Examples of org.apache.hadoop.hbase.client.Scan

org.apache.hadoop.hbase.client.Scan
Used to perform Scan operations.
All operations are identical to {@link Get} with the exception ofinstantiation. Rather than specifying a single row, an optional startRow and stopRow may be defined. If rows are not specified, the Scanner will iterate over all rows.
To scan everything for each row, instantiate a Scan object.
To modify scanner caching for just this scan, use {@link #setCaching(int) setCaching}. If caching is NOT set, we will use the caching value of the hosting {@link HTable}. See {@link HTable#setScannerCaching(int)}.
To further define the scope of what to get when scanning, perform additional methods as outlined below.
To get all columns from specific families, execute {@link #addFamily(byte[]) addFamily}for each family to retrieve.
To get specific columns, execute {@link #addColumn(byte[],byte[]) addColumn}for each column to retrieve.
To only retrieve columns within a specific range of version timestamps, execute {@link #setTimeRange(long,long) setTimeRange}.
To only retrieve columns with a specific timestamp, execute {@link #setTimeStamp(long) setTimestamp}.
To limit the number of versions of each column to be returned, execute {@link #setMaxVersions(int) setMaxVersions}.
To limit the maximum number of values returned for each call to next(), execute {@link #setBatch(int) setBatch}.
To add a filter, execute {@link #setFilter(org.apache.hadoop.hbase.filter.Filter) setFilter}.
Expert: To explicitly disable server-side block caching for this scan, execute {@link #setCacheBlocks(boolean)}.

    results.close();
    return count;
  }


  public int countRows(final HTable table, final byte[]... families) throws IOException {
    Scan scan = new Scan();
    for (byte[] family: families) {
      scan.addFamily(family);
    }
    ResultScanner results = table.getScanner(scan);
    int count = 0;
    for (@SuppressWarnings("unused") Result res : results) {
      count++;

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  /**
   * Return an md5 digest of the entire contents of a table.
   */
  public String checksumRows(final HTable table) throws Exception {
    Scan scan = new Scan();
    ResultScanner results = table.getScanner(scan);
    MessageDigest digest = MessageDigest.getInstance("MD5");
    for (Result res : results) {
      digest.update(res.getRow());
    }

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   */
  public List<byte[]> getMetaTableRows() throws IOException {
    // TODO: Redo using MetaReader class
    HTable t = new HTable(new Configuration(this.conf), HConstants.META_TABLE_NAME);
    List<byte[]> rows = new ArrayList<byte[]>();
    ResultScanner s = t.getScanner(new Scan());
    for (Result result : s) {
      LOG.info("getMetaTableRows: row -> " +
        Bytes.toStringBinary(result.getRow()));
      rows.add(result.getRow());
    }

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   */
  public List<byte[]> getMetaTableRows(byte[] tableName) throws IOException {
    // TODO: Redo using MetaReader.
    HTable t = new HTable(new Configuration(this.conf), HConstants.META_TABLE_NAME);
    List<byte[]> rows = new ArrayList<byte[]>();
    ResultScanner s = t.getScanner(new Scan());
    for (Result result : s) {
      byte[] val = result.getValue(HConstants.CATALOG_FAMILY, HConstants.REGIONINFO_QUALIFIER);
      if (val == null) {
        LOG.error("No region info for row " + Bytes.toString(result.getRow()));
        // TODO figure out what to do for this new hosed case.

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  public void waitUntilAllRegionsAssigned(final int countOfRegions)
  throws IOException {
    HTable meta = new HTable(getConfiguration(), HConstants.META_TABLE_NAME);
    while (true) {
      int rows = 0;
      Scan scan = new Scan();
      scan.addColumn(HConstants.CATALOG_FAMILY, HConstants.SERVER_QUALIFIER);
      ResultScanner s = meta.getScanner(scan);
      for (Result r = null; (r = s.next()) != null;) {
        byte [] b =
          r.getValue(HConstants.CATALOG_FAMILY, HConstants.SERVER_QUALIFIER);
        if (b == null || b.length <= 0) {

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   * has no actual methods of querying itself, and relies on StoreScanner.
   */
  public static List<KeyValue> getFromStoreFile(Store store,
                                                Get get) throws IOException {
    MultiVersionConsistencyControl.resetThreadReadPoint();
    Scan scan = new Scan(get);
    InternalScanner scanner = (InternalScanner) store.getScanner(scan,
        scan.getFamilyMap().get(store.getFamily().getName()));


    List<KeyValue> result = new ArrayList<KeyValue>();
    scanner.next(result);
    if (!result.isEmpty()) {
      // verify that we are on the row we want:

