Function cast_struct_array

datafusion/physical-expr/src/expressions/cast.rs:402–421

(
        column: &str,
        input_field: Field,
        target_field: Field,
        input_array: StructArray,
    )

    }

    fn cast_struct_array(
        column: &str,
        input_field: Field,
        target_field: Field,
        input_array: StructArray,
    ) -> Result<StructArray> {
        let schema = Arc::new(Schema::new(vec![input_field]));
        let batch = RecordBatch::try_new(
            Arc::clone(&schema),
            vec![Arc::new(input_array) as ArrayRef],
        )?;
        let expr = CastExpr::new_with_target_field(
            col(column, schema.as_ref())?,
            Arc::new(target_field),
            None,
        );

        let result = expr.evaluate(&batch)?.into_array(batch.num_rows())?;
        Ok(as_struct_array(result.as_ref())?.clone())
    }

    // runs an end-to-end test of physical type cast
    // 1. construct a record batch with a column "a" of type A