apacheGH-38432: [C++][Parquet] Encoding: Dict Arrow Decoder tiny regr…

…ession fix
mapleFU · Nov 19, 2023 · a50f3fa · a50f3fa
1 parent 46c226e
commit a50f3fa
Showing 1 changed file with 14 additions and 2 deletions.
diff --git a/cpp/src/parquet/encoding.cc b/cpp/src/parquet/encoding.cc
@@ -904,7 +904,12 @@ class DecoderImpl : virtual public Decoder {
 
  protected:
   explicit DecoderImpl(const ColumnDescriptor* descr, Encoding::type encoding)
-      : descr_(descr), encoding_(encoding), num_values_(0), data_(NULLPTR), len_(0) {}
+      : descr_(descr),
+        encoding_(encoding),
+        num_values_(0),
+        data_(NULLPTR),
+        len_(0),
+        type_length_(0) {}
 
   // For accessing type-specific metadata, like FIXED_LEN_BYTE_ARRAY
   const ColumnDescriptor* descr_;
@@ -1196,6 +1201,10 @@ struct ArrowBinaryHelper<ByteArrayType> {
         chunk_space_remaining_(::arrow::kBinaryMemoryLimit -
                                acc_->builder->value_data_length()) {}
 
+  // Prepare will Reserve the number of entries remaining in the current chunk.
+  // If estimated_data_length is provided, it will also Reserve the estimated data length,
+  // and the caller should remember to call `UnsafeAppend` instead of `Append` to avoid
+  // double counting the data length.
   Status Prepare(std::optional<int64_t> estimated_data_length = {}) {
     RETURN_NOT_OK(acc_->builder->Reserve(entries_remaining_));
     if (estimated_data_length.has_value()) {
@@ -1205,6 +1214,9 @@ struct ArrowBinaryHelper<ByteArrayType> {
     return Status::OK();
   }
 
+  // If estimated_remaining_data_length is provided, it will also Reserve the estimated
+  // data length, and the caller should remember to call `UnsafeAppend` instead of
+  // `Append` to avoid double counting the data length.
   Status PrepareNextInput(int64_t next_value_length,
                           std::optional<int64_t> estimated_remaining_data_length = {}) {
     if (ARROW_PREDICT_FALSE(!CanFit(next_value_length))) {
@@ -1983,7 +1995,7 @@ class DictByteArrayDecoderImpl : public DictDecoderImpl<ByteArrayType>,
     int values_decoded = 0;
 
     ArrowBinaryHelper<ByteArrayType> helper(out, num_values);
-    RETURN_NOT_OK(helper.Prepare(len_));
+    RETURN_NOT_OK(helper.Prepare());
 
     auto dict_values = reinterpret_cast<const ByteArray*>(dictionary_->data());