From be70804d17087206ee9896a9a0fd3141eb40f635 Mon Sep 17 00:00:00 2001
From: Paul Masurel <paul@quickwit.io>
Date: Wed, 4 May 2022 16:43:04 +0900
Subject: [PATCH] Removed AtomicUsize.

---
 src/core/executor.rs | 34 +++++++++++++++++++---------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/src/core/executor.rs b/src/core/executor.rs
index f5e15d2b4..def78eb93 100644
--- a/src/core/executor.rs
+++ b/src/core/executor.rs
@@ -1,8 +1,8 @@
-use std::sync::atomic::AtomicUsize;
-
 use crossbeam::channel;
 use rayon::{ThreadPool, ThreadPoolBuilder};
 
+use crate::TantivyError;
+
 /// Search executor whether search request are single thread or multithread.
 ///
 /// We don't expose Rayon thread pool directly here for several reasons.
@@ -55,10 +55,13 @@ impl Executor {
                     let (fruit_sender, fruit_receiver) = channel::unbounded();
                     pool.scope(|scope| {
                         for (idx, arg) in args.into_iter().enumerate() {
-                            let idx = AtomicUsize::new(idx);
-                            scope.spawn(|_| {
-                                let fruit = f(arg);
-                                if let Err(err) = fruit_sender.send((idx.into_inner(), fruit)) {
+                            // We name references for f and fruit_sender_ref because we do not
+                            // want these two to be moved into the closure.
+                            let f_ref = &f;
+                            let fruit_sender_ref = &fruit_sender;
+                            scope.spawn(move |_| {
+                                let fruit = f_ref(arg);
+                                if let Err(err) = fruit_sender_ref.send((idx, fruit)) {
                                     error!(
                                         "Failed to send search task. It probably means all search \
                                          threads have panicked. {:?}",
@@ -73,18 +76,19 @@ impl Executor {
                     // This is important as it makes it possible for the fruit_receiver iteration to
                     // terminate.
                 };
-                // This is lame, but safe.
-                let mut results_with_position = Vec::with_capacity(num_fruits);
+                let mut result_placeholders: Vec<Option<R>> =
+                    std::iter::repeat_with(|| None).take(num_fruits).collect();
                 for (pos, fruit_res) in fruit_receiver {
                     let fruit = fruit_res?;
-                    results_with_position.push((pos, fruit));
+                    result_placeholders[pos] = Some(fruit);
                 }
-                results_with_position.sort_by_key(|(pos, _)| *pos);
-                assert_eq!(results_with_position.len(), num_fruits);
-                Ok(results_with_position
-                    .into_iter()
-                    .map(|(_, fruit)| fruit)
-                    .collect::<Vec<_>>())
+                let results: Vec<R> = result_placeholders.into_iter().flatten().collect();
+                if results.len() != num_fruits {
+                    return Err(TantivyError::InternalError(
+                        "One of the mapped execution failed.".to_string(),
+                    ));
+                }
+                Ok(results)
             }
         }
     }