rok commented on code in PR #14341:
URL: https://github.com/apache/arrow/pull/14341#discussion_r1122203542
##########
cpp/src/parquet/encoding.cc:
##########
@@ -2900,6 +2900,124 @@ class RleBooleanDecoder : public DecoderImpl, virtual
public BooleanDecoder {
// ----------------------------------------------------------------------
// DELTA_BYTE_ARRAY
+// 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 {
+ AssertBaseBinary(values);
+ const auto& data = values.data();
Review Comment:
Indeed. Added.
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