datafusion-functions 38.0.0

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// 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;

use arrow::array::{ArrayRef, OffsetSizeTrait};
use arrow::datatypes::DataType;

use datafusion_common::{cast::as_generic_string_array, internal_err, Result};
use datafusion_expr::ColumnarValue;
use datafusion_expr::TypeSignature::*;
use datafusion_expr::{ScalarUDFImpl, Signature, Volatility};

use crate::utils::make_scalar_function;

/// Returns true if string starts with prefix.
/// starts_with('alphabet', 'alph') = 't'
pub fn starts_with<T: OffsetSizeTrait>(args: &[ArrayRef]) -> Result<ArrayRef> {
    let left = as_generic_string_array::<T>(&args[0])?;
    let right = as_generic_string_array::<T>(&args[1])?;

    let result = arrow::compute::kernels::comparison::starts_with(left, right)?;

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

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

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

impl StartsWithFunc {
    pub fn new() -> Self {
        use DataType::*;
        Self {
            signature: Signature::one_of(
                vec![
                    Exact(vec![Utf8, Utf8]),
                    Exact(vec![Utf8, LargeUtf8]),
                    Exact(vec![LargeUtf8, Utf8]),
                    Exact(vec![LargeUtf8, LargeUtf8]),
                ],
                Volatility::Immutable,
            ),
        }
    }
}

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

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

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

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

        Ok(Boolean)
    }

    fn invoke(&self, args: &[ColumnarValue]) -> Result<ColumnarValue> {
        match args[0].data_type() {
            DataType::Utf8 => make_scalar_function(starts_with::<i32>, vec![])(args),
            DataType::LargeUtf8 => {
                return make_scalar_function(starts_with::<i64>, vec![])(args);
            }
            _ => internal_err!("Unsupported data type"),
        }
    }
}