/**
  * Use PreIncrement hook of BaseRegionObserver to overcome deficiencies in Increment
  * implementation (HBASE-10254): 1) Lack of recognition and identification of when the key value
  * to increment doesn't exist 2) Lack of the ability to set the timestamp of the updated key
  * value. Works the same as existing region.increment(), except assumes there is a single column
  * to increment and uses Phoenix LONG encoding.
  *
  * @author jtaylor
  * @since 3.0.0
  */
 @Override
 public Result preIncrement(
     final ObserverContext<RegionCoprocessorEnvironment> e, final Increment increment)
     throws IOException {
   RegionCoprocessorEnvironment env = e.getEnvironment();
   // We need to set this to prevent region.increment from being called
   e.bypass();
   e.complete();
   HRegion region = env.getRegion();
   byte[] row = increment.getRow();
   TimeRange tr = increment.getTimeRange();
   region.startRegionOperation();
   try {
     Integer lid = region.getLock(null, row, true);
     try {
       long maxTimestamp = tr.getMax();
       if (maxTimestamp == HConstants.LATEST_TIMESTAMP) {
         maxTimestamp = EnvironmentEdgeManager.currentTimeMillis();
         tr = new TimeRange(tr.getMin(), maxTimestamp);
       }
       Get get = new Get(row);
       get.setTimeRange(tr.getMin(), tr.getMax());
       for (Map.Entry<byte[], NavigableMap<byte[], Long>> entry :
           increment.getFamilyMap().entrySet()) {
         byte[] cf = entry.getKey();
         for (byte[] cq : entry.getValue().keySet()) {
           get.addColumn(cf, cq);
         }
       }
       Result result = region.get(get);
       if (result.isEmpty()) {
         return getErrorResult(
             row, maxTimestamp, SQLExceptionCode.SEQUENCE_UNDEFINED.getErrorCode());
       }
       KeyValue currentValueKV = Sequence.getCurrentValueKV(result);
       KeyValue incrementByKV = Sequence.getIncrementByKV(result);
       KeyValue cacheSizeKV = Sequence.getCacheSizeKV(result);
       long value =
           PDataType.LONG
               .getCodec()
               .decodeLong(currentValueKV.getBuffer(), currentValueKV.getValueOffset(), null);
       long incrementBy =
           PDataType.LONG
               .getCodec()
               .decodeLong(incrementByKV.getBuffer(), incrementByKV.getValueOffset(), null);
       int cacheSize =
           PDataType.INTEGER
               .getCodec()
               .decodeInt(cacheSizeKV.getBuffer(), cacheSizeKV.getValueOffset(), null);
       value += incrementBy * cacheSize;
       byte[] valueBuffer = new byte[PDataType.LONG.getByteSize()];
       PDataType.LONG.getCodec().encodeLong(value, valueBuffer, 0);
       Put put = new Put(row, currentValueKV.getTimestamp());
       // Hold timestamp constant for sequences, so that clients always only see the latest value
       // regardless of when they connect.
       KeyValue newCurrentValueKV =
           KeyValueUtil.newKeyValue(
               row,
               currentValueKV.getFamily(),
               currentValueKV.getQualifier(),
               currentValueKV.getTimestamp(),
               valueBuffer);
       put.add(newCurrentValueKV);
       @SuppressWarnings("unchecked")
       Pair<Mutation, Integer>[] mutations = new Pair[1];
       mutations[0] = new Pair<Mutation, Integer>(put, lid);
       region.batchMutate(mutations);
       return Sequence.replaceCurrentValueKV(result, newCurrentValueKV);
     } finally {
       region.releaseRowLock(lid);
     }
   } catch (Throwable t) {
     ServerUtil.throwIOException("Increment of sequence " + Bytes.toStringBinary(row), t);
     return null; // Impossible
   } finally {
     region.closeRegionOperation();
   }
 }
  /**
   * Override the preAppend for checkAndPut and checkAndDelete, as we need the ability to a) set the
   * TimeRange for the Get being done and b) return something back to the client to indicate
   * success/failure
   */
  @SuppressWarnings("deprecation")
  @Override
  public Result preAppend(
      final ObserverContext<RegionCoprocessorEnvironment> e, final Append append)
      throws IOException {
    byte[] opBuf = append.getAttribute(OPERATION_ATTRIB);
    if (opBuf == null) {
      return null;
    }
    Op op = Op.values()[opBuf[0]];

    long clientTimestamp = HConstants.LATEST_TIMESTAMP;
    byte[] clientTimestampBuf = append.getAttribute(MAX_TIMERANGE_ATTRIB);
    if (clientTimestampBuf != null) {
      clientTimestamp = Bytes.toLong(clientTimestampBuf);
    }
    boolean hadClientTimestamp = (clientTimestamp != HConstants.LATEST_TIMESTAMP);
    if (hadClientTimestamp) {
      // Prevent race condition of creating two sequences at the same timestamp
      // by looking for a sequence at or after the timestamp at which it'll be
      // created.
      if (op == Op.CREATE_SEQUENCE) {
        clientTimestamp++;
      }
    } else {
      clientTimestamp = EnvironmentEdgeManager.currentTimeMillis();
      clientTimestampBuf = Bytes.toBytes(clientTimestamp);
    }

