rocksdb/db/seqno_time_test.cc

//  Copyright (c) Meta Platforms, Inc. and affiliates.
//
//  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).

#include "db/db_test_util.h"
#include "db/periodic_work_scheduler.h"
#include "db/seqno_to_time_mapping.h"
#include "port/stack_trace.h"
#include "test_util/mock_time_env.h"

#ifndef ROCKSDB_LITE

namespace ROCKSDB_NAMESPACE {

class SeqnoTimeTest : public DBTestBase {
 public:
  SeqnoTimeTest() : DBTestBase("seqno_time_test", /*env_do_fsync=*/false) {
    mock_clock_ = std::make_shared<MockSystemClock>(env_->GetSystemClock());
    mock_env_ = std::make_unique<CompositeEnvWrapper>(env_, mock_clock_);
  }

 protected:
  std::unique_ptr<Env> mock_env_;
  std::shared_ptr<MockSystemClock> mock_clock_;

  void SetUp() override {
    mock_clock_->InstallTimedWaitFixCallback();
    SyncPoint::GetInstance()->SetCallBack(
        "DBImpl::StartPeriodicWorkScheduler:Init", [&](void* arg) {
          auto* periodic_work_scheduler_ptr =
              reinterpret_cast<PeriodicWorkScheduler**>(arg);
          *periodic_work_scheduler_ptr =
              PeriodicWorkTestScheduler::Default(mock_clock_);
        });
  }
};

TEST_F(SeqnoTimeTest, BasicSeqnoToTimeMapping) {
  Options options = CurrentOptions();
  options.preclude_last_level_data_seconds = 10000;
  options.env = mock_env_.get();
  options.disable_auto_compactions = true;
  DestroyAndReopen(options);

  std::set<uint64_t> checked_file_nums;
  SequenceNumber start_seq = dbfull()->GetLatestSequenceNumber();
  // Write a key every 10 seconds
  for (int i = 0; i < 200; i++) {
    ASSERT_OK(Put(Key(i), "value"));
    dbfull()->TEST_WaitForPeridicWorkerRun(
        [&] { mock_clock_->MockSleepForSeconds(static_cast<int>(10)); });
  }
  ASSERT_OK(Flush());
  TablePropertiesCollection tables_props;
  ASSERT_OK(dbfull()->GetPropertiesOfAllTables(&tables_props));
  ASSERT_EQ(tables_props.size(), 1);
  auto it = tables_props.begin();
  SeqnoToTimeMapping tp_mapping;
  ASSERT_OK(tp_mapping.Add(it->second->seqno_to_time_mapping));
  ASSERT_OK(tp_mapping.Sort());
  ASSERT_FALSE(tp_mapping.Empty());
  auto seqs = tp_mapping.TEST_GetInternalMapping();
  ASSERT_GE(seqs.size(), 19);
  ASSERT_LE(seqs.size(), 21);
  SequenceNumber seq_end = dbfull()->GetLatestSequenceNumber();
  for (auto i = start_seq; i < start_seq + 10; i++) {
    ASSERT_LE(tp_mapping.GetOldestApproximateTime(i), (i + 1) * 10);
  }
  start_seq += 10;
  for (auto i = start_seq; i < seq_end; i++) {
    // The result is within the range
    ASSERT_GE(tp_mapping.GetOldestApproximateTime(i), (i - 10) * 10);
    ASSERT_LE(tp_mapping.GetOldestApproximateTime(i), (i + 10) * 10);
  }
  checked_file_nums.insert(it->second->orig_file_number);
  start_seq = seq_end;

