rtpsw commented on code in PR #34311:
URL: https://github.com/apache/arrow/pull/34311#discussion_r1116869071
##########
cpp/src/arrow/compute/row/grouper.h:
##########
@@ -30,6 +30,49 @@
namespace arrow {
namespace compute {
+/// \brief A segment of contiguous rows for grouping
+struct ARROW_EXPORT GroupingSegment {
+ int64_t offset;
+ int64_t length;
+ bool is_open;
+ bool extends;
+};
+
+inline bool operator==(const GroupingSegment& segment1, const GroupingSegment&
segment2) {
+ return segment1.offset == segment2.offset && segment1.length ==
segment2.length &&
+ segment1.is_open == segment2.is_open && segment1.extends ==
segment2.extends;
+}
+inline bool operator!=(const GroupingSegment& segment1, const GroupingSegment&
segment2) {
+ return !(segment1 == segment2);
+}
+
+/// \brief Computes grouping segments for a batch. Each segment covers rows
with identical
+/// values in the batch. The values in the batch are often selected as keys
from a larger
+/// batch.
+class ARROW_EXPORT GroupingSegmenter {
+ public:
+ virtual ~GroupingSegmenter() = default;
+
+ /// \brief Construct a GroupingSegmenter which receives the specified key
types
+ static Result<std::unique_ptr<GroupingSegmenter>> Make(
+ const std::vector<TypeHolder>& key_types, bool nullable_keys = false,
+ ExecContext* ctx = default_exec_context());
+
+ /// \brief Return the key types of this segmenter
+ virtual const std::vector<TypeHolder>& key_types() const = 0;
+
+ /// \brief Reset this grouping segmenter
+ virtual Status Reset() = 0;
+
+ /// \brief Get the next segment for the given batch starting from the given
offset
+ virtual Result<GroupingSegment> GetNextSegment(const ExecSpan& batch,
+ int64_t offset) = 0;
+
+ /// \brief Get the next segment for the given batch starting from the given
offset
+ virtual Result<GroupingSegment> GetNextSegment(const ExecBatch& batch,
Review Comment:
An `ExecSpan` is [a
view](https://github.com/apache/arrow/blob/e8e50a3ca96ec8eb2f2beb383cf9005ce1c93486/cpp/src/arrow/compute/exec.h#L348-L350)
into an `ExecBatch`. The latter owns the memory of its members while the
former doesn't. Another difference is that an `ExecSpan` cannot be chunked, as
its values (i.e., columns) can only be a view into an array, but `ExecBatch`
can have chunked array values.
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