[ARROW-11594] [Rust] Support pretty printing with NullArrays

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.0
• Component/s: Rust
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/27463
• Assignee: Andrew Lamb
• Reporter: Andrew Lamb
• Created: 11/Feb/21 11:55
• Updated: 11/Jan/23 08:20
• Resolved: 14/Feb/21 10:43

Description

The whole point of `NullArray::new_with_type` is to to be able to cheaply construct entirely null columns, with a smaller memory footprint.

Currently trying to print them out causes a painic:

    #[test]
    fn test_pretty_format_null() -> Result<()> {
        // define a schema.
        let schema = Arc::new(Schema::new(vec![
            Field::new("a", DataType::Utf8, true),
            Field::new("b", DataType::Int32, true),
        ]));

        let num_rows = 4;

        // define data (null)
        let batch = RecordBatch::try_new(
            schema,
            vec![
                Arc::new(NullArray::new_with_type(num_rows, DataType::Utf8)),
                Arc::new(NullArray::new_with_type(num_rows, DataType::Int32)),
            ],
        )?;

        let table = pretty_format_batches(&[batch])?;
}

Panics:

failures:

---- util::pretty::tests::test_pretty_format_null stdout ----
thread 'util::pretty::tests::test_pretty_format_null' panicked at 'called `Option::unwrap()` on a `None` value', arrow/src/util/display.rs:201:27

Issue Links

• links to: GitHub Pull Request #9468