在Hbase表上查询行键的后缀部分

Question

I have an hbase table whose key is composite key part1_part2_part3 Now I want to query result for a keyword on part3 of rowkey. So is there any optimal way of querying other than scanning all rows and checking existence of keyword in part3?

Answer 1

Have you tried using HBase filters ? If not, you could use RowFilter with SubstringComparator to achieve this. This is how RowFilter is used :

public class RowFilterDemo {

    public static void main(String[] args) throws IOException {

        Configuration conf = HBaseConfiguration.create();
        HTable table = new HTable(conf, "demo_table");
        Scan s = new Scan();
        Filter f = new RowFilter(CompareOp.EQUAL, new SubstringComparator("_part3"));
        s.setFilter(f);
        ResultScanner rs = table.getScanner(s);
        for(Result r : rs){
            for (KeyValue kv : r.raw()){
                System.out.println("RowKey : " + Bytes.toString(r.getRow()));
                System.out.println("Qualifier : " + Bytes.toString(kv.getQualifier()));
                System.out.println("Value : " + Bytes.toString(kv.getValue()));
            }

        }
        rs.close();
        table.close();
    }
}

This will return all the rows whose rowkey contain _part3 .

Another approach could be to tweak your rowkey design a bit by reversing them and using PrefixFilter to fetch the data. Given a prefix, specified when you instantiate the filter instance, all rows that match this prefix are returned to the client.

In that case the rowkey would be part3_part2_part1 . And the code to fetch the data will be :

Filter filter = new PrefixFilter(Bytes.toBytes("part3_"));
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();

This approach also gives you the ability to perform range scans using Scan.startRow() and Scan.stopRow() methods. This will be much more efficient than using Filters.

A more advanced approach would be to use HBase FuzzyRowFilter . But in order to use it your rowkeys must be of same length .

- So is there any optimal way of querying other than scanning all rows and checking existence of keyword in part3?

Change your design if possible and use range queries.

HTH