LINQ查询的索引 [英] Indexes for LINQ queries

问题描述

请告知，有没有一种标准的方法可以使这样的查询更快

Please advise is there a standard way to make queries like this faster

var res = qlist.Where(o => o.left >= x && o.right >= x).ToList()

qlist对象最多可以包含一百万个元素，并且这种查询可能非常慢.是否有linq或类似的索引?

qlist object can contain up to million elements and such query can be very slow. Are there any indexes for linq or something similar?

谢谢

更新: 抱歉，无法在评论中回答. 它是linq-to-objects，目的是缓存数据库.

Update: Sorry cannot answer in comments. It is linq-to-objects, the aim is to cache DB.

推荐答案

除了告诉您为此使用数据库外(如已写过)，您还可以通过两种方式提高性能:

Besides of telling you to use database for that (as written already), you can improve performance in two ways:

1. 使用AsParallel:

1. Use AsParallel:

var res = qlist.AsParallel().Where(o => o.left> = x& o.right> = x).ToList();

var res = qlist.AsParallel().Where(o => o.left >= x && o.right >= x).ToList();

您可以将项目插入两个不同的排序列表，一个通过left插入，另一个通过right插入.对于给定的x，通过二进制搜索找到等于(或几乎等于)的项目，然后从两个列表中获取该项目之后的所有项目.最终结果应该是从两个列表中选择的项目.我不知道这是否更有效.这取决于您要执行多少插入操作以及要找到多少项.

You can insert your items into two different sorted lists, one by left and the other by right. For a given x, find the item that equals (or nearly equals) to it with a binary search, and take all items after that item from both lists. The final result should be items that were selected from both lists. I don't know if it is more efficient. It depends how many inserts you do and how much items you'll find.

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