From this test case, we can know that we should not treat Null as UTF8 data type _Originally posted by @liukun4515 in https://github.com/apache/arrow-datafusion/pull/2764#discussion_r904468132_ From the implemention: 1. https://github.com/apache/arrow-datafusion/blob/3da59e8877620a095efae102b0177e7e6a76f65b/datafusion/physical-expr/src/expressions/in_list.rs#L163 2. https://github.com/apache/arrow-datafusion/blob/3da59e8877620a095efae102b0177e7e6a76f65b/datafusion/physical-expr/src/expressions/in_list.rs#L111