text: // Copyright (c) 2011 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/db.h"
  #include "leveldb/filter_policy.h"
  #include "db/db_impl.h"
  #include "db/filename.h"
  #include "db/version_set.h"
  #include "db/write_batch_internal.h"
  #include "leveldb/cache.h"
  #include "leveldb/env.h"
  #include "leveldb/table.h"
  #include "util/hash.h"
  #include "util/logging.h"
  #include "util/mutexlock.h"
  #include "util/testharness.h"
  #include "util/testutil.h"
  
  namespace leveldb {
  
  static std::string RandomString(Random* rnd, int len) {
    std::string r;
    test::RandomString(rnd, len, &r);
    return r;
  }
  
  namespace {
  class AtomicCounter {
   private:
    port::Mutex mu_;
    int count_;
   public:
    AtomicCounter() : count_(0) { }
    void Increment() {
      IncrementBy(1);
    }
    void IncrementBy(int count) {
      MutexLock l(&mu_);
      count_ += count;
    }
    int Read() {
      MutexLock l(&mu_);
      return count_;
    }
    void Reset() {
      MutexLock l(&mu_);
      count_ = 0;
    }
  };
  
  void DelayMilliseconds(int millis) {
    Env::Default()->SleepForMicroseconds(millis * 1000);
  }
  }
  
  // Special Env used to delay background operations
  class SpecialEnv : public EnvWrapper {
   public:
    // sstable/log Sync() calls are blocked while this pointer is non-NULL.
    port::AtomicPointer delay_data_sync_;
  
    // sstable/log Sync() calls return an error.
    port::AtomicPointer data_sync_error_;
  
    // Simulate no-space errors while this pointer is non-NULL.
    port::AtomicPointer no_space_;
  
    // Simulate non-writable file system while this pointer is non-NULL
    port::AtomicPointer non_writable_;
  
    // Force sync of manifest files to fail while this pointer is non-NULL
    port::AtomicPointer manifest_sync_error_;
  
    // Force write to manifest files to fail while this pointer is non-NULL
    port::AtomicPointer manifest_write_error_;
  
    bool count_random_reads_;
    AtomicCounter random_read_counter_;
  
  <<<<<<< HEAD
    AtomicCounter sleep_counter_;
    AtomicCounter sleep_time_counter_;
  
  =======
  >>>>>>> 3b4ed770f88229b11bf62b90f128f3054b17ab36
    explicit SpecialEnv(Env* base) : EnvWrapper(base) {
      delay_data_sync_.Release_Store(NULL);
      data_sync_error_.Release_Store(NULL);
      no_space_.Release_Store(NULL);
      non_writable_.Release_Store(NULL);
      count_random_reads_ = false;
      manifest_sync_error_.Release_Store(NULL);
      manifest_write_error_.Release_Store(NULL);
    }
  
    Status NewWritableFile(const std::string& f, WritableFile** r) {
      class DataFile : public WritableFile {
       private:
        SpecialEnv* env_;
        WritableFile* base_;
  
       public:
        DataFile(SpecialEnv* env, WritableFile* base)
            : env_(env),
              base_(base) {
        }
        ~DataFile() { delete base_; }
        Status Append(const Slice& data) {
          if (env_->no_space_.Acquire_Load() != NULL) {
            // Drop writes on the floor
            return Status::OK();
          } else {
            return base_->Append(data);
          }
        }
        Status Close() { return base_->Close(); }
        Status Flush() { return base_->Flush(); }
        Status Sync() {
  <<<<<<< HEAD
          while (env_->delay_sstable_sync_.Acquire_Load() != NULL) {
  =======
          if (env_->data_sync_error_.Acquire_Load() != NULL) {
            return Status::IOError("simulated data sync error");
          }
          while (env_->delay_data_sync_.Acquire_Load() != NULL) {
  >>>>>>> 3b4ed770f88229b11bf62b90f128f3054b17ab36
            DelayMilliseconds(100);
          }
          return base_->Sync();
        }
      };
      class ManifestFile : public WritableFile {
       private:
        SpecialEnv* env_;
        WritableFile* base_;
       public:
        ManifestFile(SpecialEnv* env, WritableFile* b) : env_(env), base_(b) { }
        ~ManifestFile() { delete base_; }
        Status Append(const Slice& data) {
          if (env_->manifest_write_error_.Acquire_Load() != NULL) {
            return Status::IOError("simulated writer error");
          } else {
            return base_->Append(data);
          }
        }
        Status Close() { return base_->Close(); }
        Status Flush() { return base_->Flush(); }
        Status Sync() {
          if (env_->manifest_sync_error_.Acquire_Load() != NULL) {
            return Status::IOError("simulated sync error");
          } else {
            return base_->Sync();
          }
        }
      };
  
      if (non_writable_.Acquire_Load() != NULL) {
        return Status::IOError("simulated write error");
      }
  
      Status s = target()->NewWritableFile(f, r);
      if (s.ok()) {
        if (strstr(f.c_str(), ".ldb") != NULL ||
            strstr(f.c_str(), ".log") != NULL) {
          *r = new DataFile(this, *r);
        } else if (strstr(f.c_str(), "MANIFEST") != NULL) {
          *r = new ManifestFile(this, *r);
        }
      }
      return s;
    }
  
    Status NewRandomAccessFile(const std::string& f, RandomAccessFile** r) {
      class CountingFile : public RandomAccessFile {
       private:
        RandomAccessFile* target_;
        AtomicCounter* counter_;
       public:
        CountingFile(RandomAccessFile* target, AtomicCounter* counter)
            : target_(target), counter_(counter) {
        }
        virtual ~CountingFile() { delete target_; }
        virtual Status Read(uint64_t offset, size_t n, Slice* result,
                            char* scratch) const {
          counter_->Increment();
          return target_->Read(offset, n, result, scratch);
        }
      };
  
      Status s = target()->NewRandomAccessFile(f, r);
      if (s.ok() && count_random_reads_) {
        *r = new CountingFile(*r, &random_read_counter_);
      }
      return s;
    }
  <<<<<<< HEAD
  
    virtual void SleepForMicroseconds(int micros) {
      sleep_counter_.Increment();
      sleep_time_counter_.IncrementBy(micros);
    }
  
  =======
  >>>>>>> 3b4ed770f88229b11bf62b90f128f3054b17ab36
  };
  
  class DBTest {
   private:
    const FilterPolicy* filter_policy_;
  
    // Sequence of option configurations to try
    enum OptionConfig {
      kDefault,
      kFilter,
      kUncompressed,
      kEnd
    };
    int option_config_;
  
   public:
    std::string dbname_;
    SpecialEnv* env_;
    DB* db_;
  
    Options last_options_;
  
    DBTest() : option_config_(kDefault),
               env_(new SpecialEnv(Env::Default())) {
      filter_policy_ = NewBloomFilterPolicy(10);
      dbname_ = test::TmpDir() + "/db_test";
      DestroyDB(dbname_, Options());
      db_ = NULL;
      Reopen();
    }
  
    ~DBTest() {
      delete db_;
      DestroyDB(dbname_, Options());
      delete env_;
      delete filter_policy_;
    }
  
    // Switch to a fresh database with the next option configuration to
    // test.  Return false if there are no more configurations to test.
    bool ChangeOptions() {
      option_config_++;
      if (option_config_ >= kEnd) {
        return false;
      } else {
        DestroyAndReopen();
        return true;
      }
    }
  
    // Return the current option configuration.
    Options CurrentOptions() {
      Options options;
      switch (option_config_) {
        case kFilter:
          options.filter_policy = filter_policy_;
          break;
        case kUncompressed:
          options.compression = kNoCompression;
          break;
        default:
          break;
      }
      return options;
    }
  
    DBImpl* dbfull() {
      return reinterpret_cast<DBImpl*>(db_);
    }
  
    void Reopen(Options* options = NULL) {
      ASSERT_OK(TryReopen(options));
    }
  
    void Close() {
      delete db_;
      db_ = NULL;
    }
  
    void DestroyAndReopen(Options* options = NULL) {
      delete db_;
      db_ = NULL;
      DestroyDB(dbname_, Options());
      ASSERT_OK(TryReopen(options));
    }
  
    Status TryReopen(Options* options) {
      delete db_;
      db_ = NULL;
      Options opts;
      if (options != NULL) {
        opts = *options;
      } else {
        opts = CurrentOptions();
        opts.create_if_missing = true;
      }
      last_options_ = opts;
  
      return DB::Open(opts, dbname_, &db_);
    }
  
    Status Put(const std::string& k, const std::string& v) {
      return db_->Put(WriteOptions(), k, v);
    }
  
    Status Delete(const std::string& k) {
      return db_->Delete(WriteOptions(), k);
    }
  
    std::string Get(const std::string& k, const Snapshot* snapshot = NULL) {
      ReadOptions options;
      options.snapshot = snapshot;
      std::string result;
      Status s = db_->Get(options, k, &result);
      if (s.IsNotFound()) {
        result = "NOT_FOUND";
      } else if (!s.ok()) {
        result = s.ToString();
      }
      return result;
    }
  
    // Return a string that contains all key,value pairs in order,
    // formatted like "(k1->v1)(k2->v2)".
    std::string Contents() {
      std::vector<std::string> forward;
      std::string result;
      Iterator* iter = db_->NewIterator(ReadOptions());
      for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
        std::string s = IterStatus(iter);
        result.push_back('(');
        result.append(s);
        result.push_back(')');
        forward.push_back(s);
      }
  
