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)}.

   *
   * @param firstRow  The first row to start at.
   * @throws IOException When restarting fails.
   */
  public void restart(byte[] firstRow) throws IOException {
    currentScan = new Scan(scan);
    currentScan.setStartRow(firstRow);
    currentScan.setAttribute(Scan.SCAN_ATTRIBUTES_METRICS_ENABLE,
      Bytes.toBytes(Boolean.TRUE));
    this.scanner = this.htable.getScanner(currentScan);
    if (logScannerActivity) {

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    // load table descriptor
    HTableDescriptor htd = FSTableDescriptors.getTableDescriptorFromFs(fs,
        snapshotDir);


    Scan scan = TableMapReduceUtil.convertStringToScan(conf
      .get(TableInputFormat.SCAN));
    Path tableDir = new Path(conf.get(TABLE_DIR_KEY));


    List<InputSplit> splits = new ArrayList<InputSplit>();
    for (String regionName : snapshotRegionNames) {
      // load region descriptor
      Path regionDir = new Path(snapshotDir, regionName);
      HRegionInfo hri = HRegionFileSystem.loadRegionInfoFileContent(fs,
          regionDir);


      if (CellUtil.overlappingKeys(scan.getStartRow(), scan.getStopRow(),
          hri.getStartKey(), hri.getEndKey())) {
        // compute HDFS locations from snapshot files (which will get the locations for
        // referred hfiles)
        List<String> hosts = getBestLocations(conf,
          HRegion.computeHDFSBlocksDistribution(conf, htd, hri, tableDir));

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    public void map(ImmutableBytesWritable row, final Result value,
                    Context context)
        throws IOException {
      if (replicatedScanner == null) {
        Configuration conf = context.getConfiguration();
        final Scan scan = new Scan();
        scan.setCaching(conf.getInt(TableInputFormat.SCAN_CACHEDROWS, 1));
        long startTime = conf.getLong(NAME + ".startTime", 0);
        long endTime = conf.getLong(NAME + ".endTime", Long.MAX_VALUE);
        String families = conf.get(NAME + ".families", null);
        if(families != null) {
          String[] fams = families.split(",");
          for(String fam : fams) {
            scan.addFamily(Bytes.toBytes(fam));
          }
        }
        scan.setTimeRange(startTime, endTime);
        HConnectionManager.execute(new HConnectable<Void>(conf) {
          @Override
          public Void connect(HConnection conn) throws IOException {
            String zkClusterKey = conf.get(NAME + ".peerQuorumAddress");
            Configuration peerConf = HBaseConfiguration.create(conf);
            ZKUtil.applyClusterKeyToConf(peerConf, zkClusterKey);


            HTable replicatedTable = new HTable(peerConf, conf.get(NAME + ".tableName"));
            scan.setStartRow(value.getRow());
            replicatedScanner = replicatedTable.getScanner(scan);
            return null;
          }
        });
      }

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    TableRecordReader trr = this.tableRecordReader;
    // if no table record reader was provided use default
    if (trr == null) {
      trr = new TableRecordReader();
    }
    Scan sc = new Scan(this.scan);
    sc.setStartRow(tSplit.getStartRow());
    sc.setStopRow(tSplit.getEndRow());
    trr.setScan(sc);
    trr.setHTable(table);
    return trr;
  }

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   * Gets the scan defining the actual details like columns etc.
   *
   * @return The internal scan instance.
   */
  public Scan getScan() {
    if (this.scan == null) this.scan = new Scan();
    return scan;
  }

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    LOG.info("Peer Quorum Address: " + peerQuorumAddress);


    Job job = new Job(conf, NAME + "_" + tableName);
    job.setJarByClass(VerifyReplication.class);


    Scan scan = new Scan();
    scan.setTimeRange(startTime, endTime);
    if(families != null) {
      String[] fams = families.split(",");
      for(String fam : fams) {
        scan.addFamily(Bytes.toBytes(fam));
      }
    }
    TableMapReduceUtil.initTableMapperJob(tableName, scan,
        Verifier.class, null, null, job);

