struct_expressions.rs

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// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
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//
//   http://www.apache.org/licenses/LICENSE-2.0
//
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// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

//! Struct expressions

use arrow::array::*;
use arrow::datatypes::{DataType, Field};
use datafusion_common::{exec_err, not_impl_err, DataFusionError, Result};
use datafusion_expr::ColumnarValue;
use std::sync::Arc;

fn array_struct(args: &[ArrayRef]) -> Result<ArrayRef> {
    // do not accept 0 arguments.
    if args.is_empty() {
        return exec_err!("struct requires at least one argument");
    }

    let vec: Vec<_> = args
        .iter()
        .enumerate()
        .map(|(i, arg)| {
            let field_name = format!("c{i}");
            match arg.data_type() {
                DataType::Utf8
                | DataType::LargeUtf8
                | DataType::Boolean
                | DataType::Float32
                | DataType::Float64
                | DataType::Int8
                | DataType::Int16
                | DataType::Int32
                | DataType::Int64
                | DataType::UInt8
                | DataType::UInt16
                | DataType::UInt32
                | DataType::UInt64 => Ok((
                    Arc::new(Field::new(
                        field_name.as_str(),
                        arg.data_type().clone(),
                        true,
                    )),
                    arg.clone(),
                )),
                data_type => {
                    not_impl_err!("Struct is not implemented for type '{data_type:?}'.")
                }
            }
        })
        .collect::<Result<Vec<_>>>()?;

    Ok(Arc::new(StructArray::from(vec)))
}

/// put values in a struct array.
pub fn struct_expr(values: &[ColumnarValue]) -> Result<ColumnarValue> {
    let arrays = values
        .iter()
        .map(|x| {
            Ok(match x {
                ColumnarValue::Array(array) => array.clone(),
                ColumnarValue::Scalar(scalar) => scalar.to_array()?.clone(),
            })
        })
        .collect::<Result<Vec<ArrayRef>>>()?;
    Ok(ColumnarValue::Array(array_struct(arrays.as_slice())?))
}

#[cfg(test)]
mod tests {
    use super::*;
    use datafusion_common::cast::as_struct_array;
    use datafusion_common::ScalarValue;

    #[test]
    fn test_struct() {
        // struct(1, 2, 3) = {"c0": 1, "c1": 2, "c2": 3}
        let args = [
            ColumnarValue::Scalar(ScalarValue::Int64(Some(1))),
            ColumnarValue::Scalar(ScalarValue::Int64(Some(2))),
            ColumnarValue::Scalar(ScalarValue::Int64(Some(3))),
        ];
        let struc = struct_expr(&args)
            .expect("failed to initialize function struct")
            .into_array(1)
            .expect("Failed to convert to array");
        let result =
            as_struct_array(&struc).expect("failed to initialize function struct");
        assert_eq!(
            &Int64Array::from(vec![1]),
            result
                .column_by_name("c0")
                .unwrap()
                .clone()
                .as_any()
                .downcast_ref::<Int64Array>()
                .unwrap()
        );
        assert_eq!(
            &Int64Array::from(vec![2]),
            result
                .column_by_name("c1")
                .unwrap()
                .clone()
                .as_any()
                .downcast_ref::<Int64Array>()
                .unwrap()
        );
        assert_eq!(
            &Int64Array::from(vec![3]),
            result
                .column_by_name("c2")
                .unwrap()
                .clone()
                .as_any()
                .downcast_ref::<Int64Array>()
                .unwrap()
        );
    }
}