hash

What is alternative hashing for String keys in Java 8?

由 混江龙づ霸主 提交于 2020-01-10 13:41:28
问题 Java 8 is providing alternative hashing for String keys to improve performance when a large number of key hash code collisions are encountered. Can anybody explain what is that and how it will work? 回答1: From this email of core-lib-devs@openjkd : A new interface Hashable32 is introduced. Hashable32 provides a method hash32() String implements Hashable32 and hash32() method HashMap et al recognize String and invoke hash32() rather than hashCode() The revisions of the code: Murmur3 : https:/

What is alternative hashing for String keys in Java 8?

由 我的梦境 提交于 2020-01-10 13:40:56
问题 Java 8 is providing alternative hashing for String keys to improve performance when a large number of key hash code collisions are encountered. Can anybody explain what is that and how it will work? 回答1: From this email of core-lib-devs@openjkd : A new interface Hashable32 is introduced. Hashable32 provides a method hash32() String implements Hashable32 and hash32() method HashMap et al recognize String and invoke hash32() rather than hashCode() The revisions of the code: Murmur3 : https:/

XSLT: Obtaining or matching hashes for base64 encoded data

由 扶醉桌前 提交于 2020-01-10 09:22:24
问题 I need to find a way to find a way to find the hash for the base64 encoded data in the XML node //note/resource/data , or somehow otherwise match it to the hash value in the node //note/content/en-note//en-media@hash See below for the full XML file Please suggest a way to {obtain|match} using XSLT 4aaafc3e14314027bb1d89cf7d59a06c {from|with} R0lGODlhEAAQAPMAMcDAwP/crv/erbigfVdLOyslHQAAAAECAwECAwECAwECAwECAwECAwECAwEC AwECAyH/C01TT0ZGSUNFOS4wGAAAAAxtc09QTVNPRkZJQ0U5LjAHgfNAGQAh/wtNU09GRklDRTku

XSLT: Obtaining or matching hashes for base64 encoded data

由 吃可爱长大的小学妹 提交于 2020-01-10 09:21:38
问题 I need to find a way to find a way to find the hash for the base64 encoded data in the XML node //note/resource/data , or somehow otherwise match it to the hash value in the node //note/content/en-note//en-media@hash See below for the full XML file Please suggest a way to {obtain|match} using XSLT 4aaafc3e14314027bb1d89cf7d59a06c {from|with} R0lGODlhEAAQAPMAMcDAwP/crv/erbigfVdLOyslHQAAAAECAwECAwECAwECAwECAwECAwECAwEC AwECAyH/C01TT0ZGSUNFOS4wGAAAAAxtc09QTVNPRkZJQ0U5LjAHgfNAGQAh/wtNU09GRklDRTku

分库分表？如何做到永不迁移数据和避免热点？

由 笑着哭i 提交于 2020-01-10 08:56:28
前言 中大型项目中，一旦遇到数据量比较大，小伙伴应该都知道就应该对数据进行拆分了。 有垂直和水平两种 。 垂直拆分比较简单，也就是本来一个数据库，数据量大之后，从业务角度进行拆分多个库。如下图，独立的拆分出订单库和用户库。 水平拆分的概念，是同一个业务数据量大之后，进行水平拆分。 上图中订单数据达到了4000万，我们也知道mysql单表存储量推荐是百万级，如果不进行处理，mysql单表数据太大，会导致性能变慢。使用方案可以参考数据进行水平拆分。把4000万数据拆分4张表或者更多。当然也可以分库，再分表；把压力从数据库层级分开。 分库分表方案 分库分表方案中有常用的方案，hash取模和range范围方案；分库分表方案最主要就是路由算法，把路由的key按照指定的算法进行路由存放。下边来介绍一下两个方案的特点。 hash取模方案 在我们设计系统之前，可以先预估一下大概这几年的订单量，如：4000万。每张表我们可以容纳1000万，也我们可以设计4张表进行存储。 那具体如何路由存储的呢？hash的方案就是对指定的路由key（如：id）对分表总数进行取模，上图中，id=12的订单，对4进行取模，也就是会得到0，那此订单会放到0表中。id=13的订单，取模得到为1，就会放到1表中。为什么对4取模，是因为分表总数是4。 优点： 订单数据可以均匀的放到那4张表中，这样此订单进行操作时