      // Check reverse iteration results are the reverse of forward results
      size_t matched = 0;
      for (iter->SeekToLast(); iter->Valid(); iter->Prev()) {
        ASSERT_LT(matched, forward.size());
        ASSERT_EQ(IterStatus(iter), forward[forward.size() - matched - 1]);
        matched++;
      }
      ASSERT_EQ(matched, forward.size());
  
      delete iter;
      return result;
    }
  
    std::string AllEntriesFor(const Slice& user_key) {
      Iterator* iter = dbfull()->TEST_NewInternalIterator();
      InternalKey target(user_key, kMaxSequenceNumber, kTypeValue);
      iter->Seek(target.Encode());
      std::string result;
      if (!iter->status().ok()) {
        result = iter->status().ToString();
      } else {
        result = "[ ";
        bool first = true;
        while (iter->Valid()) {
          ParsedInternalKey ikey;
          if (!ParseInternalKey(iter->key(), &ikey)) {
            result += "CORRUPTED";
          } else {
            if (last_options_.comparator->Compare(ikey.user_key, user_key) != 0) {
              break;
            }
            if (!first) {
              result += ", ";
            }
            first = false;
            switch (ikey.type) {
              case kTypeValue:
                result += iter->value().ToString();
                break;
              case kTypeDeletion:
                result += "DEL";
                break;
            }
          }
          iter->Next();
        }
        if (!first) {
          result += " ";
        }
        result += "]";
      }
      delete iter;
      return result;
    }
  
    int NumTableFilesAtLevel(int level) {
      std::string property;
      ASSERT_TRUE(
          db_->GetProperty("leveldb.num-files-at-level" + NumberToString(level),
                           &property));
      return atoi(property.c_str());
    }
  
    int TotalTableFiles() {
      int result = 0;
      for (int level = 0; level < config::kNumLevels; level++) {
        result += NumTableFilesAtLevel(level);
      }
      return result;
    }
  
    // Return spread of files per level
    std::string FilesPerLevel() {
      std::string result;
      int last_non_zero_offset = 0;
      for (int level = 0; level < config::kNumLevels; level++) {
        int f = NumTableFilesAtLevel(level);
        char buf[100];
        snprintf(buf, sizeof(buf), "%s%d", (level ? "," : ""), f);
        result += buf;
        if (f > 0) {
          last_non_zero_offset = result.size();
        }
      }
      result.resize(last_non_zero_offset);
      return result;
    }
  
    int CountFiles() {
      std::vector<std::string> files;
      env_->GetChildren(dbname_, &files);
      return static_cast<int>(files.size());
    }
  
    uint64_t Size(const Slice& start, const Slice& limit) {
      Range r(start, limit);
      uint64_t size;
      db_->GetApproximateSizes(&r, 1, &size);
      return size;
    }
  
    void Compact(const Slice& start, const Slice& limit) {
      db_->CompactRange(&start, &limit);
    }
  
    // Do n memtable compactions, each of which produces an sstable
    // covering the range [small,large].
    void MakeTables(int n, const std::string& small, const std::string& large) {
      for (int i = 0; i < n; i++) {
        Put(small, "begin");
        Put(large, "end");
        dbfull()->TEST_CompactMemTable();
      }
    }
  
    // Prevent pushing of new sstables into deeper levels by adding
    // tables that cover a specified range to all levels.
    void FillLevels(const std::string& smallest, const std::string& largest) {
      MakeTables(config::kNumLevels, smallest, largest);
    }
  
    void DumpFileCounts(const char* label) {
      fprintf(stderr, "---\n%s:\n", label);
      fprintf(stderr, "maxoverlap: %lld\n",
              static_cast<long long>(
                  dbfull()->TEST_MaxNextLevelOverlappingBytes()));
      for (int level = 0; level < config::kNumLevels; level++) {
        int num = NumTableFilesAtLevel(level);
        if (num > 0) {
          fprintf(stderr, "  level %3d : %d files\n", level, num);
        }
      }
    }
  
    std::string DumpSSTableList() {
      std::string property;
      db_->GetProperty("leveldb.sstables", &property);
      return property;
    }
  
    std::string IterStatus(Iterator* iter) {
      std::string result;
      if (iter->Valid()) {
        result = iter->key().ToString() + "->" + iter->value().ToString();
      } else {
        result = "(invalid)";
      }
      return result;
    }
  
    bool DeleteAnSSTFile() {
      std::vector<std::string> filenames;
      ASSERT_OK(env_->GetChildren(dbname_, &filenames));
      uint64_t number;
      FileType type;
      for (size_t i = 0; i < filenames.size(); i++) {
        if (ParseFileName(filenames[i], &number, &type) && type == kTableFile) {
          ASSERT_OK(env_->DeleteFile(TableFileName(dbname_, number)));
          return true;
        }
      }
      return false;
    }
  <<<<<<< HEAD
  =======
  
    // Returns number of files renamed.
    int RenameLDBToSST() {
      std::vector<std::string> filenames;
      ASSERT_OK(env_->GetChildren(dbname_, &filenames));
      uint64_t number;
      FileType type;
      int files_renamed = 0;
      for (size_t i = 0; i < filenames.size(); i++) {
        if (ParseFileName(filenames[i], &number, &type) && type == kTableFile) {
          const std::string from = TableFileName(dbname_, number);
          const std::string to = SSTTableFileName(dbname_, number);
          ASSERT_OK(env_->RenameFile(from, to));
          files_renamed++;
        }
      }
      return files_renamed;
    }
  >>>>>>> 3b4ed770f88229b11bf62b90f128f3054b17ab36
  };
  
  TEST(DBTest, Empty) {
    do {
      ASSERT_TRUE(db_ != NULL);
      ASSERT_EQ("NOT_FOUND", Get("foo"));
    } while (ChangeOptions());
  }
  
  TEST(DBTest, ReadWrite) {
    do {
      ASSERT_OK(Put("foo", "v1"));
      ASSERT_EQ("v1", Get("foo"));
      ASSERT_OK(Put("bar", "v2"));
      ASSERT_OK(Put("foo", "v3"));
      ASSERT_EQ("v3", Get("foo"));
      ASSERT_EQ("v2", Get("bar"));
    } while (ChangeOptions());
  }
  
  TEST(DBTest, PutDeleteGet) {
    do {
      ASSERT_OK(db_->Put(WriteOptions(), "foo", "v1"));
      ASSERT_EQ("v1", Get("foo"));
      ASSERT_OK(db_->Put(WriteOptions(), "foo", "v2"));
      ASSERT_EQ("v2", Get("foo"));
      ASSERT_OK(db_->Delete(WriteOptions(), "foo"));
      ASSERT_EQ("NOT_FOUND", Get("foo"));
    } while (ChangeOptions());
  }
  
  TEST(DBTest, GetFromImmutableLayer) {
    do {
      Options options = CurrentOptions();
      options.env = env_;
      options.write_buffer_size = 100000;  // Small write buffer
      Reopen(&options);
  
      ASSERT_OK(Put("foo", "v1"));
      ASSERT_EQ("v1", Get("foo"));
  
      env_->delay_data_sync_.Release_Store(env_);      // Block sync calls
      Put("k1", std::string(100000, 'x'));             // Fill memtable
      Put("k2", std::string(100000, 'y'));             // Trigger compaction
      ASSERT_EQ("v1", Get("foo"));
      env_->delay_data_sync_.Release_Store(NULL);      // Release sync calls
    } while (ChangeOptions());
  }
  
  TEST(DBTest, GetFromVersions) {
    do {
      ASSERT_OK(Put("foo", "v1"));
      dbfull()->TEST_CompactMemTable();
      ASSERT_EQ("v1", Get("foo"));
    } while (ChangeOptions());
  }
  
  TEST(DBTest, GetSnapshot) {
    do {
      // Try with both a short key and a long key
      for (int i = 0; i < 2; i++) {
        std::string key = (i == 0) ? std::string("foo") : std::string(200, 'x');
        ASSERT_OK(Put(key, "v1"));
        const Snapshot* s1 = db_->GetSnapshot();
        ASSERT_OK(Put(key, "v2"));
        ASSERT_EQ("v2", Get(key));
        ASSERT_EQ("v1", Get(key, s1));
        dbfull()->TEST_CompactMemTable();
        ASSERT_EQ("v2", Get(key));
        ASSERT_EQ("v1", Get(key, s1));
        db_->ReleaseSnapshot(s1);
      }
    } while (ChangeOptions());
  }
  
  TEST(DBTest, GetLevel0Ordering) {
    do {
      // Check that we process level-0 files in correct order.  The code
      // below generates two level-0 files where the earlier one comes
      // before the later one in the level-0 file list since the earlier
      // one has a smaller "smallest" key.
      ASSERT_OK(Put("bar", "b"));
      ASSERT_OK(Put("foo", "v1"));
      dbfull()->TEST_CompactMemTable();
      ASSERT_OK(Put("foo", "v2"));
      dbfull()->TEST_CompactMemTable();
      ASSERT_EQ("v2", Get("foo"));
    } while (ChangeOptions());
  }
  
  TEST(DBTest, GetOrderedByLevels) {
    do {
      ASSERT_OK(Put("foo", "v1"));
      Compact("a", "z");
      ASSERT_EQ("v1", Get("foo"));
      ASSERT_OK(Put("foo", "v2"));
      ASSERT_EQ("v2", Get("foo"));
      dbfull()->TEST_CompactMemTable();
      ASSERT_EQ("v2", Get("foo"));
    } while (ChangeOptions());
  }
  
  TEST(DBTest, GetPicksCorrectFile) {
    do {
      // Arrange to have multiple files in a non-level-0 level.
      ASSERT_OK(Put("a", "va"));
      Compact("a", "b");
      ASSERT_OK(Put("x", "vx"));
      Compact("x", "y");
      ASSERT_OK(Put("f", "vf"));
      Compact("f", "g");
      ASSERT_EQ("va", Get("a"));
      ASSERT_EQ("vf", Get("f"));
      ASSERT_EQ("vx", Get("x"));
    } while (ChangeOptions());
  }
  
  TEST(DBTest, GetEncountersEmptyLevel) {
    do {
      // Arrange for the following to happen:
      //   * sstable A in level 0
      //   * nothing in level 1
      //   * sstable B in level 2
      // Then do enough Get() calls to arrange for an automatic compaction
      // of sstable A.  A bug would cause the compaction to be marked as
      // occurring at level 1 (instead of the correct level 0).
  
