pitrou commented on code in PR #14753:
URL: https://github.com/apache/arrow/pull/14753#discussion_r1039786012
##########
cpp/src/arrow/compute/kernels/vector_sort_internal.h:
##########
@@ -456,6 +458,402 @@ Status SortChunkedArray(ExecContext* ctx, uint64_t*
indices_begin, uint64_t* ind
const ChunkedArray& values, SortOrder sort_order,
NullPlacement null_placement);
+// ----------------------------------------------------------------------
+// Helpers for Sort/SelectK implementations
+
+struct SortField {
+ int field_index;
+ SortOrder order;
+};
+
+inline Status CheckNonNested(const FieldRef& ref) {
+ if (ref.IsNested()) {
+ return Status::KeyError("Nested keys not supported for SortKeys");
+ }
+ return Status::OK();
+}
+
+template <typename T>
+Result<T> PrependInvalidColumn(Result<T> res) {
+ if (res.ok()) return res;
+ return res.status().WithMessage("Invalid sort key column: ",
res.status().message());
+}
+
+// Return the field indices of the sort keys, deduplicating them along the way
+inline Result<std::vector<SortField>> FindSortKeys(
Review Comment:
The definition for this can be moved in a `.cc` file IMHO.
##########
cpp/src/arrow/compute/kernels/vector_sort_internal.h:
##########
@@ -456,6 +458,402 @@ Status SortChunkedArray(ExecContext* ctx, uint64_t*
indices_begin, uint64_t* ind
const ChunkedArray& values, SortOrder sort_order,
NullPlacement null_placement);
+// ----------------------------------------------------------------------
+// Helpers for Sort/SelectK implementations
+
+struct SortField {
+ int field_index;
+ SortOrder order;
+};
+
+inline Status CheckNonNested(const FieldRef& ref) {
+ if (ref.IsNested()) {
+ return Status::KeyError("Nested keys not supported for SortKeys");
+ }
+ return Status::OK();
+}
+
+template <typename T>
+Result<T> PrependInvalidColumn(Result<T> res) {
+ if (res.ok()) return res;
+ return res.status().WithMessage("Invalid sort key column: ",
res.status().message());
+}
+
+// Return the field indices of the sort keys, deduplicating them along the way
+inline Result<std::vector<SortField>> FindSortKeys(
+ const Schema& schema, const std::vector<SortKey>& sort_keys) {
+ std::vector<SortField> fields;
+ std::unordered_set<int> seen;
+ fields.reserve(sort_keys.size());
+ seen.reserve(sort_keys.size());
+
+ for (const auto& sort_key : sort_keys) {
+ RETURN_NOT_OK(CheckNonNested(sort_key.target));
+
+ ARROW_ASSIGN_OR_RAISE(auto match,
+
PrependInvalidColumn(sort_key.target.FindOne(schema)));
+ if (seen.insert(match[0]).second) {
+ fields.push_back({match[0], sort_key.order});
+ }
+ }
+ return fields;
+}
+
+template <typename ResolvedSortKey, typename ResolvedSortKeyFactory>
+Result<std::vector<ResolvedSortKey>> ResolveSortKeys(
+ const Schema& schema, const std::vector<SortKey>& sort_keys,
+ ResolvedSortKeyFactory&& factory) {
+ ARROW_ASSIGN_OR_RAISE(const auto fields, FindSortKeys(schema, sort_keys));
+ std::vector<ResolvedSortKey> resolved;
+ resolved.reserve(fields.size());
+ std::transform(fields.begin(), fields.end(), std::back_inserter(resolved),
factory);
+ return resolved;
+}
+
+template <typename ResolvedSortKey, typename TableOrBatch>
+Result<std::vector<ResolvedSortKey>> ResolveSortKeys(
+ const TableOrBatch& table_or_batch, const std::vector<SortKey>& sort_keys)
{
+ return ResolveSortKeys<ResolvedSortKey>(
+ *table_or_batch.schema(), sort_keys, [&](const SortField& f) {
+ return ResolvedSortKey{table_or_batch.column(f.field_index), f.order};
+ });
+}
+
+// Returns nullptr if no column matching `ref` is found, or if the FieldRef is
+// a nested reference.
+inline std::shared_ptr<ChunkedArray> GetTableColumn(const Table& table,
+ const FieldRef& ref) {
+ if (ref.IsNested()) return nullptr;
+
+ if (auto name = ref.name()) {
+ return table.GetColumnByName(*name);
+ }
+
+ auto index = ref.field_path()->indices()[0];
+ if (index >= table.num_columns()) return nullptr;
+ return table.column(index);
+}
+
+// We could try to reproduce the concrete Array classes' facilities
+// (such as cached raw values pointer) in a separate hierarchy of
+// physical accessors, but doing so ends up too cumbersome.
+// Instead, we simply create the desired concrete Array objects.
