Method DoReads

src/leveldb/db/autocompact_test.cc:59–104

Read through the first n keys repeatedly and check that they get compacted (verified by checking the size of the key space).

// Read through the first n keys repeatedly and check that they get
// compacted (verified by checking the size of the key space).
void AutoCompactTest::DoReads(int n) {
  std::string value(kValueSize, 'x');
  DBImpl* dbi = reinterpret_cast<DBImpl*>(db_);

  // Fill database
  for (int i = 0; i < kCount; i++) {
    ASSERT_OK(db_->Put(WriteOptions(), Key(i), value));
  }
  ASSERT_OK(dbi->TEST_CompactMemTable());

  // Delete everything
  for (int i = 0; i < kCount; i++) {
    ASSERT_OK(db_->Delete(WriteOptions(), Key(i)));
  }
  ASSERT_OK(dbi->TEST_CompactMemTable());

  // Get initial measurement of the space we will be reading.
  const int64_t initial_size = Size(Key(0), Key(n));
  const int64_t initial_other_size = Size(Key(n), Key(kCount));

  // Read until size drops significantly.
  std::string limit_key = Key(n);
  for (int read = 0; true; read++) {
    ASSERT_LT(read, 100) << "Taking too long to compact";
    Iterator* iter = db_->NewIterator(ReadOptions());
    for (iter->SeekToFirst();
         iter->Valid() && iter->key().ToString() < limit_key; iter->Next()) {
      // Drop data
    }
    delete iter;
    // Wait a little bit to allow any triggered compactions to complete.
    Env::Default()->SleepForMicroseconds(1000000);
    uint64_t size = Size(Key(0), Key(n));
    fprintf(stderr, "iter %3d => %7.3f MB [other %7.3f MB]\n", read + 1,
            size / 1048576.0, Size(Key(n), Key(kCount)) / 1048576.0);
    if (size <= initial_size / 10) {
      break;
    }
  }

  // Verify that the size of the key space not touched by the reads
  // is pretty much unchanged.
  const int64_t final_other_size = Size(Key(n), Key(kCount));
  ASSERT_LE(final_other_size, initial_other_size + 1048576);
  ASSERT_GE(final_other_size, initial_other_size / 5 - 1048576);
}

TEST(AutoCompactTest, ReadAll) { DoReads(kCount); }