.Net Core 3.1 中的 IEnumerable.OrderBy().First() 优化是否记录在任何地方？

Question

.Net Core 版本之一（我不确定是哪个）引入了优化，如果您编写这样的代码：

int smallest = new[]{ 7, 2, 4, 6, 0, 1, 6, 9, 8 }.OrderBy(i => i).First();

那么它的复杂度是O(N)而不是O(N.Log(N))。

这在任何地方都有记录吗？如果它不是“官方的”，我不想依赖这种优化。

---

显示 .Net Core 和 .Net Framework 之间差异的示例代码：

using System;
using System.Collections.Generic;
using System.Linq;

namespace Demo
{
    static class Program
    {
        static void Main()
        {
            int[] test = { 7, 2, 4, 6, 0, 1, 6, 9, 8 };

            var comparer = new Comparer();
            var _ = test.OrderBy(i => i, comparer).First();
        }
    }

    class Comparer : IComparer<int>
    {
        public int Compare(int x, int y)
        {
            Console.WriteLine($"Comparing {x} with {y}");
            return x.CompareTo(y);
        }
    }
}

使用 .Net Framework 在线试用：https : //dotnetfiddle.net/XItXYL

使用 .Net Core 在线试用：https : //dotnetfiddle.net/swlc0O

.Net Framework 4.8 的输出：

Comparing 0 with 7
Comparing 0 with 8
Comparing 0 with 9
Comparing 0 with 6
Comparing 0 with 1
Comparing 0 with 0
Comparing 0 with 2
Comparing 0 with 6
Comparing 0 with 4
Comparing 0 with 2
Comparing 0 with 0
Comparing 7 with 2
Comparing 7 with 4
Comparing 7 with 6
Comparing 7 with 7
Comparing 7 with 8
Comparing 7 with 9
Comparing 7 with 6
Comparing 7 with 1
Comparing 7 with 7
Comparing 7 with 1
Comparing 9 with 7
Comparing 9 with 9
Comparing 9 with 8
Comparing 7 with 7
Comparing 7 with 8
Comparing 7 with 7
Comparing 6 with 2
Comparing 6 with 4
Comparing 6 with 6
Comparing 6 with 1
Comparing 6 with 6
Comparing 6 with 6
Comparing 6 with 1
Comparing 6 with 6
Comparing 6 with 6
Comparing 4 with 2
Comparing 4 with 4
Comparing 4 with 1
Comparing 2 with 2
Comparing 2 with 1

.Net Core 3.1 的输出：

Comparing 2 with 7
Comparing 4 with 2
Comparing 6 with 2
Comparing 0 with 2
Comparing 1 with 0
Comparing 6 with 0
Comparing 9 with 0
Comparing 8 with 0

Answer 1

“此优化是否已记录”问题的答案是：是（某种程度）。

请参阅https://github.com/dotnet/runtime/issues/14867了解讨论以及实现它的 GitHub 提交的链接。