Modifying a Table

Function Description

In HBase, table information is modified using the modifyTable method of org.apache.hadoop.hbase.client.Admin.

Sample Code

public void testModifyTable() {
  LOG.info("Entering testModifyTable.");

  // Specify the column family name.
  byte[] familyName = Bytes.toBytes("education");
  Admin admin = null;
  try {
    // Instantiate an Admin object.
    admin = conn.getAdmin();
    // Obtain the table descriptor.
    HTableDescriptor htd = admin.getTableDescriptor(tableName);
    // Check whether the column family is specified before modification.
    if (!htd.hasFamily(familyName)) {
      // Create the column descriptor.
      HColumnDescriptor hcd = new HColumnDescriptor(familyName);
      htd.addFamily(hcd);
      // Disable the table to get the table offline before modifying
      // the table.
      admin.disableTable(tableName);
      // Submit a modifyTable request.
      admin.modifyTable(tableName, htd);  //Note [1]
      // Enable the table to get the table online after modifying the
      // table.
      admin.enableTable(tableName);
    }
    LOG.info("Modify table successfully.");
  } catch (IOException e) {
    LOG.error("Modify table failed " ,e);
  } finally {
    if (admin != null) {
      try {
        // Close the Admin object.
        admin.close();
      } catch (IOException e) {
        LOG.error("Close admin failed " ,e);
      }
    }
  }
  LOG.info("Exiting testModifyTable.");
}

Precautions

Note [1] Only after the disableTable API is called, the table can be modified by calling the modifyTable API. Then, call the enableTable API to enable the table again.