25'ten fazla konu seçemezsiniz
Konular bir harf veya rakamla başlamalı, kısa çizgiler ('-') içerebilir ve en fazla 35 karakter uzunluğunda olabilir.
154 satır
3.7 KiB
154 satır
3.7 KiB
// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#include "gtest/gtest.h"
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#include "leveldb/filter_policy.h"
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#include "util/coding.h"
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#include "util/logging.h"
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#include "util/testutil.h"
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namespace leveldb {
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static const int kVerbose = 1;
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static Slice Key(int i, char* buffer) {
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EncodeFixed32(buffer, i);
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return Slice(buffer, sizeof(uint32_t));
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}
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class BloomTest : public testing::Test {
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public:
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BloomTest() : policy_(NewBloomFilterPolicy(10)) {}
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~BloomTest() { delete policy_; }
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void Reset() {
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keys_.clear();
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filter_.clear();
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}
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void Add(const Slice& s) { keys_.push_back(s.ToString()); }
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void Build() {
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std::vector<Slice> key_slices;
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for (size_t i = 0; i < keys_.size(); i++) {
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key_slices.push_back(Slice(keys_[i]));
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}
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filter_.clear();
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policy_->CreateFilter(&key_slices[0], static_cast<int>(key_slices.size()),
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&filter_);
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keys_.clear();
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if (kVerbose >= 2) DumpFilter();
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}
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size_t FilterSize() const { return filter_.size(); }
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void DumpFilter() {
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std::fprintf(stderr, "F(");
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for (size_t i = 0; i + 1 < filter_.size(); i++) {
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const unsigned int c = static_cast<unsigned int>(filter_[i]);
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for (int j = 0; j < 8; j++) {
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std::fprintf(stderr, "%c", (c & (1 << j)) ? '1' : '.');
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}
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}
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std::fprintf(stderr, ")\n");
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}
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bool Matches(const Slice& s) {
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if (!keys_.empty()) {
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Build();
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}
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return policy_->KeyMayMatch(s, filter_);
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}
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double FalsePositiveRate() {
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char buffer[sizeof(int)];
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int result = 0;
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for (int i = 0; i < 10000; i++) {
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if (Matches(Key(i + 1000000000, buffer))) {
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result++;
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}
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}
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return result / 10000.0;
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}
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private:
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const FilterPolicy* policy_;
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std::string filter_;
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std::vector<std::string> keys_;
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};
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TEST_F(BloomTest, EmptyFilter) {
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ASSERT_TRUE(!Matches("hello"));
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ASSERT_TRUE(!Matches("world"));
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}
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TEST_F(BloomTest, Small) {
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Add("hello");
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Add("world");
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ASSERT_TRUE(Matches("hello"));
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ASSERT_TRUE(Matches("world"));
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ASSERT_TRUE(!Matches("x"));
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ASSERT_TRUE(!Matches("foo"));
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}
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static int NextLength(int length) {
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if (length < 10) {
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length += 1;
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} else if (length < 100) {
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length += 10;
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} else if (length < 1000) {
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length += 100;
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} else {
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length += 1000;
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}
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return length;
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}
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TEST_F(BloomTest, VaryingLengths) {
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char buffer[sizeof(int)];
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// Count number of filters that significantly exceed the false positive rate
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int mediocre_filters = 0;
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int good_filters = 0;
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for (int length = 1; length <= 10000; length = NextLength(length)) {
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Reset();
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for (int i = 0; i < length; i++) {
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Add(Key(i, buffer));
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}
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Build();
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ASSERT_LE(FilterSize(), static_cast<size_t>((length * 10 / 8) + 40))
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<< length;
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// All added keys must match
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for (int i = 0; i < length; i++) {
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ASSERT_TRUE(Matches(Key(i, buffer)))
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<< "Length " << length << "; key " << i;
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}
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// Check false positive rate
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double rate = FalsePositiveRate();
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if (kVerbose >= 1) {
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std::fprintf(stderr,
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"False positives: %5.2f%% @ length = %6d ; bytes = %6d\n",
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rate * 100.0, length, static_cast<int>(FilterSize()));
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}
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ASSERT_LE(rate, 0.02); // Must not be over 2%
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if (rate > 0.0125)
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mediocre_filters++; // Allowed, but not too often
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else
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good_filters++;
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}
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if (kVerbose >= 1) {
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std::fprintf(stderr, "Filters: %d good, %d mediocre\n", good_filters,
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mediocre_filters);
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}
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ASSERT_LE(mediocre_filters, good_filters / 5);
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}
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// Different bits-per-byte
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} // namespace leveldb
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