Method SelectColumns

be/src/exec/orc/hdfs-orc-scanner.cc:711–758

}

Status HdfsOrcScanner::SelectColumns(const TupleDescriptor& tuple_desc) {
  list<const orc::Type*> selected_nodes;
  stack<const SlotDescriptor*> pos_slots;
  // Select columns for all non-position slots.
  RETURN_IF_ERROR(ResolveColumns(tuple_desc, &selected_nodes, &pos_slots));

  for (auto t : selected_nodes) selected_type_ids_.push_back(t->getColumnId());

  // Select columns for array positions. Due to ORC-450 we can't materialize array
  // offsets without materializing its items, so we should still select the item or any
  // sub column of the item. To be simple, we choose the max column id in the subtree
  // of the ARRAY node.
  // We process the deeper position slots first since it may introduce an item column
  // that can also serve the position slot of upper arrays. E.g. for 'array_col' as
  // array<struct<c1:int,c2:int,c3:array<int>>>, if both 'array_col.pos' and
  // 'array_col.item.c3.pos' are needed, we just need to select 'array_col.item.c3.item'
  // in the ORC lib, then we get offsets(indices) of both the inner and outer arrays.
  while (!pos_slots.empty()) {
    const SlotDescriptor* pos_slot_desc = pos_slots.top();
    pos_slots.pop();
    const orc::Type* array_node = nullptr;
    bool pos_field = false;
    bool missing_field = false;
    RETURN_IF_ERROR(schema_resolver_->ResolveColumn(pos_slot_desc->col_path(),
        &array_node, &pos_field, &missing_field));
    if (HasChildrenSelected(*array_node, selected_type_ids_)) continue;
    selected_type_ids_.push_back(array_node->getMaximumColumnId());
    VLOG(3) << "Add ORC column " << array_node->getMaximumColumnId() << " for "
        << PrintColPath(*scan_node_->hdfs_table(), pos_slot_desc->col_path(),
           schema_resolver_);
    selected_nodes.push_back(array_node);
  }

  // Select "CurrentTransaction" when we need to validate rows.
  if (row_batches_need_validation_) {
    // In case of zero-slot scans (e.g. count(*) over the table) we only select the
    // 'currentTransaction' column.
    if (scan_node_->IsZeroSlotTableScan()) selected_type_ids_.clear();
    if (std::find(selected_type_ids_.begin(), selected_type_ids_.end(),
        CURRENT_TRANSCACTION_TYPE_ID) == selected_type_ids_.end()) {
      selected_type_ids_.push_back(CURRENT_TRANSCACTION_TYPE_ID);
    }
  }

  COUNTER_SET(num_cols_counter_, static_cast<int64_t>(selected_type_ids_.size()));
  row_reader_options_.includeTypes(selected_type_ids_);
  return Status::OK();
}

Status HdfsOrcScanner::ProcessSplit() {
  DCHECK(scan_node_->HasRowBatchQueue());