      // Step 1: First place sstables in levels 0 and 2
      int compaction_count = 0;
      while (NumTableFilesAtLevel(0) == 0 ||
             NumTableFilesAtLevel(2) == 0) {
        ASSERT_LE(compaction_count, 100) << "could not fill levels 0 and 2";
        compaction_count++;
        Put("a", "begin");
        Put("z", "end");
        dbfull()->TEST_CompactMemTable();
      }
  
      // Step 2: clear level 1 if necessary.
      dbfull()->TEST_CompactRange(1, NULL, NULL);
      ASSERT_EQ(NumTableFilesAtLevel(0), 1);
      ASSERT_EQ(NumTableFilesAtLevel(1), 0);
      ASSERT_EQ(NumTableFilesAtLevel(2), 1);
  
      // Step 3: read a bunch of times
      for (int i = 0; i < 1000; i++) {
        ASSERT_EQ("NOT_FOUND", Get("missing"));
      }
  
      // Step 4: Wait for compaction to finish
      DelayMilliseconds(1000);
  
      ASSERT_EQ(NumTableFilesAtLevel(0), 0);
    } while (ChangeOptions());
  }
  
  TEST(DBTest, IterEmpty) {
    Iterator* iter = db_->NewIterator(ReadOptions());
  
    iter->SeekToFirst();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
  
    iter->SeekToLast();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
  
    iter->Seek("foo");
    ASSERT_EQ(IterStatus(iter), "(invalid)");
  
    delete iter;
  }
  
  TEST(DBTest, IterSingle) {
    ASSERT_OK(Put("a", "va"));
    Iterator* iter = db_->NewIterator(ReadOptions());
  
    iter->SeekToFirst();
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
    iter->SeekToFirst();
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
  
    iter->SeekToLast();
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
    iter->SeekToLast();
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
  
    iter->Seek("");
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
  
    iter->Seek("a");
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
  
    iter->Seek("b");
    ASSERT_EQ(IterStatus(iter), "(invalid)");
  
    delete iter;
  }
  
  TEST(DBTest, IterMulti) {
    ASSERT_OK(Put("a", "va"));
    ASSERT_OK(Put("b", "vb"));
    ASSERT_OK(Put("c", "vc"));
    Iterator* iter = db_->NewIterator(ReadOptions());
  
    iter->SeekToFirst();
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "b->vb");
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "c->vc");
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
    iter->SeekToFirst();
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
  
    iter->SeekToLast();
    ASSERT_EQ(IterStatus(iter), "c->vc");
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "b->vb");
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
    iter->SeekToLast();
    ASSERT_EQ(IterStatus(iter), "c->vc");
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
  
    iter->Seek("");
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Seek("a");
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Seek("ax");
    ASSERT_EQ(IterStatus(iter), "b->vb");
    iter->Seek("b");
    ASSERT_EQ(IterStatus(iter), "b->vb");
    iter->Seek("z");
    ASSERT_EQ(IterStatus(iter), "(invalid)");
  
    // Switch from reverse to forward
    iter->SeekToLast();
    iter->Prev();
    iter->Prev();
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "b->vb");
  
    // Switch from forward to reverse
    iter->SeekToFirst();
    iter->Next();
    iter->Next();
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "b->vb");
  
    // Make sure iter stays at snapshot
    ASSERT_OK(Put("a",  "va2"));
    ASSERT_OK(Put("a2", "va3"));
    ASSERT_OK(Put("b",  "vb2"));
    ASSERT_OK(Put("c",  "vc2"));
    ASSERT_OK(Delete("b"));
    iter->SeekToFirst();
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "b->vb");
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "c->vc");
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
    iter->SeekToLast();
    ASSERT_EQ(IterStatus(iter), "c->vc");
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "b->vb");
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
  
    delete iter;
  }
  
  TEST(DBTest, IterSmallAndLargeMix) {
    ASSERT_OK(Put("a", "va"));
    ASSERT_OK(Put("b", std::string(100000, 'b')));
    ASSERT_OK(Put("c", "vc"));
    ASSERT_OK(Put("d", std::string(100000, 'd')));
    ASSERT_OK(Put("e", std::string(100000, 'e')));
  
    Iterator* iter = db_->NewIterator(ReadOptions());
  
    iter->SeekToFirst();
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "b->" + std::string(100000, 'b'));
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "c->vc");
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "d->" + std::string(100000, 'd'));
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "e->" + std::string(100000, 'e'));
    iter->Next();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
  
    iter->SeekToLast();
    ASSERT_EQ(IterStatus(iter), "e->" + std::string(100000, 'e'));
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "d->" + std::string(100000, 'd'));
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "c->vc");
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "b->" + std::string(100000, 'b'));
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "a->va");
    iter->Prev();
    ASSERT_EQ(IterStatus(iter), "(invalid)");
  
    delete iter;
  }
  
  TEST(DBTest, IterMultiWithDelete) {
    do {
      ASSERT_OK(Put("a", "va"));
      ASSERT_OK(Put("b", "vb"));
      ASSERT_OK(Put("c", "vc"));
      ASSERT_OK(Delete("b"));
      ASSERT_EQ("NOT_FOUND", Get("b"));
  
      Iterator* iter = db_->NewIterator(ReadOptions());
      iter->Seek("c");
      ASSERT_EQ(IterStatus(iter), "c->vc");
      iter->Prev();
      ASSERT_EQ(IterStatus(iter), "a->va");
      delete iter;
    } while (ChangeOptions());
  }
  
  TEST(DBTest, Recover) {
    do {
      ASSERT_OK(Put("foo", "v1"));
      ASSERT_OK(Put("baz", "v5"));
  
      Reopen();
      ASSERT_EQ("v1", Get("foo"));
  
      ASSERT_EQ("v1", Get("foo"));
      ASSERT_EQ("v5", Get("baz"));
      ASSERT_OK(Put("bar", "v2"));
      ASSERT_OK(Put("foo", "v3"));
  
      Reopen();
      ASSERT_EQ("v3", Get("foo"));
      ASSERT_OK(Put("foo", "v4"));
      ASSERT_EQ("v4", Get("foo"));
      ASSERT_EQ("v2", Get("bar"));
      ASSERT_EQ("v5", Get("baz"));
    } while (ChangeOptions());
  }
  
  TEST(DBTest, RecoveryWithEmptyLog) {
    do {
      ASSERT_OK(Put("foo", "v1"));
      ASSERT_OK(Put("foo", "v2"));
      Reopen();
      Reopen();
      ASSERT_OK(Put("foo", "v3"));
      Reopen();
      ASSERT_EQ("v3", Get("foo"));
    } while (ChangeOptions());
  }
  
  // Check that writes done during a memtable compaction are recovered
  // if the database is shutdown during the memtable compaction.
  TEST(DBTest, RecoverDuringMemtableCompaction) {
    do {
      Options options = CurrentOptions();
      options.env = env_;
      options.write_buffer_size = 1000000;
      Reopen(&options);
  
      // Trigger a long memtable compaction and reopen the database during it
      ASSERT_OK(Put("foo", "v1"));                         // Goes to 1st log file
      ASSERT_OK(Put("big1", std::string(10000000, 'x')));  // Fills memtable
      ASSERT_OK(Put("big2", std::string(1000, 'y')));      // Triggers compaction
      ASSERT_OK(Put("bar", "v2"));                         // Goes to new log file
  
      Reopen(&options);
      ASSERT_EQ("v1", Get("foo"));
      ASSERT_EQ("v2", Get("bar"));
      ASSERT_EQ(std::string(10000000, 'x'), Get("big1"));
      ASSERT_EQ(std::string(1000, 'y'), Get("big2"));
    } while (ChangeOptions());
  }
  
  static std::string Key(int i) {
    char buf[100];
    snprintf(buf, sizeof(buf), "key%06d", i);
    return std::string(buf);
  }
  
  TEST(DBTest, MinorCompactionsHappen) {
    Options options = CurrentOptions();
    options.write_buffer_size = 10000;
    Reopen(&options);
  
    const int N = 500;
  
    int starting_num_tables = TotalTableFiles();
    for (int i = 0; i < N; i++) {
      ASSERT_OK(Put(Key(i), Key(i) + std::string(1000, 'v')));
    }
    int ending_num_tables = TotalTableFiles();
    ASSERT_GT(ending_num_tables, starting_num_tables);
  
    for (int i = 0; i < N; i++) {
      ASSERT_EQ(Key(i) + std::string(1000, 'v'), Get(Key(i)));
    }
  
