rocksdb/table/plain/plain_table_bloom.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 <vector>
#include <string>

#include "rocksdb/slice.h"

#include "port/port.h"
#include "util/hash.h"

#include <memory>

namespace rocksdb {
class Slice;
class Allocator;
class Logger;

// A legacy Bloom filter implementation used by Plain Table db format, for
// schema backward compatibility. Not for use in new filter applications.
class PlainTableBloomV1 {
 public:
  // allocator: pass allocator to bloom filter, hence trace the usage of memory
  // total_bits: fixed total bits for the bloom
  // num_probes: number of hash probes for a single key
  // locality:  If positive, optimize for cache line locality, 0 otherwise.
  // hash_func:  customized hash function
  // huge_page_tlb_size:  if >0, try to allocate bloom bytes from huge page TLB
  //                      within this page size. Need to reserve huge pages for
  //                      it to be allocated, like:
  //                         sysctl -w vm.nr_hugepages=20
  //                     See linux doc Documentation/vm/hugetlbpage.txt
  explicit PlainTableBloomV1(uint32_t num_probes = 6);
  void SetTotalBits(Allocator* allocator, uint32_t total_bits,
                    uint32_t locality, size_t huge_page_tlb_size,
                    Logger* logger);

  ~PlainTableBloomV1() {}

  // Assuming single threaded access to this function.
  void AddHash(uint32_t hash);

  // Multithreaded access to this function is OK
  bool MayContainHash(uint32_t hash) const;

  void Prefetch(uint32_t hash);

  uint32_t GetNumBlocks() const { return kNumBlocks; }

  Slice GetRawData() const {
    return Slice(reinterpret_cast<char*>(data_), GetTotalBits() / 8);
  }

  void SetRawData(unsigned char* raw_data, uint32_t total_bits,
                  uint32_t num_blocks = 0);

  uint32_t GetTotalBits() const { return kTotalBits; }

  bool IsInitialized() const { return kNumBlocks > 0 || kTotalBits > 0; }

 private:
  uint32_t kTotalBits;
  uint32_t kNumBlocks;
  const uint32_t kNumProbes;

  uint8_t* data_;
};

#if defined(_MSC_VER)
#pragma warning(push)
// local variable is initialized but not referenced
#pragma warning(disable : 4189)
#endif
inline void PlainTableBloomV1::Prefetch(uint32_t h) {
  if (kNumBlocks != 0) {
    uint32_t b = ((h >> 11 | (h << 21)) % kNumBlocks) * (CACHE_LINE_SIZE * 8);
    PREFETCH(&(data_[b / 8]), 0, 3);
  }
}
#if defined(_MSC_VER)
#pragma warning(pop)
#endif

inline bool PlainTableBloomV1::MayContainHash(uint32_t h) const {
  assert(IsInitialized());
  const uint32_t delta = (h >> 17) | (h << 15);  // Rotate right 17 bits
  if (kNumBlocks != 0) {
    uint32_t b = ((h >> 11 | (h << 21)) % kNumBlocks) * (CACHE_LINE_SIZE * 8);
    for (uint32_t i = 0; i < kNumProbes; ++i) {
      // Since CACHE_LINE_SIZE is defined as 2^n, this line will be optimized
      //  to a simple and operation by compiler.
      const uint32_t bitpos = b + (h % (CACHE_LINE_SIZE * 8));
      if ((data_[bitpos / 8] & (1 << (bitpos % 8))) == 0) {
        return false;
      }
      // Rotate h so that we don't reuse the same bytes.
      h = h / (CACHE_LINE_SIZE * 8) +
          (h % (CACHE_LINE_SIZE * 8)) * (0x20000000U / CACHE_LINE_SIZE);
      h += delta;
    }
  } else {
    for (uint32_t i = 0; i < kNumProbes; ++i) {
      const uint32_t bitpos = h % kTotalBits;
      if ((data_[bitpos / 8] & (1 << (bitpos % 8))) == 0) {
        return false;
      }
      h += delta;
    }
  }
  return true;
}

inline void PlainTableBloomV1::AddHash(uint32_t h) {
  assert(IsInitialized());
  const uint32_t delta = (h >> 17) | (h << 15);  // Rotate right 17 bits
  if (kNumBlocks != 0) {
    uint32_t b = ((h >> 11 | (h << 21)) % kNumBlocks) * (CACHE_LINE_SIZE * 8);
    for (uint32_t i = 0; i < kNumProbes; ++i) {
      // Since CACHE_LINE_SIZE is defined as 2^n, this line will be optimized
      // to a simple and operation by compiler.
      const uint32_t bitpos = b + (h % (CACHE_LINE_SIZE * 8));
      data_[bitpos / 8] |= (1 << (bitpos % 8));
      // Rotate h so that we don't reuse the same bytes.
      h = h / (CACHE_LINE_SIZE * 8) +
          (h % (CACHE_LINE_SIZE * 8)) * (0x20000000U / CACHE_LINE_SIZE);
      h += delta;
    }
  } else {
    for (uint32_t i = 0; i < kNumProbes; ++i) {
      const uint32_t bitpos = h % kTotalBits;
      data_[bitpos / 8] |= (1 << (bitpos % 8));
      h += delta;
    }
  }
}

class BloomBlockBuilder {
 public:
  static const std::string kBloomBlock;

  explicit BloomBlockBuilder(uint32_t num_probes = 6) : bloom_(num_probes) {}

  void SetTotalBits(Allocator* allocator, uint32_t total_bits,
                    uint32_t locality, size_t huge_page_tlb_size,
                    Logger* logger) {
    bloom_.SetTotalBits(allocator, total_bits, locality, huge_page_tlb_size,
                        logger);
  }

  uint32_t GetNumBlocks() const { return bloom_.GetNumBlocks(); }

  void AddKeysHashes(const std::vector<uint32_t>& keys_hashes);

  Slice Finish();

 private:
  PlainTableBloomV1 bloom_;
};

};  // namespace rocksdb