datafusion-functions 48.0.0

// Licensed to the Apache Software Foundation (ASF) under one
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// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

use std::any::Any;
use std::sync::Arc;

use arrow::array::{ArrayRef, AsArray};
use arrow::datatypes::DataType::{Float32, Float64};
use arrow::datatypes::{DataType, Float32Type, Float64Type};

use datafusion_common::{exec_err, Result};
use datafusion_expr::sort_properties::{ExprProperties, SortProperties};
use datafusion_expr::{
    ColumnarValue, Documentation, ScalarFunctionArgs, ScalarUDFImpl, Signature,
    Volatility,
};
use datafusion_macros::user_doc;

use crate::utils::make_scalar_function;

#[user_doc(
    doc_section(label = "Math Functions"),
    description = r#"Returns the sign of a number.
Negative numbers return `-1`.
Zero and positive numbers return `1`."#,
    syntax_example = "signum(numeric_expression)",
    standard_argument(name = "numeric_expression", prefix = "Numeric")
)]
#[derive(Debug)]
pub struct SignumFunc {
    signature: Signature,
}

impl Default for SignumFunc {
    fn default() -> Self {
        SignumFunc::new()
    }
}

impl SignumFunc {
    pub fn new() -> Self {
        use DataType::*;
        Self {
            signature: Signature::uniform(
                1,
                vec![Float64, Float32],
                Volatility::Immutable,
            ),
        }
    }
}

impl ScalarUDFImpl for SignumFunc {
    fn as_any(&self) -> &dyn Any {
        self
    }

    fn name(&self) -> &str {
        "signum"
    }

    fn signature(&self) -> &Signature {
        &self.signature
    }

    fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
        match &arg_types[0] {
            Float32 => Ok(Float32),
            _ => Ok(Float64),
        }
    }

    fn output_ordering(&self, input: &[ExprProperties]) -> Result<SortProperties> {
        // Non-decreasing for all real numbers x.
        Ok(input[0].sort_properties)
    }

    fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
        make_scalar_function(signum, vec![])(&args.args)
    }

    fn documentation(&self) -> Option<&Documentation> {
        self.doc()
    }
}

/// signum SQL function
pub fn signum(args: &[ArrayRef]) -> Result<ArrayRef> {
    match args[0].data_type() {
        Float64 => Ok(Arc::new(
            args[0]
                .as_primitive::<Float64Type>()
                .unary::<_, Float64Type>(
                    |x: f64| {
                        if x == 0_f64 {
                            0_f64
                        } else {
                            x.signum()
                        }
                    },
                ),
        ) as ArrayRef),

        Float32 => Ok(Arc::new(
            args[0]
                .as_primitive::<Float32Type>()
                .unary::<_, Float32Type>(
                    |x: f32| {
                        if x == 0_f32 {
                            0_f32
                        } else {
                            x.signum()
                        }
                    },
                ),
        ) as ArrayRef),

        other => exec_err!("Unsupported data type {other:?} for function signum"),
    }
}

#[cfg(test)]
mod test {
    use std::sync::Arc;

    use arrow::array::{ArrayRef, Float32Array, Float64Array};
    use arrow::datatypes::{DataType, Field};
    use datafusion_common::cast::{as_float32_array, as_float64_array};
    use datafusion_expr::{ColumnarValue, ScalarFunctionArgs, ScalarUDFImpl};

    use crate::math::signum::SignumFunc;

    #[test]
    fn test_signum_f32() {
        let array = Arc::new(Float32Array::from(vec![
            -1.0,
            -0.0,
            0.0,
            1.0,
            -0.01,
            0.01,
            f32::NAN,
            f32::INFINITY,
            f32::NEG_INFINITY,
        ]));
        let arg_fields = vec![Field::new("a", DataType::Float32, false).into()];
        let args = ScalarFunctionArgs {
            args: vec![ColumnarValue::Array(Arc::clone(&array) as ArrayRef)],
            arg_fields,
            number_rows: array.len(),
            return_field: Field::new("f", DataType::Float32, true).into(),
        };
        let result = SignumFunc::new()
            .invoke_with_args(args)
            .expect("failed to initialize function signum");

        match result {
            ColumnarValue::Array(arr) => {
                let floats = as_float32_array(&arr)
                    .expect("failed to convert result to a Float32Array");

                assert_eq!(floats.len(), 9);
                assert_eq!(floats.value(0), -1.0);
                assert_eq!(floats.value(1), 0.0);
                assert_eq!(floats.value(2), 0.0);
                assert_eq!(floats.value(3), 1.0);
                assert_eq!(floats.value(4), -1.0);
                assert_eq!(floats.value(5), 1.0);
                assert!(floats.value(6).is_nan());
                assert_eq!(floats.value(7), 1.0);
                assert_eq!(floats.value(8), -1.0);
            }
            ColumnarValue::Scalar(_) => {
                panic!("Expected an array value")
            }
        }
    }

    #[test]
    fn test_signum_f64() {
        let array = Arc::new(Float64Array::from(vec![
            -1.0,
            -0.0,
            0.0,
            1.0,
            -0.01,
            0.01,
            f64::NAN,
            f64::INFINITY,
            f64::NEG_INFINITY,
        ]));
        let arg_fields = vec![Field::new("a", DataType::Float64, false).into()];
        let args = ScalarFunctionArgs {
            args: vec![ColumnarValue::Array(Arc::clone(&array) as ArrayRef)],
            arg_fields,
            number_rows: array.len(),
            return_field: Field::new("f", DataType::Float64, true).into(),
        };
        let result = SignumFunc::new()
            .invoke_with_args(args)
            .expect("failed to initialize function signum");

        match result {
            ColumnarValue::Array(arr) => {
                let floats = as_float64_array(&arr)
                    .expect("failed to convert result to a Float32Array");

                assert_eq!(floats.len(), 9);
                assert_eq!(floats.value(0), -1.0);
                assert_eq!(floats.value(1), 0.0);
                assert_eq!(floats.value(2), 0.0);
                assert_eq!(floats.value(3), 1.0);
                assert_eq!(floats.value(4), -1.0);
                assert_eq!(floats.value(5), 1.0);
                assert!(floats.value(6).is_nan());
                assert_eq!(floats.value(7), 1.0);
                assert_eq!(floats.value(8), -1.0);
            }
            ColumnarValue::Scalar(_) => {
                panic!("Expected an array value")
            }
        }
    }
}