Method Concat

be/src/exprs/string-functions-ir.cc:1242–1276

NULL handling of function Concat and ConcatWs are different. Function concat was reimplemented to keep the original NULL handling.

// Function concat was reimplemented to keep the original
// NULL handling.
StringVal StringFunctions::Concat(
    FunctionContext* context, int num_children, const StringVal* strs) {
  DCHECK_GE(num_children, 1);
  DCHECK(strs != nullptr);
  // Pass through if there's only one argument.
  if (num_children == 1) return strs[0];

  // Loop once to compute the final size and reserve space.
  int64_t total_size = 0;
  for (int32_t i = 0; i < num_children; ++i) {
    if (strs[i].is_null) return StringVal::null();
    total_size += strs[i].len;
  }

  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 total_size is zero, directly returns empty string
  if (total_size <= 0) return StringVal();

  StringVal result(context, total_size);
  if (UNLIKELY(result.is_null)) return StringVal::null();

  // Loop again to append the data.
  uint8_t* ptr = result.ptr;
  for (int32_t i = 0; i < num_children; ++i) {
    Ubsan::MemCpy(ptr, strs[i].ptr, strs[i].len);
    ptr += strs[i].len;
  }
  return result;
}

StringVal StringFunctions::ConcatWs(FunctionContext* context, const StringVal& sep,
    int num_children, const StringVal* strs) {