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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