datafusion_functions/string/
btrim.rs

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// 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 arrow::array::{ArrayRef, OffsetSizeTrait};
use arrow::datatypes::DataType;
use std::any::Any;

use datafusion_common::{exec_err, Result};
use datafusion_expr::function::Hint;
use datafusion_expr::TypeSignature::*;
use datafusion_expr::{ColumnarValue, Volatility};
use datafusion_expr::{ScalarUDFImpl, Signature};

use crate::string::common::*;
use crate::utils::{make_scalar_function, utf8_to_str_type};

/// Returns the longest string with leading and trailing characters removed. If the characters are not specified, whitespace is removed.
/// btrim('xyxtrimyyx', 'xyz') = 'trim'
fn btrim<T: OffsetSizeTrait>(args: &[ArrayRef]) -> Result<ArrayRef> {
    let use_string_view = args[0].data_type() == &DataType::Utf8View;
    general_trim::<T>(args, TrimType::Both, use_string_view)
}

#[derive(Debug)]
pub struct BTrimFunc {
    signature: Signature,
    aliases: Vec<String>,
}

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

impl BTrimFunc {
    pub fn new() -> Self {
        use DataType::*;
        Self {
            signature: Signature::one_of(
                vec![
                    // Planner attempts coercion to the target type starting with the most preferred candidate.
                    // For example, given input `(Utf8View, Utf8)`, it first tries coercing to `(Utf8View, Utf8View)`.
                    // If that fails, it proceeds to `(Utf8, Utf8)`.
                    Exact(vec![Utf8View, Utf8View]),
                    Exact(vec![Utf8, Utf8]),
                    Exact(vec![Utf8View]),
                    Exact(vec![Utf8]),
                ],
                Volatility::Immutable,
            ),
            aliases: vec![String::from("trim")],
        }
    }
}

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

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

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

    fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
        utf8_to_str_type(&arg_types[0], "btrim")
    }

    fn invoke(&self, args: &[ColumnarValue]) -> Result<ColumnarValue> {
        match args[0].data_type() {
            DataType::Utf8 | DataType::Utf8View => make_scalar_function(
                btrim::<i32>,
                vec![Hint::Pad, Hint::AcceptsSingular],
            )(args),
            DataType::LargeUtf8 => make_scalar_function(
                btrim::<i64>,
                vec![Hint::Pad, Hint::AcceptsSingular],
            )(args),
            other => exec_err!(
                "Unsupported data type {other:?} for function btrim,\
                expected Utf8, LargeUtf8 or Utf8View."
            ),
        }
    }

    fn aliases(&self) -> &[String] {
        &self.aliases
    }
}