    Reopen();
  
    for (int i = 0; i < N; i++) {
      ASSERT_EQ(Key(i) + std::string(1000, 'v'), Get(Key(i)));
    }
  }
  
  TEST(DBTest, RecoverWithLargeLog) {
    {
      Options options = CurrentOptions();
      Reopen(&options);
      ASSERT_OK(Put("big1", std::string(200000, '1')));
      ASSERT_OK(Put("big2", std::string(200000, '2')));
      ASSERT_OK(Put("small3", std::string(10, '3')));
      ASSERT_OK(Put("small4", std::string(10, '4')));
      ASSERT_EQ(NumTableFilesAtLevel(0), 0);
    }
  
    // Make sure that if we re-open with a small write buffer size that
    // we flush table files in the middle of a large log file.
    Options options = CurrentOptions();
    options.write_buffer_size = 100000;
    Reopen(&options);
    ASSERT_EQ(NumTableFilesAtLevel(0), 3);
    ASSERT_EQ(std::string(200000, '1'), Get("big1"));
    ASSERT_EQ(std::string(200000, '2'), Get("big2"));
    ASSERT_EQ(std::string(10, '3'), Get("small3"));
    ASSERT_EQ(std::string(10, '4'), Get("small4"));
    ASSERT_GT(NumTableFilesAtLevel(0), 1);
  }
  
  TEST(DBTest, CompactionsGenerateMultipleFiles) {
    Options options = CurrentOptions();
    options.write_buffer_size = 100000000;        // Large write buffer
    Reopen(&options);
  
    Random rnd(301);
  
    // Write 8MB (80 values, each 100K)
    ASSERT_EQ(NumTableFilesAtLevel(0), 0);
    std::vector<std::string> values;
    for (int i = 0; i < 80; i++) {
      values.push_back(RandomString(&rnd, 100000));
      ASSERT_OK(Put(Key(i), values[i]));
    }
  
    // Reopening moves updates to level-0
    Reopen(&options);
    dbfull()->TEST_CompactRange(0, NULL, NULL);
  
    ASSERT_EQ(NumTableFilesAtLevel(0), 0);
    ASSERT_GT(NumTableFilesAtLevel(1), 1);
    for (int i = 0; i < 80; i++) {
      ASSERT_EQ(Get(Key(i)), values[i]);
    }
  }
  
  TEST(DBTest, RepeatedWritesToSameKey) {
    Options options = CurrentOptions();
    options.env = env_;
    options.write_buffer_size = 100000;  // Small write buffer
    Reopen(&options);
  
    // We must have at most one file per level except for level-0,
    // which may have up to kL0_StopWritesTrigger files.
    const int kMaxFiles = config::kNumLevels + config::kL0_StopWritesTrigger;
  
    Random rnd(301);
    std::string value = RandomString(&rnd, 2 * options.write_buffer_size);
    for (int i = 0; i < 5 * kMaxFiles; i++) {
      Put("key", value);
      ASSERT_LE(TotalTableFiles(), kMaxFiles);
      fprintf(stderr, "after %d: %d files\n", int(i+1), TotalTableFiles());
    }
  }
  
  TEST(DBTest, SparseMerge) {
    Options options = CurrentOptions();
    options.compression = kNoCompression;
    Reopen(&options);
  
    FillLevels("A", "Z");
  
    // Suppose there is:
    //    small amount of data with prefix A
    //    large amount of data with prefix B
    //    small amount of data with prefix C
    // and that recent updates have made small changes to all three prefixes.
    // Check that we do not do a compaction that merges all of B in one shot.
    const std::string value(1000, 'x');
    Put("A", "va");
    // Write approximately 100MB of "B" values
    for (int i = 0; i < 100000; i++) {
      char key[100];
      snprintf(key, sizeof(key), "B%010d", i);
      Put(key, value);
    }
    Put("C", "vc");
    dbfull()->TEST_CompactMemTable();
    dbfull()->TEST_CompactRange(0, NULL, NULL);
  
    // Make sparse update
    Put("A",    "va2");
    Put("B100", "bvalue2");
    Put("C",    "vc2");
    dbfull()->TEST_CompactMemTable();
  
    // Compactions should not cause us to create a situation where
    // a file overlaps too much data at the next level.
    ASSERT_LE(dbfull()->TEST_MaxNextLevelOverlappingBytes(), 20*1048576);
    dbfull()->TEST_CompactRange(0, NULL, NULL);
    ASSERT_LE(dbfull()->TEST_MaxNextLevelOverlappingBytes(), 20*1048576);
    dbfull()->TEST_CompactRange(1, NULL, NULL);
    ASSERT_LE(dbfull()->TEST_MaxNextLevelOverlappingBytes(), 20*1048576);
  }
  
  static bool Between(uint64_t val, uint64_t low, uint64_t high) {
    bool result = (val >= low) && (val <= high);
    if (!result) {
      fprintf(stderr, "Value %llu is not in range [%llu, %llu]\n",
              (unsigned long long)(val),
              (unsigned long long)(low),
              (unsigned long long)(high));
    }
    return result;
  }
  
  TEST(DBTest, ApproximateSizes) {
    do {
      Options options = CurrentOptions();
      options.write_buffer_size = 100000000;        // Large write buffer
      options.compression = kNoCompression;
      DestroyAndReopen();
  
      ASSERT_TRUE(Between(Size("", "xyz"), 0, 0));
      Reopen(&options);
      ASSERT_TRUE(Between(Size("", "xyz"), 0, 0));
  
      // Write 8MB (80 values, each 100K)
      ASSERT_EQ(NumTableFilesAtLevel(0), 0);
      const int N = 80;
      static const int S1 = 100000;
      static const int S2 = 105000;  // Allow some expansion from metadata
      Random rnd(301);
      for (int i = 0; i < N; i++) {
        ASSERT_OK(Put(Key(i), RandomString(&rnd, S1)));
      }
  
      // 0 because GetApproximateSizes() does not account for memtable space
      ASSERT_TRUE(Between(Size("", Key(50)), 0, 0));
  
      // Check sizes across recovery by reopening a few times
      for (int run = 0; run < 3; run++) {
        Reopen(&options);
  
        for (int compact_start = 0; compact_start < N; compact_start += 10) {
          for (int i = 0; i < N; i += 10) {
            ASSERT_TRUE(Between(Size("", Key(i)), S1*i, S2*i));
            ASSERT_TRUE(Between(Size("", Key(i)+".suffix"), S1*(i+1), S2*(i+1)));
            ASSERT_TRUE(Between(Size(Key(i), Key(i+10)), S1*10, S2*10));
          }
          ASSERT_TRUE(Between(Size("", Key(50)), S1*50, S2*50));
          ASSERT_TRUE(Between(Size("", Key(50)+".suffix"), S1*50, S2*50));
  
          std::string cstart_str = Key(compact_start);
          std::string cend_str = Key(compact_start + 9);
          Slice cstart = cstart_str;
          Slice cend = cend_str;
          dbfull()->TEST_CompactRange(0, &cstart, &cend);
        }
  
        ASSERT_EQ(NumTableFilesAtLevel(0), 0);
        ASSERT_GT(NumTableFilesAtLevel(1), 0);
      }
    } while (ChangeOptions());
  }
  
  TEST(DBTest, ApproximateSizes_MixOfSmallAndLarge) {
    do {
      Options options = CurrentOptions();
      options.compression = kNoCompression;
      Reopen();
  
      Random rnd(301);
      std::string big1 = RandomString(&rnd, 100000);
      ASSERT_OK(Put(Key(0), RandomString(&rnd, 10000)));
      ASSERT_OK(Put(Key(1), RandomString(&rnd, 10000)));
      ASSERT_OK(Put(Key(2), big1));
      ASSERT_OK(Put(Key(3), RandomString(&rnd, 10000)));
      ASSERT_OK(Put(Key(4), big1));
      ASSERT_OK(Put(Key(5), RandomString(&rnd, 10000)));
      ASSERT_OK(Put(Key(6), RandomString(&rnd, 300000)));
      ASSERT_OK(Put(Key(7), RandomString(&rnd, 10000)));
  
      // Check sizes across recovery by reopening a few times
      for (int run = 0; run < 3; run++) {
        Reopen(&options);
  
        ASSERT_TRUE(Between(Size("", Key(0)), 0, 0));
        ASSERT_TRUE(Between(Size("", Key(1)), 10000, 11000));
        ASSERT_TRUE(Between(Size("", Key(2)), 20000, 21000));
        ASSERT_TRUE(Between(Size("", Key(3)), 120000, 121000));
        ASSERT_TRUE(Between(Size("", Key(4)), 130000, 131000));
        ASSERT_TRUE(Between(Size("", Key(5)), 230000, 231000));
        ASSERT_TRUE(Between(Size("", Key(6)), 240000, 241000));
        ASSERT_TRUE(Between(Size("", Key(7)), 540000, 541000));
        ASSERT_TRUE(Between(Size("", Key(8)), 550000, 560000));
  
        ASSERT_TRUE(Between(Size(Key(3), Key(5)), 110000, 111000));
  
        dbfull()->TEST_CompactRange(0, NULL, NULL);
      }
    } while (ChangeOptions());
  }
  
  TEST(DBTest, IteratorPinsRef) {
    Put("foo", "hello");
  
    // Get iterator that will yield the current contents of the DB.
    Iterator* iter = db_->NewIterator(ReadOptions());
  
