Method ConcatWs

be/src/exprs/string-functions-ir.cc:1278–1336

}

StringVal StringFunctions::ConcatWs(FunctionContext* context, const StringVal& sep,
    int num_children, const StringVal* strs) {
  DCHECK_GE(num_children, 1);
  DCHECK(strs != nullptr);
  if (sep.is_null) return StringVal::null();

  // Loop once to compute valid start index, final string size and valid string object
  // count.
  int32_t valid_num_children = 0;
  int32_t valid_start_index = -1;
  int64_t total_size = 0;
  for (int32_t i = 0; i < num_children; ++i) {
    if (strs[i].is_null) continue;

    if (valid_start_index == -1) {
      valid_start_index = i;
      // Calculate the space required by first valid string object.
      total_size += strs[i].len;
    } else {
      // Calculate the space required by subsequent valid string object.
      total_size += sep.len + strs[i].len;
    }
    // Record the count of valid string object.
    valid_num_children++;
  }

  if (total_size > StringVal::MAX_LENGTH) {
    context->SetError(Substitute(ERROR_CHARACTER_LIMIT_EXCEEDED,
        "Concatenated string length",
        PrettyPrinter::Print(StringVal::MAX_LENGTH, TUnit::BYTES)).c_str());
    return StringVal::null();
  }

  // If all data are invalid, or data size is zero, return empty string.
  if (valid_start_index < 0 || total_size <= 0) {
    return StringVal();
  }
  DCHECK_GT(valid_num_children, 0);

  // Pass through if there's only one argument.
  if (valid_num_children == 1) return strs[valid_start_index];

  // Reserve space needed by final result.
  StringVal result(context, total_size);
  if (UNLIKELY(result.is_null)) return StringVal::null();

  // Loop to append the data.
  uint8_t* ptr = result.ptr;
  Ubsan::MemCpy(ptr, strs[valid_start_index].ptr, strs[valid_start_index].len);
  ptr += strs[valid_start_index].len;
  for (int32_t i = valid_start_index + 1; i < num_children; ++i) {
    if (strs[i].is_null) continue;
    Ubsan::MemCpy(ptr, sep.ptr, sep.len);
    ptr += sep.len;
    Ubsan::MemCpy(ptr, strs[i].ptr, strs[i].len);
    ptr += strs[i].len;
  }
  return result;