[GitHub] [arrow] lidavidm commented on a change in pull request #12124: ARROW-14093: [C++] subtract(date, date) -> duration kernel

[GitBox <gi...@apache.org>]

lidavidm commented on a change in pull request #12124:
URL: https://github.com/apache/arrow/pull/12124#discussion_r796630304



##########
File path: cpp/src/arrow/compute/kernels/scalar_arithmetic.cc
##########
@@ -1611,6 +1636,23 @@ Result<ValueDescr> ResolveDecimalDivisionOutput(KernelContext*,
       });
 }
 
+Result<ValueDescr> ResolveTemporalOutput(KernelContext*,
+                                         const std::vector<ValueDescr>& args) {
+  auto left_type = checked_cast<const TimestampType*>(args[0].type.get());
+  auto right_type = checked_cast<const TimestampType*>(args[1].type.get());
+  DCHECK_EQ(left_type->id(), right_type->id());
+
+  if ((left_type->timezone() == "" || right_type->timezone() == "") &&
+      left_type->timezone() != right_type->timezone()) {
+    RETURN_NOT_OK(
+        Status::Invalid("Subtraction of zoned and non-zoned times is ambivalent. (",
+                        left_type->timezone(), right_type->timezone(), ")."));
+  }
+
+  auto type = duration(std::max(left_type->unit(), right_type->unit()));

Review comment:
       nit, but as used, the units should always match right?

##########
File path: cpp/src/arrow/compute/kernels/scalar_arithmetic.cc
##########
@@ -2437,14 +2462,35 @@ void RegisterScalarArithmetic(FunctionRegistry* registry) {
                                   std::move(exec)));
   }
 
+  // Add subtract(date32, date32) -> duration(TimeUnit::SECOND)
+  InputType in_type_date_32(date32());
+  auto exec_date_32 = ScalarBinaryEqualTypes<Int64Type, Date32Type, SubtractDate32>::Exec;
+  DCHECK_OK(subtract->AddKernel({in_type_date_32, in_type_date_32},
+                                duration(TimeUnit::SECOND), std::move(exec_date_32)));
+
+  // Add subtract(date64, date64) -> duration(TimeUnit::MILLI)
+  InputType in_type_date_64(date64());
+  auto exec_date_64 = ScalarBinaryEqualTypes<Int64Type, Date64Type, Subtract>::Exec;
+  DCHECK_OK(subtract->AddKernel({in_type_date_64, in_type_date_64},
+                                duration(TimeUnit::MILLI), std::move(exec_date_64)));
+
   DCHECK_OK(registry->AddFunction(std::move(subtract)));
 
   // ----------------------------------------------------------------------
   auto subtract_checked = MakeArithmeticFunctionNotNull<SubtractChecked>(
       "subtract_checked", &sub_checked_doc);
   AddDecimalBinaryKernels<SubtractChecked>("subtract_checked", subtract_checked.get());
 
-  // Add subtract(timestamp, duration) -> timestamp
+  // Add subtract_checked(timestamp, timestamp) -> duration
+  for (auto unit : TimeUnit::values()) {
+    InputType in_type(match::TimestampTypeUnit(unit));

Review comment:
       Looks good to me, thanks.

##########
File path: cpp/src/arrow/compute/kernels/scalar_arithmetic.cc
##########
@@ -1611,6 +1636,23 @@ Result<ValueDescr> ResolveDecimalDivisionOutput(KernelContext*,
       });
 }
 
+Result<ValueDescr> ResolveTemporalOutput(KernelContext*,
+                                         const std::vector<ValueDescr>& args) {
+  auto left_type = checked_cast<const TimestampType*>(args[0].type.get());
+  auto right_type = checked_cast<const TimestampType*>(args[1].type.get());
+  DCHECK_EQ(left_type->id(), right_type->id());
+
+  if ((left_type->timezone() == "" || right_type->timezone() == "") &&
+      left_type->timezone() != right_type->timezone()) {
+    RETURN_NOT_OK(
+        Status::Invalid("Subtraction of zoned and non-zoned times is ambivalent. (",

Review comment:
       nit: "ambiguous" or "undefined"?




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