  // Write a key every 1 seconds
  for (int i = 0; i < 200; i++) {
    ASSERT_OK(Put(Key(i + 190), "value"));
    dbfull()->TEST_WaitForPeridicWorkerRun(
        [&] { mock_clock_->MockSleepForSeconds(static_cast<int>(1)); });
  }
  seq_end = dbfull()->GetLatestSequenceNumber();
  ASSERT_OK(Flush());
  tables_props.clear();
  ASSERT_OK(dbfull()->GetPropertiesOfAllTables(&tables_props));
  ASSERT_EQ(tables_props.size(), 2);
  it = tables_props.begin();
  while (it != tables_props.end()) {
    if (!checked_file_nums.count(it->second->orig_file_number)) {
      break;
    }
    it++;
  }
  ASSERT_TRUE(it != tables_props.end());

  tp_mapping.Clear();
  ASSERT_OK(tp_mapping.Add(it->second->seqno_to_time_mapping));
  ASSERT_OK(tp_mapping.Sort());
  seqs = tp_mapping.TEST_GetInternalMapping();
  // There only a few time sample
  ASSERT_GE(seqs.size(), 1);
  ASSERT_LE(seqs.size(), 3);
  for (auto i = start_seq; i < seq_end; i++) {
    // The result is not very accurate, as there is more data write within small
    // range of time
    ASSERT_GE(tp_mapping.GetOldestApproximateTime(i), (i - start_seq) + 1000);
    ASSERT_LE(tp_mapping.GetOldestApproximateTime(i), (i - start_seq) + 3000);
  }
  checked_file_nums.insert(it->second->orig_file_number);
  start_seq = seq_end;

  // Write a key every 200 seconds
  for (int i = 0; i < 200; i++) {
    ASSERT_OK(Put(Key(i + 380), "value"));
    dbfull()->TEST_WaitForPeridicWorkerRun(
        [&] { mock_clock_->MockSleepForSeconds(static_cast<int>(200)); });
  }
  seq_end = dbfull()->GetLatestSequenceNumber();
  ASSERT_OK(Flush());
  tables_props.clear();
  ASSERT_OK(dbfull()->GetPropertiesOfAllTables(&tables_props));
  ASSERT_EQ(tables_props.size(), 3);
  it = tables_props.begin();
  while (it != tables_props.end()) {
    if (!checked_file_nums.count(it->second->orig_file_number)) {
      break;
    }
    it++;
  }
  ASSERT_TRUE(it != tables_props.end());

  tp_mapping.Clear();
  ASSERT_OK(tp_mapping.Add(it->second->seqno_to_time_mapping));
  ASSERT_OK(tp_mapping.Sort());
  seqs = tp_mapping.TEST_GetInternalMapping();
  // The sequence number -> time entries should be maxed
  ASSERT_GE(seqs.size(), 99);
  ASSERT_LE(seqs.size(), 101);
  for (auto i = start_seq; i < seq_end - 99; i++) {
    // likely the first 100 entries reports 0
    ASSERT_LE(tp_mapping.GetOldestApproximateTime(i), (i - start_seq) + 3000);
  }
  start_seq += 101;

  for (auto i = start_seq; i < seq_end; i++) {
    ASSERT_GE(tp_mapping.GetOldestApproximateTime(i),
              (i - start_seq) * 200 + 22200);
    ASSERT_LE(tp_mapping.GetOldestApproximateTime(i),
              (i - start_seq) * 200 + 22600);
  }
  checked_file_nums.insert(it->second->orig_file_number);
  start_seq = seq_end;

  // Write a key every 100 seconds
  for (int i = 0; i < 200; i++) {
    ASSERT_OK(Put(Key(i + 570), "value"));
    dbfull()->TEST_WaitForPeridicWorkerRun(
        [&] { mock_clock_->MockSleepForSeconds(static_cast<int>(100)); });
  }
  seq_end = dbfull()->GetLatestSequenceNumber();
  ASSERT_OK(Flush());
  tables_props.clear();
  ASSERT_OK(dbfull()->GetPropertiesOfAllTables(&tables_props));
  ASSERT_EQ(tables_props.size(), 4);
  it = tables_props.begin();
  while (it != tables_props.end()) {
    if (!checked_file_nums.count(it->second->orig_file_number)) {
      break;
    }
    it++;
  }
  ASSERT_TRUE(it != tables_props.end());
  tp_mapping.Clear();
  ASSERT_OK(tp_mapping.Add(it->second->seqno_to_time_mapping));
  ASSERT_OK(tp_mapping.Sort());
  seqs = tp_mapping.TEST_GetInternalMapping();
  ASSERT_GE(seqs.size(), 99);
  ASSERT_LE(seqs.size(), 101);

