Scaning using HBase Shell
The scan command is used to view the data in HTable. Using the scan command, you can get the table data. Its syntax is as follows:
scan ‘<table name>’
Example
The following example shows how to read data from a table using the scan command. Here we are reading the emp table.
hbase(main):010:0> scan 'emp' ROW COLUMN + CELL 1 column = personal data:city, timestamp = 1417521848375, value = hyderabad 1 column = personal data:name, timestamp = 1417521785385, value = ramu 1 column = professional data:designation, timestamp = 1417585277,value = manager 1 column = professional data:salary, timestamp = 1417521903862, value = 50000 1 row(s) in 0.0370 seconds
Scanning Using Java API
The complete program to scan the entire table data using java API is as follows.
import java.io.IOException; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.hbase.HBaseConfiguration; import org.apache.hadoop.hbase.util.Bytes; 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; public class ScanTable{ public static void main(String args[]) throws IOException{ // Instantiating Configuration class Configuration config = HBaseConfiguration.create(); // Instantiating HTable class HTable table = new HTable(config, "emp"); // Instantiating the Scan class Scan scan = new Scan(); // Scanning the required columns scan.addColumn(Bytes.toBytes("personal"), Bytes.toBytes("name")); scan.addColumn(Bytes.toBytes("personal"), Bytes.toBytes("city")); // Getting the scan result ResultScanner scanner = table.getScanner(scan); // Reading values from scan result for (Result result = scanner.next(); result != null; result = scanner.next()) System.out.println("Found row : " + result); //closing the scanner scanner.close(); } }
Compile and execute the above program as shown below.
$javac ScanTable.java $java ScanTable
The following should be the output:
Found row : keyvalues={row1/personal:city/1418275612888/Put/vlen=5/mvcc=0, row1/personal:name/1418035791555/Put/vlen=4/mvcc=0}
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