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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 std::sync::atomic::{AtomicUsize, Ordering};
/// A utility struct that can be used to generate unique aliases when optimizing queries
#[derive(Debug)]
pub struct AliasGenerator {
next_id: AtomicUsize,
}
impl Default for AliasGenerator {
fn default() -> Self {
Self {
next_id: AtomicUsize::new(1),
}
}
}
impl AliasGenerator {
/// Create a new [`AliasGenerator`]
pub fn new() -> Self {
Self::default()
}
/// Advance the counter to at least `min_id`, ensuring future aliases
/// won't collide with already-existing ones.
///
/// For example, if the query already contains an alias `alias_42`, then calling
/// `update_min_id(42)` will ensure that future aliases generated by this
/// [`AliasGenerator`] will start from `alias_43`.
pub fn update_min_id(&self, min_id: usize) {
self.next_id.fetch_max(min_id + 1, Ordering::Relaxed);
}
/// Return a unique alias with the provided prefix
pub fn next(&self, prefix: &str) -> String {
let id = self.next_id.fetch_add(1, Ordering::Relaxed);
format!("{prefix}_{id}")
}
}