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rocksdb/db/prefix_test.cc
Venkatesh Radhakrishnan 9d50afc3b9 Prefix-based iterating only shows keys in prefix 
Summary:
MyRocks testing found an issue that while iterating over keys
that are outside the prefix, sometimes wrong results were seen for keys
outside the prefix. We now tighten the range of keys seen with a new
read option called prefix_seen_at_start. This remembers the starting
prefix and then compares it on a Next for equality of prefix. If they
are from a different prefix, it sets valid to false.

Test Plan: PrefixTest.PrefixValid

Reviewers: IslamAbdelRahman, sdong, yhchiang, anthony

Reviewed By: anthony

Subscribers: spetrunia, hermanlee4, yoshinorim, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D50211
2015-11-05 13:24:05 -08:00

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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
#ifndef ROCKSDB_LITE
#ifndef GFLAGS
#include <cstdio>
int main() {
fprintf(stderr, "Please install gflags to run this test... Skipping...\n");
return 0;
}
#else
#include <algorithm>
#include <iostream>
#include <vector>
#include <gflags/gflags.h>
#include "rocksdb/comparator.h"
#include "rocksdb/db.h"
#include "rocksdb/filter_policy.h"
#include "rocksdb/perf_context.h"
#include "rocksdb/slice_transform.h"
#include "rocksdb/memtablerep.h"
#include "rocksdb/table.h"
#include "util/histogram.h"
#include "util/stop_watch.h"
#include "util/string_util.h"
#include "util/testharness.h"
using GFLAGS::ParseCommandLineFlags;
DEFINE_bool(trigger_deadlock, false,
"issue delete in range scan to trigger PrefixHashMap deadlock");
DEFINE_int32(bucket_count, 100000, "number of buckets");
DEFINE_uint64(num_locks, 10001, "number of locks");
DEFINE_bool(random_prefix, false, "randomize prefix");
DEFINE_uint64(total_prefixes, 100000, "total number of prefixes");
DEFINE_uint64(items_per_prefix, 1, "total number of values per prefix");
DEFINE_int64(write_buffer_size, 33554432, "");
DEFINE_int32(max_write_buffer_number, 2, "");
DEFINE_int32(min_write_buffer_number_to_merge, 1, "");
DEFINE_int32(skiplist_height, 4, "");
DEFINE_int32(memtable_prefix_bloom_bits, 10000000, "");
DEFINE_int32(memtable_prefix_bloom_probes, 10, "");
DEFINE_int32(memtable_prefix_bloom_huge_page_tlb_size, 2 * 1024 * 1024, "");
DEFINE_int32(value_size, 40, "");
// Path to the database on file system
const std::string kDbName = rocksdb::test::TmpDir() + "/prefix_test";
namespace rocksdb {
struct TestKey {
uint64_t prefix;
uint64_t sorted;
TestKey(uint64_t _prefix, uint64_t _sorted)
: prefix(_prefix), sorted(_sorted) {}
};
// return a slice backed by test_key
inline Slice TestKeyToSlice(const TestKey& test_key) {
return Slice((const char*)&test_key, sizeof(test_key));
}
inline const TestKey* SliceToTestKey(const Slice& slice) {
return (const TestKey*)slice.data();
}
class TestKeyComparator : public Comparator {
public:
// Compare needs to be aware of the possibility of a and/or b is
// prefix only
virtual int Compare(const Slice& a, const Slice& b) const override {
const TestKey* key_a = SliceToTestKey(a);
const TestKey* key_b = SliceToTestKey(b);
if (key_a->prefix != key_b->prefix) {
if (key_a->prefix < key_b->prefix) return -1;
if (key_a->prefix > key_b->prefix) return 1;
} else {
EXPECT_TRUE(key_a->prefix == key_b->prefix);
// note, both a and b could be prefix only
if (a.size() != b.size()) {
// one of them is prefix
EXPECT_TRUE(
(a.size() == sizeof(uint64_t) && b.size() == sizeof(TestKey)) ||
(b.size() == sizeof(uint64_t) && a.size() == sizeof(TestKey)));
if (a.size() < b.size()) return -1;
if (a.size() > b.size()) return 1;
} else {
// both a and b are prefix
if (a.size() == sizeof(uint64_t)) {
return 0;
}
// both a and b are whole key
EXPECT_TRUE(a.size() == sizeof(TestKey) && b.size() == sizeof(TestKey));
if (key_a->sorted < key_b->sorted) return -1;
if (key_a->sorted > key_b->sorted) return 1;
if (key_a->sorted == key_b->sorted) return 0;
}
}
return 0;
}
virtual const char* Name() const override {
return "TestKeyComparator";
}
virtual void FindShortestSeparator(std::string* start,
const Slice& limit) const override {}