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   * @return
   * @throws IOException
   */
  private byte[][] getResults(HTable table, int numEvents) throws IOException{
    byte[][] results = new byte[numEvents+1][];
    Scan scan = new Scan();
    scan.addColumn(columnFamily.getBytes(),plCol.getBytes());
    scan.setStartRow( Bytes.toBytes("default"));
    ResultScanner rs = table.getScanner(scan);
    byte[] out = null;
    int i = 0;
    try {
      for (Result r = rs.next(); r != null; r = rs.next()) {
        out = r.getValue(columnFamily.getBytes(), plCol.getBytes());


        if(i >= results.length - 1){
          rs.close();
          throw new FlumeException("More results than expected in the table." +
              "Expected = " + numEvents +". Found = " + i);
        }
        results[i++] = out;
        System.out.println(out);
      }
    } finally {
      rs.close();
    }


    Assert.assertEquals(i, results.length - 1);
    scan = new Scan();
    scan.addColumn(columnFamily.getBytes(),inColumn.getBytes());
    scan.setStartRow(Bytes.toBytes("incRow"));
    rs = table.getScanner(scan);
    out = null;
    try {
      for (Result r = rs.next(); r != null; r = rs.next()) {
        out = r.getValue(columnFamily.getBytes(), inColumn.getBytes());

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   * @return
   * @throws IOException
   */
  private byte[][] getResults(HTable table, int numEvents) throws IOException{
    byte[][] results = new byte[numEvents+1][];
    Scan scan = new Scan();
    scan.addColumn(columnFamily.getBytes(),plCol.getBytes());
    scan.setStartRow( Bytes.toBytes("default"));
    ResultScanner rs = table.getScanner(scan);
    byte[] out = null;
    int i = 0;
    try {
      for (Result r = rs.next(); r != null; r = rs.next()) {
        out = r.getValue(columnFamily.getBytes(), plCol.getBytes());


        if(i >= results.length - 1){
          rs.close();
          throw new FlumeException("More results than expected in the table." +
              "Expected = " + numEvents +". Found = " + i);
        }
        results[i++] = out;
        System.out.println(out);
      }
    } finally {
      rs.close();
    }


    Assert.assertEquals(i, results.length - 1);
    scan = new Scan();
    scan.addColumn(columnFamily.getBytes(),inColumn.getBytes());
    scan.setStartRow(Bytes.toBytes("incRow"));
    rs = table.getScanner(scan);
    out = null;
    try {
      for (Result r = rs.next(); r != null; r = rs.next()) {
        out = r.getValue(columnFamily.getBytes(), inColumn.getBytes());

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    assertNoErrors(doFsck(conf, false));


    // Now let's mess it up and change the assignment in .META. to
    // point to a different region server
    HTable meta = new HTable(conf, HTableDescriptor.META_TABLEDESC.getName());
    ResultScanner scanner = meta.getScanner(new Scan());


    resforloop:
    for (Result res : scanner) {
      long startCode = Bytes.toLong(res.getValue(HConstants.CATALOG_FAMILY,
          HConstants.STARTCODE_QUALIFIER));


      for (JVMClusterUtil.RegionServerThread rs :
          TEST_UTIL.getHBaseCluster().getRegionServerThreads()) {


        ServerName sn = rs.getRegionServer().getServerName();


        // When we find a diff RS, change the assignment and break
        if (startCode != sn.getStartcode()) {
          Put put = new Put(res.getRow());
          put.setWriteToWAL(false);
          put.add(HConstants.CATALOG_FAMILY, HConstants.SERVER_QUALIFIER,
            Bytes.toBytes(sn.getHostAndPort()));
          put.add(HConstants.CATALOG_FAMILY, HConstants.STARTCODE_QUALIFIER,
            Bytes.toBytes(sn.getStartcode()));
          meta.put(put);
          break resforloop;
        }
      }
    }


    // Try to fix the data
    assertErrors(doFsck(conf, true), new ERROR_CODE[]{
        ERROR_CODE.SERVER_DOES_NOT_MATCH_META});


    // fixing assignments require opening regions is not synchronous.  To make
    // the test pass consistently so for now we bake in some sleep to let it
    // finish.  1s seems sufficient.
    Thread.sleep(1000);


    // Should be fixed now
    assertNoErrors(doFsck(conf, false));


    // comment needed - what is the purpose of this line
    HTable t = new HTable(conf, Bytes.toBytes(table));
    ResultScanner s = t.getScanner(new Scan());
    s.close();
    t.close();


    scanner.close();
    meta.close();

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  /**
   * Counts the number of row to verify data loss or non-dataloss.
   */
  int countRows() throws IOException {
     Scan s = new Scan();
     ResultScanner rs = tbl.getScanner(s);
     int i = 0;
     while(rs.next() !=null) {
       i++;
     }

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