    // Write to force compactions
    Put("foo", "newvalue1");
    for (int i = 0; i < 100; i++) {
      ASSERT_OK(Put(Key(i), Key(i) + std::string(100000, 'v'))); // 100K values
    }
    Put("foo", "newvalue2");
  
    iter->SeekToFirst();
    ASSERT_TRUE(iter->Valid());
    ASSERT_EQ("foo", iter->key().ToString());
    ASSERT_EQ("hello", iter->value().ToString());
    iter->Next();
    ASSERT_TRUE(!iter->Valid());
    delete iter;
  }
  
  TEST(DBTest, Snapshot) {
    do {
      Put("foo", "v1");
      const Snapshot* s1 = db_->GetSnapshot();
      Put("foo", "v2");
      const Snapshot* s2 = db_->GetSnapshot();
      Put("foo", "v3");
      const Snapshot* s3 = db_->GetSnapshot();
  
      Put("foo", "v4");
      ASSERT_EQ("v1", Get("foo", s1));
      ASSERT_EQ("v2", Get("foo", s2));
      ASSERT_EQ("v3", Get("foo", s3));
      ASSERT_EQ("v4", Get("foo"));
  
      db_->ReleaseSnapshot(s3);
      ASSERT_EQ("v1", Get("foo", s1));
      ASSERT_EQ("v2", Get("foo", s2));
      ASSERT_EQ("v4", Get("foo"));
  
      db_->ReleaseSnapshot(s1);
      ASSERT_EQ("v2", Get("foo", s2));
      ASSERT_EQ("v4", Get("foo"));
  
      db_->ReleaseSnapshot(s2);
      ASSERT_EQ("v4", Get("foo"));
    } while (ChangeOptions());
  }
  
  TEST(DBTest, HiddenValuesAreRemoved) {
    do {
      Random rnd(301);
      FillLevels("a", "z");
  
      std::string big = RandomString(&rnd, 50000);
      Put("foo", big);
      Put("pastfoo", "v");
      const Snapshot* snapshot = db_->GetSnapshot();
      Put("foo", "tiny");
      Put("pastfoo2", "v2");        // Advance sequence number one more
  
      ASSERT_OK(dbfull()->TEST_CompactMemTable());
      ASSERT_GT(NumTableFilesAtLevel(0), 0);
  
      ASSERT_EQ(big, Get("foo", snapshot));
      ASSERT_TRUE(Between(Size("", "pastfoo"), 50000, 60000));
      db_->ReleaseSnapshot(snapshot);
      ASSERT_EQ(AllEntriesFor("foo"), "[ tiny, " + big + " ]");
      Slice x("x");
      dbfull()->TEST_CompactRange(0, NULL, &x);
      ASSERT_EQ(AllEntriesFor("foo"), "[ tiny ]");
      ASSERT_EQ(NumTableFilesAtLevel(0), 0);
      ASSERT_GE(NumTableFilesAtLevel(1), 1);
      dbfull()->TEST_CompactRange(1, NULL, &x);
      ASSERT_EQ(AllEntriesFor("foo"), "[ tiny ]");
  
      ASSERT_TRUE(Between(Size("", "pastfoo"), 0, 1000));
    } while (ChangeOptions());
  }
  
  TEST(DBTest, DeletionMarkers1) {
    Put("foo", "v1");
    ASSERT_OK(dbfull()->TEST_CompactMemTable());
    const int last = config::kMaxMemCompactLevel;
    ASSERT_EQ(NumTableFilesAtLevel(last), 1);   // foo => v1 is now in last level
  
    // Place a table at level last-1 to prevent merging with preceding mutation
    Put("a", "begin");
    Put("z", "end");
    dbfull()->TEST_CompactMemTable();
    ASSERT_EQ(NumTableFilesAtLevel(last), 1);
    ASSERT_EQ(NumTableFilesAtLevel(last-1), 1);
  
    Delete("foo");
    Put("foo", "v2");
    ASSERT_EQ(AllEntriesFor("foo"), "[ v2, DEL, v1 ]");
    ASSERT_OK(dbfull()->TEST_CompactMemTable());  // Moves to level last-2
    ASSERT_EQ(AllEntriesFor("foo"), "[ v2, DEL, v1 ]");
    Slice z("z");
    dbfull()->TEST_CompactRange(last-2, NULL, &z);
    // DEL eliminated, but v1 remains because we aren't compacting that level
    // (DEL can be eliminated because v2 hides v1).
    ASSERT_EQ(AllEntriesFor("foo"), "[ v2, v1 ]");
    dbfull()->TEST_CompactRange(last-1, NULL, NULL);
    // Merging last-1 w/ last, so we are the base level for "foo", so
    // DEL is removed.  (as is v1).
    ASSERT_EQ(AllEntriesFor("foo"), "[ v2 ]");
  }
  
  TEST(DBTest, DeletionMarkers2) {
    Put("foo", "v1");
    ASSERT_OK(dbfull()->TEST_CompactMemTable());
    const int last = config::kMaxMemCompactLevel;
    ASSERT_EQ(NumTableFilesAtLevel(last), 1);   // foo => v1 is now in last level
  
    // Place a table at level last-1 to prevent merging with preceding mutation
    Put("a", "begin");
    Put("z", "end");
    dbfull()->TEST_CompactMemTable();
    ASSERT_EQ(NumTableFilesAtLevel(last), 1);
    ASSERT_EQ(NumTableFilesAtLevel(last-1), 1);
  
    Delete("foo");
    ASSERT_EQ(AllEntriesFor("foo"), "[ DEL, v1 ]");
    ASSERT_OK(dbfull()->TEST_CompactMemTable());  // Moves to level last-2
    ASSERT_EQ(AllEntriesFor("foo"), "[ DEL, v1 ]");
    dbfull()->TEST_CompactRange(last-2, NULL, NULL);
    // DEL kept: "last" file overlaps
    ASSERT_EQ(AllEntriesFor("foo"), "[ DEL, v1 ]");
    dbfull()->TEST_CompactRange(last-1, NULL, NULL);
    // Merging last-1 w/ last, so we are the base level for "foo", so
    // DEL is removed.  (as is v1).
    ASSERT_EQ(AllEntriesFor("foo"), "[ ]");
  }
  
  TEST(DBTest, OverlapInLevel0) {
    do {
      ASSERT_EQ(config::kMaxMemCompactLevel, 2) << "Fix test to match config";
  
      // Fill levels 1 and 2 to disable the pushing of new memtables to levels > 0.
      ASSERT_OK(Put("100", "v100"));
      ASSERT_OK(Put("999", "v999"));
      dbfull()->TEST_CompactMemTable();
      ASSERT_OK(Delete("100"));
      ASSERT_OK(Delete("999"));
      dbfull()->TEST_CompactMemTable();
      ASSERT_EQ("0,1,1", FilesPerLevel());
  
      // Make files spanning the following ranges in level-0:
      //  files[0]  200 .. 900
      //  files[1]  300 .. 500
      // Note that files are sorted by smallest key.
      ASSERT_OK(Put("300", "v300"));
      ASSERT_OK(Put("500", "v500"));
      dbfull()->TEST_CompactMemTable();
      ASSERT_OK(Put("200", "v200"));
      ASSERT_OK(Put("600", "v600"));
      ASSERT_OK(Put("900", "v900"));
      dbfull()->TEST_CompactMemTable();
      ASSERT_EQ("2,1,1", FilesPerLevel());
  
      // Compact away the placeholder files we created initially
      dbfull()->TEST_CompactRange(1, NULL, NULL);
      dbfull()->TEST_CompactRange(2, NULL, NULL);
      ASSERT_EQ("2", FilesPerLevel());
  
      // Do a memtable compaction.  Before bug-fix, the compaction would
      // not detect the overlap with level-0 files and would incorrectly place
      // the deletion in a deeper level.
      ASSERT_OK(Delete("600"));
      dbfull()->TEST_CompactMemTable();
      ASSERT_EQ("3", FilesPerLevel());
      ASSERT_EQ("NOT_FOUND", Get("600"));
    } while (ChangeOptions());
  }
  
  TEST(DBTest, L0_CompactionBug_Issue44_a) {
    Reopen();
    ASSERT_OK(Put("b", "v"));
    Reopen();
    ASSERT_OK(Delete("b"));
    ASSERT_OK(Delete("a"));
    Reopen();
    ASSERT_OK(Delete("a"));
    Reopen();
    ASSERT_OK(Put("a", "v"));
    Reopen();
    Reopen();
    ASSERT_EQ("(a->v)", Contents());
    DelayMilliseconds(1000);  // Wait for compaction to finish
    ASSERT_EQ("(a->v)", Contents());
  }
  
  TEST(DBTest, L0_CompactionBug_Issue44_b) {
    Reopen();
    Put("","");
    Reopen();
    Delete("e");
    Put("","");
    Reopen();
    Put("c", "cv");
    Reopen();
    Put("","");
    Reopen();
    Put("","");
    DelayMilliseconds(1000);  // Wait for compaction to finish
    Reopen();
    Put("d","dv");
    Reopen();
    Put("","");
    Reopen();
    Delete("d");
    Delete("b");
    Reopen();
    ASSERT_EQ("(->)(c->cv)", Contents());
    DelayMilliseconds(1000);  // Wait for compaction to finish
    ASSERT_EQ("(->)(c->cv)", Contents());
  }
  