virtual void FindShortSuccessor(std::string* key) const override {}
};
namespace {
void PutKey(DB* db, WriteOptions write_options, uint64_t prefix,
uint64_t suffix, const Slice& value) {
TestKey test_key(prefix, suffix);
Slice key = TestKeyToSlice(test_key);
ASSERT_OK(db->Put(write_options, key, value));
}
void SeekIterator(Iterator* iter, uint64_t prefix, uint64_t suffix) {
TestKey test_key(prefix, suffix);
Slice key = TestKeyToSlice(test_key);
iter->Seek(key);
}
const std::string kNotFoundResult = "NOT_FOUND";
std::string Get(DB* db, const ReadOptions& read_options, uint64_t prefix,
uint64_t suffix) {
TestKey test_key(prefix, suffix);
Slice key = TestKeyToSlice(test_key);
std::string result;
Status s = db->Get(read_options, key, &result);
if (s.IsNotFound()) {
result = kNotFoundResult;
} else if (!s.ok()) {
result = s.ToString();
}
return result;
}
} // namespace
class PrefixTest : public testing::Test {
public:
std::shared_ptr<DB> OpenDb() {
DB* db;
options.create_if_missing = true;
options.write_buffer_size = FLAGS_write_buffer_size;
options.max_write_buffer_number = FLAGS_max_write_buffer_number;
options.min_write_buffer_number_to_merge =
FLAGS_min_write_buffer_number_to_merge;
options.memtable_prefix_bloom_bits = FLAGS_memtable_prefix_bloom_bits;
options.memtable_prefix_bloom_probes = FLAGS_memtable_prefix_bloom_probes;
options.memtable_prefix_bloom_huge_page_tlb_size =
FLAGS_memtable_prefix_bloom_huge_page_tlb_size;
options.prefix_extractor.reset(NewFixedPrefixTransform(8));
BlockBasedTableOptions bbto;
bbto.filter_policy.reset(NewBloomFilterPolicy(10, false));
bbto.whole_key_filtering = false;
options.table_factory.reset(NewBlockBasedTableFactory(bbto));
Status s = DB::Open(options, kDbName, &db);
EXPECT_OK(s);
return std::shared_ptr<DB>(db);
}
void FirstOption() {
option_config_ = kBegin;
}
bool NextOptions(int bucket_count) {
// skip some options
option_config_++;
if (option_config_ < kEnd) {
options.prefix_extractor.reset(NewFixedPrefixTransform(8));
switch(option_config_) {
case kHashSkipList:
options.memtable_factory.reset(
NewHashSkipListRepFactory(bucket_count, FLAGS_skiplist_height));
return true;
case kHashLinkList:
options.memtable_factory.reset(
NewHashLinkListRepFactory(bucket_count));
return true;
case kHashLinkListHugePageTlb:
options.memtable_factory.reset(
NewHashLinkListRepFactory(bucket_count, 2 * 1024 * 1024));
return true;
case kHashLinkListTriggerSkipList:
options.memtable_factory.reset(
NewHashLinkListRepFactory(bucket_count, 0, 3));
return true;
default:
return false;
}
}
return false;
}
PrefixTest() : option_config_(kBegin) {
options.comparator = new TestKeyComparator();
}
~PrefixTest() {
delete options.comparator;
}
protected:
enum OptionConfig {
kBegin,
kHashSkipList,
kHashLinkList,
kHashLinkListHugePageTlb,
kHashLinkListTriggerSkipList,
kEnd
};
int option_config_;
Options options;
};
TEST_F(PrefixTest, TestResult) {
for (int num_buckets = 1; num_buckets <= 2; num_buckets++) {
FirstOption();
while (NextOptions(num_buckets)) {
std::cout << "*** Mem table: " << options.memtable_factory->Name()
<< " number of buckets: " << num_buckets
<< std::endl;
DestroyDB(kDbName, Options());
auto db = OpenDb();
WriteOptions write_options;
ReadOptions read_options;
// 1. Insert one row.
Slice v16("v16");
PutKey(db.get(), write_options, 1, 6, v16);
std::unique_ptr<Iterator> iter(db->NewIterator(read_options));
SeekIterator(iter.get(), 1, 6);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v16 == iter->value());
SeekIterator(iter.get(), 1, 5);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v16 == iter->value());
SeekIterator(iter.get(), 1, 5);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v16 == iter->value());
iter->Next();
ASSERT_TRUE(!iter->Valid());
SeekIterator(iter.get(), 2, 0);
ASSERT_TRUE(!iter->Valid());
ASSERT_EQ(v16.ToString(), Get(db.get(), read_options, 1, 6));
ASSERT_EQ(kNotFoundResult, Get(db.get(), read_options, 1, 5));
ASSERT_EQ(kNotFoundResult, Get(db.get(), read_options, 1, 7));
ASSERT_EQ(kNotFoundResult, Get(db.get(), read_options, 0, 6));
ASSERT_EQ(kNotFoundResult, Get(db.get(), read_options, 2, 6));
// 2. Insert an entry for the same prefix as the last entry in the bucket.