  checked_file_nums.insert(it->second->orig_file_number);

  // re-enable compaction
  ASSERT_OK(dbfull()->SetOptions({
      {"disable_auto_compactions", "false"},
  }));

  ASSERT_OK(dbfull()->TEST_WaitForCompact());

  tables_props.clear();
  ASSERT_OK(dbfull()->GetPropertiesOfAllTables(&tables_props));
  ASSERT_GE(tables_props.size(), 1);
  it = tables_props.begin();
  while (it != tables_props.end()) {
    if (!checked_file_nums.count(it->second->orig_file_number)) {
      break;
    }
    it++;
  }
  ASSERT_TRUE(it != tables_props.end());
  tp_mapping.Clear();
  ASSERT_OK(tp_mapping.Add(it->second->seqno_to_time_mapping));
  ASSERT_OK(tp_mapping.Sort());
  seqs = tp_mapping.TEST_GetInternalMapping();
  ASSERT_GE(seqs.size(), 99);
  ASSERT_LE(seqs.size(), 101);
  for (auto i = start_seq; i < seq_end - 99; i++) {
    // likely the first 100 entries reports 0
    ASSERT_LE(tp_mapping.GetOldestApproximateTime(i), (i - start_seq) + 3000);
  }
  start_seq += 101;

  for (auto i = start_seq; i < seq_end; i++) {
    ASSERT_GE(tp_mapping.GetOldestApproximateTime(i),
              (i - start_seq) * 100 + 52200);
    ASSERT_LE(tp_mapping.GetOldestApproximateTime(i),
              (i - start_seq) * 100 + 52400);
  }
  ASSERT_OK(db_->Close());
}

// TODO(zjay): Disabled, until New CF bug with preclude_last_level_data_seconds
//  is fixed
TEST_F(SeqnoTimeTest, DISABLED_MultiCFs) {
  Options options = CurrentOptions();
  options.preclude_last_level_data_seconds = 0;
  options.env = mock_env_.get();
  options.stats_dump_period_sec = 0;
  options.stats_persist_period_sec = 0;
  ReopenWithColumnFamilies({"default"}, options);

  auto scheduler = dbfull()->TEST_GetPeriodicWorkScheduler();
  ASSERT_FALSE(scheduler->TEST_HasValidTask(
      dbfull(), PeriodicWorkTaskNames::kRecordSeqnoTime));

  // Write some data and increase the current time
  for (int i = 0; i < 200; i++) {
    ASSERT_OK(Put(Key(i), "value"));
    dbfull()->TEST_WaitForPeridicWorkerRun(
        [&] { mock_clock_->MockSleepForSeconds(static_cast<int>(100)); });
  }
  ASSERT_OK(Flush());
  TablePropertiesCollection tables_props;
  ASSERT_OK(dbfull()->GetPropertiesOfAllTables(&tables_props));
  ASSERT_EQ(tables_props.size(), 1);
  auto it = tables_props.begin();
  ASSERT_TRUE(it->second->seqno_to_time_mapping.empty());

  ASSERT_TRUE(dbfull()->TEST_GetSeqnoToTimeMapping().Empty());

  Options options_1 = options;
  options_1.preclude_last_level_data_seconds = 10000;  // 10k
  CreateColumnFamilies({"one"}, options_1);
  ASSERT_TRUE(scheduler->TEST_HasValidTask(
      dbfull(), PeriodicWorkTaskNames::kRecordSeqnoTime));

