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ARROW-14827: [C++] Temporal component extraction function for extracting dst indicator #12370

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ARROW-14827: [C++] Temporal component extraction function for extracting dst indicator #12370

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1 change: 1 addition & 0 deletions cpp/src/arrow/compute/api_scalar.cc
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Expand Up @@ -773,6 +773,7 @@ SCALAR_EAGER_UNARY(Day, "day")
SCALAR_EAGER_UNARY(DayOfYear, "day_of_year")
SCALAR_EAGER_UNARY(Hour, "hour")
SCALAR_EAGER_UNARY(YearMonthDay, "year_month_day")
SCALAR_EAGER_UNARY(IsDaylightSavings, "is_dst")
SCALAR_EAGER_UNARY(ISOCalendar, "iso_calendar")
SCALAR_EAGER_UNARY(ISOWeek, "iso_week")
SCALAR_EAGER_UNARY(ISOYear, "iso_year")
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12 changes: 12 additions & 0 deletions cpp/src/arrow/compute/api_scalar.h
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Expand Up @@ -1374,6 +1374,18 @@ ARROW_EXPORT Result<Datum> AssumeTimezone(const Datum& values,
AssumeTimezoneOptions options,
ExecContext* ctx = NULLPTR);

/// \brief IsDaylightSavings extracts if currently observing daylight savings for each
/// element of `values`
///
/// \param[in] values input to extract daylight savings indicator from
/// \param[in] ctx the function execution context, optional
/// \return the resulting datum
///
/// \since 8.0.0
/// \note API not yet finalized
ARROW_EXPORT Result<Datum> IsDaylightSavings(const Datum& values,
ExecContext* ctx = NULLPTR);

/// \brief Finds either the FIRST, LAST, or ALL items with a key that matches the given
/// query key in a map.
///
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11 changes: 11 additions & 0 deletions cpp/src/arrow/compute/kernels/scalar_temporal_test.cc
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Expand Up @@ -475,6 +475,8 @@ TEST_F(ScalarTemporalTest, TestTemporalComponentExtractionWithDifferentUnits) {
year_month_day);
CheckScalarUnary("day_of_week", unit, times_seconds_precision, int64(), day_of_week);
CheckScalarUnary("day_of_year", unit, times_seconds_precision, int64(), day_of_year);
ASSERT_RAISES(Invalid,
IsDaylightSavings(ArrayFromJSON(unit, times_seconds_precision)));
CheckScalarUnary("iso_year", unit, times_seconds_precision, int64(), iso_year);
CheckScalarUnary("iso_week", unit, times_seconds_precision, int64(), iso_week);
CheckScalarUnary("us_week", unit, times_seconds_precision, int64(), us_week);
Expand Down Expand Up @@ -570,6 +572,9 @@ TEST_F(ScalarTemporalTest, TestZoned1) {
auto day_of_week = "[2, 1, 5, 1, 1, 0, 6, 2, 3, 5, 6, 5, 5, 5, 6, 5, null]";
auto day_of_year =
"[365, 60, 365, 137, 365, 364, 363, 364, 365, 2, 3, 365, 365, 362, 363, 365, null]";
std::string is_dst =
"[false, false, false, false, false, false, false, false, false, false, false, "
"false, false, false, false, false, null]";
auto iso_year =
"[1970, 2000, 1898, 2033, 2020, 2020, 2019, 2009, 2009, 2009, 2009, 2005, 2005, "
"2008, 2008, 2011, null]";
Expand Down Expand Up @@ -604,6 +609,7 @@ TEST_F(ScalarTemporalTest, TestZoned1) {
CheckScalarUnary("year_month_day", ArrayFromJSON(unit, times), year_month_day);
CheckScalarUnary("day_of_week", unit, times, int64(), day_of_week);
CheckScalarUnary("day_of_year", unit, times, int64(), day_of_year);
CheckScalarUnary("is_dst", unit, times, boolean(), is_dst);
CheckScalarUnary("iso_year", unit, times, int64(), iso_year);
CheckScalarUnary("iso_week", unit, times, int64(), iso_week);
CheckScalarUnary("us_week", unit, times, int64(), us_week);
Expand Down Expand Up @@ -644,6 +650,9 @@ TEST_F(ScalarTemporalTest, TestZoned2) {
auto day_of_week = "[3, 2, 6, 2, 2, 1, 0, 3, 4, 6, 0, 6, 5, 6, 0, 6, null]";
auto day_of_year =
"[1, 61, 1, 138, 1, 365, 364, 365, 1, 3, 4, 1, 365, 363, 364, 1, null]";
std::string is_dst =
"[false, true, false, false, true, true, true, true, true, true, true, true, "
"true, true, true, true, null]";
auto iso_year =
"[1970, 2000, 1898, 2033, 2020, 2020, 2020, 2009, 2009, 2009, 2010, 2005, 2005, "
"2008, 2009, 2011, null]";
Expand Down Expand Up @@ -679,6 +688,7 @@ TEST_F(ScalarTemporalTest, TestZoned2) {
year_month_day);
CheckScalarUnary("day_of_week", unit, times_seconds_precision, int64(), day_of_week);
CheckScalarUnary("day_of_year", unit, times_seconds_precision, int64(), day_of_year);
CheckScalarUnary("is_dst", unit, times_seconds_precision, boolean(), is_dst);
CheckScalarUnary("iso_year", unit, times_seconds_precision, int64(), iso_year);
CheckScalarUnary("iso_week", unit, times_seconds_precision, int64(), iso_week);
CheckScalarUnary("us_week", unit, times_seconds_precision, int64(), us_week);
Expand Down Expand Up @@ -710,6 +720,7 @@ TEST_F(ScalarTemporalTest, TestNonexistentTimezone) {
ASSERT_RAISES(Invalid, YearMonthDay(timestamp_array));
ASSERT_RAISES(Invalid, DayOfWeek(timestamp_array));
ASSERT_RAISES(Invalid, DayOfYear(timestamp_array));
ASSERT_RAISES(Invalid, IsDaylightSavings(timestamp_array));
ASSERT_RAISES(Invalid, ISOYear(timestamp_array));
ASSERT_RAISES(Invalid, Week(timestamp_array));
ASSERT_RAISES(Invalid, ISOCalendar(timestamp_array));
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51 changes: 50 additions & 1 deletion cpp/src/arrow/compute/kernels/scalar_temporal_unary.cc
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Expand Up @@ -48,7 +48,6 @@ using arrow_vendored::date::Monday;
using arrow_vendored::date::months;
using arrow_vendored::date::round;
using arrow_vendored::date::Sunday;
using arrow_vendored::date::sys_days;
using arrow_vendored::date::sys_time;
using arrow_vendored::date::trunc;
using arrow_vendored::date::weekday;
Expand Down Expand Up @@ -133,6 +132,26 @@ struct AssumeTimezoneExtractor
}
};

