datafusion_common/
alias.rs

1// Licensed to the Apache Software Foundation (ASF) under one
2// or more contributor license agreements.  See the NOTICE file
3// distributed with this work for additional information
4// regarding copyright ownership.  The ASF licenses this file
5// to you under the Apache License, Version 2.0 (the
6// "License"); you may not use this file except in compliance
7// with the License.  You may obtain a copy of the License at
8//
9//   http://www.apache.org/licenses/LICENSE-2.0
10//
11// Unless required by applicable law or agreed to in writing,
12// software distributed under the License is distributed on an
13// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14// KIND, either express or implied.  See the License for the
15// specific language governing permissions and limitations
16// under the License.
17
18use std::sync::atomic::{AtomicUsize, Ordering};
19
20/// A utility struct that can be used to generate unique aliases when optimizing queries
21#[derive(Debug)]
22pub struct AliasGenerator {
23    next_id: AtomicUsize,
24}
25
26impl Default for AliasGenerator {
27    fn default() -> Self {
28        Self {
29            next_id: AtomicUsize::new(1),
30        }
31    }
32}
33
34impl AliasGenerator {
35    /// Create a new [`AliasGenerator`]
36    pub fn new() -> Self {
37        Self::default()
38    }
39
40    /// Advance the counter to at least `min_id`, ensuring future aliases
41    /// won't collide with already-existing ones.
42    ///
43    /// For example, if the query already contains an alias `alias_42`, then calling
44    /// `update_min_id(42)` will ensure that future aliases generated by this
45    /// [`AliasGenerator`] will start from `alias_43`.
46    pub fn update_min_id(&self, min_id: usize) {
47        self.next_id.fetch_max(min_id + 1, Ordering::Relaxed);
48    }
49
50    /// Return a unique alias with the provided prefix
51    pub fn next(&self, prefix: &str) -> String {
52        let id = self.next_id.fetch_add(1, Ordering::Relaxed);
53        format!("{prefix}_{id}")
54    }
55}
datafusion_common/alias.rs

datafusion_common/
alias.rs