redis内置集群通信机制

由 廉价感情. 提交于 2020-01-10 03:56:17
你能聊聊redis cluster集群模式的原理吗？ 1、面试题redis集群模式的工作原理能说一下么？在集群模式下，redis的key是如何寻址的？分布式寻址都有哪些算法？了解一致性hash算法吗？ 2、面试官心理分析 在以前，如果前几年的时候，一般来说，redis如果要搞几个节点，每个节点存储一部分的数据，得借助一些中间件来实现，比如说有codis，或者twemproxy，都有。有一些redis中间件，你读写redis中间件，redis中间件负责将你的数据分布式存储在多台机器上的redis实例中。这两年，redis不断在发展，redis也不断的有新的版本，redis cluster，redis集群模式，你可以做到在多台机器上，部署多个redis实例，每个实例存储一部分的数据，同时每个redis实例可以挂redis从实例，自动确保说，如果redis主实例挂了，会自动切换到redis从实例顶上来。现在redis的新版本，大家都是用redis cluster的，也就是redis原生支持的redis集群模式，那么面试官肯定会就redis cluster对你来个几连炮。要是你没用过redis cluster，正常，以前很多人用codis之类的客户端来支持集群，但是起码你得研究一下redis cluster吧。 redis如何在保持读写分离+高可用的架构下，还能横向扩容支持1T+的海量数据

How to write qHash for a QSet<SomeClass*> container?

由 痞子三分冷 提交于 2020-01-10 02:48:36
问题 I need to implement a set of sets in my application. Using QSet with a custom class requires providing a qHash() function and an operator== . The code is as follows: class Custom{ int x; int y; //some other irrelevant here } inline uint qHash(Custom* c){ return (qHash(c->x) ^ qHash(c->y)); } bool operator==(Custom &c1, Custom &c2){ return ((c1.x==c2.x) && (c1.y == c2.y)); } //now I can use: QSet<Custom*> How can I implement qHash(QSet<Custom*>) , to be able to use QSet< QSet<SomeClass*> > ?

Ruby: How to find the key of the largest value in a hash?

由 杀马特。学长 韩版系。学妹 提交于 2020-01-10 02:18:46
问题 Hello I'm trying to find the largest value in my hash. I made a search in google and I found this code: def largest_hash_key(hash) key = hash.sort{|a,b| a[1] <=> b[1]}.last puts key end hash = { "n" => 100, "m" => 100, "y" => 300, "d" => 200, "a" => 0 } largest_hash_key(hash) in this code "puts" prints the largest key and value e.x y300. So, how I can modify the code in order to find the largest value and put it's key in to_s variable? 回答1: This is O(n): h = {"n" => 100, "m" => 100, "y" =>

MD5 Signing a HttpServletResponse

由 我与影子孤独终老i 提交于 2020-01-09 23:21:07
问题 I'm looking for a way to inspect the contents of a HttpServletResponse to sign them with a MD5 hash. The pseudocode might look like this process(Response response, Request request){ defaultProcessingFor(response,request); dispatcher.handle(response,request); // Here I want to read the contents of the Response object (now filled with data) to create a MD5 hash with them and add it to a header. } Is that possible? 回答1: Yes, that's possible. You need to decorate the response with help of

[Sql-Server]what data type to use for password salt and hash values and what length?

由 二次信任 提交于 2020-01-09 19:07:28
问题 I am generating salt and hash values from my passwords by using, string salt = CreateSalt(TxtPassword.Text.Length); string hash = CreatePasswordHash(TxtPassword.Text, salt); private static string CreateSalt(int size) { //Generate a cryptographic random number. RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider(); byte[] buff = new byte[size]; rng.GetBytes(buff); // Return a Base64 string representation of the random number. return Convert.ToBase64String(buff); } private static string
订阅 hash