wgtmac commented on code in PR #14341:
URL: https://github.com/apache/arrow/pull/14341#discussion_r1159204933
##########
cpp/src/parquet/encoding.cc:
##########
@@ -3037,11 +3083,242 @@ class RleBooleanDecoder : public DecoderImpl, virtual
public BooleanDecoder {
// ----------------------------------------------------------------------
// DELTA_BYTE_ARRAY
-class DeltaByteArrayDecoder : public DecoderImpl,
- virtual public TypedDecoder<ByteArrayType> {
+/// Delta Byte Array encoding also known as incremental encoding or front
compression:
+/// for each element in a sequence of strings, store the prefix length of the
previous
+/// entry plus the suffix.
+///
+/// This is stored as a sequence of delta-encoded prefix lengths
(DELTA_BINARY_PACKED),
+/// followed by the suffixes encoded as delta length byte arrays
+/// (DELTA_LENGTH_BYTE_ARRAY).
+
+// ----------------------------------------------------------------------
+// DeltaByteArrayEncoder
+
+template <typename DType>
+class DeltaByteArrayEncoder : public EncoderImpl, virtual public
TypedEncoder<DType> {
public:
- explicit DeltaByteArrayDecoder(const ColumnDescriptor* descr,
+ using T = typename DType::c_type;
+
+ explicit DeltaByteArrayEncoder(const ColumnDescriptor* descr,
MemoryPool* pool =
::arrow::default_memory_pool())
+ : EncoderImpl(descr, Encoding::DELTA_BYTE_ARRAY, pool),
+ sink_(pool),
+ prefix_length_encoder_(nullptr, pool),
+ suffix_encoder_(nullptr, pool),
+ last_value_(""),
+ kEmpty(ByteArray(0, nullptr)) {}
+
+ std::shared_ptr<Buffer> FlushValues() override;
+
+ int64_t EstimatedDataEncodedSize() override {
+ return prefix_length_encoder_.EstimatedDataEncodedSize() +
+ suffix_encoder_.EstimatedDataEncodedSize();
+ }
+
+ using TypedEncoder<DType>::Put;
+
+ void Put(const ::arrow::Array& values) override;
+
+ void Put(const T* buffer, int num_values) override;
+
+ void PutSpaced(const T* src, int num_values, const uint8_t* valid_bits,
+ int64_t valid_bits_offset) override {
+ if (valid_bits != NULLPTR) {
+ PARQUET_ASSIGN_OR_THROW(
+ buffer_, ::arrow::AllocateBuffer(num_values * sizeof(T),
this->memory_pool()));
+ T* data = reinterpret_cast<T*>(buffer_->mutable_data());
+ int num_valid_values = ::arrow::util::internal::SpacedCompress<T>(
+ src, num_values, valid_bits, valid_bits_offset, data);
+ Put(data, num_valid_values);
+ } else {
+ Put(src, num_values);
+ }
+ }
+
+ protected:
+ template <typename ArrayType>
+ void PutBinaryArray(const ArrayType& array) {
+ auto previous_len = static_cast<uint32_t>(last_value_.size());
+ std::string_view last_value_view = last_value_;
+
+ PARQUET_THROW_NOT_OK(::arrow::VisitArraySpanInline<typename
ArrayType::TypeClass>(
+ *array.data(),
+ [&](::std::string_view view) {
+ if (ARROW_PREDICT_FALSE(view.size() >= kMaxByteArraySize)) {
+ return Status::Invalid("Parquet cannot store strings with size 2GB
or more");
+ }
+ // Convert to ByteArray, so it can be passed to the suffix_encoder_.
+ const ByteArray src{view};
+
+ uint32_t j = 0;
+ const uint32_t common_length = std::min(previous_len, src.len);
+ while (j < common_length) {
+ if (last_value_view[j] != view[j]) {
+ break;
+ }
+ j++;
+ }
+ previous_len = src.len;
+ prefix_length_encoder_.Put({static_cast<int32_t>(j)}, 1);
+
+ last_value_view = view;
+ const auto suffix_length = static_cast<uint32_t>(src.len - j);
+ if (suffix_length == 0) {
+ suffix_encoder_.Put(&kEmpty, 1);
Review Comment:
```
[----------] 3 tests from DeltaByteArrayEncodingAdHoc
[ RUN ] DeltaByteArrayEncodingAdHoc.ArrowBinaryDirectPut
/arrow/cpp/src/arrow/buffer_builder.h:138:27: runtime error: null pointer
passed as argument 2, which is declared to never be null
/usr/include/string.h:44:28: note: nonnull attribute specified here
#0 0x55a380a6b658 in arrow::BufferBuilder::UnsafeAppend(void const*,
long) /arrow/cpp/src/arrow/buffer_builder.h:138:5
#1 0x7f976e1ca580 in parquet::(anonymous
namespace)::DeltaLengthByteArrayEncoder<parquet::PhysicalType<(parquet::Type::type)6>
>::Put(parquet::ByteArray const*, int)
/arrow/cpp/src/parquet/encoding.cc:2719:11
#2 0x7f976e1f7f7f in void parquet::(anonymous
namespace)::DeltaByteArrayEncoder<parquet::PhysicalType<(parquet::Type::type)6>
>::PutBinaryArray<arrow::BinaryArray>(arrow::BinaryArray
const&)::'lambda'(std::basic_string_view<char, std::char_traits<char>
>)::operator()(std::basic_string_view<char, std::char_traits<char> >) const
/arrow/cpp/src/parquet/encoding.cc:3150:5
```
The ASAN & UBSAN check fails here, though the line number does not appear to
be precise. If `suffix_length` is 0, we probably can skip calling
`suffix_encoder_.Put` as there is nothing to concatenate.
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