Hbase Java API:检索与部分行键匹配的所有行

Question

在Python模块happybase中,我可以检索具有以给定字符串开头的行键的所有行(即,使用部分行键进行搜索).

假设我有一个格式为(ID | TYPE | DATE)的rowkey,我可以通过以下方式找到ID为1且TYPE为A的所有行:

import happybase
connection = happybase.Connection('hmaster-host.com')
table = connection.table('table_name')
for key, data in table.scan(row_prefix="1|A|"):
    print key, data

到目前为止,这是一个完全客户端的Java程序,适用于任何尝试使用Java HBase API进行基础操作的人,但我只能使用完整的行键搜索一行:

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
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.util.Bytes;
//class foo {
public static void main(String[] args) {
    Configuration conf = new Configuration();
    conf.addResource(new Path("C:\\core-site.xml"));
    conf.addResource(new Path("C:\\hbase-site.xml"));
    HTable table = new HTable(conf, "table_name");
    Result row = table.get(new Get(Bytes.toBytes("1|A|2014-01-01 00:00")));
    printRow(row); 
}
public static void printRow(Result result) {
    String returnString = "";
    returnString += Bytes.toString(result.getValue(Bytes.toBytes("cf"), Bytes.toBytes("id"))) + ", ";
    returnString += Bytes.toString(result.getValue(Bytes.toBytes("cf"), Bytes.toBytes("type"))) + ", ";
    returnString += Bytes.toString(result.getValue(Bytes.toBytes("cf"), Bytes.toBytes("date")));
    System.out.println(returnString);
}
//}

其中"cf"是列族的名称.

回答:

import java.io.IOException;
import java.util.Iterator;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
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.PrefixFilter;
import org.apache.hadoop.hbase.util.Bytes;
//class foo {
public static void main(String[] args) {
    Configuration conf = new Configuration();
    conf.addResource(new Path("C:\\core-site.xml"));
    conf.addResource(new Path("C:\\hbase-site.xml"));
    HTable table = new HTable(conf, "table_name");
    byte[] prefix = Bytes.toBytes("1|A|");
    Scan scan = new Scan(prefix);
    Filter prefixFilter = new PrefixFilter(prefix);
    scan.setFilter(prefixFilter);
    ResultScanner resultScanner = table.getScanner(scan);
    printRows(resultScanner);
    //Result row = table.get(new Get(Bytes.toBytes("1|A|2014-01-01 00:00")));
    //printRow(row); 
}
public static void printRows(ResultScanner resultScanner) {
    for (Iterator<Result> iterator = results.iterator(); iterator.hasNext();) {
        printRow(iterator.next();
    }
}
public static void printRow(Result result) {
    String returnString = "";
    returnString += Bytes.toString(result.getValue(Bytes.toBytes("cf"), Bytes.toBytes("id"))) + ", ";
    returnString += Bytes.toString(result.getValue(Bytes.toBytes("cf"), Bytes.toBytes("type"))) + ", ";
    returnString += Bytes.toString(result.getValue(Bytes.toBytes("cf"), Bytes.toBytes("date")));
    System.out.println(returnString);
}
//}

请注意,我使用该setFilter方法,而下面的答案使用该addFilter方法,因为我们使用不同的API.

Answer 1

您正在使用HTable get操作,因此您只返回一行(请注意,您也可以在此处指定前缀,而不必提供完整的密钥)

如果你想要回到多行,你应该使用a Scan

byte[] prefix=Bytes.toBytes("1|A|");
Scan scan = new Scan(prefix);
PrefixFilter prefixFilter = new PrefixFilter(prefix);
scan.addFilter(prefixFilter);
ResultScanner resultScanner = table.getScanner(scan);