UniqueIndexKeyGenerator.java

package org.apache.hadoop.hbase.client.tableindexed;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.Map;

import org.apache.hadoop.hbase.util.Bytes;

/**
 * Creates index row keys which exactly match the indexed column. This allows a
 * direct get() lookup on the index table, but at the cost that the column
 * values must be unique.
 * 
 * If you are indexing a column which can have duplicated values, consider
 * {@link SimpleIndexKeyGenerator}.
 */
public class UniqueIndexKeyGenerator implements IndexKeyGenerator {
  private byte[] column;

  /**
   * @param column the column to index
   */
  public UniqueIndexKeyGenerator(byte[] column) {
    this.column = column;
  }

  public UniqueIndexKeyGenerator() {
    // For Writable
  }

  /** {@inheritDoc} */
  public byte[] createIndexKey(byte[] rowKey, Map<byte[], byte[]> columns) {
    return columns.get(column).clone();
  }

  /** {@inheritDoc} */
  public void readFields(DataInput in) throws IOException {
    column = Bytes.readByteArray(in);
  }

  /** {@inheritDoc} */
  public void write(DataOutput out) throws IOException {
    Bytes.writeByteArray(out, column);
  }

}