datafusion_functions/string/
to_hex.rs

// 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::any::Any;
use std::sync::{Arc, OnceLock};

use arrow::array::{ArrayRef, GenericStringArray, OffsetSizeTrait};
use arrow::datatypes::{
    ArrowNativeType, ArrowPrimitiveType, DataType, Int32Type, Int64Type,
};

use crate::utils::make_scalar_function;
use datafusion_common::cast::as_primitive_array;
use datafusion_common::Result;
use datafusion_common::{exec_err, plan_err};
use datafusion_expr::scalar_doc_sections::DOC_SECTION_STRING;
use datafusion_expr::{ColumnarValue, Documentation};
use datafusion_expr::{ScalarUDFImpl, Signature, Volatility};

/// Converts the number to its equivalent hexadecimal representation.
/// to_hex(2147483647) = '7fffffff'
pub fn to_hex<T: ArrowPrimitiveType>(args: &[ArrayRef]) -> Result<ArrayRef>
where
    T::Native: OffsetSizeTrait,
{
    let integer_array = as_primitive_array::<T>(&args[0])?;

    let result = integer_array
        .iter()
        .map(|integer| {
            if let Some(value) = integer {
                if let Some(value_usize) = value.to_usize() {
                    Ok(Some(format!("{value_usize:x}")))
                } else if let Some(value_isize) = value.to_isize() {
                    Ok(Some(format!("{value_isize:x}")))
                } else {
                    exec_err!("Unsupported data type {integer:?} for function to_hex")
                }
            } else {
                Ok(None)
            }
        })
        .collect::<Result<GenericStringArray<i32>>>()?;

    Ok(Arc::new(result) as ArrayRef)
}

#[derive(Debug)]
pub struct ToHexFunc {
    signature: Signature,
}

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

impl ToHexFunc {
    pub fn new() -> Self {
        use DataType::*;
        Self {
            signature: Signature::uniform(1, vec![Int64], Volatility::Immutable),
        }
    }
}

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

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

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

    fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
        use DataType::*;

        Ok(match arg_types[0] {
            Int8 | Int16 | Int32 | Int64 => Utf8,
            _ => {
                return plan_err!("The to_hex function can only accept integers.");
            }
        })
    }

    fn invoke(&self, args: &[ColumnarValue]) -> Result<ColumnarValue> {
        match args[0].data_type() {
            DataType::Int32 => make_scalar_function(to_hex::<Int32Type>, vec![])(args),
            DataType::Int64 => make_scalar_function(to_hex::<Int64Type>, vec![])(args),
            other => exec_err!("Unsupported data type {other:?} for function to_hex"),
        }
    }

    fn documentation(&self) -> Option<&Documentation> {
        Some(get_to_hex_doc())
    }
}

static DOCUMENTATION: OnceLock<Documentation> = OnceLock::new();

fn get_to_hex_doc() -> &'static Documentation {
    DOCUMENTATION.get_or_init(|| {
        Documentation::builder()
            .with_doc_section(DOC_SECTION_STRING)
            .with_description("Converts an integer to a hexadecimal string.")
            .with_syntax_example("to_hex(int)")
            .with_sql_example(
                r#"```sql
> select to_hex(12345689);
+-------------------------+
| to_hex(Int64(12345689)) |
+-------------------------+
| bc6159                  |
+-------------------------+
```"#,
            )
            .with_standard_argument("int", Some("Integer"))
            .build()
            .unwrap()
    })
}

#[cfg(test)]
mod tests {
    use arrow::array::{Int32Array, StringArray};

    use datafusion_common::cast::as_string_array;

    use super::*;

    #[test]
    // Test to_hex function for zero
    fn to_hex_zero() -> Result<()> {
        let array = vec![0].into_iter().collect::<Int32Array>();
        let array_ref = Arc::new(array);
        let hex_value_arc = to_hex::<Int32Type>(&[array_ref])?;
        let hex_value = as_string_array(&hex_value_arc)?;
        let expected = StringArray::from(vec![Some("0")]);
        assert_eq!(&expected, hex_value);

        Ok(())
    }

    #[test]
    // Test to_hex function for positive number
    fn to_hex_positive_number() -> Result<()> {
        let array = vec![100].into_iter().collect::<Int32Array>();
        let array_ref = Arc::new(array);
        let hex_value_arc = to_hex::<Int32Type>(&[array_ref])?;
        let hex_value = as_string_array(&hex_value_arc)?;
        let expected = StringArray::from(vec![Some("64")]);
        assert_eq!(&expected, hex_value);

        Ok(())
    }

    #[test]
    // Test to_hex function for negative number
    fn to_hex_negative_number() -> Result<()> {
        let array = vec![-1].into_iter().collect::<Int32Array>();
        let array_ref = Arc::new(array);
        let hex_value_arc = to_hex::<Int32Type>(&[array_ref])?;
        let hex_value = as_string_array(&hex_value_arc)?;
        let expected = StringArray::from(vec![Some("ffffffffffffffff")]);
        assert_eq!(&expected, hex_value);

        Ok(())
    }
}
datafusion_functions/string/to_hex.rs

datafusion_functions/string/
to_hex.rs