+inline std::shared_ptr<Array> GetPhysicalArray(
+ const Array& array, const std::shared_ptr<DataType>& physical_type) {
+ auto new_data = array.data()->Copy();
+ new_data->type = physical_type;
+ return MakeArray(std::move(new_data));
+}
+
+inline ArrayVector GetPhysicalChunks(const ArrayVector& chunks,
+ const std::shared_ptr<DataType>&
physical_type) {
+ ArrayVector physical(chunks.size());
+ std::transform(chunks.begin(), chunks.end(), physical.begin(),
+ [&](const std::shared_ptr<Array>& array) {
+ return GetPhysicalArray(*array, physical_type);
+ });
+ return physical;
+}
+
+inline ArrayVector GetPhysicalChunks(const ChunkedArray& chunked_array,
+ const std::shared_ptr<DataType>&
physical_type) {
+ return GetPhysicalChunks(chunked_array.chunks(), physical_type);
+}
+
+// Compare two records in a single column (either from a batch or table)
+template <typename ResolvedSortKey>
+struct ColumnComparator {
+ using Location = typename ResolvedSortKey::LocationType;
+
+ ColumnComparator(const ResolvedSortKey& sort_key, NullPlacement
null_placement)
+ : sort_key_(sort_key), null_placement_(null_placement) {}
+
+ virtual ~ColumnComparator() = default;
+
+ virtual int Compare(const Location& left, const Location& right) const = 0;
+
+ ResolvedSortKey sort_key_;
+ NullPlacement null_placement_;
+};
+
+template <typename ResolvedSortKey, typename Type>
+struct ConcreteColumnComparator : public ColumnComparator<ResolvedSortKey> {
+ using ArrayType = typename TypeTraits<Type>::ArrayType;
+ using Location = typename ResolvedSortKey::LocationType;
+
+ using ColumnComparator<ResolvedSortKey>::ColumnComparator;
+
+ int Compare(const Location& left, const Location& right) const override {
+ const auto& sort_key = this->sort_key_;
+
+ const auto chunk_left = sort_key.template GetChunk<ArrayType>(left);
+ const auto chunk_right = sort_key.template GetChunk<ArrayType>(right);
+ if (sort_key.null_count > 0) {
+ const bool is_null_left = chunk_left.IsNull();
+ const bool is_null_right = chunk_right.IsNull();
+ if (is_null_left && is_null_right) {
+ return 0;
+ } else if (is_null_left) {
+ return this->null_placement_ == NullPlacement::AtStart ? -1 : 1;
+ } else if (is_null_right) {
+ return this->null_placement_ == NullPlacement::AtStart ? 1 : -1;
+ }
+ }
+ return CompareTypeValues<Type>(chunk_left.Value(), chunk_right.Value(),
+ sort_key.order, this->null_placement_);
+ }
+};
+
+template <typename ResolvedSortKey>
+struct ConcreteColumnComparator<ResolvedSortKey, NullType>
+ : public ColumnComparator<ResolvedSortKey> {
+ using Location = typename ResolvedSortKey::LocationType;
+
+ using ColumnComparator<ResolvedSortKey>::ColumnComparator;
+
+ int Compare(const Location& left, const Location& right) const override {
return 0; }
+};
+
+// Compare two records in the same RecordBatch or Table
+// (indexing is handled through ResolvedSortKey)
+template <typename ResolvedSortKey>
+class MultipleKeyComparator {
+ public:
+ using Location = typename ResolvedSortKey::LocationType;
+
+ MultipleKeyComparator(const std::vector<ResolvedSortKey>& sort_keys,
+ NullPlacement null_placement)
+ : sort_keys_(sort_keys), null_placement_(null_placement) {
+ status_ &= MakeComparators();
+ }
+
+ Status status() const { return status_; }
+
+ // Returns true if the left-th value should be ordered before the
+ // right-th value, false otherwise. The start_sort_key_index-th
+ // sort key and subsequent sort keys are used for comparison.
+ bool Compare(const Location& left, const Location& right, size_t
start_sort_key_index) {
+ return CompareInternal(left, right, start_sort_key_index) < 0;
+ }
+
+ bool Equals(const Location& left, const Location& right, size_t
start_sort_key_index) {
+ return CompareInternal(left, right, start_sort_key_index) == 0;
+ }
+
+ private:
+ struct ColumnComparatorFactory {
+#define VISIT(TYPE) \
+ Status Visit(const TYPE& type) { return VisitGeneric(type); }
+
+ VISIT_SORTABLE_PHYSICAL_TYPES(VISIT)
+ VISIT(NullType)
+
+#undef VISIT
+
+ Status Visit(const DataType& type) {
+ return Status::TypeError("Unsupported type for batch or table sorting: ",
+ type.ToString());
+ }
+
+ template <typename Type>
+ Status VisitGeneric(const Type& type) {
+ res.reset(
+ new ConcreteColumnComparator<ResolvedSortKey, Type>{sort_key,
null_placement});
+ return Status::OK();
+ }
+
+ const ResolvedSortKey& sort_key;
+ NullPlacement null_placement;
+ std::unique_ptr<ColumnComparator<ResolvedSortKey>> res;
+ };
+
+ Status MakeComparators() {
+ column_comparators_.reserve(sort_keys_.size());
+
+ for (const auto& sort_key : sort_keys_) {
+ ColumnComparatorFactory factory{sort_key, null_placement_, nullptr};
+ RETURN_NOT_OK(VisitTypeInline(*sort_key.type, &factory));
+ column_comparators_.push_back(std::move(factory.res));
+ }
+ return Status::OK();
+ }
+
+ // Compare two records in the same table and return -1, 0 or 1.
+ //
+ // -1: The left is less than the right.
+ // 0: The left equals to the right.
+ // 1: The left is greater than the right.
+ //
+ // This supports null and NaN. Null is processed in this and NaN
+ // is processed in CompareTypeValue().
+ int CompareInternal(const Location& left, const Location& right,
+ size_t start_sort_key_index) {
+ const auto num_sort_keys = sort_keys_.size();
+ for (size_t i = start_sort_key_index; i < num_sort_keys; ++i) {
+ const int r = column_comparators_[i]->Compare(left, right);
+ if (r != 0) {
+ return r;
+ }
+ }
+ return 0;
+ }
+
+ const std::vector<ResolvedSortKey>& sort_keys_;
+ const NullPlacement null_placement_;
+ std::vector<std::unique_ptr<ColumnComparator<ResolvedSortKey>>>
column_comparators_;
+ Status status_;
+};
+
+// Sort a batch using a single sort and multiple-key comparisons.
+class MultipleKeyRecordBatchSorter : public TypeVisitor {
Review Comment:
I'm not sure it's useful to expose this internal class in a `.h` file? By
the looks of it, only `MultipleKeyRecordBatchSorter::ResolvedSortKey` is used
by the select-k kernels?