  // Write some data to the default CF (without preclude_last_level feature)
  for (int i = 0; i < 200; i++) {
    ASSERT_OK(Put(Key(i), "value"));
    dbfull()->TEST_WaitForPeridicWorkerRun(
        [&] { mock_clock_->MockSleepForSeconds(static_cast<int>(100)); });
  }
  ASSERT_OK(Flush());

  // in memory mapping won't increase because CFs with preclude_last_level
  // feature doesn't have memtable
  auto queue = dbfull()->TEST_GetSeqnoToTimeMapping().TEST_GetInternalMapping();
  ASSERT_LT(queue.size(), 5);

  // Write some data to the CF one
  for (int i = 0; i < 20; i++) {
    ASSERT_OK(Put(1, Key(i), "value"));
    dbfull()->TEST_WaitForPeridicWorkerRun(
        [&] { mock_clock_->MockSleepForSeconds(static_cast<int>(10)); });
  }
  ASSERT_OK(Flush(1));
  tables_props.clear();
  ASSERT_OK(dbfull()->GetPropertiesOfAllTables(handles_[1], &tables_props));
  ASSERT_EQ(tables_props.size(), 1);
  it = tables_props.begin();
  SeqnoToTimeMapping tp_mapping;
  ASSERT_OK(tp_mapping.Add(it->second->seqno_to_time_mapping));
  ASSERT_OK(tp_mapping.Sort());
  ASSERT_FALSE(tp_mapping.Empty());
  auto seqs = tp_mapping.TEST_GetInternalMapping();
  ASSERT_GE(seqs.size(), 1);
  ASSERT_LE(seqs.size(), 3);

  // Create one more CF with larger preclude_last_level time
  Options options_2 = options;
  options_2.preclude_last_level_data_seconds = 1000000;  // 1m
  CreateColumnFamilies({"two"}, options_2);

  // Add more data to CF "two" to fill the in memory mapping
  for (int i = 0; i < 2000; i++) {
    ASSERT_OK(Put(2, Key(i), "value"));
    dbfull()->TEST_WaitForPeridicWorkerRun(
        [&] { mock_clock_->MockSleepForSeconds(static_cast<int>(100)); });
  }
  seqs = dbfull()->TEST_GetSeqnoToTimeMapping().TEST_GetInternalMapping();
  ASSERT_GE(seqs.size(), 1000 - 1);
  ASSERT_LE(seqs.size(), 1000 + 1);

  ASSERT_OK(Flush(2));
  tables_props.clear();
  ASSERT_OK(dbfull()->GetPropertiesOfAllTables(handles_[2], &tables_props));
  ASSERT_EQ(tables_props.size(), 1);
  it = tables_props.begin();
  tp_mapping.Clear();
  ASSERT_OK(tp_mapping.Add(it->second->seqno_to_time_mapping));
  ASSERT_OK(tp_mapping.Sort());
  seqs = tp_mapping.TEST_GetInternalMapping();
  // the max encoded entries is 100
  ASSERT_GE(seqs.size(), 100 - 1);
  ASSERT_LE(seqs.size(), 100 + 1);

  // Write some data to default CF, as all memtable with preclude_last_level
  // enabled have flushed, the in-memory seqno->time mapping should be cleared
  for (int i = 0; i < 10; i++) {
    ASSERT_OK(Put(0, Key(i), "value"));
    dbfull()->TEST_WaitForPeridicWorkerRun(
        [&] { mock_clock_->MockSleepForSeconds(static_cast<int>(100)); });
  }
  seqs = dbfull()->TEST_GetSeqnoToTimeMapping().TEST_GetInternalMapping();
  ASSERT_LE(seqs.size(), 5);
  ASSERT_OK(Flush(0));

