rtpsw commented on code in PR #34311:
URL: https://github.com/apache/arrow/pull/34311#discussion_r1127052647
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cpp/src/arrow/compute/row/grouper.cc:
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@@ -39,12 +43,330 @@
namespace arrow {
using internal::checked_cast;
+using internal::PrimitiveScalarBase;
namespace compute {
namespace {
-struct GrouperImpl : Grouper {
+constexpr uint32_t kNoGroupId = std::numeric_limits<uint32_t>::max();
+
+using group_id_t = std::remove_const<decltype(kNoGroupId)>::type;
+using GroupIdType = CTypeTraits<group_id_t>::ArrowType;
+auto g_group_id_type = std::make_shared<GroupIdType>();
+
+inline const uint8_t* GetValuesAsBytes(const ArraySpan& data, int64_t offset =
0) {
+ DCHECK_GT(data.type->byte_width(), 0);
+ int64_t absolute_byte_offset = (data.offset + offset) *
data.type->byte_width();
+ return data.GetValues<uint8_t>(1, absolute_byte_offset);
+}
+
+template <typename Value>
+Status CheckForGetNextSegment(const std::vector<Value>& values, int64_t length,
+ int64_t offset, const std::vector<TypeHolder>&
key_types) {
+ if (offset < 0 || offset > length) {
+ return Status::Invalid("invalid grouping segmenter offset: ", offset);
+ }
+ if (values.size() != key_types.size()) {
+ return Status::Invalid("expected batch size ", key_types.size(), " but got
",
+ values.size());
+ }
+ for (size_t i = 0; i < key_types.size(); i++) {
+ const auto& value = values[i];
+ const auto& key_type = key_types[i];
+ if (*value.type() != *key_type.type) {
+ return Status::Invalid("expected batch value ", i, " of type ",
*key_type.type,
+ " but got ", *value.type());
+ }
+ }
+ return Status::OK();
+}
+
+template <typename Batch>
+enable_if_t<std::is_same<Batch, ExecSpan>::value || std::is_same<Batch,
ExecBatch>::value,
+ Status>
+CheckForGetNextSegment(const Batch& batch, int64_t offset,
+ const std::vector<TypeHolder>& key_types) {
+ return CheckForGetNextSegment(batch.values, batch.length, offset, key_types);
+}
+
+struct BaseRowSegmenter : public RowSegmenter {
+ explicit BaseRowSegmenter(const std::vector<TypeHolder>& key_types)
+ : key_types_(key_types) {}
+
+ const std::vector<TypeHolder>& key_types() const override { return
key_types_; }
+
+ std::vector<TypeHolder> key_types_;
+};
+
+Segment MakeSegment(int64_t batch_length, int64_t offset, int64_t length, bool
extends) {
+ return Segment{offset, length, offset + length >= batch_length, extends};
+}
+
+int64_t GetMatchLength(const uint8_t* match_bytes, int64_t match_width,
+ const uint8_t* array_bytes, int64_t offset, int64_t
length) {
+ int64_t cursor, byte_cursor;
+ for (cursor = offset, byte_cursor = match_width * cursor; cursor < length;
+ cursor++, byte_cursor += match_width) {
+ if (memcmp(match_bytes, array_bytes + byte_cursor,
+ static_cast<size_t>(match_width)) != 0) {
+ break;
+ }
+ }
+ return std::min(cursor, length) - offset;
+}
+
+using ExtendFunc = std::function<bool(const void*)>;
+constexpr bool kDefaultExtends = true;
+constexpr bool kEmptyExtends = true;
+
+struct NoKeysSegmenter : public BaseRowSegmenter {
+ static std::unique_ptr<RowSegmenter> Make() {
+ return std::make_unique<NoKeysSegmenter>();
+ }
+
+ NoKeysSegmenter() : BaseRowSegmenter({}) {}
+
+ Status Reset() override { return Status::OK(); }
+
+ Result<Segment> GetNextSegment(const ExecSpan& batch, int64_t offset)
override {
+ ARROW_RETURN_NOT_OK(CheckForGetNextSegment(batch, offset, {}));
+ return MakeSegment(batch.length, offset, batch.length - offset,
kDefaultExtends);
+ }
+};
+
+struct SimpleKeySegmenter : public BaseRowSegmenter {
+ static Result<std::unique_ptr<RowSegmenter>> Make(TypeHolder key_type) {
+ return std::make_unique<SimpleKeySegmenter>(key_type);
+ }
+
+ explicit SimpleKeySegmenter(TypeHolder key_type)
+ : BaseRowSegmenter({key_type}), key_type_(key_types_[0]),
save_key_data_() {}
+
+ Status CheckType(const DataType& type) {
+ if (!is_fixed_width(type)) {
+ return Status::Invalid("SimpleKeySegmenter does not support type ",
type);
+ }
+ return Status::OK();
+ }
+
+ Status Reset() override {
+ save_key_data_.resize(0);
+ return Status::OK();
+ }
+
+ // Checks whether the given grouping data extends the current segment, i.e.,
is equal to
+ // previously seen grouping data, which is updated with each invocation.
