Ah - the Result<T> is for error handling. So either: 1) Return arrow::Status from this function, and use the ARROW_ASSIGN_OR_RAISE macro:
ARROW_ASSIGN_OR_RAISE(auto scalar, arrow::MakeScalar(...)); ..., cp::literal(std::move(scalar)) ... 2) For experimentation purposes, just assume it'll succeed: ..., cp::literal(*arrow::MakeScalar(...)) ... 3) Directly construct the right scalar (https://github.com/apache/arrow/blob/master/cpp/src/arrow/scalar.h#L340): ..., cp::literal(std::make_shared<arrow::Time64Scalar>(time, TimeUnit::NANO)) ... -David On Mon, Feb 7, 2022, at 12:23, Li Jin wrote: > So I think I am getting close... now I have > > cp::Expression predicate = cp::call( > "equal", > {...} > > cp::literal(arrow::MakeScalar(arrow::time64(arrow::TimeUnit::NANO), time))} > ); > > And got > > /usr/include/arrow/compute/exec/expression.h:143:18: error: no matching > conversion for functional-style cast from > 'arrow::Result<std::shared_ptr<arrow::Scalar>>' to 'arrow::Datum' > return literal(Datum(std::forward<Arg>(arg))); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ > /home/icexelloss/workspace/bamboo-streaming/examples/msw_filter_time.cc:66:44: > note: in instantiation of function template > specialization > 'arrow::compute::literal<arrow::Result<std::shared_ptr<arrow::Scalar>>>' > requested here > > cp::literal(arrow::MakeScalar(arrow::time64(arrow::TimeUnit::NANO), time))} > > Any help / pointers are much appreciated! > > On Mon, Feb 7, 2022 at 12:13 PM Li Jin <ice.xell...@gmail.com> wrote: > >> Another question - what is the correct way of creating a constant Scalar >> that represents a time64 from a string in C++ (e.g. "10:00:00") ? >> >> I am trying to use cp::literal(arrow::MakeScalar(...)) but not sure what >> to fill in the body of MakeScalar >> >> On Mon, Feb 7, 2022 at 12:05 PM Li Jin <ice.xell...@gmail.com> wrote: >> >>> Hello, >>> >>> Did some more work on this. Follow up question on this: >>> >>> I am doing a >>> >>> {cp::call("cast", >>> >>> {cp::field_ref("time_ns")}, >>> >>> cp::CastOptions::Safe(arrow::timestamp(arrow::TimeUnit::NANO, timezone)))}, >>> >>> And got: >>> >>> NotImplemented: Unsupported cast from uint64 to timestamp using function >>> cast_timestamp >>> >>> Is this the wrong way to convert uint64 to timestamp or is it just not >>> supported right now? >>> >>> On Thu, Feb 3, 2022 at 12:29 PM Rok Mihevc <rok.mih...@gmail.com> wrote: >>> >>>> By the way - if you're extracting components to segment time you might >>>> prefer temporal rounding >>>> >>>> https://arrow.apache.org/docs/dev/cpp/compute.html?highlight=floor_temporal#conversions >>>> . >>>> >>>> On Thu, Feb 3, 2022 at 5:19 PM Li Jin <ice.xell...@gmail.com> wrote: >>>> > >>>> > Gotcha. Thanks for the pointer! >>>> > >>>> > On Thu, Feb 3, 2022 at 11:06 AM Rok Mihevc <rok.mih...@gmail.com> >>>> wrote: >>>> > >>>> > > > Gotcha. "Assume timezone" is like "tz_localize" in pandas. >>>> > > >>>> > > Indeed! >>>> > > >>>> > > > I didn't see any target timezone information being passed in the >>>> "cast" >>>> > > > function - how would I do that? >>>> > > >>>> > > Just cast with: >>>> > > auto options = CastOptions::Safe(timestamp(TimeUnit::NANO, >>>> > > "America/New_York")); >>>> > > See examples in: >>>> > > >>>> > > >>>> https://github.com/apache/arrow/blob/master/cpp/src/arrow/compute/kernels/scalar_cast_test.cc >>>> > > >>>> >>>