    RegionCoprocessorEnvironment env = e.getEnvironment();
    // We need to set this to prevent region.append from being called
    e.bypass();
    e.complete();
    HRegion region = env.getRegion();
    byte[] row = append.getRow();
    region.startRegionOperation();
    try {
      Integer lid = region.getLock(null, row, true);
      try {
        KeyValue keyValue = append.getFamilyMap().values().iterator().next().iterator().next();
        byte[] family = keyValue.getFamily();
        byte[] qualifier = keyValue.getQualifier();

        Get get = new Get(row);
        get.setTimeRange(MetaDataProtocol.MIN_TABLE_TIMESTAMP, clientTimestamp);
        get.addColumn(family, qualifier);
        Result result = region.get(get);
        if (result.isEmpty()) {
          if (op == Op.DROP_SEQUENCE || op == Op.RESET_SEQUENCE) {
            return getErrorResult(
                row, clientTimestamp, SQLExceptionCode.SEQUENCE_UNDEFINED.getErrorCode());
          }
        } else {
          if (op == Op.CREATE_SEQUENCE) {
            return getErrorResult(
                row, clientTimestamp, SQLExceptionCode.SEQUENCE_ALREADY_EXIST.getErrorCode());
          }
        }
        Mutation m = null;
        switch (op) {
          case RESET_SEQUENCE:
            KeyValue currentValueKV = result.raw()[0];
            long expectedValue =
                PDataType.LONG
                    .getCodec()
                    .decodeLong(append.getAttribute(CURRENT_VALUE_ATTRIB), 0, null);
            long value =
                PDataType.LONG
                    .getCodec()
                    .decodeLong(currentValueKV.getBuffer(), currentValueKV.getValueOffset(), null);
            // Timestamp should match exactly, or we may have the wrong sequence
            if (expectedValue != value || currentValueKV.getTimestamp() != clientTimestamp) {
              return new Result(
                  Collections.singletonList(
                      KeyValueUtil.newKeyValue(
                          row,
                          PhoenixDatabaseMetaData.SEQUENCE_FAMILY_BYTES,
                          QueryConstants.EMPTY_COLUMN_BYTES,
                          currentValueKV.getTimestamp(),
                          ByteUtil.EMPTY_BYTE_ARRAY)));
            }
            m = new Put(row, currentValueKV.getTimestamp());
            m.getFamilyMap().putAll(append.getFamilyMap());
            break;
          case DROP_SEQUENCE:
            m = new Delete(row, clientTimestamp, null);
            break;
          case CREATE_SEQUENCE:
            m = new Put(row, clientTimestamp);
            m.getFamilyMap().putAll(append.getFamilyMap());
            break;
        }
        if (!hadClientTimestamp) {
          for (List<KeyValue> kvs : m.getFamilyMap().values()) {
            for (KeyValue kv : kvs) {
              kv.updateLatestStamp(clientTimestampBuf);
            }
          }
        }
        @SuppressWarnings("unchecked")
        Pair<Mutation, Integer>[] mutations = new Pair[1];
        mutations[0] = new Pair<Mutation, Integer>(m, lid);
        region.batchMutate(mutations);
        long serverTimestamp = MetaDataUtil.getClientTimeStamp(m);
        // Return result with single KeyValue. The only piece of information
        // the client cares about is the timestamp, which is the timestamp of
        // when the mutation was actually performed (useful in the case of .
        return new Result(
            Collections.singletonList(
                KeyValueUtil.newKeyValue(
                    row,
                    PhoenixDatabaseMetaData.SEQUENCE_FAMILY_BYTES,
                    QueryConstants.EMPTY_COLUMN_BYTES,
                    serverTimestamp,
                    SUCCESS_VALUE)));
      } finally {
        region.releaseRowLock(lid);
      }
    } catch (Throwable t) {
      ServerUtil.throwIOException("Increment of sequence " + Bytes.toStringBinary(row), t);
      return null; // Impossible
    } finally {
      region.closeRegionOperation();
    }
  }