Timestamp Based Scans in HBase?

Question

For Example for hbase table 'test_table', Values inserted are:

Row1 - Val1 => t
Row1 - Val2 => t + 3
Row1 - Val3 => t + 5

Row2 - Val1 => t
Row2 - Val2 => t + 3
Row2 - Val3 => t + 5

on scan 'test_table' where version = t + 4 should return

Row1 - Val1 => t + 3
Row2 - Val2 => t + 3

How do i achieve time stamp based scans (Based on latest available value less than or equal to the timestamp) in HBase?

Do you want to make it in HBase shell or write a program for this? Take a look here on how to get the list of keys from the table: stackoverflow.com/questions/5218085/…, for each key you can issue get and get the timestamped entries stackoverflow.com/questions/8321741/…, then filter them based on your condition — 0x0FFF

0x0FFF 0x0FFF · Accepted Answer · 2014-11-15T22:00:17

Consider this table:

hbase(main):009:0> create 't1', { NAME => 'f1', VERSIONS => 100 }
hbase(main):010:0> put 't1', 'key1', 'f1:a', 'value1'
hbase(main):011:0> put 't1', 'key1', 'f1:a', 'value2'
hbase(main):012:0> put 't1', 'key1', 'f1:a', 'value3'
hbase(main):013:0> put 't1', 'key2', 'f1:a', 'value4'
hbase(main):014:0> put 't1', 'key2', 'f1:a', 'value5'
hbase(main):015:0> put 't1', 'key1', 'f1:a', 'value6'

Here's its scan in shell with all the versions:

hbase(main):003:0> scan 't1', {VERSIONS => 100 }
ROW              COLUMN+CELL
 key1            column=f1:a, timestamp=1416083314098, value=value6
 key1            column=f1:a, timestamp=1416083294981, value=value3
 key1            column=f1:a, timestamp=1416083293273, value=value2
 key1            column=f1:a, timestamp=1416083291009, value=value1
 key2            column=f1:a, timestamp=1416083305050, value=value5
 key2            column=f1:a, timestamp=1416083299840, value=value4

Here's the scan limited to a specific timestamp, as you requested:

hbase(main):002:0> scan 't1', { TIMERANGE => [0, 1416083300000] }
ROW              COLUMN+CELL
 key1            column=f1:a, timestamp=1416083294981, value=value3
 key2            column=f1:a, timestamp=1416083299840, value=value4

Here's the same in Java code:

package org.example.test;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.client.*;
import org.apache.hadoop.hbase.util.Bytes;
import java.io.IOException;

public class test {
    public static void main (String[] args) throws IOException {
        HTable table = new HTable(HBaseConfiguration.create(), "t1");
        Scan s = new Scan();
        s.setMaxVersions(1);
        s.setTimeRange (0L, 1416083300000L);
        ResultScanner scanner = table.getScanner(s);
        for (Result rr = scanner.next(); rr != null; rr = scanner.next()) {
            System.out.println(Bytes.toString(rr.getRow()) + " => " +
                    Bytes.toString(rr.getValue(Bytes.toBytes("f1"), Bytes.toBytes("a"))));
        }
    }
}

Be aware that specifying the time range maximal value is excluded, which means that if you want to get the last value for all the keys with maximum timestamp T, you should specify upper bound of the range to T+1

Timestamp Based Scans in HBase?

1 Answers