fix: reject negative ln inputs

Author: akmhatey-ai

datafusion/functions/src/math/ln.rs

@@ -0,0 +1,132 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// 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::sync::Arc;
+
+use arrow::array::{ArrayRef, AsArray, Float32Array, Float64Array};
+use arrow::datatypes::{DataType, Float32Type, Float64Type};
+use arrow::error::ArrowError;
+use datafusion_common::{Result, exec_err, utils::take_function_args};
+use datafusion_expr::interval_arithmetic::Interval;
+use datafusion_expr::sort_properties::{ExprProperties, SortProperties};
+use datafusion_expr::{
+    ColumnarValue, Documentation, ScalarFunctionArgs, ScalarUDFImpl, Signature,
+    Volatility,
+};
+
+use super::{bounds::unbounded_bounds, get_ln_doc, ln_order};
+
+#[derive(Debug, PartialEq, Eq, Hash)]
+pub struct LnFunc {
+    signature: Signature,
+}
+
+impl Default for LnFunc {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl LnFunc {
+    pub fn new() -> Self {
+        use DataType::*;
+        Self {
+            signature: Signature::uniform(
+                1,
+                vec![Float64, Float32],
+                Volatility::Immutable,
+            ),
+        }
+    }
+}
+
+impl ScalarUDFImpl for LnFunc {
+    fn name(&self) -> &str {
+        "ln"
+    }
+
+    fn signature(&self) -> &Signature {
+        &self.signature
+    }
+
+    fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
+        match &arg_types[0] {
+            DataType::Float32 => Ok(DataType::Float32),
+            _ => Ok(DataType::Float64),
+        }
+    }
+
+    fn output_ordering(&self, input: &[ExprProperties]) -> Result<SortProperties> {
+        ln_order(input)
+    }
+
+    fn evaluate_bounds(&self, inputs: &[&Interval]) -> Result<Interval> {
+        unbounded_bounds(inputs)
+    }
+
+    fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
+        let args = ColumnarValue::values_to_arrays(&args.args)?;
+        let [arg] = take_function_args(self.name(), args)?;
+
+        let arr: ArrayRef = match arg.data_type() {
+            DataType::Float64 => {
+                let result: Float64Array = arg
+                    .as_primitive::<Float64Type>()
+                    .try_unary(checked_ln_f64)?;
+                Arc::new(result) as ArrayRef
+            }
+            DataType::Float32 => {
+                let result: Float32Array = arg
+                    .as_primitive::<Float32Type>()
+                    .try_unary(checked_ln_f32)?;
+                Arc::new(result) as ArrayRef
+            }
+            other => {
+                return exec_err!(
+                    "Unsupported data type {other:?} for function {}",
+                    self.name()
+                );
+            }
+        };
+
+        Ok(ColumnarValue::Array(arr))
+    }
+
+    fn documentation(&self) -> Option<&Documentation> {
+        Some(get_ln_doc())
+    }
+}
+
+fn checked_ln_f64(value: f64) -> Result<f64, ArrowError> {
+    if value < 0.0 {
+        Err(ArrowError::ComputeError(
+            "Cannot take logarithm of a negative number".to_string(),
+        ))
+    } else {
+        Ok(value.ln())
+    }
+}
+
+fn checked_ln_f32(value: f32) -> Result<f32, ArrowError> {
+    if value < 0.0 {
+        Err(ArrowError::ComputeError(
+            "Cannot take logarithm of a negative number".to_string(),
+        ))
+    } else {
+        Ok(value.ln())
+    }
+}

datafusion/functions/src/math/mod.rs

@@ -31,6 +31,7 @@ pub mod floor;
 pub mod gcd;
 pub mod iszero;
 pub mod lcm;
+pub mod ln;
 pub mod log;
 pub mod monotonicity;
 pub mod nans;
@@ -148,14 +149,7 @@ make_udf_function!(gcd::GcdFunc, gcd);
 make_udf_function!(nans::IsNanFunc, isnan);
 make_udf_function!(iszero::IsZeroFunc, iszero);
 make_udf_function!(lcm::LcmFunc, lcm);
-make_math_unary_udf!(
-    LnFunc,
-    ln,
-    ln,
-    super::ln_order,
-    super::bounds::unbounded_bounds,
-    super::get_ln_doc
-);
+make_udf_function!(ln::LnFunc, ln);
 make_math_unary_udf!(
     Log2Func,
     log2,

datafusion/sqllogictest/test_files/scalar.slt

@@ -581,14 +581,20 @@ select ln(0);
 ----
 -Infinity
 
-# ln with columns (round is needed to normalize the outputs of different operating systems)
-query RRR rowsort
-select round(ln(a), 5), round(ln(b), 5), round(ln(c), 5) from signed_integers;
+# ln with positive column values (round is needed to normalize the outputs of different operating systems)
+query R rowsort
+select round(ln(a), 5) from signed_integers where a > 0;
 ----
-0.69315 NaN 4.81218
-1.38629 NULL NULL
-NaN 4.60517 NaN
-NaN 9.21034 NaN
+0.69315
+1.38629
+
+# ln rejects negative scalar inputs
+query error Arrow error: Compute error: Cannot take logarithm of a negative number
+select ln((-1.0)::float8);
+
+# ln rejects negative column inputs
+query error Arrow error: Compute error: Cannot take logarithm of a negative number
+select round(ln(a), 5) from signed_integers;
 
 ## log