bkietz commented on a change in pull request #10390:
URL: https://github.com/apache/arrow/pull/10390#discussion_r639136875
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File path: cpp/src/arrow/compute/kernels/scalar_arithmetic.cc
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@@ -516,6 +562,202 @@ std::shared_ptr<ScalarFunction>
MakeUnarySignedArithmeticFunctionNotNull(
return func;
}
+using MinMaxState = OptionsWrapper<ElementWiseAggregateOptions>;
+
+// Implement a variadic scalar min/max kernel.
+template <typename OutType, typename Op>
+struct ScalarMinMax {
+ using OutValue = typename GetOutputType<OutType>::T;
+
+ static void ExecScalar(const ExecBatch& batch,
+ const ElementWiseAggregateOptions& options, Scalar*
out) {
+ // All arguments are scalar
+ OutValue value{};
+ bool valid = false;
+ for (const auto& arg : batch.values) {
+ // Ignore non-scalar arguments so we can use it in the
mixed-scalar-and-array case
+ if (!arg.is_scalar()) continue;
+ const auto& scalar = *arg.scalar();
+ if (!scalar.is_valid) {
+ if (options.skip_nulls) continue;
+ out->is_valid = false;
+ return;
+ }
+ if (!valid) {
+ value = UnboxScalar<OutType>::Unbox(scalar);
+ valid = true;
+ } else {
+ value = Op::Call(value, UnboxScalar<OutType>::Unbox(scalar));
+ }
+ }
+ out->is_valid = valid;
+ if (valid) {
+ BoxScalar<OutType>::Box(value, out);
+ }
+ }
+
+ static Status Exec(KernelContext* ctx, const ExecBatch& batch, Datum* out) {
+ const ElementWiseAggregateOptions& options = MinMaxState::Get(ctx);
+ const auto descrs = batch.GetDescriptors();
+ bool all_scalar = true;
+ bool any_scalar = false;
+ size_t first_array_index = batch.values.size();
+ for (size_t i = 0; i < batch.values.size(); i++) {
+ const auto& datum = batch.values[i];
+ all_scalar &= datum.descr().shape == ValueDescr::SCALAR;
+ any_scalar |= datum.descr().shape == ValueDescr::SCALAR;
+ if (first_array_index >= batch.values.size() &&
+ datum.descr().shape == ValueDescr::ARRAY) {
+ first_array_index = i;
+ }
+ }
+ if (all_scalar) {
+ ExecScalar(batch, options, out->scalar().get());
+ return Status::OK();
+ }
+
+ ArrayData* output = out->mutable_array();
+
+ // Exactly one array (output = input)
+ if (batch.values.size() == 1) {
+ *output = *batch[0].array();
+ return Status::OK();
+ }
+
+ // At least one array, two or more arguments
+ DCHECK_GE(first_array_index, 0);
+ DCHECK_LT(first_array_index, batch.values.size());
+ DCHECK(batch.values[first_array_index].is_array());
+ if (any_scalar) {
Review comment:
Handling scalars should happen before the output == input bail. If the
folded scalar is null then we can either ignore it (skip_nulls=true) or emit a
null array without examining any array inputs (skip_nulls=false). After that
we're guaranteed to have a valid scalar (for which MakeArrayFromScalar will not
materialize a validity bitmap, so you can drop the BitmapXor etc)
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