[I] [Arrow] Consider faster way to check if a `Field` has an extension type [arrow-rs]

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

alamb opened a new issue, #8474:
URL: https://github.com/apache/arrow-rs/issues/8474

   **Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
   
   As @mbrobbel  pointed out in https://github.com/apache/arrow-rs/pull/8408/files#r2378240955:
   
   There are currently two APIs for seeing if a Field has an extension type:
   
   * [`Field::extension_type`](https://docs.rs/arrow/latest/arrow/datatypes/struct.Field.html#method.extension_type) that panics if the field does not have the extension type
   * [`Field::try_extension_type`](https://docs.rs/arrow/latest/arrow/datatypes/struct.Field.html#method.try_extension_type) that returns an `ArrowError` if the field does not have the extension type
   
   There is no good API to quickly tell if a Field has an extension type. The current way is like
   ```rust
   if field.try_extension_type<TheExtensionType>().is_ok() {
    // field has extension type
   }
   ```
   
   Works, but it requires creating an `ArrowError` if the field is not the requested type, which is slow as it allocates a String
   
   in https://github.com/apache/arrow-rs/pull/8408 I came up with this to avoid the problem, but it is not obvious and somewhat redundant:
   
   ```rust
       // Check the name (= quick and cheap) and only try_extension_type if the name matches
       // to avoid unnecessary String allocations in ArrowError
       if field.extension_type_name()? != VariantType::NAME {
           return None;
       }
       match field.try_extension_type::<VariantType>() {
           Ok(VariantType) => Some(LogicalType::Variant),
           // Given check above, this should not error, but if it does ignore
           Err(_e) => None,
       }
   ```
   
   **Describe the solution you'd like**
   A clearer way to test for extension types.
   
   Maybe the documentation I added in https://github.com/apache/arrow-rs/pull/8408 is sufficient
   
   **Describe alternatives you've considered**
   <!--
   A clear and concise description of any alternative solutions or features you've considered.
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   **Additional context**
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   Add any other context or screenshots about the feature request here.
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Re: [I] [Arrow] Consider faster way to check if a `Field` has an extension type [arrow-rs]

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

alamb closed issue #8474: [Arrow] Consider faster way to check if a `Field` has an extension type
URL: https://github.com/apache/arrow-rs/issues/8474


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