Class Scanner

src/Scanner.java:86–1604

Creates a scanner to read data sequentially from HBase. This class is not synchronized as it's expected to be used from a single thread at a time. It's rarely (if ever?) useful to scan concurrently from a shared scanner using multiple threads. If you want to optimize large tab

 * All strings are assumed to use the platform's default charset.
 */
public final class Scanner {

  private static final Logger LOG = LoggerFactory.getLogger(Scanner.class);

  /**
   * The default maximum number of {@link KeyValue}s the server is allowed
   * to return in a single RPC response to a {@link Scanner}.
   * <p>
   * This default value is exposed only as a hint but the value itself
   * is not part of the API and is subject to change without notice.
   * @see #setMaxNumKeyValues
   */
  public static final int DEFAULT_MAX_NUM_KVS = 4096;

  /**
   * The default maximum number of rows to scan per RPC.
   * <p>
   * This default value is exposed only as a hint but the value itself
   * is not part of the API and is subject to change without notice.
   * @see #setMaxNumRows
   */
  public static final int DEFAULT_MAX_NUM_ROWS = 128;

  /** Special reference we use to indicate we're done scanning.  */
  private static final RegionInfo DONE =
    new RegionInfo(EMPTY_ARRAY, EMPTY_ARRAY, EMPTY_ARRAY);

  private final HBaseClient client;
  private final byte[] table;

  private boolean is_reversed = false;
  private boolean is_first_reverse_region = true;

  /**
   * The key to start scanning from.  An empty array means "start from the
   * first key in the table".  This key is updated each time we move on to
   * another row, so that in the event of a failure, we know what was the
   * last key previously returned.  Note that this doesn't entail that the
   * full row was returned.  Depending on the failure, we may not know if
   * the last key returned was only a subset of a row or a full row, so it
   * may not be possible to gracefully recover from certain errors without
   * re-scanning and re-returning the same data twice.
   */
  private byte[] start_key = EMPTY_ARRAY;

  /**
   * The last key to scan up to (exclusive).
   * An empty array means "scan until the last key in the table".
   */
  private byte[] stop_key = EMPTY_ARRAY;

  private byte[][] families;
  private byte[][][] qualifiers;

  /** Filter to apply on the scanner.  */
  private ScanFilter filter;

  /** Minimum {@link KeyValue} timestamp to scan.  */