bkietz commented on a change in pull request #8894:
URL: https://github.com/apache/arrow/pull/8894#discussion_r552835857
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File path: cpp/src/arrow/compute/kernels/scalar_cast_temporal.cc
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@@ -256,14 +251,47 @@ struct CastFunctor<Date64Type, Date32Type> {
template <>
struct CastFunctor<Date32Type, Date64Type> {
static void Exec(KernelContext* ctx, const ExecBatch& batch, Datum* out) {
- // TODO: Make this work on scalar inputs
DCHECK_EQ(batch[0].kind(), Datum::ARRAY);
ShiftTime<int64_t, int32_t>(ctx, util::DIVIDE, kMillisecondsInDay,
*batch[0].array(),
out->mutable_array());
}
};
+// ----------------------------------------------------------------------
+// date32, date64 to timestamp
+
+template <>
+struct CastFunctor<TimestampType, Date32Type> {
+ static void Exec(KernelContext* ctx, const ExecBatch& batch, Datum* out) {
+ DCHECK_EQ(batch[0].kind(), Datum::ARRAY);
+
+ const auto& out_type = checked_cast<const TimestampType&>(*out->type());
+ // get conversion SECOND -> unit
+ auto conversion = util::GetTimestampConversion(TimeUnit::SECOND,
out_type.unit());
+ DCHECK_EQ(conversion.first, util::MULTIPLY);
+
+ // multiply to achieve days -> unit
+ conversion.second *= kMillisecondsInDay / 1000;
+ ShiftTime<int32_t, int64_t>(ctx, util::MULTIPLY, conversion.second,
*batch[0].array(),
+ out->mutable_array());
+ }
+};
+
+template <>
+struct CastFunctor<TimestampType, Date64Type> {
+ static void Exec(KernelContext* ctx, const ExecBatch& batch, Datum* out) {
+ DCHECK_EQ(batch[0].kind(), Datum::ARRAY);
+
+ const auto& out_type = checked_cast<const TimestampType&>(*out->type());
+
+ // date64 is ms since epoch
+ auto conversion = util::GetTimestampConversion(TimeUnit::MILLI,
out_type.unit());
+ ShiftTime<int64_t, int64_t>(ctx, conversion.first, conversion.second,
+ *batch[0].array(), out->mutable_array());
Review comment:
There is a fast path for this.
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