Method InitTupleBuffer

be/src/exec/hdfs-scanner.h:637–664

Initialize a dense array of 'num_tuples' tuples. TODO: we could do better here if we inlined the tuple and null indicator byte widths with codegen to eliminate all the branches in memcpy()/memset().

  /// TODO: we could do better here if we inlined the tuple and null indicator byte
  /// widths with codegen to eliminate all the branches in memcpy()/memset().
  void InitTupleBuffer(
      Tuple* template_tuple, uint8_t* __restrict__ tuple_mem, int64_t num_tuples) {
    const TupleDescriptor* desc = scan_node_->tuple_desc();
    const int tuple_byte_size = desc->byte_size();
    // Handle the different template/non-template cases with different loops to avoid
    // unnecessary branches inside the loop.
    if (template_tuple != nullptr) {
      for (int64_t i = 0; i < num_tuples; ++i) {
        InitTupleFromTemplate(
            template_tuple, reinterpret_cast<Tuple*>(tuple_mem), tuple_byte_size);
        tuple_mem += tuple_byte_size;
      }
    } else if (tuple_byte_size <= CACHELINE_SIZE) {
      // If each tuple fits in a cache line, it is quicker to zero the whole memory buffer
      // instead of just the null indicators. This is because we are fetching the cache
      // line anyway and zeroing a cache line is cheap (a couple of AVX2 instructions)
      // compared with the overhead of calling memset() row-by-row.
      memset(tuple_mem, 0, num_tuples * tuple_byte_size);
    } else {
      const int null_bytes_offset = desc->null_bytes_offset();
      const int num_null_bytes = desc->num_null_bytes();
      for (int64_t i = 0; i < num_tuples; ++i) {
        reinterpret_cast<Tuple*>(tuple_mem)->ClearNullBits(
            null_bytes_offset, num_null_bytes);
        tuple_mem += tuple_byte_size;
      }
    }
  }

  /// Returns true iff 'template_tuple' is non-NULL.
  /// Not inlined in IR so it can be replaced with a constant.