You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
154 regels
3.7 KiB
154 regels
3.7 KiB
// 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 "gtest/gtest.h"
|
|
#include "leveldb/filter_policy.h"
|
|
#include "util/coding.h"
|
|
#include "util/logging.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 : public testing::Test {
|
|
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], static_cast<int>(key_slices.size()),
|
|
&filter_);
|
|
keys_.clear();
|
|
if (kVerbose >= 2) DumpFilter();
|
|
}
|
|
|
|
size_t FilterSize() const { return filter_.size(); }
|
|
|
|
void DumpFilter() {
|
|
std::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++) {
|
|
std::fprintf(stderr, "%c", (c & (1 << j)) ? '1' : '.');
|
|
}
|
|
}
|
|
std::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;
|
|
}
|
|
|
|
private:
|
|
const FilterPolicy* policy_;
|
|
std::string filter_;
|
|
std::vector<std::string> keys_;
|
|
};
|
|
|
|
TEST_F(BloomTest, EmptyFilter) {
|
|
ASSERT_TRUE(!Matches("hello"));
|
|
ASSERT_TRUE(!Matches("world"));
|
|
}
|
|
|
|
TEST_F(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_F(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) {
|
|
std::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) {
|
|
std::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
|