Method Open

be/src/exec/system-table-scanner.cc:125–166

      {}

Status QueryScanner::Open() {
  ImpalaServer* server = ExecEnv::GetInstance()->impala_server();

  // Get a sorted list of state snapshots for all active queries. This mimics the
  // behavior of ImpalaHttpHandler::QueryStateHandler. Using snapshots avoids potential
  // memory violations of trying to use a ClientRequestState pointer without holding a
  // shared_ptr to the QueryDriver and avoids keeping the query open longer than
  // necessary (via that shared_ptr). The cost is that we allocate memory for the
  // QueryStateRecords, which should be relatively small.
  {
    SCOPED_TIMER(active_query_collection_timer_);
    server->query_driver_map_.DoFuncForAllEntries(
        [&](const std::shared_ptr<QueryDriver>& query_driver) {
          query_records_.emplace_back(make_shared<QueryStateExpanded>(
              *query_driver->GetActiveClientRequestState()));
        });
  }

  unordered_set<TUniqueId> running_queries;
  running_queries.reserve(query_records_.size());
  for (const auto& r : query_records_) {
    running_queries.insert(r->base_state->id);
  }

  // It's possible for a query to appear in both query_driver_map_ and completed_queries_
  // if it's been added to completed_queries_ in CloseClientRequestState and has not yet
  // been removed from query_driver_map_ in QueryDriver::Unregister. Collection order
  // ensures we don't miss one by collecting before it's been added to completed_queries_,
  // then after it's added to completed_queries_ and removed from query_driver_map_.
  // Avoid adding entries if they already exist.
  {
    SCOPED_TIMER(pending_query_collection_timer_);
    for (const auto& r : server->GetCompletedQueries()) {
      if (running_queries.find(r->base_state->id) == running_queries.end()) {
        query_records_.emplace_back(r);
      }
    }
  }

  if (query_records_.empty()) eos_ = true;
  return Status::OK();
}

static void WriteEvent(const QueryStateExpanded& query, const SlotDescriptor* slot_desc,
    void* slot, QueryEvent name) {