void StressTest::VerifyIterator()

in db_stress_tool/db_stress_test_base.cc [1257:1390]
110 lines of code
42 McCabe index (conditional complexity)

void StressTest::VerifyIterator(ThreadState* thread,
                                ColumnFamilyHandle* cmp_cfh,
                                const ReadOptions& ro, Iterator* iter,
                                Iterator* cmp_iter, LastIterateOp op,
                                const Slice& seek_key,
                                const std::string& op_logs, bool* diverged) {
  if (*diverged) {
    return;
  }

  if (op == kLastOpSeekToFirst && ro.iterate_lower_bound != nullptr) {
    // SeekToFirst() with lower bound is not well defined.
    *diverged = true;
    return;
  } else if (op == kLastOpSeekToLast && ro.iterate_upper_bound != nullptr) {
    // SeekToLast() with higher bound is not well defined.
    *diverged = true;
    return;
  } else if (op == kLastOpSeek && ro.iterate_lower_bound != nullptr &&
             (options_.comparator->CompareWithoutTimestamp(
                  *ro.iterate_lower_bound, /*a_has_ts=*/false, seek_key,
                  /*b_has_ts=*/false) >= 0 ||
              (ro.iterate_upper_bound != nullptr &&
               options_.comparator->CompareWithoutTimestamp(
                   *ro.iterate_lower_bound, /*a_has_ts=*/false,
                   *ro.iterate_upper_bound, /*b_has_ts*/ false) >= 0))) {
    // Lower bound behavior is not well defined if it is larger than
    // seek key or upper bound. Disable the check for now.
    *diverged = true;
    return;
  } else if (op == kLastOpSeekForPrev && ro.iterate_upper_bound != nullptr &&
             (options_.comparator->CompareWithoutTimestamp(
                  *ro.iterate_upper_bound, /*a_has_ts=*/false, seek_key,
                  /*b_has_ts=*/false) <= 0 ||
              (ro.iterate_lower_bound != nullptr &&
               options_.comparator->CompareWithoutTimestamp(
                   *ro.iterate_lower_bound, /*a_has_ts=*/false,
                   *ro.iterate_upper_bound, /*b_has_ts=*/false) >= 0))) {
    // Uppder bound behavior is not well defined if it is smaller than
    // seek key or lower bound. Disable the check for now.
    *diverged = true;
    return;
  }

  const SliceTransform* pe = (ro.total_order_seek || ro.auto_prefix_mode)
                                 ? nullptr
                                 : options_.prefix_extractor.get();
  const Comparator* cmp = options_.comparator;

  if (iter->Valid() && !cmp_iter->Valid()) {
    if (pe != nullptr) {
      if (!pe->InDomain(seek_key)) {
        // Prefix seek a non-in-domain key is undefined. Skip checking for
        // this scenario.
        *diverged = true;
        return;
      } else if (!pe->InDomain(iter->key())) {
        // out of range is iterator key is not in domain anymore.
        *diverged = true;
        return;
      } else if (pe->Transform(iter->key()) != pe->Transform(seek_key)) {
        *diverged = true;
        return;
      }
    }
    fprintf(stderr,
            "Control interator is invalid but iterator has key %s "
            "%s\n",
            iter->key().ToString(true).c_str(), op_logs.c_str());

    *diverged = true;
  } else if (cmp_iter->Valid()) {
    // Iterator is not valid. It can be legimate if it has already been
    // out of upper or lower bound, or filtered out by prefix iterator.
    const Slice& total_order_key = cmp_iter->key();

    if (pe != nullptr) {
      if (!pe->InDomain(seek_key)) {
        // Prefix seek a non-in-domain key is undefined. Skip checking for
        // this scenario.
        *diverged = true;
        return;
      }

      if (!pe->InDomain(total_order_key) ||
          pe->Transform(total_order_key) != pe->Transform(seek_key)) {
        // If the prefix is exhausted, the only thing needs to check
        // is the iterator isn't return a position in prefix.
        // Either way, checking can stop from here.
        *diverged = true;
        if (!iter->Valid() || !pe->InDomain(iter->key()) ||
            pe->Transform(iter->key()) != pe->Transform(seek_key)) {
          return;
        }
        fprintf(stderr,
                "Iterator stays in prefix but contol doesn't"
                " iterator key %s control iterator key %s %s\n",
                iter->key().ToString(true).c_str(),
                cmp_iter->key().ToString(true).c_str(), op_logs.c_str());
      }
    }
    // Check upper or lower bounds.
    if (!*diverged) {
      if ((iter->Valid() && iter->key() != cmp_iter->key()) ||
          (!iter->Valid() &&
           (ro.iterate_upper_bound == nullptr ||
            cmp->CompareWithoutTimestamp(total_order_key, /*a_has_ts=*/false,
                                         *ro.iterate_upper_bound,
                                         /*b_has_ts=*/false) < 0) &&
           (ro.iterate_lower_bound == nullptr ||
            cmp->CompareWithoutTimestamp(total_order_key, /*a_has_ts=*/false,
                                         *ro.iterate_lower_bound,
                                         /*b_has_ts=*/false) > 0))) {
        fprintf(stderr,
                "Iterator diverged from control iterator which"
                " has value %s %s\n",
                total_order_key.ToString(true).c_str(), op_logs.c_str());
        if (iter->Valid()) {
          fprintf(stderr, "iterator has value %s\n",
                  iter->key().ToString(true).c_str());
        } else {
          fprintf(stderr, "iterator is not valid\n");
        }
        *diverged = true;
      }
    }
  }
  if (*diverged) {
    fprintf(stderr, "Control CF %s\n", cmp_cfh->GetName().c_str());
    thread->stats.AddErrors(1);
    // Fail fast to preserve the DB state.
    thread->shared->SetVerificationFailure();
  }
}