Slice v17("v17");
PutKey(db.get(), write_options, 1, 7, v17);
iter.reset(db->NewIterator(read_options));
SeekIterator(iter.get(), 1, 7);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v17 == iter->value());
SeekIterator(iter.get(), 1, 6);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v16 == iter->value());
iter->Next();
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v17 == iter->value());
iter->Next();
ASSERT_TRUE(!iter->Valid());
SeekIterator(iter.get(), 2, 0);
ASSERT_TRUE(!iter->Valid());
// 3. Insert an entry for the same prefix as the head of the bucket.
Slice v15("v15");
PutKey(db.get(), write_options, 1, 5, v15);
iter.reset(db->NewIterator(read_options));
SeekIterator(iter.get(), 1, 7);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v17 == iter->value());
SeekIterator(iter.get(), 1, 5);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v15 == iter->value());
iter->Next();
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v16 == iter->value());
iter->Next();
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v17 == iter->value());
SeekIterator(iter.get(), 1, 5);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v15 == iter->value());
ASSERT_EQ(v15.ToString(), Get(db.get(), read_options, 1, 5));
ASSERT_EQ(v16.ToString(), Get(db.get(), read_options, 1, 6));
ASSERT_EQ(v17.ToString(), Get(db.get(), read_options, 1, 7));
// 4. Insert an entry with a larger prefix
Slice v22("v22");
PutKey(db.get(), write_options, 2, 2, v22);
iter.reset(db->NewIterator(read_options));
SeekIterator(iter.get(), 2, 2);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v22 == iter->value());
SeekIterator(iter.get(), 2, 0);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v22 == iter->value());
SeekIterator(iter.get(), 1, 5);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v15 == iter->value());
SeekIterator(iter.get(), 1, 7);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v17 == iter->value());
// 5. Insert an entry with a smaller prefix
Slice v02("v02");
PutKey(db.get(), write_options, 0, 2, v02);
iter.reset(db->NewIterator(read_options));
SeekIterator(iter.get(), 0, 2);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v02 == iter->value());
SeekIterator(iter.get(), 0, 0);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v02 == iter->value());
SeekIterator(iter.get(), 2, 0);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v22 == iter->value());
SeekIterator(iter.get(), 1, 5);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v15 == iter->value());
SeekIterator(iter.get(), 1, 7);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v17 == iter->value());
// 6. Insert to the beginning and the end of the first prefix
Slice v13("v13");
Slice v18("v18");
PutKey(db.get(), write_options, 1, 3, v13);
PutKey(db.get(), write_options, 1, 8, v18);
iter.reset(db->NewIterator(read_options));
SeekIterator(iter.get(), 1, 7);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v17 == iter->value());
SeekIterator(iter.get(), 1, 3);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v13 == iter->value());
iter->Next();
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v15 == iter->value());
iter->Next();
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v16 == iter->value());
iter->Next();
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v17 == iter->value());
iter->Next();
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v18 == iter->value());
SeekIterator(iter.get(), 0, 0);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v02 == iter->value());
SeekIterator(iter.get(), 2, 0);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v22 == iter->value());
ASSERT_EQ(v22.ToString(), Get(db.get(), read_options, 2, 2));
ASSERT_EQ(v02.ToString(), Get(db.get(), read_options, 0, 2));
ASSERT_EQ(v13.ToString(), Get(db.get(), read_options, 1, 3));
ASSERT_EQ(v15.ToString(), Get(db.get(), read_options, 1, 5));
ASSERT_EQ(v16.ToString(), Get(db.get(), read_options, 1, 6));
ASSERT_EQ(v17.ToString(), Get(db.get(), read_options, 1, 7));
ASSERT_EQ(v18.ToString(), Get(db.get(), read_options, 1, 8));
}
}
}
// Show results in prefix
TEST_F(PrefixTest, PrefixValid) {
for (int num_buckets = 1; num_buckets <= 2; num_buckets++) {
FirstOption();
while (NextOptions(num_buckets)) {
std::cout << "*** Mem table: " << options.memtable_factory->Name()
<< " number of buckets: " << num_buckets << std::endl;