##########
cpp/src/arrow/compute/kernels/vector_sort_internal.h:
##########
@@ -456,6 +458,402 @@ Status SortChunkedArray(ExecContext* ctx, uint64_t*
indices_begin, uint64_t* ind
const ChunkedArray& values, SortOrder sort_order,
NullPlacement null_placement);
+// ----------------------------------------------------------------------
+// Helpers for Sort/SelectK implementations
+
+struct SortField {
+ int field_index;
+ SortOrder order;
+};
+
+inline Status CheckNonNested(const FieldRef& ref) {
+ if (ref.IsNested()) {
+ return Status::KeyError("Nested keys not supported for SortKeys");
+ }
+ return Status::OK();
+}
+
+template <typename T>
+Result<T> PrependInvalidColumn(Result<T> res) {
+ if (res.ok()) return res;
+ return res.status().WithMessage("Invalid sort key column: ",
res.status().message());
+}
+
+// Return the field indices of the sort keys, deduplicating them along the way
+inline Result<std::vector<SortField>> FindSortKeys(
+ const Schema& schema, const std::vector<SortKey>& sort_keys) {
+ std::vector<SortField> fields;
+ std::unordered_set<int> seen;
+ fields.reserve(sort_keys.size());
+ seen.reserve(sort_keys.size());
+
+ for (const auto& sort_key : sort_keys) {
+ RETURN_NOT_OK(CheckNonNested(sort_key.target));
+
+ ARROW_ASSIGN_OR_RAISE(auto match,
+
PrependInvalidColumn(sort_key.target.FindOne(schema)));
+ if (seen.insert(match[0]).second) {
+ fields.push_back({match[0], sort_key.order});
+ }
+ }
+ return fields;
+}
+
+template <typename ResolvedSortKey, typename ResolvedSortKeyFactory>
+Result<std::vector<ResolvedSortKey>> ResolveSortKeys(
+ const Schema& schema, const std::vector<SortKey>& sort_keys,
+ ResolvedSortKeyFactory&& factory) {
+ ARROW_ASSIGN_OR_RAISE(const auto fields, FindSortKeys(schema, sort_keys));
+ std::vector<ResolvedSortKey> resolved;
+ resolved.reserve(fields.size());
+ std::transform(fields.begin(), fields.end(), std::back_inserter(resolved),
factory);
+ return resolved;
+}
+
+template <typename ResolvedSortKey, typename TableOrBatch>
+Result<std::vector<ResolvedSortKey>> ResolveSortKeys(
+ const TableOrBatch& table_or_batch, const std::vector<SortKey>& sort_keys)
{
+ return ResolveSortKeys<ResolvedSortKey>(
+ *table_or_batch.schema(), sort_keys, [&](const SortField& f) {
+ return ResolvedSortKey{table_or_batch.column(f.field_index), f.order};
+ });
+}
+
+// Returns nullptr if no column matching `ref` is found, or if the FieldRef is
+// a nested reference.
+inline std::shared_ptr<ChunkedArray> GetTableColumn(const Table& table,
+ const FieldRef& ref) {
+ if (ref.IsNested()) return nullptr;
+
+ if (auto name = ref.name()) {
+ return table.GetColumnByName(*name);
+ }
+
+ auto index = ref.field_path()->indices()[0];
+ if (index >= table.num_columns()) return nullptr;
+ return table.column(index);
+}
+
+// We could try to reproduce the concrete Array classes' facilities
+// (such as cached raw values pointer) in a separate hierarchy of
+// physical accessors, but doing so ends up too cumbersome.
+// Instead, we simply create the desired concrete Array objects.
+inline std::shared_ptr<Array> GetPhysicalArray(
+ const Array& array, const std::shared_ptr<DataType>& physical_type) {
+ auto new_data = array.data()->Copy();
+ new_data->type = physical_type;
+ return MakeArray(std::move(new_data));
+}
+
+inline ArrayVector GetPhysicalChunks(const ArrayVector& chunks,
+ const std::shared_ptr<DataType>&
physical_type) {
+ ArrayVector physical(chunks.size());
+ std::transform(chunks.begin(), chunks.end(), physical.begin(),
+ [&](const std::shared_ptr<Array>& array) {
+ return GetPhysicalArray(*array, physical_type);
+ });
+ return physical;
+}
+
+inline ArrayVector GetPhysicalChunks(const ChunkedArray& chunked_array,
+ const std::shared_ptr<DataType>&
physical_type) {
+ return GetPhysicalChunks(chunked_array.chunks(), physical_type);
+}
+
+// Compare two records in a single column (either from a batch or table)
+template <typename ResolvedSortKey>
+struct ColumnComparator {
+ using Location = typename ResolvedSortKey::LocationType;
+
+ ColumnComparator(const ResolvedSortKey& sort_key, NullPlacement
null_placement)
+ : sort_key_(sort_key), null_placement_(null_placement) {}
+
+ virtual ~ColumnComparator() = default;
+
+ virtual int Compare(const Location& left, const Location& right) const = 0;
+
+ ResolvedSortKey sort_key_;
+ NullPlacement null_placement_;
+};
+
+template <typename ResolvedSortKey, typename Type>
+struct ConcreteColumnComparator : public ColumnComparator<ResolvedSortKey> {
+ using ArrayType = typename TypeTraits<Type>::ArrayType;
+ using Location = typename ResolvedSortKey::LocationType;
+
+ using ColumnComparator<ResolvedSortKey>::ColumnComparator;
+
+ int Compare(const Location& left, const Location& right) const override {
+ const auto& sort_key = this->sort_key_;
+
+ const auto chunk_left = sort_key.template GetChunk<ArrayType>(left);
+ const auto chunk_right = sort_key.template GetChunk<ArrayType>(right);
+ if (sort_key.null_count > 0) {
+ const bool is_null_left = chunk_left.IsNull();
+ const bool is_null_right = chunk_right.IsNull();
+ if (is_null_left && is_null_right) {
+ return 0;
+ } else if (is_null_left) {
+ return this->null_placement_ == NullPlacement::AtStart ? -1 : 1;
+ } else if (is_null_right) {
+ return this->null_placement_ == NullPlacement::AtStart ? 1 : -1;
+ }
+ }
+ return CompareTypeValues<Type>(chunk_left.Value(), chunk_right.Value(),
+ sort_key.order, this->null_placement_);
+ }
+};
+
+template <typename ResolvedSortKey>
+struct ConcreteColumnComparator<ResolvedSortKey, NullType>
+ : public ColumnComparator<ResolvedSortKey> {
+ using Location = typename ResolvedSortKey::LocationType;
+
+ using ColumnComparator<ResolvedSortKey>::ColumnComparator;
+
+ int Compare(const Location& left, const Location& right) const override {
return 0; }
+};
+
+// Compare two records in the same RecordBatch or Table
+// (indexing is handled through ResolvedSortKey)
+template <typename ResolvedSortKey>
+class MultipleKeyComparator {
+ public:
+ using Location = typename ResolvedSortKey::LocationType;
+
+ MultipleKeyComparator(const std::vector<ResolvedSortKey>& sort_keys,
+ NullPlacement null_placement)
+ : sort_keys_(sort_keys), null_placement_(null_placement) {
+ status_ &= MakeComparators();
+ }
+
+ Status status() const { return status_; }
+
+ // Returns true if the left-th value should be ordered before the
+ // right-th value, false otherwise. The start_sort_key_index-th
+ // sort key and subsequent sort keys are used for comparison.
