[GitHub] [arrow] felipecrv opened a new issue, #35141: [C++] Add versions of IsNull/IsValid that take an ArrowType tparam so implementation can be statically dispatched

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

felipecrv opened a new issue, #35141:
URL: https://github.com/apache/arrow/issues/35141

   ### Describe the enhancement requested
   
   #34408 introduced more branches to the implementations of `IsNull` and `IsValid` testing the type to of the array to dispatch specific implementations for a few special types. Although these branches are easy on the branch predictor, it's good to offer users that know the type ahead of time a way to eliminate those branches completely from their loops.
   
   Proposed implementation using `if constexpr`:
   
   ```cpp
       template <typename ArrowType>
       bool IsNullFast(int64_t i) const {
         return !IsValidFast<ArrowType>(i);
       }
   
       template <typename ArrowType>
       bool IsValidFast(int64_t i) const {
         if constexpr (ArrowType::type_id == Type::NA) {
           return false;
         } else if constexpr (ArrowType::type_id == Type::SPARSE_UNION) {
           return !internal::IsNullSparseUnion(*this, i);
         } else if constexpr (ArrowType::type_id == Type::DENSE_UNION) {
           return !internal::IsNullDenseUnion(*this, i);
         } else if constexpr (ArrowType::type_id == Type::RUN_END_ENCODED) {
           return !internal::IsNullRunEndEncoded(*this, i);
         } else {
           if (buffers[0] != NULLPTR) {
             return bit_util::GetBit(buffers[0]->data(), i + offset);
           }
           return null_count.load() != length;
         }
     }
   ```
   
   ### Component(s)
   
   C++


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[GitHub] [arrow] felipecrv commented on issue #35141: [C++] Add versions of IsNull/IsValid that take an ArrowType tparam so implementation can be statically dispatched

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

felipecrv commented on issue #35141:
URL: https://github.com/apache/arrow/issues/35141#issuecomment-1509042393

   take


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