DestroyDB(kDbName, Options());
auto db = OpenDb();
WriteOptions write_options;
ReadOptions read_options;
// Insert keys with common prefix and one key with different
Slice v16("v16");
Slice v17("v17");
Slice v18("v18");
Slice v19("v19");
PutKey(db.get(), write_options, 12345, 6, v16);
PutKey(db.get(), write_options, 12345, 7, v17);
PutKey(db.get(), write_options, 12345, 8, v18);
PutKey(db.get(), write_options, 12345, 9, v19);
PutKey(db.get(), write_options, 12346, 8, v16);
db->Flush(FlushOptions());
db->Delete(write_options, TestKeyToSlice(TestKey(12346, 8)));
db->Flush(FlushOptions());
read_options.prefix_same_as_start = true;
std::unique_ptr<Iterator> iter(db->NewIterator(read_options));
SeekIterator(iter.get(), 12345, 6);
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v16 == iter->value());
iter->Next();
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v17 == iter->value());
iter->Next();
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v18 == iter->value());
iter->Next();
ASSERT_TRUE(iter->Valid());
ASSERT_TRUE(v19 == iter->value());
iter->Next();
ASSERT_FALSE(iter->Valid());
ASSERT_EQ(kNotFoundResult, Get(db.get(), read_options, 12346, 8));
}
}
}
TEST_F(PrefixTest, DynamicPrefixIterator) {
while (NextOptions(FLAGS_bucket_count)) {
std::cout << "*** Mem table: " << options.memtable_factory->Name()
<< std::endl;
DestroyDB(kDbName, Options());
auto db = OpenDb();
WriteOptions write_options;
ReadOptions read_options;
std::vector<uint64_t> prefixes;
for (uint64_t i = 0; i < FLAGS_total_prefixes; ++i) {
prefixes.push_back(i);
}
if (FLAGS_random_prefix) {
std::random_shuffle(prefixes.begin(), prefixes.end());
}
HistogramImpl hist_put_time;
HistogramImpl hist_put_comparison;
// insert x random prefix, each with y continuous element.
for (auto prefix : prefixes) {
for (uint64_t sorted = 0; sorted < FLAGS_items_per_prefix; sorted++) {
TestKey test_key(prefix, sorted);
Slice key = TestKeyToSlice(test_key);
std::string value(FLAGS_value_size, 0);
perf_context.Reset();
StopWatchNano timer(Env::Default(), true);
ASSERT_OK(db->Put(write_options, key, value));
hist_put_time.Add(timer.ElapsedNanos());
hist_put_comparison.Add(perf_context.user_key_comparison_count);
}
}
std::cout << "Put key comparison: \n" << hist_put_comparison.ToString()
<< "Put time: \n" << hist_put_time.ToString();
// test seek existing keys
HistogramImpl hist_seek_time;
HistogramImpl hist_seek_comparison;
std::unique_ptr<Iterator> iter(db->NewIterator(read_options));
for (auto prefix : prefixes) {
TestKey test_key(prefix, FLAGS_items_per_prefix / 2);
Slice key = TestKeyToSlice(test_key);
std::string value = "v" + ToString(0);
perf_context.Reset();
StopWatchNano timer(Env::Default(), true);
auto key_prefix = options.prefix_extractor->Transform(key);
uint64_t total_keys = 0;
for (iter->Seek(key);
iter->Valid() && iter->key().starts_with(key_prefix);
iter->Next()) {
if (FLAGS_trigger_deadlock) {
std::cout << "Behold the deadlock!\n";
db->Delete(write_options, iter->key());
}
total_keys++;
}
hist_seek_time.Add(timer.ElapsedNanos());
hist_seek_comparison.Add(perf_context.user_key_comparison_count);
ASSERT_EQ(total_keys, FLAGS_items_per_prefix - FLAGS_items_per_prefix/2);
}
std::cout << "Seek key comparison: \n"
<< hist_seek_comparison.ToString()
<< "Seek time: \n"
<< hist_seek_time.ToString();
// test non-existing keys
HistogramImpl hist_no_seek_time;
HistogramImpl hist_no_seek_comparison;
for (auto prefix = FLAGS_total_prefixes;
prefix < FLAGS_total_prefixes + 10000;
prefix++) {
TestKey test_key(prefix, 0);
Slice key = TestKeyToSlice(test_key);
perf_context.Reset();
StopWatchNano timer(Env::Default(), true);
iter->Seek(key);
hist_no_seek_time.Add(timer.ElapsedNanos());
hist_no_seek_comparison.Add(perf_context.user_key_comparison_count);
ASSERT_TRUE(!iter->Valid());
}
std::cout << "non-existing Seek key comparison: \n"
<< hist_no_seek_comparison.ToString()
<< "non-existing Seek time: \n"
<< hist_no_seek_time.ToString();
}
}
}
int main(int argc, char** argv) {
::testing::InitGoogleTest(&argc, argv);
ParseCommandLineFlags(&argc, &argv, true);
std::cout << kDbName << "\n";
return RUN_ALL_TESTS();
}
#endif // GFLAGS
#else
#include <stdio.h>
int main(int argc, char** argv) {
fprintf(stderr,
"SKIPPED as HashSkipList and HashLinkList are not supported in "
"ROCKSDB_LITE\n");
return 0;
}
#endif // !ROCKSDB_LITE
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