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        KeyValueTestUtil.create(r1, CF_STR, "a", 5, KeyValue.Type.Put, "dont-care"),
    };
    KeyValueScanner [] scanners = new KeyValueScanner[] {
      new KeyValueScanFixture(KeyValue.COMPARATOR, kvs)
    };
    Scan scanSpec = new Scan(Bytes.toBytes(r1));
    scanSpec.setTimeRange(0, 6);
    scanSpec.setMaxVersions();
    StoreScanner scan =
      new StoreScanner(scanSpec, CF, Long.MAX_VALUE,
        KeyValue.COMPARATOR, getCols("a"), scanners);
    List<KeyValue> results = new ArrayList<KeyValue>();
    assertEquals(true, scan.next(results));
    assertEquals(5, results.size());
    assertEquals(kvs[kvs.length - 1], results.get(0));
    // Scan limited TimeRange
    scanSpec = new Scan(Bytes.toBytes(r1));
    scanSpec.setTimeRange(1, 3);
    scanSpec.setMaxVersions();
    scan = new StoreScanner(scanSpec, CF, Long.MAX_VALUE,
      KeyValue.COMPARATOR, getCols("a"), scanners);
    results = new ArrayList<KeyValue>();
    assertEquals(true, scan.next(results));
    assertEquals(2, results.size());
    // Another range.
    scanSpec = new Scan(Bytes.toBytes(r1));
    scanSpec.setTimeRange(5, 10);
    scanSpec.setMaxVersions();
    scan = new StoreScanner(scanSpec, CF, Long.MAX_VALUE,
      KeyValue.COMPARATOR, getCols("a"), scanners);
    results = new ArrayList<KeyValue>();
    assertEquals(true, scan.next(results));
    assertEquals(1, results.size());
    // See how TimeRange and Versions interact.
    // Another range.
    scanSpec = new Scan(Bytes.toBytes(r1));
    scanSpec.setTimeRange(0, 10);
    scanSpec.setMaxVersions(3);
    scan = new StoreScanner(scanSpec, CF, Long.MAX_VALUE,
      KeyValue.COMPARATOR, getCols("a"), scanners);
    results = new ArrayList<KeyValue>();
    assertEquals(true, scan.next(results));
    assertEquals(3, results.size());

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    };
    KeyValueScanner [] scanners = new KeyValueScanner[] {
      new KeyValueScanFixture(KeyValue.COMPARATOR, kvs)
    };


    Scan scanSpec = new Scan(Bytes.toBytes("R1"));
    // this only uses maxVersions (default=1) and TimeRange (default=all)
    StoreScanner scan =
      new StoreScanner(scanSpec, CF, Long.MAX_VALUE,
          KeyValue.COMPARATOR, getCols("a"),
          scanners);

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    KeyValueScanner [] scanners = new KeyValueScanner[] {
        new KeyValueScanFixture(KeyValue.COMPARATOR,
            kvs)
    };


    Scan scanSpec = new Scan(Bytes.toBytes("R1"));
    // this only uses maxVersions (default=1) and TimeRange (default=all)
    StoreScanner scan =
      new StoreScanner(scanSpec, CF, Long.MAX_VALUE,
          KeyValue.COMPARATOR, getCols("a"),
          scanners);

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        KeyValueTestUtil.create("R1", "cf", "a", 1, KeyValue.Type.Delete, "dont-care"),
    };
    KeyValueScanner [] scanners = new KeyValueScanner[] {
        new KeyValueScanFixture(KeyValue.COMPARATOR, kvs)
    };
    Scan scanSpec = new Scan(Bytes.toBytes("R1"));
    StoreScanner scan =
      new StoreScanner(scanSpec, CF, Long.MAX_VALUE, KeyValue.COMPARATOR,
          getCols("a"), scanners);


    List<KeyValue> results = new ArrayList<KeyValue>();

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