  // trigger compaction for CF "two" and make sure the compaction output has
  // seqno_to_time_mapping
  for (int j = 0; j < 3; j++) {
    for (int i = 0; i < 200; i++) {
      ASSERT_OK(Put(2, Key(i), "value"));
      dbfull()->TEST_WaitForPeridicWorkerRun(
          [&] { mock_clock_->MockSleepForSeconds(static_cast<int>(100)); });
    }
    ASSERT_OK(Flush(2));
  }
  ASSERT_OK(dbfull()->TEST_WaitForCompact());
  tables_props.clear();
  ASSERT_OK(dbfull()->GetPropertiesOfAllTables(handles_[2], &tables_props));
  ASSERT_EQ(tables_props.size(), 1);
  it = tables_props.begin();
  tp_mapping.Clear();
  ASSERT_OK(tp_mapping.Add(it->second->seqno_to_time_mapping));
  ASSERT_OK(tp_mapping.Sort());
  seqs = tp_mapping.TEST_GetInternalMapping();
  ASSERT_GE(seqs.size(), 99);
  ASSERT_LE(seqs.size(), 101);

  for (int j = 0; j < 2; j++) {
    for (int i = 0; i < 200; i++) {
      ASSERT_OK(Put(0, Key(i), "value"));
      dbfull()->TEST_WaitForPeridicWorkerRun(
          [&] { mock_clock_->MockSleepForSeconds(static_cast<int>(100)); });
    }
    ASSERT_OK(Flush(0));
  }
  ASSERT_OK(dbfull()->TEST_WaitForCompact());
  tables_props.clear();
  ASSERT_OK(dbfull()->GetPropertiesOfAllTables(handles_[0], &tables_props));
  ASSERT_EQ(tables_props.size(), 1);
  it = tables_props.begin();
  ASSERT_TRUE(it->second->seqno_to_time_mapping.empty());

  // Write some data to CF "two", but don't flush to accumulate
  for (int i = 0; i < 1000; i++) {
    ASSERT_OK(Put(2, Key(i), "value"));
    dbfull()->TEST_WaitForPeridicWorkerRun(
        [&] { mock_clock_->MockSleepForSeconds(static_cast<int>(100)); });
  }
  ASSERT_GE(
      dbfull()->TEST_GetSeqnoToTimeMapping().TEST_GetInternalMapping().size(),
      500);
  // After dropping CF "one", the in-memory mapping will be change to only
  // follow CF "two" options.
  ASSERT_OK(db_->DropColumnFamily(handles_[1]));
  ASSERT_LE(
      dbfull()->TEST_GetSeqnoToTimeMapping().TEST_GetInternalMapping().size(),
      100 + 5);

  // After dropping CF "two", the in-memory mapping is also clear.
  ASSERT_OK(db_->DropColumnFamily(handles_[2]));
  ASSERT_EQ(
      dbfull()->TEST_GetSeqnoToTimeMapping().TEST_GetInternalMapping().size(),
      0);

  // And the timer worker is stopped
  ASSERT_FALSE(scheduler->TEST_HasValidTask(
      dbfull(), PeriodicWorkTaskNames::kRecordSeqnoTime));
  Close();
}

TEST_F(SeqnoTimeTest, SeqnoToTimeMappingUniversal) {
  Options options = CurrentOptions();
  options.compaction_style = kCompactionStyleUniversal;
  options.preclude_last_level_data_seconds = 10000;
  options.env = mock_env_.get();