  TEST(DBTest, ComparatorCheck) {
    class NewComparator : public Comparator {
     public:
      virtual const char* Name() const { return "leveldb.NewComparator"; }
      virtual int Compare(const Slice& a, const Slice& b) const {
        return BytewiseComparator()->Compare(a, b);
      }
      virtual void FindShortestSeparator(std::string* s, const Slice& l) const {
        BytewiseComparator()->FindShortestSeparator(s, l);
      }
      virtual void FindShortSuccessor(std::string* key) const {
        BytewiseComparator()->FindShortSuccessor(key);
      }
    };
    NewComparator cmp;
    Options new_options = CurrentOptions();
    new_options.comparator = &cmp;
    Status s = TryReopen(&new_options);
    ASSERT_TRUE(!s.ok());
    ASSERT_TRUE(s.ToString().find("comparator") != std::string::npos)
        << s.ToString();
  }
  
  TEST(DBTest, CustomComparator) {
    class NumberComparator : public Comparator {
     public:
      virtual const char* Name() const { return "test.NumberComparator"; }
      virtual int Compare(const Slice& a, const Slice& b) const {
        return ToNumber(a) - ToNumber(b);
      }
      virtual void FindShortestSeparator(std::string* s, const Slice& l) const {
        ToNumber(*s);     // Check format
        ToNumber(l);      // Check format
      }
      virtual void FindShortSuccessor(std::string* key) const {
        ToNumber(*key);   // Check format
      }
     private:
      static int ToNumber(const Slice& x) {
        // Check that there are no extra characters.
        ASSERT_TRUE(x.size() >= 2 && x[0] == '[' && x[x.size()-1] == ']')
            << EscapeString(x);
        int val;
        char ignored;
        ASSERT_TRUE(sscanf(x.ToString().c_str(), "[%i]%c", &val, &ignored) == 1)
            << EscapeString(x);
        return val;
      }
    };
    NumberComparator cmp;
    Options new_options = CurrentOptions();
    new_options.create_if_missing = true;
    new_options.comparator = &cmp;
    new_options.filter_policy = NULL;     // Cannot use bloom filters
    new_options.write_buffer_size = 1000;  // Compact more often
    DestroyAndReopen(&new_options);
    ASSERT_OK(Put("[10]", "ten"));
    ASSERT_OK(Put("[0x14]", "twenty"));
    for (int i = 0; i < 2; i++) {
      ASSERT_EQ("ten", Get("[10]"));
      ASSERT_EQ("ten", Get("[0xa]"));
      ASSERT_EQ("twenty", Get("[20]"));
      ASSERT_EQ("twenty", Get("[0x14]"));
      ASSERT_EQ("NOT_FOUND", Get("[15]"));
      ASSERT_EQ("NOT_FOUND", Get("[0xf]"));
      Compact("[0]", "[9999]");
    }
  
    for (int run = 0; run < 2; run++) {
      for (int i = 0; i < 1000; i++) {
        char buf[100];
        snprintf(buf, sizeof(buf), "[%d]", i*10);
        ASSERT_OK(Put(buf, buf));
      }
      Compact("[0]", "[1000000]");
    }
  }
  
  TEST(DBTest, ManualCompaction) {
    ASSERT_EQ(config::kMaxMemCompactLevel, 2)
        << "Need to update this test to match kMaxMemCompactLevel";
  
    MakeTables(3, "p", "q");
    ASSERT_EQ("1,1,1", FilesPerLevel());
  
    // Compaction range falls before files
    Compact("", "c");
    ASSERT_EQ("1,1,1", FilesPerLevel());
  
    // Compaction range falls after files
    Compact("r", "z");
    ASSERT_EQ("1,1,1", FilesPerLevel());
  
    // Compaction range overlaps files
    Compact("p1", "p9");
    ASSERT_EQ("0,0,1", FilesPerLevel());
  
    // Populate a different range
    MakeTables(3, "c", "e");
    ASSERT_EQ("1,1,2", FilesPerLevel());
  
    // Compact just the new range
    Compact("b", "f");
    ASSERT_EQ("0,0,2", FilesPerLevel());
  
    // Compact all
    MakeTables(1, "a", "z");
    ASSERT_EQ("0,1,2", FilesPerLevel());
    db_->CompactRange(NULL, NULL);
    ASSERT_EQ("0,0,1", FilesPerLevel());
  }
  
  TEST(DBTest, DBOpen_Options) {
    std::string dbname = test::TmpDir() + "/db_options_test";
    DestroyDB(dbname, Options());
  
    // Does not exist, and create_if_missing == false: error
    DB* db = NULL;
    Options opts;
    opts.create_if_missing = false;
    Status s = DB::Open(opts, dbname, &db);
    ASSERT_TRUE(strstr(s.ToString().c_str(), "does not exist") != NULL);
    ASSERT_TRUE(db == NULL);
  
    // Does not exist, and create_if_missing == true: OK
    opts.create_if_missing = true;
    s = DB::Open(opts, dbname, &db);
    ASSERT_OK(s);
    ASSERT_TRUE(db != NULL);
  
    delete db;
    db = NULL;
  
    // Does exist, and error_if_exists == true: error
    opts.create_if_missing = false;
    opts.error_if_exists = true;
    s = DB::Open(opts, dbname, &db);
    ASSERT_TRUE(strstr(s.ToString().c_str(), "exists") != NULL);
    ASSERT_TRUE(db == NULL);
  
    // Does exist, and error_if_exists == false: OK
    opts.create_if_missing = true;
    opts.error_if_exists = false;
    s = DB::Open(opts, dbname, &db);
    ASSERT_OK(s);
    ASSERT_TRUE(db != NULL);
  
    delete db;
    db = NULL;
  }
  
  TEST(DBTest, Locking) {
    DB* db2 = NULL;
    Status s = DB::Open(CurrentOptions(), dbname_, &db2);
    ASSERT_TRUE(!s.ok()) << "Locking did not prevent re-opening db";
  }
  
  // Check that number of files does not grow when we are out of space
  TEST(DBTest, NoSpace) {
    Options options = CurrentOptions();
    options.env = env_;
    Reopen(&options);
  
    ASSERT_OK(Put("foo", "v1"));
    ASSERT_EQ("v1", Get("foo"));
    Compact("a", "z");
    const int num_files = CountFiles();
    env_->no_space_.Release_Store(env_);   // Force out-of-space errors
    for (int i = 0; i < 10; i++) {
      for (int level = 0; level < config::kNumLevels-1; level++) {
        dbfull()->TEST_CompactRange(level, NULL, NULL);
      }
    }
    env_->no_space_.Release_Store(NULL);
    ASSERT_LT(CountFiles(), num_files + 3);
  }
  
  TEST(DBTest, ExponentialBackoff) {
    Options options = CurrentOptions();
    options.env = env_;
    Reopen(&options);
  
    ASSERT_OK(Put("foo", "v1"));
    ASSERT_EQ("v1", Get("foo"));
    Compact("a", "z");
    env_->non_writable_.Release_Store(env_);  // Force errors for new files
    env_->sleep_counter_.Reset();
    env_->sleep_time_counter_.Reset();
    for (int i = 0; i < 5; i++) {
      dbfull()->TEST_CompactRange(2, NULL, NULL);
    }
    env_->non_writable_.Release_Store(NULL);
  
    // Wait for compaction to finish
    DelayMilliseconds(1000);
  
    ASSERT_GE(env_->sleep_counter_.Read(), 5);
    ASSERT_LT(env_->sleep_counter_.Read(), 10);
    ASSERT_GE(env_->sleep_time_counter_.Read(), 10e6);
  }
  
  TEST(DBTest, NonWritableFileSystem) {
    Options options = CurrentOptions();
    options.write_buffer_size = 1000;
    options.env = env_;
    Reopen(&options);
    ASSERT_OK(Put("foo", "v1"));
    env_->non_writable_.Release_Store(env_);  // Force errors for new files
    std::string big(100000, 'x');
    int errors = 0;
    for (int i = 0; i < 20; i++) {
      fprintf(stderr, "iter %d; errors %d\n", i, errors);
      if (!Put("foo", big).ok()) {
        errors++;
        DelayMilliseconds(100);
      }
    }
    ASSERT_GT(errors, 0);
    env_->non_writable_.Release_Store(NULL);
  }
  
  TEST(DBTest, WriteSyncError) {
    // Check that log sync errors cause the DB to disallow future writes.
  
