Method HllUpdate

be/src/exprs/aggregate-functions-ir.cc:2139–2156

// Always inline in IR so that constants can be replaced.
template <typename T>
IR_ALWAYS_INLINE void AggregateFunctions::HllUpdate(
    FunctionContext* ctx, const T& src, StringVal* dst, int precision) {
  if (src.is_null) return;
  DCHECK(!dst->is_null);

  const int& hll_len = dst->len;
  DCHECK_IN_RANGE(hll_len, MIN_HLL_LEN, MAX_HLL_LEN);

  uint64_t hash_value =
      AnyValUtil::Hash64(src, *ctx->GetArgType(0), HashUtil::FNV64_SEED);
  // Use the lower bits to index into the number of streams and then find the first 1 bit
  // after the index bits.
  int idx = hash_value & (hll_len - 1);
  const uint8_t first_one_bit = 1
      + BitUtil::CountTrailingZeros(
            hash_value >> precision, sizeof(hash_value) * CHAR_BIT - precision);
  dst->ptr[idx] = ::max(dst->ptr[idx], first_one_bit);
}

// Update function for NDV() that accepts an expression only.
template <typename T>