add logs in return status

Signed-off-by: tabokie <xy.tao@outlook.com>

db/db_impl/db_impl_merge.cc

@@ -113,14 +113,29 @@ Status DBImpl::MergeDisjointInstances(const MergeInstanceOptions& merge_options,
  auto* comparator = this_cfd->user_comparator();
  using CfRange = std::pair<PinnableSlice, PinnableSlice>;
  std::vector<CfRange> db_ranges;
+ std::string ranges_str;
  auto process_cf = [&](ColumnFamilyData* cfd) {
  assert(cfd && s.ok());
  PinnableSlice smallest, largest;
  bool found = false;
+ // assert memtable is empty.
+ if (!merge_options.merge_memtable) {
+ cfd->GetMemtablesUserKeyRange(&smallest, &largest, &found);
+ if (found) {
+ s = Status::InvalidArgument(std::string("Memtable is not empty: ") +
+ smallest.ToString(true) + ", " +
+ largest.ToString(true));
+ return;
+ }
+ }
  s = cfd->GetUserKeyRange(&smallest, &largest, &found);
  if (s.ok() && found) {
+ ranges_str.append(smallest.ToString(true) + ", " +
+ largest.ToString(true) + ";");
  db_ranges.emplace_back(
  std::make_pair(std::move(smallest), std::move(largest)));
+ } else {
+ ranges_str.append("empty;");
  }
  };
  process_cf(this_cfd);
@@ -146,7 +161,8 @@ Status DBImpl::MergeDisjointInstances(const MergeInstanceOptions& merge_options,
  comparator->Compare(last_largest, range.first) < 0) {
  last_largest = range.second;
  } else {
- return Status::InvalidArgument("Source DBs have overlapping range");
+ return Status::InvalidArgument(
+ std::string("Source DBs have overlapping range: ") + ranges_str);
  }
  }
  }