| // 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. |
| |
| #include "leveldb/filter_policy.h" |
| |
| #include "util/coding.h" |
| #include "util/logging.h" |
| #include "util/testharness.h" |
| #include "util/testutil.h" |
| |
| namespace leveldb { |
| |
| static const int kVerbose = 1; |
| |
| static Slice Key(int i, char* buffer) { |
| EncodeFixed32(buffer, i); |
| return Slice(buffer, sizeof(uint32_t)); |
| } |
| |
| class BloomTest { |
| private: |
| const FilterPolicy* policy_; |
| std::string filter_; |
| std::vector<std::string> keys_; |
| |
| public: |
| BloomTest() : policy_(NewBloomFilterPolicy(10)) { } |
| |
| ~BloomTest() { |
| delete policy_; |
| } |
| |
| void Reset() { |
| keys_.clear(); |
| filter_.clear(); |
| } |
| |
| void Add(const Slice& s) { |
| keys_.push_back(s.ToString()); |
| } |
| |
| void Build() { |
| std::vector<Slice> key_slices; |
| for (size_t i = 0; i < keys_.size(); i++) { |
| key_slices.push_back(Slice(keys_[i])); |
| } |
| filter_.clear(); |
| policy_->CreateFilter(&key_slices[0], key_slices.size(), &filter_); |
| keys_.clear(); |
| if (kVerbose >= 2) DumpFilter(); |
| } |
| |
| size_t FilterSize() const { |
| return filter_.size(); |
| } |
| |
| void DumpFilter() { |
| fprintf(stderr, "F("); |
| for (size_t i = 0; i+1 < filter_.size(); i++) { |
| const unsigned int c = static_cast<unsigned int>(filter_[i]); |
| for (int j = 0; j < 8; j++) { |
| fprintf(stderr, "%c", (c & (1 <<j)) ? '1' : '.'); |
| } |
| } |
| fprintf(stderr, ")\n"); |
| } |
| |
| bool Matches(const Slice& s) { |
| if (!keys_.empty()) { |
| Build(); |
| } |
| return policy_->KeyMayMatch(s, filter_); |
| } |
| |
| double FalsePositiveRate() { |
| char buffer[sizeof(int)]; |
| int result = 0; |
| for (int i = 0; i < 10000; i++) { |
| if (Matches(Key(i + 1000000000, buffer))) { |
| result++; |
| } |
| } |
| return result / 10000.0; |
| } |
| }; |
| |
| TEST(BloomTest, EmptyFilter) { |
| ASSERT_TRUE(! Matches("hello")); |
| ASSERT_TRUE(! Matches("world")); |
| } |
| |
| TEST(BloomTest, Small) { |
| Add("hello"); |
| Add("world"); |
| ASSERT_TRUE(Matches("hello")); |
| ASSERT_TRUE(Matches("world")); |
| ASSERT_TRUE(! Matches("x")); |
| ASSERT_TRUE(! Matches("foo")); |
| } |
| |
| static int NextLength(int length) { |
| if (length < 10) { |
| length += 1; |
| } else if (length < 100) { |
| length += 10; |
| } else if (length < 1000) { |
| length += 100; |
| } else { |
| length += 1000; |
| } |
| return length; |
| } |
| |
| TEST(BloomTest, VaryingLengths) { |
| char buffer[sizeof(int)]; |
| |
| // Count number of filters that significantly exceed the false positive rate |
| int mediocre_filters = 0; |
| int good_filters = 0; |
| |
| for (int length = 1; length <= 10000; length = NextLength(length)) { |
| Reset(); |
| for (int i = 0; i < length; i++) { |
| Add(Key(i, buffer)); |
| } |
| Build(); |
| |
| ASSERT_LE(FilterSize(), static_cast<size_t>((length * 10 / 8) + 40)) |
| << length; |
| |
| // All added keys must match |
| for (int i = 0; i < length; i++) { |
| ASSERT_TRUE(Matches(Key(i, buffer))) |
| << "Length " << length << "; key " << i; |
| } |
| |
| // Check false positive rate |
| double rate = FalsePositiveRate(); |
| if (kVerbose >= 1) { |
| fprintf(stderr, "False positives: %5.2f%% @ length = %6d ; bytes = %6d\n", |
| rate*100.0, length, static_cast<int>(FilterSize())); |
| } |
| ASSERT_LE(rate, 0.02); // Must not be over 2% |
| if (rate > 0.0125) mediocre_filters++; // Allowed, but not too often |
| else good_filters++; |
| } |
| if (kVerbose >= 1) { |
| fprintf(stderr, "Filters: %d good, %d mediocre\n", |
| good_filters, mediocre_filters); |
| } |
| ASSERT_LE(mediocre_filters, good_filters/5); |
| } |
| |
| // Different bits-per-byte |
| |
| } // namespace leveldb |
| |
| int main(int argc, char** argv) { |
| return leveldb::test::RunAllTests(); |
| } |