  DestroyAndReopen(options);

  for (int j = 0; j < 3; j++) {
    for (int i = 0; i < 100; i++) {
      ASSERT_OK(Put(Key(i), "value"));
      dbfull()->TEST_WaitForPeridicWorkerRun(
          [&] { mock_clock_->MockSleepForSeconds(static_cast<int>(10)); });
    }
    ASSERT_OK(Flush());
  }
  TablePropertiesCollection tables_props;
  ASSERT_OK(dbfull()->GetPropertiesOfAllTables(&tables_props));
  ASSERT_EQ(tables_props.size(), 3);
  for (const auto& props : tables_props) {
    ASSERT_FALSE(props.second->seqno_to_time_mapping.empty());
    SeqnoToTimeMapping tp_mapping;
    ASSERT_OK(tp_mapping.Add(props.second->seqno_to_time_mapping));
    ASSERT_OK(tp_mapping.Sort());
    ASSERT_FALSE(tp_mapping.Empty());
    auto seqs = tp_mapping.TEST_GetInternalMapping();
    ASSERT_GE(seqs.size(), 10 - 1);
    ASSERT_LE(seqs.size(), 10 + 1);
  }

  // Trigger a compaction
  for (int i = 0; i < 100; i++) {
    ASSERT_OK(Put(Key(i), "value"));
    dbfull()->TEST_WaitForPeridicWorkerRun(
        [&] { mock_clock_->MockSleepForSeconds(static_cast<int>(10)); });
  }
  ASSERT_OK(Flush());
  ASSERT_OK(dbfull()->TEST_WaitForCompact());
  tables_props.clear();
  ASSERT_OK(dbfull()->GetPropertiesOfAllTables(&tables_props));
  ASSERT_EQ(tables_props.size(), 1);

  auto it = tables_props.begin();
  SeqnoToTimeMapping tp_mapping;
  ASSERT_FALSE(it->second->seqno_to_time_mapping.empty());
  ASSERT_OK(tp_mapping.Add(it->second->seqno_to_time_mapping));
  Close();
}

TEST_F(SeqnoTimeTest, MappingAppend) {
  SeqnoToTimeMapping test(/*max_time_duration=*/100, /*max_capacity=*/10);

  // ignore seqno == 0, as it may mean the seqno is zeroed out
  ASSERT_FALSE(test.Append(0, 9));

  ASSERT_TRUE(test.Append(3, 10));
  auto size = test.Size();
  // normal add
  ASSERT_TRUE(test.Append(10, 11));
  size++;
  ASSERT_EQ(size, test.Size());

  // Append unsorted
  ASSERT_FALSE(test.Append(8, 12));
  ASSERT_EQ(size, test.Size());

  // Append with the same seqno, newer time will be accepted
  ASSERT_TRUE(test.Append(10, 12));
  ASSERT_EQ(size, test.Size());
  // older time will be ignored
  ASSERT_FALSE(test.Append(10, 9));
  ASSERT_EQ(size, test.Size());

  // new seqno with old time will be ignored
  ASSERT_FALSE(test.Append(12, 8));
  ASSERT_EQ(size, test.Size());
}

TEST_F(SeqnoTimeTest, GetOldestApproximateTime) {
  SeqnoToTimeMapping test(/*max_time_duration=*/100, /*max_capacity=*/10);

  ASSERT_EQ(test.GetOldestApproximateTime(10), kUnknownSeqnoTime);

  test.Append(3, 10);

  ASSERT_EQ(test.GetOldestApproximateTime(2), kUnknownSeqnoTime);
  ASSERT_EQ(test.GetOldestApproximateTime(3), 10);
  ASSERT_EQ(test.GetOldestApproximateTime(10), 10);

  test.Append(10, 100);

  test.Append(100, 1000);
  ASSERT_EQ(test.GetOldestApproximateTime(10), 100);
  ASSERT_EQ(test.GetOldestApproximateTime(40), 100);
  ASSERT_EQ(test.GetOldestApproximateTime(111), 1000);
}

TEST_F(SeqnoTimeTest, Sort) {
  SeqnoToTimeMapping test;

  // single entry
  test.Add(10, 11);
  ASSERT_OK(test.Sort());
  ASSERT_EQ(test.Size(), 1);

  // duplicate, should be removed by sort
  test.Add(10, 11);
  // same seqno, but older time, should be removed
  test.Add(10, 9);

