[jira] [Assigned] (ARROW-10136) [Rust][Arrow] Nulls are transformed into "" after filtering for StringArray

["Apache Arrow JIRA Bot (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-10136?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Apache Arrow JIRA Bot reassigned ARROW-10136:
---------------------------------------------

    Assignee: Apache Arrow JIRA Bot  (was: Andrew Lamb)

> [Rust][Arrow] Nulls are transformed into "" after filtering for StringArray
> ---------------------------------------------------------------------------
>
>                 Key: ARROW-10136
>                 URL: https://issues.apache.org/jira/browse/ARROW-10136
>             Project: Apache Arrow
>          Issue Type: Bug
>            Reporter: Andrew Lamb
>            Assignee: Apache Arrow JIRA Bot
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> When I use the filter kernel with Null strings, any input column that was Null turns into an empty string after filtering.
> For example, this test (in filter.rs) should pass:
> {code}
>     #[test]
>     fn test_filter_string_array_with_null() {
>         let a = StringArray::from(vec![Some("hello"), None, Some("world"), None]);
>         let b = BooleanArray::from(vec![true, false, false, true]);
>         let c = filter(&a, &b).unwrap();
>         let d = c.as_ref().as_any().downcast_ref::<StringArray>().unwrap();
>         assert_eq!(2, d.len());
>         assert_eq!("hello", d.value(0));
>         assert_eq!(true, d.is_null(1));
>     }
> {code}
> But instead it fails (the second element in the output array should be null )
> {code}
> ---- compute::kernels::filter::tests::test_filter_string_array_with_null stdout ----
> thread 'compute::kernels::filter::tests::test_filter_string_array_with_null' panicked at 'assertion failed: `(left == right)`
>   left: `true`,
>  right: `false`', arrow/src/compute/kernels/filter.rs:686:9
> note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
> {code}



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