rok commented on code in PR #14341:
URL: https://github.com/apache/arrow/pull/14341#discussion_r1256735619
##########
cpp/src/parquet/encoding.cc:
##########
@@ -3037,12 +3083,230 @@ 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, reinterpret_cast<const uint8_t*>(""))) {}
+
+ 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:
+ template <typename VisitorType>
+ void PutInternal(const T* src, int num_values) {
+ if (num_values == 0) {
+ return;
+ }
+ uint32_t len = descr_->type_length();
Review Comment:
Indeed!
##########
cpp/src/parquet/encoding.cc:
##########
@@ -3037,12 +3083,230 @@ 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, reinterpret_cast<const uint8_t*>(""))) {}
+
+ 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:
+ template <typename VisitorType>
+ void PutInternal(const T* src, int num_values) {
+ if (num_values == 0) {
+ return;
+ }
+ uint32_t len = descr_->type_length();
+
+ std::string_view last_value_view = last_value_;
+ constexpr int kBatchSize = 256;
+ std::array<int32_t, kBatchSize> prefix_lengths;
+ std::array<ByteArray, kBatchSize> suffixes;
+ auto visitor = VisitorType{src, len};
+
+ for (int i = 0; i < num_values; i += kBatchSize) {
+ const int batch_size = std::min(kBatchSize, num_values - i);
+
+ for (int j = 0; j < batch_size; ++j) {
+ auto view = visitor[i + j];
Review Comment:
Changed.
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