rok commented on code in PR #14191:
URL: https://github.com/apache/arrow/pull/14191#discussion_r1019579381
##########
cpp/src/parquet/encoding.cc:
##########
@@ -2062,6 +2064,202 @@ class DictByteArrayDecoderImpl : public
DictDecoderImpl<ByteArrayType>,
}
};
+// ----------------------------------------------------------------------
+// DeltaBitPackEncoder
+
+template <typename DType>
+class DeltaBitPackEncoder : public EncoderImpl, virtual public
TypedEncoder<DType> {
+ public:
+ using T = typename DType::c_type;
+
+ explicit DeltaBitPackEncoder(const ColumnDescriptor* descr, MemoryPool* pool)
+ : EncoderImpl(descr, Encoding::DELTA_BINARY_PACKED, pool),
+ values_per_block_(128),
+ mini_blocks_per_block_(4),
+ values_per_mini_block_(values_per_block_ / mini_blocks_per_block_),
+ values_current_block_(0),
+ total_value_count_(0),
+ first_value_(0),
+ current_value_(0),
+ sink_(pool),
+ bits_buffer_(AllocateBuffer(pool, (4 + values_per_block_) *
sizeof(T))),
+ bit_writer_(bits_buffer_->mutable_data(),
static_cast<int>(bits_buffer_->size())),
+ deltas_(std::vector<T>(values_per_block_)) {}
+
+ std::shared_ptr<Buffer> FlushValues() override;
+
+ int64_t EstimatedDataEncodedSize() override { return 4 * sizeof(T) +
sink_.length(); }
+
+ 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;
+
+ protected:
+ const uint32_t values_per_block_;
+ const uint32_t mini_blocks_per_block_;
+ const uint32_t values_per_mini_block_;
+ uint32_t values_current_block_;
+ uint32_t total_value_count_;
+ T first_value_;
+ T current_value_;
+ ::arrow::BufferBuilder sink_;
+ std::shared_ptr<ResizableBuffer> bits_buffer_;
+ ::arrow::bit_util::BitWriter bit_writer_;
+ std::vector<T> deltas_;
+
+ private:
+ void FlushBlock();
+};
+
+template <typename DType>
+void DeltaBitPackEncoder<DType>::Put(const T* src, int num_values) {
+ if (num_values == 0) {
+ return;
+ }
+
+ int idx = 0;
+ if (total_value_count_ == 0) {
+ current_value_ = src[0];
+ first_value_ = current_value_;
+ idx = 1;
+ }
+ total_value_count_ += num_values;
+
+ while (idx < num_values) {
+ T value = src[idx];
+ deltas_[values_current_block_] = SafeSignedSubtract(value, current_value_);
+ current_value_ = value;
+ idx++;
+ values_current_block_++;
+ if (values_current_block_ == values_per_block_) {
+ FlushBlock();
+ }
+ }
+}
+
+template <typename DType>
+void DeltaBitPackEncoder<DType>::FlushBlock() {
+ if (values_current_block_ == 0) {
+ return;
+ }
+
+ const T min_delta =
+ *std::min_element(deltas_.begin(), deltas_.begin() +
values_current_block_);
+ DCHECK(bit_writer_.PutZigZagVlqInt(min_delta));
+
+ uint8_t* bit_width_offsets =
bit_writer_.GetNextBytePtr(mini_blocks_per_block_);
+ DCHECK(bit_width_offsets != nullptr);
+
+ for (uint32_t i = 0; i < mini_blocks_per_block_; i++) {
+ const uint32_t n = std::min(values_per_mini_block_, values_current_block_);
+ if (n == 0) {
+ DCHECK(bit_writer_.PutAlignedOffset<int8_t>(bit_width_offsets++,
int8_t(32), 1));
+ for (uint32_t j = 0; j < values_per_mini_block_; j++) {
+ DCHECK(bit_writer_.PutAligned<T>(0, 4));
+ }
+ continue;
+ }
+
+ const uint32_t start = i * values_per_mini_block_;
+ const T max_delta =
+ *std::max_element(deltas_.begin() + start, deltas_.begin() + start +
n);
+
+ const T max_delta_diff = SafeSignedSubtract(max_delta, min_delta);
+ int8_t num_bits;
+ if constexpr (std::is_same<T, int64_t>::value) {
+ num_bits = bit_util::NumRequiredBits(max_delta_diff);
+ } else {
+ num_bits =
bit_util::NumRequiredBits(static_cast<uint32_t>(max_delta_diff));
+ }
+ const int32_t num_bytes =
+ static_cast<const int32_t>(bit_util::BytesForBits(num_bits));
+ DCHECK(bit_writer_.PutAlignedOffset<int8_t>(bit_width_offsets++, num_bits,
1));
+
+ for (uint32_t j = start; j < start + n; j++) {
+ const T value = SafeSignedSubtract(deltas_[j], min_delta);
+ DCHECK(bit_writer_.PutAligned<T>(value, num_bytes));
+ }
+ for (uint32_t j = n; j < values_per_mini_block_; j++) {
+ DCHECK(bit_writer_.PutAligned<T>(0, num_bytes));
+ }
+ values_current_block_ -= n;
+ }
+ DCHECK_EQ(values_current_block_, 0);
+
+ bit_writer_.Flush();
+ PARQUET_THROW_NOT_OK(sink_.Append(bit_writer_.buffer(),
bit_writer_.bytes_written()));
+ bit_writer_.Clear();
+}
+
+template <typename DType>
+std::shared_ptr<Buffer> DeltaBitPackEncoder<DType>::FlushValues() {
+ if (values_current_block_ != 0) {
+ FlushBlock();
+ }
+
+ std::shared_ptr<ResizableBuffer> header_buffer = AllocateBuffer(pool_, 32);
+ ::arrow::bit_util::BitWriter header_writer(header_buffer->mutable_data(),
+
static_cast<int>(header_buffer->size()));
+ if (!header_writer.PutVlqInt(values_per_block_) ||
+ !header_writer.PutVlqInt(mini_blocks_per_block_) ||
+ !header_writer.PutVlqInt(total_value_count_) ||
+ !header_writer.PutZigZagVlqInt(first_value_)) {
+ throw ParquetException("cannot write");
Review Comment:
Changed. This message should never be reached as the written to buffer
should always be big enough for the 4 ints written.
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