aucahuasi commented on a change in pull request #11257:
URL: https://github.com/apache/arrow/pull/11257#discussion_r718535676
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File path: cpp/src/arrow/compute/kernels/aggregate_basic.cc
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@@ -121,6 +122,84 @@ Result<std::unique_ptr<KernelState>>
CountInit(KernelContext*,
static_cast<const CountOptions&>(*args.options));
}
+// ----------------------------------------------------------------------
+// Distinct Count implementation
+
+template <typename Type>
+struct CountDistinctImpl : public ScalarAggregator {
+ using MemoTable = typename arrow::internal::HashTraits<Type>::MemoTableType;
+
+ explicit CountDistinctImpl(MemoryPool* memory_pool, CountOptions options)
+ : options(std::move(options)), memo_table_(new MemoTable(memory_pool,
0)) {}
+
+ Status Consume(KernelContext*, const ExecBatch& batch) override {
+ if (batch[0].is_array()) {
+ const ArrayData& arr = *batch[0].array();
+ auto visit_null = [&]() {
+ if (this->nulls > 0) return Status::OK();
+ ++this->nulls;
+ return Status::OK();
+ };
+ auto visit_value = [&](typename Type::c_type arg) {
+ int y;
+ RETURN_NOT_OK(memo_table_->GetOrInsert(arg, &y));
+ return Status::OK();
+ };
+ RETURN_NOT_OK(VisitArrayDataInline<Type>(arr, visit_value, visit_null));
+ this->non_nulls += this->memo_table_->size();
+ } else {
+ const Scalar& input = *batch[0].scalar();
+ this->nulls += !input.is_valid * batch.length;
+ this->non_nulls += input.is_valid * batch.length;
+ }
+ return Status::OK();
+ }
+
+ Status MergeFrom(KernelContext*, KernelState&& src) override {
+ const auto& other_state = checked_cast<const CountDistinctImpl&>(src);
+ this->non_nulls += other_state.non_nulls;
+ this->nulls += other_state.nulls;
+ return Status::OK();
+ }
+
+ Status Finalize(KernelContext* ctx, Datum* out) override {
+ const auto& state = checked_cast<const CountDistinctImpl&>(*ctx->state());
+ switch (state.options.mode) {
+ case CountOptions::ONLY_VALID:
+ *out = Datum(state.non_nulls);
+ break;
+ case CountOptions::ALL:
+ *out = Datum(state.non_nulls + state.nulls);
+ break;
+ case CountOptions::ONLY_NULL:
+ *out = Datum(state.nulls);
+ break;
+ default:
+ DCHECK(false) << "unreachable";
+ }
+ return Status::OK();
+ }
+
+ CountOptions options;
+ int64_t non_nulls = 0;
Review comment:
Thanks, I did that for my first local version. I changed it to have more
similar implementation to count, but I think it wasn't the best choice.
Let me improve this part!
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