  // unuseful ones, should be removed by sort
  test.Add(11, 9);
  test.Add(9, 8);

  // Good ones
  test.Add(1, 10);
  test.Add(100, 100);

  ASSERT_OK(test.Sort());

  auto seqs = test.TEST_GetInternalMapping();

  std::deque<SeqnoToTimeMapping::SeqnoTimePair> expected;
  expected.emplace_back(1, 10);
  expected.emplace_back(10, 11);
  expected.emplace_back(100, 100);

  ASSERT_EQ(expected, seqs);
}

TEST_F(SeqnoTimeTest, EncodeDecodeBasic) {
  SeqnoToTimeMapping test(0, 1000);

  std::string output;
  test.Encode(output, 0, 1000, 100);
  ASSERT_TRUE(output.empty());

  for (int i = 1; i <= 1000; i++) {
    ASSERT_TRUE(test.Append(i, i * 10));
  }
  test.Encode(output, 0, 1000, 100);

  ASSERT_FALSE(output.empty());

  SeqnoToTimeMapping decoded;
  ASSERT_OK(decoded.Add(output));
  ASSERT_OK(decoded.Sort());
  ASSERT_EQ(decoded.Size(), SeqnoToTimeMapping::kMaxSeqnoTimePairsPerSST);
  ASSERT_EQ(test.Size(), 1000);

  for (SequenceNumber seq = 0; seq <= 1000; seq++) {
    // test has the more accurate time mapping, encode only pick
    // kMaxSeqnoTimePairsPerSST number of entries, which is less accurate
    uint64_t target_time = test.GetOldestApproximateTime(seq);
    ASSERT_GE(decoded.GetOldestApproximateTime(seq),
              target_time < 200 ? 0 : target_time - 200);
    ASSERT_LE(decoded.GetOldestApproximateTime(seq), target_time);
  }
}

TEST_F(SeqnoTimeTest, EncodeDecodePerferNewTime) {
  SeqnoToTimeMapping test(0, 10);

  test.Append(1, 10);
  test.Append(5, 17);
  test.Append(6, 25);
  test.Append(8, 30);

  std::string output;
  test.Encode(output, 1, 10, 0, 3);

  SeqnoToTimeMapping decoded;
  ASSERT_OK(decoded.Add(output));
  ASSERT_OK(decoded.Sort());

  ASSERT_EQ(decoded.Size(), 3);

  auto seqs = decoded.TEST_GetInternalMapping();
  std::deque<SeqnoToTimeMapping::SeqnoTimePair> expected;
  expected.emplace_back(1, 10);
  expected.emplace_back(6, 25);
  expected.emplace_back(8, 30);
  ASSERT_EQ(expected, seqs);

  // Add a few large time number
  test.Append(10, 100);
  test.Append(13, 200);
  test.Append(16, 300);

  output.clear();
  test.Encode(output, 1, 20, 0, 4);
  decoded.Clear();
  ASSERT_OK(decoded.Add(output));
  ASSERT_OK(decoded.Sort());
  ASSERT_EQ(decoded.Size(), 4);

  expected.clear();
  expected.emplace_back(1, 10);
  // entry #6, #8 are skipped as they are too close to #1.
  // entry #100 is also within skip range, but if it's skipped, there not enough
  // number to fill 4 entries, so select it.
  expected.emplace_back(10, 100);
  expected.emplace_back(13, 200);
  expected.emplace_back(16, 300);
  seqs = decoded.TEST_GetInternalMapping();
  ASSERT_EQ(expected, seqs);
}

}  // namespace ROCKSDB_NAMESPACE

#endif  // ROCKSDB_LITE

int main(int argc, char** argv) {
  ROCKSDB_NAMESPACE::port::InstallStackTraceHandler();
  ::testing::InitGoogleTest(&argc, argv);
  return RUN_ALL_TESTS();
}