+ bool Compare(const Location& left, const Location& right, size_t
start_sort_key_index) {
+ return CompareInternal(left, right, start_sort_key_index) < 0;
+ }
+
+ bool Equals(const Location& left, const Location& right, size_t
start_sort_key_index) {
+ return CompareInternal(left, right, start_sort_key_index) == 0;
+ }
+
+ private:
+ struct ColumnComparatorFactory {
+#define VISIT(TYPE) \
+ Status Visit(const TYPE& type) { return VisitGeneric(type); }
+
+ VISIT_SORTABLE_PHYSICAL_TYPES(VISIT)
+ VISIT(NullType)
+
+#undef VISIT
+
+ Status Visit(const DataType& type) {
+ return Status::TypeError("Unsupported type for batch or table sorting: ",
+ type.ToString());
+ }
+
+ template <typename Type>
+ Status VisitGeneric(const Type& type) {
+ res.reset(
+ new ConcreteColumnComparator<ResolvedSortKey, Type>{sort_key,
null_placement});
+ return Status::OK();
+ }
+
+ const ResolvedSortKey& sort_key;
+ NullPlacement null_placement;
+ std::unique_ptr<ColumnComparator<ResolvedSortKey>> res;
+ };
+
+ Status MakeComparators() {
+ column_comparators_.reserve(sort_keys_.size());
+
+ for (const auto& sort_key : sort_keys_) {
+ ColumnComparatorFactory factory{sort_key, null_placement_, nullptr};
+ RETURN_NOT_OK(VisitTypeInline(*sort_key.type, &factory));
+ column_comparators_.push_back(std::move(factory.res));
+ }
+ return Status::OK();
+ }
+
+ // Compare two records in the same table and return -1, 0 or 1.
+ //
+ // -1: The left is less than the right.
+ // 0: The left equals to the right.
+ // 1: The left is greater than the right.
+ //
+ // This supports null and NaN. Null is processed in this and NaN
+ // is processed in CompareTypeValue().
+ int CompareInternal(const Location& left, const Location& right,
+ size_t start_sort_key_index) {
+ const auto num_sort_keys = sort_keys_.size();
+ for (size_t i = start_sort_key_index; i < num_sort_keys; ++i) {
+ const int r = column_comparators_[i]->Compare(left, right);
+ if (r != 0) {
+ return r;
+ }
+ }
+ return 0;
+ }
+
+ const std::vector<ResolvedSortKey>& sort_keys_;
+ const NullPlacement null_placement_;
+ std::vector<std::unique_ptr<ColumnComparator<ResolvedSortKey>>>
column_comparators_;
+ Status status_;
+};
+
+// Sort a batch using a single sort and multiple-key comparisons.
+class MultipleKeyRecordBatchSorter : public TypeVisitor {
Review Comment:
(same for other classes above perhaps)
##########
cpp/src/arrow/compute/kernels/vector_select_k.cc:
##########
@@ -0,0 +1,858 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include <queue>
+
+#include "arrow/compute/kernels/vector_sort_internal.h"
+#include "arrow/compute/registry.h"
+
+namespace arrow {
+
+using internal::checked_cast;
+
+namespace compute::internal {
+
+namespace {
+
+// ----------------------------------------------------------------------
+// TopK/BottomK implementations
+
+const SelectKOptions* GetDefaultSelectKOptions() {
+ static const auto kDefaultSelectKOptions = SelectKOptions::Defaults();
+ return &kDefaultSelectKOptions;
+}
+
+const FunctionDoc select_k_unstable_doc(
+ "Select the indices of the first `k` ordered elements from the input",
+ ("This function selects an array of indices of the first `k` ordered
elements\n"
+ "from the `input` array, record batch or table specified in the column
keys\n"
+ "(`options.sort_keys`). Output is not guaranteed to be stable.\n"
+ "Null values are considered greater than any other value and are\n"
+ "therefore ordered at the end. For floating-point types, NaNs are
considered\n"
+ "greater than any other non-null value, but smaller than null values."),
+ {"input"}, "SelectKOptions", /*options_required=*/true);
+
+Result<std::shared_ptr<ArrayData>> MakeMutableUInt64Array(
+ std::shared_ptr<DataType> out_type, int64_t length, MemoryPool*
memory_pool) {
+ auto buffer_size = length * sizeof(uint64_t);
+ ARROW_ASSIGN_OR_RAISE(auto data, AllocateBuffer(buffer_size, memory_pool));
+ return ArrayData::Make(uint64(), length, {nullptr, std::move(data)},
/*null_count=*/0);
+}
+
+template <SortOrder order>
+class SelectKComparator {
+ public:
+ template <typename Type>
+ bool operator()(const Type& lval, const Type& rval);
+};
+
+template <>
+class SelectKComparator<SortOrder::Ascending> {
+ public:
+ template <typename Type>
+ bool operator()(const Type& lval, const Type& rval) {
+ return lval < rval;
+ }
+};
+
+template <>
+class SelectKComparator<SortOrder::Descending> {
+ public:
+ template <typename Type>
+ bool operator()(const Type& lval, const Type& rval) {
+ return rval < lval;
+ }
+};
+
+class ArraySelecter : public TypeVisitor {
+ public:
+ ArraySelecter(ExecContext* ctx, const Array& array, const SelectKOptions&
options,
+ Datum* output)
+ : TypeVisitor(),
+ ctx_(ctx),
+ array_(array),
+ k_(options.k),
+ order_(options.sort_keys[0].order),
+ physical_type_(GetPhysicalType(array.type())),
+ output_(output) {}
+
+ Status Run() { return physical_type_->Accept(this); }
+
+#define VISIT(TYPE) \
+ Status Visit(const TYPE& type) { \
+ if (order_ == SortOrder::Ascending) { \
