mapleFU commented on code in PR #14341:
URL: https://github.com/apache/arrow/pull/14341#discussion_r1147066648
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cpp/src/parquet/encoding.cc:
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@@ -2900,8 +2929,222 @@ class RleBooleanDecoder : public DecoderImpl, virtual
public BooleanDecoder {
// ----------------------------------------------------------------------
// DELTA_BYTE_ARRAY
-class DeltaByteArrayDecoder : public DecoderImpl,
- virtual public TypedDecoder<ByteArrayType> {
+// This is 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:
+ using T = typename DType::c_type;
+
+ explicit DeltaByteArrayEncoder(const ColumnDescriptor* descr, MemoryPool*
pool)
+ : EncoderImpl(descr, Encoding::DELTA_BYTE_ARRAY,
+ pool = ::arrow::default_memory_pool()),
+ sink_(pool),
+ prefix_length_encoder_(nullptr, pool),
+ suffix_encoder_(nullptr, pool) {}
+
+ 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(auto 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:
+ void PutFixedLenByteArray(const ::arrow::FixedSizeBinaryArray& array) {
+ const uint32_t byte_width = array.byte_width();
+
+ // TODO(rok): optimize using ArrowPoolVector<int32_t>
prefix_lengths(num_values);
+
PARQUET_THROW_NOT_OK(::arrow::VisitArraySpanInline<::arrow::FixedSizeBinaryType>(
+ *array.data(),
+ [&](::std::string_view view) {
+ uint32_t previous_len = 0;
+ const ByteArray src{view};
Review Comment:
Great! Lets resolve this
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