    // (a) Cause log sync calls to fail
    Options options = CurrentOptions();
    options.env = env_;
    Reopen(&options);
    env_->data_sync_error_.Release_Store(env_);
  
    // (b) Normal write should succeed
    WriteOptions w;
    ASSERT_OK(db_->Put(w, "k1", "v1"));
    ASSERT_EQ("v1", Get("k1"));
  
    // (c) Do a sync write; should fail
    w.sync = true;
    ASSERT_TRUE(!db_->Put(w, "k2", "v2").ok());
    ASSERT_EQ("v1", Get("k1"));
    ASSERT_EQ("NOT_FOUND", Get("k2"));
  
    // (d) make sync behave normally
    env_->data_sync_error_.Release_Store(NULL);
  
    // (e) Do a non-sync write; should fail
    w.sync = false;
    ASSERT_TRUE(!db_->Put(w, "k3", "v3").ok());
    ASSERT_EQ("v1", Get("k1"));
    ASSERT_EQ("NOT_FOUND", Get("k2"));
    ASSERT_EQ("NOT_FOUND", Get("k3"));
  }
  
  TEST(DBTest, ManifestWriteError) {
    // Test for the following problem:
    // (a) Compaction produces file F
    // (b) Log record containing F is written to MANIFEST file, but Sync() fails
    // (c) GC deletes F
    // (d) After reopening DB, reads fail since deleted F is named in log record
  
    // We iterate twice.  In the second iteration, everything is the
    // same except the log record never makes it to the MANIFEST file.
    for (int iter = 0; iter < 2; iter++) {
      port::AtomicPointer* error_type = (iter == 0)
          ? &env_->manifest_sync_error_
          : &env_->manifest_write_error_;
  
      // Insert foo=>bar mapping
      Options options = CurrentOptions();
      options.env = env_;
      options.create_if_missing = true;
      options.error_if_exists = false;
      DestroyAndReopen(&options);
      ASSERT_OK(Put("foo", "bar"));
      ASSERT_EQ("bar", Get("foo"));
  
      // Memtable compaction (will succeed)
      dbfull()->TEST_CompactMemTable();
      ASSERT_EQ("bar", Get("foo"));
      const int last = config::kMaxMemCompactLevel;
      ASSERT_EQ(NumTableFilesAtLevel(last), 1);   // foo=>bar is now in last level
  
      // Merging compaction (will fail)
      error_type->Release_Store(env_);
      dbfull()->TEST_CompactRange(last, NULL, NULL);  // Should fail
      ASSERT_EQ("bar", Get("foo"));
  
      // Recovery: should not lose data
      error_type->Release_Store(NULL);
      Reopen(&options);
      ASSERT_EQ("bar", Get("foo"));
    }
  }
  
  TEST(DBTest, MissingSSTFile) {
    ASSERT_OK(Put("foo", "bar"));
    ASSERT_EQ("bar", Get("foo"));
  
    // Dump the memtable to disk.
    dbfull()->TEST_CompactMemTable();
    ASSERT_EQ("bar", Get("foo"));
  
    Close();
    ASSERT_TRUE(DeleteAnSSTFile());
    Options options = CurrentOptions();
    options.paranoid_checks = true;
    Status s = TryReopen(&options);
    ASSERT_TRUE(!s.ok());
    ASSERT_TRUE(s.ToString().find("issing") != std::string::npos)
        << s.ToString();
  }
  
  <<<<<<< HEAD
  =======
  TEST(DBTest, StillReadSST) {
    ASSERT_OK(Put("foo", "bar"));
    ASSERT_EQ("bar", Get("foo"));
  
    // Dump the memtable to disk.
    dbfull()->TEST_CompactMemTable();
    ASSERT_EQ("bar", Get("foo"));
    Close();
    ASSERT_GT(RenameLDBToSST(), 0);
    Options options = CurrentOptions();
    options.paranoid_checks = true;
    Status s = TryReopen(&options);
    ASSERT_TRUE(s.ok());
    ASSERT_EQ("bar", Get("foo"));
  }
  
  >>>>>>> 3b4ed770f88229b11bf62b90f128f3054b17ab36
  TEST(DBTest, FilesDeletedAfterCompaction) {
    ASSERT_OK(Put("foo", "v2"));
    Compact("a", "z");
    const int num_files = CountFiles();
    for (int i = 0; i < 10; i++) {
      ASSERT_OK(Put("foo", "v2"));
      Compact("a", "z");
    }
    ASSERT_EQ(CountFiles(), num_files);
  }
  
  TEST(DBTest, BloomFilter) {
    env_->count_random_reads_ = true;
    Options options = CurrentOptions();
    options.env = env_;
    options.block_cache = NewLRUCache(0);  // Prevent cache hits
    options.filter_policy = NewBloomFilterPolicy(10);
    Reopen(&options);
  
    // Populate multiple layers
    const int N = 10000;
    for (int i = 0; i < N; i++) {
      ASSERT_OK(Put(Key(i), Key(i)));
    }
    Compact("a", "z");
    for (int i = 0; i < N; i += 100) {
      ASSERT_OK(Put(Key(i), Key(i)));
    }
    dbfull()->TEST_CompactMemTable();
  
    // Prevent auto compactions triggered by seeks
    env_->delay_data_sync_.Release_Store(env_);
  
    // Lookup present keys.  Should rarely read from small sstable.
    env_->random_read_counter_.Reset();
    for (int i = 0; i < N; i++) {
      ASSERT_EQ(Key(i), Get(Key(i)));
    }
    int reads = env_->random_read_counter_.Read();
    fprintf(stderr, "%d present => %d reads\n", N, reads);
    ASSERT_GE(reads, N);
    ASSERT_LE(reads, N + 2*N/100);
  
    // Lookup present keys.  Should rarely read from either sstable.
    env_->random_read_counter_.Reset();
    for (int i = 0; i < N; i++) {
      ASSERT_EQ("NOT_FOUND", Get(Key(i) + ".missing"));
    }
    reads = env_->random_read_counter_.Read();
    fprintf(stderr, "%d missing => %d reads\n", N, reads);
    ASSERT_LE(reads, 3*N/100);
  
    env_->delay_data_sync_.Release_Store(NULL);
    Close();
    delete options.block_cache;
    delete options.filter_policy;
  }
  
  // Multi-threaded test:
  namespace {
  
  static const int kNumThreads = 4;
  static const int kTestSeconds = 10;
  static const int kNumKeys = 1000;
  
  struct MTState {
    DBTest* test;
    port::AtomicPointer stop;
    port::AtomicPointer counter[kNumThreads];
    port::AtomicPointer thread_done[kNumThreads];
  };
  
  struct MTThread {
    MTState* state;
    int id;
  };
  
  static void MTThreadBody(void* arg) {
    MTThread* t = reinterpret_cast<MTThread*>(arg);
    int id = t->id;
    DB* db = t->state->test->db_;
    uintptr_t counter = 0;
    fprintf(stderr, "... starting thread %d\n", id);
    Random rnd(1000 + id);
    std::string value;
    char valbuf[1500];
    while (t->state->stop.Acquire_Load() == NULL) {
      t->state->counter[id].Release_Store(reinterpret_cast<void*>(counter));
  
      int key = rnd.Uniform(kNumKeys);
      char keybuf[20];
      snprintf(keybuf, sizeof(keybuf), "%016d", key);
  
      if (rnd.OneIn(2)) {
        // Write values of the form <key, my id, counter>.
        // We add some padding for force compactions.
        snprintf(valbuf, sizeof(valbuf), "%d.%d.%-1000d",
                 key, id, static_cast<int>(counter));
        ASSERT_OK(db->Put(WriteOptions(), Slice(keybuf), Slice(valbuf)));
      } else {
        // Read a value and verify that it matches the pattern written above.
        Status s = db->Get(ReadOptions(), Slice(keybuf), &value);
        if (s.IsNotFound()) {
          // Key has not yet been written
        } else {
          // Check that the writer thread counter is >= the counter in the value
          ASSERT_OK(s);
          int k, w, c;
          ASSERT_EQ(3, sscanf(value.c_str(), "%d.%d.%d", &k, &w, &c)) << value;
          ASSERT_EQ(k, key);
          ASSERT_GE(w, 0);
          ASSERT_LT(w, kNumThreads);
          ASSERT_LE(static_cast<uintptr_t>(c), reinterpret_cast<uintptr_t>(
              t->state->counter[w].Acquire_Load()));
        }
      }
      counter++;
    }
    t->state->thread_done[id].Release_Store(t);
    fprintf(stderr, "... stopping thread %d after %d ops\n", id, int(counter));
  }
  
  }  // namespace
  
  TEST(DBTest, MultiThreaded) {
    do {
      // Initialize state
      MTState mt;
      mt.test = this;
      mt.stop.Release_Store(0);
      for (int id = 0; id < kNumThreads; id++) {
        mt.counter[id].Release_Store(0);
        mt.thread_done[id].Release_Store(0);
      }
  
      // Start threads
      MTThread thread[kNumThreads];
      for (int id = 0; id < kNumThreads; id++) {
        thread[id].state = &mt;
        thread[id].id = id;
        env_->StartThread(MTThreadBody, &thread[id]);
      }
  
      // Let them run for a while
      DelayMilliseconds(kTestSeconds * 1000);
  
      // Stop the threads and wait for them to finish
      mt.stop.Release_Store(&mt);
      for (int id = 0; id < kNumThreads; id++) {
        while (mt.thread_done[id].Acquire_Load() == NULL) {
          DelayMilliseconds(100);
        }
      }
    } while (ChangeOptions());
  }
  
  namespace {
  typedef std::map<std::string, std::string> KVMap;
  }
  
  class ModelDB: public DB {
   public:
    class ModelSnapshot : public Snapshot {
     public:
      KVMap map_;
    };
  
    explicit ModelDB(const Options& options): options_(options) { }
    ~ModelDB() { }
    virtual Status Put(const WriteOptions& o, const Slice& k, const Slice& v) {
      return DB::Put(o, k, v);
    }
    virtual Status Delete(const WriteOptions& o, const Slice& key) {
      return DB::Delete(o, key);
    }
    virtual Status Get(const ReadOptions& options,
                       const Slice& key, std::string* value) {
      assert(false);      // Not implemented
      return Status::NotFound(key);
    }
    virtual Iterator* NewIterator(const ReadOptions& options) {
      if (options.snapshot == NULL) {
        KVMap* saved = new KVMap;
        *saved = map_;
        return new ModelIter(saved, true);
      } else {
        const KVMap* snapshot_state =
            &(reinterpret_cast<const ModelSnapshot*>(options.snapshot)->map_);
        return new ModelIter(snapshot_state, false);
      }
    }
    virtual const Snapshot* GetSnapshot() {
      ModelSnapshot* snapshot = new ModelSnapshot;
      snapshot->map_ = map_;
      return snapshot;
    }
  