+ return SelectKthInternal<TYPE, SortOrder::Ascending>(); \
+ } \
+ return SelectKthInternal<TYPE, SortOrder::Descending>(); \
+ }
+
+ VISIT_SORTABLE_PHYSICAL_TYPES(VISIT)
+
+#undef VISIT
+
+ template <typename InType, SortOrder sort_order>
+ Status SelectKthInternal() {
+ using GetView = GetViewType<InType>;
+ using ArrayType = typename TypeTraits<InType>::ArrayType;
+
+ ArrayType arr(array_.data());
+ std::vector<uint64_t> indices(arr.length());
+
+ uint64_t* indices_begin = indices.data();
+ uint64_t* indices_end = indices_begin + indices.size();
+ std::iota(indices_begin, indices_end, 0);
+ if (k_ > arr.length()) {
+ k_ = arr.length();
+ }
+
+ const auto p = PartitionNulls<ArrayType, NonStablePartitioner>(
+ indices_begin, indices_end, arr, 0, NullPlacement::AtEnd);
+ const auto end_iter = p.non_nulls_end;
+
+ auto kth_begin = std::min(indices_begin + k_, end_iter);
+
+ SelectKComparator<sort_order> comparator;
+ auto cmp = [&arr, &comparator](uint64_t left, uint64_t right) {
+ const auto lval = GetView::LogicalValue(arr.GetView(left));
+ const auto rval = GetView::LogicalValue(arr.GetView(right));
+ return comparator(lval, rval);
+ };
+ using HeapContainer =
+ std::priority_queue<uint64_t, std::vector<uint64_t>, decltype(cmp)>;
+ HeapContainer heap(indices_begin, kth_begin, cmp);
+ for (auto iter = kth_begin; iter != end_iter && !heap.empty(); ++iter) {
+ uint64_t x_index = *iter;
+ if (cmp(x_index, heap.top())) {
+ heap.pop();
+ heap.push(x_index);
+ }
+ }
+ auto out_size = static_cast<int64_t>(heap.size());
+ ARROW_ASSIGN_OR_RAISE(auto take_indices, MakeMutableUInt64Array(uint64(),
out_size,
+
ctx_->memory_pool()));
+
+ auto* out_cbegin = take_indices->GetMutableValues<uint64_t>(1) + out_size
- 1;
+ while (heap.size() > 0) {
+ *out_cbegin = heap.top();
+ heap.pop();
+ --out_cbegin;
+ }
+ *output_ = Datum(take_indices);
+ return Status::OK();
+ }
+
+ ExecContext* ctx_;
+ const Array& array_;
+ int64_t k_;
+ SortOrder order_;
+ const std::shared_ptr<DataType> physical_type_;
+ Datum* output_;
+};
+
+template <typename ArrayType>
+struct TypedHeapItem {
+ uint64_t index;
+ uint64_t offset;
+ ArrayType* array;
+};
+
+class ChunkedArraySelecter : public TypeVisitor {
+ public:
+ ChunkedArraySelecter(ExecContext* ctx, const ChunkedArray& chunked_array,
+ const SelectKOptions& options, Datum* output)
+ : TypeVisitor(),
+ chunked_array_(chunked_array),
+ physical_type_(GetPhysicalType(chunked_array.type())),
+ physical_chunks_(GetPhysicalChunks(chunked_array_, physical_type_)),
+ k_(options.k),
+ order_(options.sort_keys[0].order),
+ ctx_(ctx),
+ output_(output) {}
+
+ Status Run() { return physical_type_->Accept(this); }
+
+#define VISIT(TYPE) \
+ Status Visit(const TYPE& type) { \
+ if (order_ == SortOrder::Ascending) { \
+ return SelectKthInternal<TYPE, SortOrder::Ascending>(); \
+ } \
+ return SelectKthInternal<TYPE, SortOrder::Descending>(); \
+ }
+
+ VISIT_SORTABLE_PHYSICAL_TYPES(VISIT)
+#undef VISIT
+
+ template <typename InType, SortOrder sort_order>
+ Status SelectKthInternal() {
+ using GetView = GetViewType<InType>;
+ using ArrayType = typename TypeTraits<InType>::ArrayType;
+ using HeapItem = TypedHeapItem<ArrayType>;
+
+ const auto num_chunks = chunked_array_.num_chunks();
+ if (num_chunks == 0) {
+ return Status::OK();
+ }
+ if (k_ > chunked_array_.length()) {
+ k_ = chunked_array_.length();
+ }
+ std::function<bool(const HeapItem&, const HeapItem&)> cmp;
+ SelectKComparator<sort_order> comparator;
+
+ cmp = [&comparator](const HeapItem& left, const HeapItem& right) -> bool {
+ const auto lval = GetView::LogicalValue(left.array->GetView(left.index));
+ const auto rval =
GetView::LogicalValue(right.array->GetView(right.index));
+ return comparator(lval, rval);
+ };
+ using HeapContainer =
+ std::priority_queue<HeapItem, std::vector<HeapItem>, decltype(cmp)>;
+
+ HeapContainer heap(cmp);
+ std::vector<std::shared_ptr<ArrayType>> chunks_holder;
+ uint64_t offset = 0;
+ for (const auto& chunk : physical_chunks_) {
+ if (chunk->length() == 0) continue;
+ chunks_holder.emplace_back(std::make_shared<ArrayType>(chunk->data()));
+ ArrayType& arr = *chunks_holder[chunks_holder.size() - 1];
+
+ std::vector<uint64_t> indices(arr.length());
+ uint64_t* indices_begin = indices.data();
+ uint64_t* indices_end = indices_begin + indices.size();
+ std::iota(indices_begin, indices_end, 0);
+
+ const auto p = PartitionNulls<ArrayType, NonStablePartitioner>(
+ indices_begin, indices_end, arr, 0, NullPlacement::AtEnd);
+ const auto end_iter = p.non_nulls_end;
+
+ auto kth_begin = std::min(indices_begin + k_, end_iter);
+ uint64_t* iter = indices_begin;
+ for (; iter != kth_begin && heap.size() < static_cast<size_t>(k_);
++iter) {
+ heap.push(HeapItem{*iter, offset, &arr});
+ }
+ for (; iter != end_iter && !heap.empty(); ++iter) {
+ uint64_t x_index = *iter;
+ const auto& xval = GetView::LogicalValue(arr.GetView(x_index));
+ auto top_item = heap.top();
+ const auto& top_value =
