arangodb/arangod/Utils/OperationCursor.h

////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2014-2016 ArangoDB GmbH, Cologne, Germany
/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
///     http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Max Neunhoeffer
////////////////////////////////////////////////////////////////////////////////

#ifndef ARANGOD_UTILS_OPERATION_CURSOR_H
#define ARANGOD_UTILS_OPERATION_CURSOR_H 1

#include "Basics/Common.h"
#include "Indexes/IndexIterator.h"
#include "Utils/OperationResult.h"

#include <velocypack/Buffer.h>
#include <velocypack/Builder.h>
#include <velocypack/Options.h>
#include <velocypack/Slice.h>
#include <velocypack/velocypack-aliases.h>

namespace arangodb {

// FORWARD declaration
class LogicalCollection;

struct OperationCursor {
 public:
  int code;

 private:
  std::unique_ptr<IndexIterator> _indexIterator;
  bool _hasMore;
  uint64_t _limit;
  uint64_t const _batchSize;

 public:
  explicit OperationCursor(int code)
      : code(code), _hasMore(false), _limit(0), _batchSize(1000) {}

  OperationCursor(IndexIterator* iterator, uint64_t batchSize)
      : code(TRI_ERROR_NO_ERROR),
        _indexIterator(iterator),
        _hasMore(_indexIterator != nullptr),
        _limit(UINT64_MAX),  // _limit is modified later on
        _batchSize(batchSize) {}

  ~OperationCursor() {}

  IndexIterator* indexIterator() const { return _indexIterator.get(); }

  LogicalCollection* collection() const;

  inline bool hasMore() {
    if (_hasMore && _limit == 0) {
      _hasMore = false;
    }
    return _hasMore;
  }

  bool ok() const { return code == TRI_ERROR_NO_ERROR; }

  bool fail() const { return !ok(); }

  bool hasExtra() const;
  bool hasCovering() const;

  /// @brief Reset the cursor
  void reset();

  /// @brief Calls cb for the next batchSize many elements
  /// returns true if there are more documents (hasMore) and false
  /// if there are none
  bool next(IndexIterator::LocalDocumentIdCallback const& callback, uint64_t batchSize);

  /// @brief Calls cb for the next batchSize many elements
  /// returns true if there are more documents (hasMore) and false
  /// if there are none
  bool nextWithExtra(IndexIterator::ExtraCallback const& callback, uint64_t batchSize);

  /// @brief Calls cb for the next batchSize many elements, complete documents
  /// returns true if there are more documents (hasMore) and false
  /// if there are none
  bool nextDocument(IndexIterator::DocumentCallback const& callback, uint64_t batchSize);

  /// @brief Calls cb for the next batchSize many elements, index-only
  /// projections returns true if there are more documents (hasMore) and false
  /// if there are none
  bool nextCovering(IndexIterator::DocumentCallback const& callback, uint64_t batchSize);

  /// @brief convenience function to retrieve all results
  void all(IndexIterator::LocalDocumentIdCallback const& callback) {
    while (next(callback, 1000)) {
    }
  }

  /// @brief convenience function to retrieve all results with extra
  void allWithExtra(IndexIterator::ExtraCallback const& callback) {
    while (nextWithExtra(callback, 1000)) {
    }
  }

  /// @brief convenience function to retrieve all results
  void allDocuments(IndexIterator::DocumentCallback const& callback, uint64_t batchSize) {
    while (nextDocument(callback, batchSize)) {
    }
  }

  /// @brief skip the next toSkip many elements.
  ///        skipped will be increased by the amount of skipped elements afterwards
  ///        Check hasMore()==true before using this
  ///        NOTE: This will throw on OUT_OF_MEMORY
  void skip(uint64_t toSkip, uint64_t& skipped);
};

}  // namespace arangodb

#endif