during rename, we delete old key and create a new one in parallel, which affects transaction atomicity

[BorysTheDev]

we run next cb in parallel on 2 shards

void Renamer::FinalizeRename() {
  auto cb = [this](Transaction* t, EngineShard* shard) {
    const ShardId shard_id = shard->shard_id();

    if (!do_copy_ && shard_id == src_sid_) {
      return DelSrc(t, shard);
    }

    if (shard_id == dest_sid_) {
      return DeserializeDest(t, shard);
    }

    return OpStatus::OK;
  };

  transaction_->Execute(std::move(cb), true);
}

Consider next flow

DelSrc() -> success
DeserializeDest(t, shard); -> ERROR
but the source is already deleted, so we lost the data

[kostasrim]

Under what conditions can DeserializeDest fail ?

I don't think we have an atomicity problem here. We should lock both of the keys when we initialize the transaction and no other transaction shall access them until we conclude.

[BorysTheDev]

Under what conditions can DeserializeDest fail ?

I don't think we have an atomicity problem here. We should lock both of the keys when we initialize the transaction and no other transaction shall access them until we conclude.

Under current, or because of OOM, or something that we can not predict

Other transactions don't matter if DeserializeDest() fails, we lose data