template <template <typename...> class Op, typename Duration, typename InType,
typename OutType>
struct DaylightSavingsExtractor
: public TemporalComponentExtractBase<Op, Duration, InType, OutType> {
using Base = TemporalComponentExtractBase<Op, Duration, InType, OutType>;

static Status Exec(KernelContext* ctx, const ExecBatch& batch, Datum* out) {
const auto& timezone = GetInputTimezone(batch.values[0]);
if (timezone.empty()) {
return Status::Invalid("Timestamps have no timezone. Cannot determine DST.");
}
ARROW_ASSIGN_OR_RAISE(auto tz, LocateZone(timezone));
using ExecTemplate = Op<Duration>;
auto op = ExecTemplate(nullptr, tz);
applicator::ScalarUnaryNotNullStateful<OutType, TimestampType, ExecTemplate> kernel{
op};
return kernel.Exec(ctx, batch, out);
}
};

template <template <typename...> class Op, typename Duration, typename InType,
typename OutType>
struct TemporalComponentExtractWeek
Expand Down Expand Up @@ -603,6 +622,22 @@ struct Nanosecond {
}
};

// ----------------------------------------------------------------------
// Extract if currently observing daylight savings

template <typename Duration>
struct IsDaylightSavings {
explicit IsDaylightSavings(const FunctionOptions* options, const time_zone* tz)
: tz_(tz) {}

template <typename T, typename Arg0>
T Call(KernelContext*, Arg0 arg, Status*) const {
return tz_->get_info(sys_time<Duration>{Duration{arg}}).save.count() != 0;
}

const time_zone* tz_;
};

// ----------------------------------------------------------------------
// Round temporal values to given frequency

Expand Down Expand Up @@ -1444,6 +1479,14 @@ const FunctionDoc assume_timezone_doc{
"AssumeTimezoneOptions",
/*options_required=*/true};

const FunctionDoc is_dst_doc{
"Extracts if currently observing daylight savings",
("IsDaylightSavings returns true if a timestamp has a daylight saving\n"
"offset in the given timezone.\n"
"Null values emit null.\n"
"An error is returned if the values do not have a defined timezone."),
{"values"}};

const FunctionDoc floor_temporal_doc{
"Round temporal values down to nearest multiple of specified time unit",
("Null values emit null.\n"
Expand Down Expand Up @@ -1607,6 +1650,12 @@ void RegisterScalarTemporalUnary(FunctionRegistry* registry) {
&assume_timezone_doc, nullptr, AssumeTimezoneState::Init);
DCHECK_OK(registry->AddFunction(std::move(assume_timezone)));

auto is_dst =
UnaryTemporalFactory<IsDaylightSavings, DaylightSavingsExtractor,
BooleanType>::Make<WithTimestamps>("is_dst", boolean(),
&is_dst_doc);
DCHECK_OK(registry->AddFunction(std::move(is_dst)));

// Temporal rounding functions
static const auto default_round_temporal_options = RoundTemporalOptions::Defaults();
auto floor_temporal = UnaryTemporalFactory<FloorTemporal, TemporalComponentExtractRound,
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2 changes: 2 additions & 0 deletions docs/source/cpp/compute.rst
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Expand Up @@ -1382,6 +1382,8 @@ For timestamps inputs with non-empty timezone, localized timestamp components wi
+--------------------+------------+-------------------+---------------+----------------------------+-------+
| hour | Unary | Timestamp, Time | Int64 | | |
+--------------------+------------+-------------------+---------------+----------------------------+-------+
| is_dst | Unary | Timestamp | Boolean | | |
+--------------------+------------+-------------------+---------------+----------------------------+-------+
| iso_week | Unary | Temporal | Int64 | | \(2) |
+--------------------+------------+-------------------+---------------+----------------------------+-------+
| iso_year | Unary | Temporal | Int64 | | \(2) |
Expand Down