rocksdb/table/block_based/filter_policy_internal.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).
// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.

#pragma once

#include <memory>
#include <string>
#include <vector>

#include "rocksdb/filter_policy.h"

namespace rocksdb {

class Slice;

// Exposes any extra information needed for testing built-in
// FilterBitsBuilders
class BuiltinFilterBitsBuilder : public FilterBitsBuilder {
 public:
  // Calculate number of bytes needed for a new filter, including
  // metadata. Passing the result to CalculateNumEntry should
  // return >= the num_entry passed in.
  virtual uint32_t CalculateSpace(const int num_entry) = 0;
};

// RocksDB built-in filter policy for Bloom or Bloom-like filters.
// This class is considered internal API and subject to change.
// See NewBloomFilterPolicy.
class BloomFilterPolicy : public FilterPolicy {
 public:
  // An internal marker for which Bloom filter implementation to use.
  // This makes it easier for tests to track or to walk over the built-in
  // set of Bloom filter policies. The only variance in BloomFilterPolicy
  // by implementation is in GetFilterBitsBuilder(), so an enum is practical
  // here vs. subclasses.
  enum Impl {
    // Implementation of Bloom filter for full and partitioned filters.
    // Set to 0 in case of value confusion with bool use_block_based_builder
    kFull = 0,
    // Deprecated block-based Bloom filter implementation.
    // Set to 1 in case of value confusion with bool use_block_based_builder
    kBlock = 1,
  };
  static const std::vector<Impl> kAllImpls;

  explicit BloomFilterPolicy(int bits_per_key, Impl impl);

  ~BloomFilterPolicy() override;

  const char* Name() const override;

  // Deprecated block-based filter only
  void CreateFilter(const Slice* keys, int n, std::string* dst) const override;

  // Deprecated block-based filter only
  bool KeyMayMatch(const Slice& key, const Slice& bloom_filter) const override;

  FilterBitsBuilder* GetFilterBitsBuilder() const override;

  // Read metadata to determine what kind of FilterBitsReader is needed
  // and return a new one. This must successfully process any filter data
  // generated by a built-in FilterBitsBuilder, regardless of the impl
  // chosen for this BloomFilterPolicy. Not compatible with CreateFilter.
  FilterBitsReader* GetFilterBitsReader(const Slice& contents) const override;

 private:
  int bits_per_key_;
  int num_probes_;
  // Selected implementation for building new SST filters
  Impl impl_;
};

}  // namespace rocksdb