CellUtil.cloneQualifier(cell))+"\t"
+new String(CellUtil.cloneValue(cell),"UTF-8")+"\t"
+cell.getTimestamp());
i++;
}
}
//输出总的行数
System.out.println(i);
ht.close();
}
hbase(main):009:0> scan 'users',{FILTER=>'FirstKeyOnlyFilter()'}
ROW COLUMN+CELL
xiaoming column=address:city, timestamp=1441997498965, value=hangzhou
xiaoming01 column=address:contry, timestamp=1442000277200, value=\xE4\xB8\xAD\xE5\x9B\xBD
xiaoming02 column=info:age, timestamp=1441998917594, value=24
xiaoming03 column=info:age, timestamp=1441998919607, value=24
zhangyifei column=address:city, timestamp=1441997499108, value=jieyang
5 row(s) in 0.0240 seconds
(adsbygoogle = window.adsbygoogle || []).push({});