+ bool Extend(const void* data) {
+ size_t byte_width = static_cast<size_t>(key_type_.type->byte_width());
+ bool extends = save_key_data_.size() != byte_width
+ ? kDefaultExtends
+ : 0 == memcmp(save_key_data_.data(), data, byte_width);
+ save_key_data_.resize(byte_width);
+ memcpy(save_key_data_.data(), data, byte_width);
+ return extends;
+ }
+
+ Result<Segment> GetNextSegment(const Scalar& scalar, int64_t offset, int64_t
length) {
+ ARROW_RETURN_NOT_OK(CheckType(*scalar.type));
+ if (!scalar.is_valid) {
+ return Status::Invalid("segmenting an invalid scalar");
+ }
+ auto data = checked_cast<const PrimitiveScalarBase&>(scalar).data();
+ bool extends = length > 0 ? Extend(data) : kEmptyExtends;
+ return MakeSegment(length, offset, length, extends);
+ }
+
+ Result<Segment> GetNextSegment(const DataType& array_type, const uint8_t*
array_bytes,
+ int64_t offset, int64_t length) {
+ RETURN_NOT_OK(CheckType(array_type));
+ int64_t byte_width = array_type.byte_width();
+ int64_t match_length = GetMatchLength(array_bytes + offset * byte_width,
byte_width,
+ array_bytes, offset, length);
+ bool extends = length > 0 ? Extend(array_bytes + offset * byte_width) :
kEmptyExtends;
+ return MakeSegment(length, offset, match_length, extends);
+ }
+
+ Result<Segment> GetNextSegment(const ExecSpan& batch, int64_t offset)
override {
+ ARROW_RETURN_NOT_OK(CheckForGetNextSegment(batch, offset, {key_type_}));
+ if (offset == batch.length) {
+ return MakeSegment(batch.length, offset, 0, kEmptyExtends);
+ }
+ const auto& value = batch.values[0];
+ if (value.is_scalar()) {
+ return GetNextSegment(*value.scalar, offset, batch.length);
+ }
+ ARROW_DCHECK(value.is_array());
+ const auto& array = value.array;
+ if (array.GetNullCount() > 0) {
+ return Status::NotImplemented("segmenting a nullable array");
+ }
+ return GetNextSegment(*array.type, GetValuesAsBytes(array), offset,
batch.length);
+ }
+
+ private:
+ TypeHolder key_type_;
+ std::vector<uint8_t> save_key_data_;
+};
+
+struct AnyKeysSegmenter : public BaseRowSegmenter {
+ static Result<std::unique_ptr<RowSegmenter>> Make(
+ const std::vector<TypeHolder>& key_types, ExecContext* ctx) {
+ ARROW_RETURN_NOT_OK(Grouper::Make(key_types, ctx)); // check types
+ return std::make_unique<AnyKeysSegmenter>(key_types, ctx);
+ }
+
+ AnyKeysSegmenter(const std::vector<TypeHolder>& key_types, ExecContext* ctx)
+ : BaseRowSegmenter(key_types),
+ ctx_(ctx),
+ grouper_(nullptr),
+ save_group_id_(kNoGroupId) {}
+
+ Status Reset() override {
+ grouper_ = nullptr;
+ save_group_id_ = kNoGroupId;
+ return Status::OK();
+ }
+
+ bool Extend(const void* data) {
+ auto group_id = *static_cast<const group_id_t*>(data);
+ bool extends =
+ save_group_id_ == kNoGroupId ? kDefaultExtends : save_group_id_ ==
group_id;
+ save_group_id_ = group_id;
+ return extends;
+ }
+
+ // Runs the grouper on a single row. This is used to determine the group id
of the
+ // first row of a new segment to see if it extends the previous segment.
+ template <typename Batch>
+ Result<group_id_t> MapGroupIdAt(const Batch& batch, int64_t offset) {
+ if (!grouper_) return kNoGroupId;
+ ARROW_ASSIGN_OR_RAISE(auto datum, grouper_->Consume(batch, offset,
+ /*length=*/1));
+ if (!datum.is_array()) {
+ return Status::Invalid("accessing unsupported datum kind ",
datum.kind());
+ }
+ const std::shared_ptr<ArrayData>& data = datum.array();
+ ARROW_DCHECK(data->GetNullCount() == 0);
+ DCHECK_EQ(data->type->id(), GroupIdType::type_id);
+ DCHECK_EQ(1, data->length);
+ const group_id_t* values = data->GetValues<group_id_t>(1);
+ return values[0];
+ }
+
+ Result<Segment> GetNextSegment(const ExecSpan& batch, int64_t offset)
override {
+ ARROW_RETURN_NOT_OK(CheckForGetNextSegment(batch, offset, key_types_));
+ if (offset == batch.length) {
+ return MakeSegment(batch.length, offset, 0, kEmptyExtends);
+ }
+ // ARROW-18311: make Grouper support Reset()
+ // so it can be cached instead of recreated below
+ //
+ // the group id must be computed prior to resetting the grouper, since it
is compared
+ // to save_group_id_, and after resetting the grouper produces
incomparable group ids
+ ARROW_ASSIGN_OR_RAISE(auto group_id, MapGroupIdAt(batch, offset));
+ ExtendFunc bound_extend = [this, group_id](const void* data) {
+ bool extends = Extend(&group_id);
+ save_group_id_ = *static_cast<const group_id_t*>(data);
+ return extends;
+ };
+ ARROW_ASSIGN_OR_RAISE(grouper_, Grouper::Make(key_types_, ctx_)); //
TODO: reset it
Review Comment:
We don't. As in the doc, the grouper just needs to be reset, and because
resetting is not supported, recreating it is another (less efficient) way of
doing it. As for the reason to do this, within each segment determined by
`segment_keys` there is further grouping determined by `keys`. As I recall,
this was discussed elsewhere. The discussions in this PR are by now numerous
enough that it's hard to keep track.
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