edponce commented on a change in pull request #11045:
URL: https://github.com/apache/arrow/pull/11045#discussion_r699859608
##########
File path: cpp/src/arrow/compute/kernels/scalar_cast_numeric.cc
##########
@@ -391,6 +391,49 @@ struct CastFunctor<O, I,
}
};
+// ----------------------------------------------------------------------
+// Integer to decimal
+
+struct IntegerToDecimal {
+ template <typename OutValue, typename IntegerType>
+ OutValue Call(KernelContext*, IntegerType val, Status* st) const {
+ auto maybe_decimal = OutValue(val).Rescale(0, out_scale_);
+ if (ARROW_PREDICT_TRUE(maybe_decimal.ok())) {
+ return maybe_decimal.MoveValueUnsafe();
+ }
+ *st = maybe_decimal.status();
+ return OutValue{};
Review comment:
Nit: Other casting kernels simply use
```c++
return {}; // zero
```
##########
File path: cpp/src/arrow/compute/kernels/scalar_cast_numeric.cc
##########
@@ -391,6 +391,49 @@ struct CastFunctor<O, I,
}
};
+// ----------------------------------------------------------------------
+// Integer to decimal
+
+struct IntegerToDecimal {
+ template <typename OutValue, typename IntegerType>
+ OutValue Call(KernelContext*, IntegerType val, Status* st) const {
+ auto maybe_decimal = OutValue(val).Rescale(0, out_scale_);
+ if (ARROW_PREDICT_TRUE(maybe_decimal.ok())) {
+ return maybe_decimal.MoveValueUnsafe();
+ }
+ *st = maybe_decimal.status();
+ return OutValue{};
+ }
+
+ int32_t out_scale_;
+};
+
+template <typename O, typename I>
+struct CastFunctor<O, I,
+ enable_if_t<is_decimal_type<O>::value &&
is_integer_type<I>::value>> {
+ static Status Exec(KernelContext* ctx, const ExecBatch& batch, Datum* out) {
+ const auto& out_type = checked_cast<const O&>(*out->type());
+ const auto out_scale = out_type.scale();
+ const auto out_precision = out_type.precision();
+
+ // verify precision and scale
+ if (out_scale < 0) {
+ return Status::Invalid("Scale must be non-negative");
+ }
+ // maximal number of decimal digits for int8/16/32/64
+ constexpr std::array<int, 4> decimal_digits{3, 5, 10, 19};
Review comment:
Since `decimal_digits` is a constant array, I would make it a `static`
data member of `CastFunctor`. Also, you can use a standard array where the size
would be implicit and is more lightweight than `std::array`:
```c++
static constexpr int decimal_digits[]{3,5, 10, 19};
```
##########
File path: cpp/src/arrow/compute/kernels/scalar_cast_numeric.cc
##########
@@ -641,6 +684,12 @@ std::shared_ptr<CastFunction> GetCastToDecimal128() {
DCHECK_OK(func->AddKernel(Type::DOUBLE, {float64()}, sig_out_ty,
CastFunctor<Decimal128Type, DoubleType>::Exec));
+ // Cast from integer
+ for (const std::shared_ptr<DataType>& in_ty : IntTypes()) {
+ auto exec = GenerateInteger<CastFunctor, Decimal128Type>(in_ty->id());
+ DCHECK_OK(func->AddKernel(in_ty->id(), {in_ty}, sig_out_ty,
std::move(exec)));
+ }
Review comment:
No need to `std::move(exec)` as it is already an rvalue (function
pointer).
##########
File path: cpp/src/arrow/compute/kernels/scalar_cast_numeric.cc
##########
@@ -664,6 +713,12 @@ std::shared_ptr<CastFunction> GetCastToDecimal256() {
DCHECK_OK(func->AddKernel(Type::DOUBLE, {float64()}, sig_out_ty,
CastFunctor<Decimal256Type, DoubleType>::Exec));
+ // Cast from integer
+ for (const std::shared_ptr<DataType>& in_ty : IntTypes()) {
+ auto exec = GenerateInteger<CastFunctor, Decimal256Type>(in_ty->id());
+ DCHECK_OK(func->AddKernel(in_ty->id(), {in_ty}, sig_out_ty,
std::move(exec)));
+ }
Review comment:
Same here, no need to `std::move(exec)`
##########
File path: cpp/src/arrow/compute/kernels/scalar_cast_numeric.cc
##########
@@ -391,6 +391,49 @@ struct CastFunctor<O, I,
}
};
+// ----------------------------------------------------------------------
+// Integer to decimal
+
+struct IntegerToDecimal {
+ template <typename OutValue, typename IntegerType>
+ OutValue Call(KernelContext*, IntegerType val, Status* st) const {
+ auto maybe_decimal = OutValue(val).Rescale(0, out_scale_);
+ if (ARROW_PREDICT_TRUE(maybe_decimal.ok())) {
+ return maybe_decimal.MoveValueUnsafe();
+ }
+ *st = maybe_decimal.status();
+ return OutValue{};
+ }
+
+ int32_t out_scale_;
+};
+
+template <typename O, typename I>
+struct CastFunctor<O, I,
+ enable_if_t<is_decimal_type<O>::value &&
is_integer_type<I>::value>> {
+ static Status Exec(KernelContext* ctx, const ExecBatch& batch, Datum* out) {
+ const auto& out_type = checked_cast<const O&>(*out->type());
+ const auto out_scale = out_type.scale();
+ const auto out_precision = out_type.precision();
+
+ // verify precision and scale
+ if (out_scale < 0) {
+ return Status::Invalid("Scale must be non-negative");
+ }
+ // maximal number of decimal digits for int8/16/32/64
+ constexpr std::array<int, 4> decimal_digits{3, 5, 10, 19};
Review comment:
Agree, local variable is better in this scenario.
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