rocksdb/include/rocksdb/flush_block_policy.h

// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under both the GPLv2 (found in the
//  COPYING file in the root directory) and Apache 2.0 License
//  (found in the LICENSE.Apache file in the root directory).

#pragma once

#include <string>
#include "rocksdb/table.h"

namespace rocksdb {

class Slice;
class BlockBuilder;
struct Options;

// FlushBlockPolicy provides a configurable way to determine when to flush a
// block in the block based tables,
class FlushBlockPolicy {
 public:
  // Keep track of the key/value sequences and return the boolean value to
  // determine if table builder should flush current data block.
  virtual bool Update(const Slice& key,
                      const Slice& value) = 0;

  virtual ~FlushBlockPolicy() { }
};

class FlushBlockPolicyFactory {
 public:
  // Return the name of the flush block policy.
  virtual const char* Name() const = 0;

  // Return a new block flush policy that flushes data blocks by data size.
  // FlushBlockPolicy may need to access the metadata of the data block
  // builder to determine when to flush the blocks.
  //
  // Callers must delete the result after any database that is using the
  // result has been closed.
  virtual FlushBlockPolicy* NewFlushBlockPolicy(
      const BlockBasedTableOptions& table_options,
      const BlockBuilder& data_block_builder) const = 0;

  virtual ~FlushBlockPolicyFactory() { }
};

class FlushBlockBySizePolicyFactory : public FlushBlockPolicyFactory {
 public:
  FlushBlockBySizePolicyFactory() {}

  const char* Name() const override { return "FlushBlockBySizePolicyFactory"; }

  FlushBlockPolicy* NewFlushBlockPolicy(
      const BlockBasedTableOptions& table_options,
      const BlockBuilder& data_block_builder) const override;

  static FlushBlockPolicy* NewFlushBlockPolicy(
      const uint64_t size, const int deviation,
      const BlockBuilder& data_block_builder);
};

}  // rocksdb