Method FirstValUpdate

be/src/exprs/aggregate-functions-ir.cc:3601–3609

template <typename T>
void AggregateFunctions::FirstValUpdate(FunctionContext* ctx, const T& src, T* dst) {
  // The first call to FirstValUpdate sets the value of dst.
  if (ctx->impl()->num_updates() > 1) return;
  // num_updates is incremented before calling Update(), so it should never be 0.
  // Remove() should never be called for FIRST_VALUE.
  DCHECK_GT(ctx->impl()->num_updates(), 0);
  DCHECK_EQ(ctx->impl()->num_removes(), 0);
  *dst = src;
}

template <>
void AggregateFunctions::FirstValUpdate(FunctionContext* ctx, const StringVal& src,