[GitHub] [arrow-rs] eddyxu opened a new issue, #3837: Concating dictionary array leads to duplicated dict values.

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

eddyxu opened a new issue, #3837:
URL: https://github.com/apache/arrow-rs/issues/3837

   **Describe the bug**
   <!--
   A clear and concise description of what the bug is.
   -->
   
   I was trying to concatenate a few DictionaryArrays using `arrow_select::concat::concat`. While the each Dictionary Array shares the same value strings. The resulted array however have all values from each DictionaryArray copied (duplicated) in the final output. 
   
   **To Reproduce**
   <!--
   Steps to reproduce the behavior:
   -->
   
   ```rust
   let arrs: Vec<Arc<DictionaryArray<Int32Type>>> = (0..10).map(|v| {
             let mut dict_builder = StringDictionaryBuilder::<Int32Type>::new();
             dict_builder.append_null();
             dict_builder.append("a").unwrap();
             dict_builder.append("b").unwrap();
             dict_builder.append("c").unwrap();
             Arc::new(dict_builder.finish())
       }).collect();
       let mut arrays: Vec<&dyn Array> = vec![];
       for b in arrs.iter() {
           arrays.push(b.as_ref());
       }
       let b = concat(arrays.as_slice()).unwrap();
       println!("Batch is: {:?}", b);
   ```
   
   Output
   ```
   Batch is: DictionaryArray {keys: PrimitiveArray<Int32>
   [
     null,
     0,
     1,
     2,
     null,
     3,
     4,
     5,
   ] values: StringArray
   [
     "a",
     "b",
     "c",
     "a",
     "b",
     "c",
   ]}
   
   ```
   **Expected behavior**
   <!--
   A clear and concise description of what you expected to happen.
   -->
   
   I'd expect the output will be
   
   ```
   DictionaryArray {keys: PrimitiveArray<Int32>
   [
     null,
     0,
     1,
     2,
     null,
     0,
     1,
      2
   ] values: StringArray
   [
     "a",
     "b",
     "c",
   ]}
   ```
   
   **Additional context**
   <!--
   Add any other context about the problem here.
   -->
   
   N/A


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[GitHub] [arrow-rs] tustvold commented on issue #3837: Concating dictionary array leads to duplicated dict values.

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

tustvold commented on issue #3837:
URL: https://github.com/apache/arrow-rs/issues/3837#issuecomment-1463598082

   This is intentional, #506 tracks doing something different here


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[GitHub] [arrow-rs] tustvold closed issue #3837: Concating dictionary array leads to duplicated dict values.

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

tustvold closed issue #3837: Concating dictionary array leads to duplicated dict values.
URL: https://github.com/apache/arrow-rs/issues/3837


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