+ GetView::LogicalValue(top_item.array->GetView(top_item.index));
+ if (comparator(xval, top_value)) {
+ heap.pop();
+ heap.push(HeapItem{x_index, offset, &arr});
+ }
+ }
+ offset += chunk->length();
+ }
+
+ auto out_size = static_cast<int64_t>(heap.size());
+ ARROW_ASSIGN_OR_RAISE(auto take_indices, MakeMutableUInt64Array(uint64(),
out_size,
+
ctx_->memory_pool()));
+ auto* out_cbegin = take_indices->GetMutableValues<uint64_t>(1) + out_size
- 1;
+ while (heap.size() > 0) {
+ auto top_item = heap.top();
+ *out_cbegin = top_item.index + top_item.offset;
+ heap.pop();
+ --out_cbegin;
+ }
+ *output_ = Datum(take_indices);
+ return Status::OK();
+ }
+
+ const ChunkedArray& chunked_array_;
+ const std::shared_ptr<DataType> physical_type_;
+ const ArrayVector physical_chunks_;
+ int64_t k_;
+ SortOrder order_;
+ ExecContext* ctx_;
+ Datum* output_;
+};
+
+class RecordBatchSelecter : public TypeVisitor {
+ private:
+ using ResolvedSortKey = MultipleKeyRecordBatchSorter::ResolvedSortKey;
+ using Comparator = MultipleKeyComparator<ResolvedSortKey>;
+
+ public:
+ RecordBatchSelecter(ExecContext* ctx, const RecordBatch& record_batch,
+ const SelectKOptions& options, Datum* output)
+ : TypeVisitor(),
+ ctx_(ctx),
+ record_batch_(record_batch),
+ k_(options.k),
+ output_(output),
+ sort_keys_(ResolveSortKeys(record_batch, options.sort_keys)),
+ comparator_(sort_keys_, NullPlacement::AtEnd) {}
+
+ Status Run() { return sort_keys_[0].type->Accept(this); }
+
+ protected:
+#define VISIT(TYPE) \
+ Status Visit(const TYPE& type) { \
+ if (sort_keys_[0].order == SortOrder::Descending) \
+ return SelectKthInternal<TYPE, SortOrder::Descending>(); \
+ return SelectKthInternal<TYPE, SortOrder::Ascending>(); \
+ }
+ VISIT_SORTABLE_PHYSICAL_TYPES(VISIT)
+#undef VISIT
+
+ static std::vector<ResolvedSortKey> ResolveSortKeys(
+ const RecordBatch& batch, const std::vector<SortKey>& sort_keys) {
+ std::vector<ResolvedSortKey> resolved;
+ for (const auto& key : sort_keys) {
+ auto array = key.target.GetOne(batch).ValueOr(nullptr);
+ resolved.emplace_back(array, key.order);
+ }
+ return resolved;
+ }
+
+ template <typename InType, SortOrder sort_order>
+ Status SelectKthInternal() {
+ using GetView = GetViewType<InType>;
+ using ArrayType = typename TypeTraits<InType>::ArrayType;
+ auto& comparator = comparator_;
+ const auto& first_sort_key = sort_keys_[0];
+ const auto& arr = checked_cast<const ArrayType&>(first_sort_key.array);
+
+ const auto num_rows = record_batch_.num_rows();
+ if (num_rows == 0) {
+ return Status::OK();
+ }
+ if (k_ > record_batch_.num_rows()) {
+ k_ = record_batch_.num_rows();
+ }
+ std::function<bool(const uint64_t&, const uint64_t&)> cmp;
+ SelectKComparator<sort_order> select_k_comparator;
+ cmp = [&](const uint64_t& left, const uint64_t& right) -> bool {
+ const auto lval = GetView::LogicalValue(arr.GetView(left));
+ const auto rval = GetView::LogicalValue(arr.GetView(right));
+ if (lval == rval) {
+ // If the left value equals to the right value,
+ // we need to compare the second and following
+ // sort keys.
+ return comparator.Compare(left, right, 1);
+ }
+ return select_k_comparator(lval, rval);
+ };
+ using HeapContainer =
+ std::priority_queue<uint64_t, std::vector<uint64_t>, decltype(cmp)>;
+
+ std::vector<uint64_t> indices(arr.length());
+ uint64_t* indices_begin = indices.data();
+ uint64_t* indices_end = indices_begin + indices.size();
+ std::iota(indices_begin, indices_end, 0);
+
+ const auto p = PartitionNulls<ArrayType, NonStablePartitioner>(
+ indices_begin, indices_end, arr, 0, NullPlacement::AtEnd);
+ const auto end_iter = p.non_nulls_end;
+
+ auto kth_begin = std::min(indices_begin + k_, end_iter);
+
+ HeapContainer heap(indices_begin, kth_begin, cmp);
+ for (auto iter = kth_begin; iter != end_iter && !heap.empty(); ++iter) {
+ uint64_t x_index = *iter;
+ auto top_item = heap.top();
+ if (cmp(x_index, top_item)) {
+ heap.pop();
+ heap.push(x_index);
+ }
+ }
+ auto out_size = static_cast<int64_t>(heap.size());
+ ARROW_ASSIGN_OR_RAISE(auto take_indices, MakeMutableUInt64Array(uint64(),
out_size,
+
ctx_->memory_pool()));
+ auto* out_cbegin = take_indices->GetMutableValues<uint64_t>(1) + out_size
- 1;
+ while (heap.size() > 0) {
+ *out_cbegin = heap.top();
+ heap.pop();
+ --out_cbegin;
+ }
+ *output_ = Datum(take_indices);
+ return Status::OK();
+ }
+
+ ExecContext* ctx_;
+ const RecordBatch& record_batch_;
+ int64_t k_;
+ Datum* output_;
+ std::vector<ResolvedSortKey> sort_keys_;
+ Comparator comparator_;
+};
+
+class TableSelecter : public TypeVisitor {
+ private:
+ struct ResolvedSortKey {
+ ResolvedSortKey(const std::shared_ptr<ChunkedArray>& chunked_array,
+ const SortOrder order)
+ : order(order),
+ type(GetPhysicalType(chunked_array->type())),
+ chunks(GetPhysicalChunks(*chunked_array, type)),
+ null_count(chunked_array->null_count()),
+ resolver(GetArrayPointers(chunks)) {}
+
+ using LocationType = int64_t;
+
+ // Find the target chunk and index in the target chunk from an
+ // index in chunked array.