    virtual void ReleaseSnapshot(const Snapshot* snapshot) {
      delete reinterpret_cast<const ModelSnapshot*>(snapshot);
    }
    virtual Status Write(const WriteOptions& options, WriteBatch* batch) {
      class Handler : public WriteBatch::Handler {
       public:
        KVMap* map_;
        virtual void Put(const Slice& key, const Slice& value) {
          (*map_)[key.ToString()] = value.ToString();
        }
        virtual void Delete(const Slice& key) {
          map_->erase(key.ToString());
        }
      };
      Handler handler;
      handler.map_ = &map_;
      return batch->Iterate(&handler);
    }
  
    virtual bool GetProperty(const Slice& property, std::string* value) {
      return false;
    }
    virtual void GetApproximateSizes(const Range* r, int n, uint64_t* sizes) {
      for (int i = 0; i < n; i++) {
        sizes[i] = 0;
      }
    }
    virtual void CompactRange(const Slice* start, const Slice* end) {
    }
  
   private:
    class ModelIter: public Iterator {
     public:
      ModelIter(const KVMap* map, bool owned)
          : map_(map), owned_(owned), iter_(map_->end()) {
      }
      ~ModelIter() {
        if (owned_) delete map_;
      }
      virtual bool Valid() const { return iter_ != map_->end(); }
      virtual void SeekToFirst() { iter_ = map_->begin(); }
      virtual void SeekToLast() {
        if (map_->empty()) {
          iter_ = map_->end();
        } else {
          iter_ = map_->find(map_->rbegin()->first);
        }
      }
      virtual void Seek(const Slice& k) {
        iter_ = map_->lower_bound(k.ToString());
      }
      virtual void Next() { ++iter_; }
      virtual void Prev() { --iter_; }
      virtual Slice key() const { return iter_->first; }
      virtual Slice value() const { return iter_->second; }
      virtual Status status() const { return Status::OK(); }
     private:
      const KVMap* const map_;
      const bool owned_;  // Do we own map_
      KVMap::const_iterator iter_;
    };
    const Options options_;
    KVMap map_;
  };
  
  static std::string RandomKey(Random* rnd) {
    int len = (rnd->OneIn(3)
               ? 1                // Short sometimes to encourage collisions
               : (rnd->OneIn(100) ? rnd->Skewed(10) : rnd->Uniform(10)));
    return test::RandomKey(rnd, len);
  }
  
  static bool CompareIterators(int step,
                               DB* model,
                               DB* db,
                               const Snapshot* model_snap,
                               const Snapshot* db_snap) {
    ReadOptions options;
    options.snapshot = model_snap;
    Iterator* miter = model->NewIterator(options);
    options.snapshot = db_snap;
    Iterator* dbiter = db->NewIterator(options);
    bool ok = true;
    int count = 0;
    for (miter->SeekToFirst(), dbiter->SeekToFirst();
         ok && miter->Valid() && dbiter->Valid();
         miter->Next(), dbiter->Next()) {
      count++;
      if (miter->key().compare(dbiter->key()) != 0) {
        fprintf(stderr, "step %d: Key mismatch: '%s' vs. '%s'\n",
                step,
                EscapeString(miter->key()).c_str(),
                EscapeString(dbiter->key()).c_str());
        ok = false;
        break;
      }
  
      if (miter->value().compare(dbiter->value()) != 0) {
        fprintf(stderr, "step %d: Value mismatch for key '%s': '%s' vs. '%s'\n",
                step,
                EscapeString(miter->key()).c_str(),
                EscapeString(miter->value()).c_str(),
                EscapeString(miter->value()).c_str());
        ok = false;
      }
    }
  
    if (ok) {
      if (miter->Valid() != dbiter->Valid()) {
        fprintf(stderr, "step %d: Mismatch at end of iterators: %d vs. %d\n",
                step, miter->Valid(), dbiter->Valid());
        ok = false;
      }
    }
    fprintf(stderr, "%d entries compared: ok=%d\n", count, ok);
    delete miter;
    delete dbiter;
    return ok;
  }
  
  TEST(DBTest, Randomized) {
    Random rnd(test::RandomSeed());
    do {
      ModelDB model(CurrentOptions());
      const int N = 10000;
      const Snapshot* model_snap = NULL;
      const Snapshot* db_snap = NULL;
      std::string k, v;
      for (int step = 0; step < N; step++) {
        if (step % 100 == 0) {
          fprintf(stderr, "Step %d of %d\n", step, N);
        }
        // TODO(sanjay): Test Get() works
        int p = rnd.Uniform(100);
        if (p < 45) {                               // Put
          k = RandomKey(&rnd);
          v = RandomString(&rnd,
                           rnd.OneIn(20)
                           ? 100 + rnd.Uniform(100)
                           : rnd.Uniform(8));
          ASSERT_OK(model.Put(WriteOptions(), k, v));
          ASSERT_OK(db_->Put(WriteOptions(), k, v));
  
        } else if (p < 90) {                        // Delete
          k = RandomKey(&rnd);
          ASSERT_OK(model.Delete(WriteOptions(), k));
          ASSERT_OK(db_->Delete(WriteOptions(), k));
  
  
        } else {                                    // Multi-element batch
          WriteBatch b;
          const int num = rnd.Uniform(8);
          for (int i = 0; i < num; i++) {
            if (i == 0 || !rnd.OneIn(10)) {
              k = RandomKey(&rnd);
            } else {
              // Periodically re-use the same key from the previous iter, so
              // we have multiple entries in the write batch for the same key
            }
            if (rnd.OneIn(2)) {
              v = RandomString(&rnd, rnd.Uniform(10));
              b.Put(k, v);
            } else {
              b.Delete(k);
            }
          }
          ASSERT_OK(model.Write(WriteOptions(), &b));
          ASSERT_OK(db_->Write(WriteOptions(), &b));
        }
  
        if ((step % 100) == 0) {
          ASSERT_TRUE(CompareIterators(step, &model, db_, NULL, NULL));
          ASSERT_TRUE(CompareIterators(step, &model, db_, model_snap, db_snap));
          // Save a snapshot from each DB this time that we'll use next
          // time we compare things, to make sure the current state is
          // preserved with the snapshot
          if (model_snap != NULL) model.ReleaseSnapshot(model_snap);
          if (db_snap != NULL) db_->ReleaseSnapshot(db_snap);
  
          Reopen();
          ASSERT_TRUE(CompareIterators(step, &model, db_, NULL, NULL));
  
          model_snap = model.GetSnapshot();
          db_snap = db_->GetSnapshot();
        }
      }
      if (model_snap != NULL) model.ReleaseSnapshot(model_snap);
      if (db_snap != NULL) db_->ReleaseSnapshot(db_snap);
    } while (ChangeOptions());
  }
  
  std::string MakeKey(unsigned int num) {
    char buf[30];
    snprintf(buf, sizeof(buf), "%016u", num);
    return std::string(buf);
  }
  
  void BM_LogAndApply(int iters, int num_base_files) {
    std::string dbname = test::TmpDir() + "/leveldb_test_benchmark";
    DestroyDB(dbname, Options());
  
    DB* db = NULL;
    Options opts;
    opts.create_if_missing = true;
    Status s = DB::Open(opts, dbname, &db);
    ASSERT_OK(s);
    ASSERT_TRUE(db != NULL);
  
    delete db;
    db = NULL;
  
    Env* env = Env::Default();
  
    port::Mutex mu;
    MutexLock l(&mu);
  
    InternalKeyComparator cmp(BytewiseComparator());
    Options options;
    VersionSet vset(dbname, &options, NULL, &cmp);
    ASSERT_OK(vset.Recover());
    VersionEdit vbase;
    uint64_t fnum = 1;
    for (int i = 0; i < num_base_files; i++) {
      InternalKey start(MakeKey(2*fnum), 1, kTypeValue);
      InternalKey limit(MakeKey(2*fnum+1), 1, kTypeDeletion);
      vbase.AddFile(2, fnum++, 1 /* file size */, start, limit);
    }
    ASSERT_OK(vset.LogAndApply(&vbase, &mu));
  
    uint64_t start_micros = env->NowMicros();
  
    for (int i = 0; i < iters; i++) {
      VersionEdit vedit;
      vedit.DeleteFile(2, fnum);
      InternalKey start(MakeKey(2*fnum), 1, kTypeValue);
      InternalKey limit(MakeKey(2*fnum+1), 1, kTypeDeletion);
      vedit.AddFile(2, fnum++, 1 /* file size */, start, limit);
      vset.LogAndApply(&vedit, &mu);
    }
    uint64_t stop_micros = env->NowMicros();
    unsigned int us = stop_micros - start_micros;
    char buf[16];
    snprintf(buf, sizeof(buf), "%d", num_base_files);
    fprintf(stderr,
            "BM_LogAndApply/%-6s   %8d iters : %9u us (%7.0f us / iter)\n",
            buf, iters, us, ((float)us) / iters);
  }
  
  }  // namespace leveldb
  
  int main(int argc, char** argv) {
    if (argc > 1 && std::string(argv[1]) == "--benchmark") {
      leveldb::BM_LogAndApply(1000, 1);
      leveldb::BM_LogAndApply(1000, 100);
      leveldb::BM_LogAndApply(1000, 10000);
      leveldb::BM_LogAndApply(100, 100000);
      return 0;
    }
  
    return leveldb::test::RunAllTests();
  }
  