pitrou commented on a change in pull request #11152:
URL: https://github.com/apache/arrow/pull/11152#discussion_r709906988
##########
File path: cpp/src/arrow/compute/kernels/aggregate_basic.cc
##########
@@ -282,6 +282,43 @@ Result<std::unique_ptr<KernelState>>
MinMaxInit(KernelContext* ctx,
return visitor.Create();
}
+// For "min" and "max" functions: dispatch to the MinMax kernel.
+Result<std::unique_ptr<KernelState>> MinOrMaxInit(KernelContext* ctx,
+ const KernelInitArgs& args) {
+ std::vector<ValueDescr> inputs = args.inputs;
+
+ ARROW_ASSIGN_OR_RAISE(auto func,
GetFunctionRegistry()->GetFunction("min_max"));
Review comment:
For the record, it's a bit of a pity to do a second registry lookup when
arriving here.
##########
File path: cpp/src/arrow/compute/kernels/aggregate_basic.cc
##########
@@ -282,6 +282,43 @@ Result<std::unique_ptr<KernelState>>
MinMaxInit(KernelContext* ctx,
return visitor.Create();
}
+// For "min" and "max" functions: dispatch to the MinMax kernel.
+Result<std::unique_ptr<KernelState>> MinOrMaxInit(KernelContext* ctx,
+ const KernelInitArgs& args) {
+ std::vector<ValueDescr> inputs = args.inputs;
+
+ ARROW_ASSIGN_OR_RAISE(auto func,
GetFunctionRegistry()->GetFunction("min_max"));
+ ARROW_ASSIGN_OR_RAISE(auto kernel, func->DispatchBest(&inputs));
+
+ KernelInitArgs new_args{kernel, inputs, args.options};
+ return kernel->init(ctx, new_args);
+}
+
+// For "min" and "max" functions: override finalize and return the actual value
+template <MinOrMax min_or_max>
+void AddMinOrMaxAggKernel(ScalarAggregateFunction* func) {
+ auto sig = KernelSignature::Make(
+ {InputType(ValueDescr::ANY)},
+ OutputType([](KernelContext*,
+ const std::vector<ValueDescr>& descrs) ->
Result<ValueDescr> {
+ // any[T] -> scalar[T]
+ return ValueDescr::Scalar(descrs.front().type);
+ }));
+
+ auto finalize = [](KernelContext* ctx, Datum* out) -> Status {
+ Datum temp;
+ RETURN_NOT_OK(checked_cast<ScalarAggregator*>(ctx->state())->Finalize(ctx,
&temp));
+ *out =
temp.scalar_as<StructScalar>().value[static_cast<uint8_t>(min_or_max)];
Review comment:
DCHECK that the result is valid?
##########
File path: docs/source/cpp/compute.rst
##########
@@ -198,6 +198,10 @@ the input to a single output value.
+---------------+-------+-------------+------------------------+----------------------------------+-------+
| mean | Unary | Numeric | Scalar Decimal/Float64 |
:struct:`ScalarAggregateOptions` | |
+---------------+-------+-------------+------------------------+----------------------------------+-------+
+| max | Unary | Numeric | Scalar Struct |
:struct:`ScalarAggregateOptions` | |
Review comment:
"max" before "mean"
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