+ template <typename ArrayType>
+ ResolvedChunk<ArrayType> GetChunk(int64_t index) const {
+ return resolver.Resolve<ArrayType>(index);
+ }
+
+ const SortOrder order;
+ const std::shared_ptr<DataType> type;
+ const ArrayVector chunks;
+ const int64_t null_count;
+ const ChunkedArrayResolver resolver;
+ };
+ using Comparator = MultipleKeyComparator<ResolvedSortKey>;
+
+ public:
+ TableSelecter(ExecContext* ctx, const Table& table, const SelectKOptions&
options,
+ Datum* output)
+ : TypeVisitor(),
+ ctx_(ctx),
+ table_(table),
+ k_(options.k),
+ output_(output),
+ sort_keys_(ResolveSortKeys(table, options.sort_keys)),
+ comparator_(sort_keys_, NullPlacement::AtEnd) {}
+
+ Status Run() { return sort_keys_[0].type->Accept(this); }
+
+ protected:
+#define VISIT(TYPE) \
+ Status Visit(const TYPE& type) { \
+ if (sort_keys_[0].order == SortOrder::Descending) \
+ return SelectKthInternal<TYPE, SortOrder::Descending>(); \
+ return SelectKthInternal<TYPE, SortOrder::Ascending>(); \
+ }
+ VISIT_SORTABLE_PHYSICAL_TYPES(VISIT)
+
+#undef VISIT
+
+ static std::vector<ResolvedSortKey> ResolveSortKeys(
+ const Table& table, const std::vector<SortKey>& sort_keys) {
+ std::vector<ResolvedSortKey> resolved;
+ for (const auto& key : sort_keys) {
+ auto chunked_array = GetTableColumn(table, key.target);
+ resolved.emplace_back(chunked_array, key.order);
+ }
+ return resolved;
+ }
+
+ // Behaves like PartitionNulls() but this supports multiple sort keys.
+ template <typename Type>
+ NullPartitionResult PartitionNullsInternal(uint64_t* indices_begin,
+ uint64_t* indices_end,
+ const ResolvedSortKey&
first_sort_key) {
+ using ArrayType = typename TypeTraits<Type>::ArrayType;
+
+ const auto p = PartitionNullsOnly<StablePartitioner>(
+ indices_begin, indices_end, first_sort_key.resolver,
first_sort_key.null_count,
+ NullPlacement::AtEnd);
+ DCHECK_EQ(p.nulls_end - p.nulls_begin, first_sort_key.null_count);
+
+ const auto q = PartitionNullLikes<ArrayType, StablePartitioner>(
+ p.non_nulls_begin, p.non_nulls_end, first_sort_key.resolver,
+ NullPlacement::AtEnd);
+
+ auto& comparator = comparator_;
+ // Sort all NaNs by the second and following sort keys.
+ std::stable_sort(q.nulls_begin, q.nulls_end, [&](uint64_t left, uint64_t
right) {
+ return comparator.Compare(left, right, 1);
+ });
+ // Sort all nulls by the second and following sort keys.
+ std::stable_sort(p.nulls_begin, p.nulls_end, [&](uint64_t left, uint64_t
right) {
+ return comparator.Compare(left, right, 1);
+ });
+
+ return q;
+ }
+
+ // XXX this implementation is rather inefficient as it computes chunk indices
+ // at every comparison. Instead we should iterate over individual batches
+ // and remember ChunkLocation entries in the max-heap.
+
+ template <typename InType, SortOrder sort_order>
+ Status SelectKthInternal() {
+ using ArrayType = typename TypeTraits<InType>::ArrayType;
+ auto& comparator = comparator_;
+ const auto& first_sort_key = sort_keys_[0];
+
+ const auto num_rows = table_.num_rows();
+ if (num_rows == 0) {
+ return Status::OK();
+ }
+ if (k_ > table_.num_rows()) {
+ k_ = table_.num_rows();
+ }
+ std::function<bool(const uint64_t&, const uint64_t&)> cmp;
+ SelectKComparator<sort_order> select_k_comparator;
+ cmp = [&](const uint64_t& left, const uint64_t& right) -> bool {
+ auto chunk_left = first_sort_key.template GetChunk<ArrayType>(left);
+ auto chunk_right = first_sort_key.template GetChunk<ArrayType>(right);
+ auto value_left = chunk_left.Value();
+ auto value_right = chunk_right.Value();
+ if (value_left == value_right) {
+ return comparator.Compare(left, right, 1);
+ }
+ return select_k_comparator(value_left, value_right);
+ };
+ using HeapContainer =
+ std::priority_queue<uint64_t, std::vector<uint64_t>, decltype(cmp)>;
+
+ std::vector<uint64_t> indices(num_rows);
+ uint64_t* indices_begin = indices.data();
+ uint64_t* indices_end = indices_begin + indices.size();
+ std::iota(indices_begin, indices_end, 0);
+
+ const auto p =
+ this->PartitionNullsInternal<InType>(indices_begin, indices_end,
first_sort_key);
+ const auto end_iter = p.non_nulls_end;
+ auto kth_begin = std::min(indices_begin + k_, end_iter);
+
+ HeapContainer heap(indices_begin, kth_begin, cmp);
+ for (auto iter = kth_begin; iter != end_iter && !heap.empty(); ++iter) {
+ uint64_t x_index = *iter;
+ uint64_t top_item = heap.top();
+ if (cmp(x_index, top_item)) {
+ heap.pop();
+ heap.push(x_index);
+ }
+ }
+ auto out_size = static_cast<int64_t>(heap.size());
+ ARROW_ASSIGN_OR_RAISE(auto take_indices, MakeMutableUInt64Array(uint64(),
out_size,
+
ctx_->memory_pool()));
+ auto* out_cbegin = take_indices->GetMutableValues<uint64_t>(1) + out_size
- 1;
+ while (heap.size() > 0) {
+ *out_cbegin = heap.top();
+ heap.pop();
+ --out_cbegin;
+ }
+ *output_ = Datum(take_indices);
+ return Status::OK();
+ }
+
+ ExecContext* ctx_;
+ const Table& table_;
+ int64_t k_;
+ Datum* output_;
+ std::vector<ResolvedSortKey> sort_keys_;
+ Comparator comparator_;
+};
+
+static Status CheckConsistency(const Schema& schema,
+ const std::vector<SortKey>& sort_keys) {
+ for (const auto& key : sort_keys) {
+ RETURN_NOT_OK(CheckNonNested(key.target));
+ RETURN_NOT_OK(PrependInvalidColumn(key.target.FindOne(schema)));
+ }
+ return Status::OK();
+}
+
+class SelectKUnstableMetaFunction : public MetaFunction {
+ public:
