Method PcUpdate

be/src/exprs/aggregate-functions-ir.cc:1528–1541

template<typename T>
void AggregateFunctions::PcUpdate(FunctionContext* c, const T& input, StringVal* dst) {
  DCHECK_EQ(dst->len, PC_INTERMEDIATE_BYTES);
  if (input.is_null) return;
  // Core of the algorithm. This is a direct translation of the code in the paper.
  // Please see the paper for details. For simple averaging, we need to compute hash
  // values NUM_PC_BITMAPS times using NUM_PC_BITMAPS different hash functions (by using a
  // different seed).
  for (int i = 0; i < NUM_PC_BITMAPS; ++i) {
    uint32_t hash_value = AnyValUtil::Hash(input, *c->GetArgType(0), i);
    const int bit_index = BitUtil::CountTrailingZeros(hash_value, PC_BITMAP_LENGTH - 1);
    // Set bitmap[i, bit_index] to 1
    SetDistinctEstimateBit(dst->ptr, i, bit_index);
  }
}

template<typename T>
void AggregateFunctions::PcsaUpdate(FunctionContext* c, const T& input, StringVal* dst) {