[GitHub] [arrow] mapleFU commented on pull request #14341: GH-32863: [C++][Parquet] Add DELTA_BYTE_ARRAY encoder to Parquet writer

["mapleFU (via GitHub)" <gi...@apache.org>]

mapleFU commented on PR #14341:
URL: https://github.com/apache/arrow/pull/14341#issuecomment-1480564576

   Personally, I think we can make it easier, like using `PutImpl(std::vector<ByteArray>, int num_values)`. When Put with arrow, we can extract it into it.
   
   Or we can:
   
   ```C++
   template <typename ParquetT>
   struct ParquetIndirectType {
     static const uint8_t* getPtr(ParquetT object) noexcept;
     static int getLen(const parquet::ColumnDescriptor* descr, ParquetT object) noexcept;
   };
   
   template <>
   struct ParquetIndirectType<parquet::ByteArray> {
     static const uint8_t* getPtr(parquet::ByteArray object) noexcept {
       return object.ptr;
     }
   
     static int getLen([[maybe_unused]] const parquet::ColumnDescriptor* descr, parquet::ByteArray object) noexcept {
       return object.len;
     }
   };
   
   template <>
   struct ParquetIndirectType<parquet::FixedLenByteArray> {
     static const uint8_t* getPtr(parquet::FixedLenByteArray object) noexcept {
       return object.ptr;
     }
   
     static int getLen(
         const parquet::ColumnDescriptor* descr, [[maybe_unused]] parquet::FixedLenByteArray object) noexcept {
       return descr->type_length();
     }
   };
   ```
   
   And use template to just write one part of the code. But it may have worse performance than your impl if compiler doesn't work well. The current skeleton is ok to me


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