+ SelectKUnstableMetaFunction()
+ : MetaFunction("select_k_unstable", Arity::Unary(),
select_k_unstable_doc,
+ GetDefaultSelectKOptions()) {}
+
+ Result<Datum> ExecuteImpl(const std::vector<Datum>& args,
+ const FunctionOptions* options,
+ ExecContext* ctx) const override {
+ const auto& select_k_options = static_cast<const
SelectKOptions&>(*options);
+ if (select_k_options.k < 0) {
+ return Status::Invalid("select_k_unstable requires a nonnegative `k`,
got ",
+ select_k_options.k);
+ }
+ if (select_k_options.sort_keys.size() == 0) {
+ return Status::Invalid("select_k_unstable requires a non-empty
`sort_keys`");
+ }
+ switch (args[0].kind()) {
+ case Datum::ARRAY:
+ return SelectKth(*args[0].make_array(), select_k_options, ctx);
+ case Datum::CHUNKED_ARRAY:
+ return SelectKth(*args[0].chunked_array(), select_k_options, ctx);
+ case Datum::RECORD_BATCH:
+ return SelectKth(*args[0].record_batch(), select_k_options, ctx);
+ case Datum::TABLE:
+ return SelectKth(*args[0].table(), select_k_options, ctx);
+ default:
+ break;
+ }
+ return Status::NotImplemented(
+ "Unsupported types for select_k operation: "
+ "values=",
+ args[0].ToString());
+ }
+
+ private:
+ Result<Datum> SelectKth(const Array& array, const SelectKOptions& options,
+ ExecContext* ctx) const {
+ Datum output;
+ ArraySelecter selecter(ctx, array, options, &output);
+ ARROW_RETURN_NOT_OK(selecter.Run());
+ return output;
+ }
+
+ Result<Datum> SelectKth(const ChunkedArray& chunked_array,
+ const SelectKOptions& options, ExecContext* ctx)
const {
+ Datum output;
+ ChunkedArraySelecter selecter(ctx, chunked_array, options, &output);
+ ARROW_RETURN_NOT_OK(selecter.Run());
+ return output;
+ }
+ Result<Datum> SelectKth(const RecordBatch& record_batch, const
SelectKOptions& options,
+ ExecContext* ctx) const {
+ ARROW_RETURN_NOT_OK(CheckConsistency(*record_batch.schema(),
options.sort_keys));
+ Datum output;
+ RecordBatchSelecter selecter(ctx, record_batch, options, &output);
+ ARROW_RETURN_NOT_OK(selecter.Run());
+ return output;
+ }
+ Result<Datum> SelectKth(const Table& table, const SelectKOptions& options,
+ ExecContext* ctx) const {
+ ARROW_RETURN_NOT_OK(CheckConsistency(*table.schema(), options.sort_keys));
+ Datum output;
+ TableSelecter selecter(ctx, table, options, &output);
+ ARROW_RETURN_NOT_OK(selecter.Run());
+ return output;
+ }
+};
+
+// ----------------------------------------------------------------------
+// Rank implementation
Review Comment:
Since you're moving the Rank implementation(s) already, might as well move
them to a dedicated `vector_rank.cc`?
##########
cpp/src/arrow/compute/kernels/vector_sort_internal.h:
##########
@@ -456,6 +458,402 @@ Status SortChunkedArray(ExecContext* ctx, uint64_t*
indices_begin, uint64_t* ind
const ChunkedArray& values, SortOrder sort_order,
NullPlacement null_placement);
+// ----------------------------------------------------------------------
+// Helpers for Sort/SelectK implementations
+
+struct SortField {
+ int field_index;
+ SortOrder order;
+};
+
+inline Status CheckNonNested(const FieldRef& ref) {
+ if (ref.IsNested()) {
+ return Status::KeyError("Nested keys not supported for SortKeys");
+ }
+ return Status::OK();
+}
+
+template <typename T>
+Result<T> PrependInvalidColumn(Result<T> res) {
+ if (res.ok()) return res;
+ return res.status().WithMessage("Invalid sort key column: ",
res.status().message());
+}
+
+// Return the field indices of the sort keys, deduplicating them along the way
+inline Result<std::vector<SortField>> FindSortKeys(
+ const Schema& schema, const std::vector<SortKey>& sort_keys) {
+ std::vector<SortField> fields;
+ std::unordered_set<int> seen;
+ fields.reserve(sort_keys.size());
+ seen.reserve(sort_keys.size());
+
+ for (const auto& sort_key : sort_keys) {
+ RETURN_NOT_OK(CheckNonNested(sort_key.target));
+
+ ARROW_ASSIGN_OR_RAISE(auto match,
+
PrependInvalidColumn(sort_key.target.FindOne(schema)));
+ if (seen.insert(match[0]).second) {
+ fields.push_back({match[0], sort_key.order});
+ }
+ }
+ return fields;
+}
+
+template <typename ResolvedSortKey, typename ResolvedSortKeyFactory>
+Result<std::vector<ResolvedSortKey>> ResolveSortKeys(
+ const Schema& schema, const std::vector<SortKey>& sort_keys,
+ ResolvedSortKeyFactory&& factory) {
+ ARROW_ASSIGN_OR_RAISE(const auto fields, FindSortKeys(schema, sort_keys));
+ std::vector<ResolvedSortKey> resolved;
+ resolved.reserve(fields.size());
+ std::transform(fields.begin(), fields.end(), std::back_inserter(resolved),
factory);
+ return resolved;
+}
+
+template <typename ResolvedSortKey, typename TableOrBatch>
+Result<std::vector<ResolvedSortKey>> ResolveSortKeys(
+ const TableOrBatch& table_or_batch, const std::vector<SortKey>& sort_keys)
{
+ return ResolveSortKeys<ResolvedSortKey>(
+ *table_or_batch.schema(), sort_keys, [&](const SortField& f) {
+ return ResolvedSortKey{table_or_batch.column(f.field_index), f.order};
+ });
+}
+
+// Returns nullptr if no column matching `ref` is found, or if the FieldRef is
+// a nested reference.
+inline std::shared_ptr<ChunkedArray> GetTableColumn(const Table& table,
Review Comment:
Hmm... `FieldPath` and `FieldRef` already support looking up a column from a
RecordBatch, I think it would be easy to add similar support for Table there.
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