key-value | 易学教程

Android persistence alternative to SQLite

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Is there any other alternative to SQLite in Android for persisting data in the phone? I am looking something like iOS coredata or something simpler like a key-value store. If we need to embed it with the apps, something that is relatively small in size is also great. Thank you for your assistance. If you need just a simple store for a couple key/value pairs, SharedPreferences is the way to go. If you are looking for something more powerful, that compares to Core Data, you should give greenDAO a try. Like Core Data, greenDAO a layer between your objects and the data store (Core Data on iOS

Tuple list from dict in Python [duplicate]

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问题 This question already has answers here : How can I convert a dictionary into a list of tuples? (11 answers) Closed last year . How can I obtain a list of key-value tuples from a dict in Python? 回答1: For Python 2.x only (thanks Alex): yourdict = {} # ... items = yourdict.items() See http://docs.python.org/library/stdtypes.html#dict.items for details. For Python 3.x only (taken from Alex's answer): yourdict = {} # ... items = list(yourdict.items()) 回答2: For a list of of tuples: my_dict.items()

ANSI C hash table implementation with data in one memory block

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I am looking for an open source C implementation of a hash table that keeps all the data in one memory block, so it can be easily send over a network let say. I can only find ones that allocate small pieces of memory for every key-value pair added to it. Thank you very much in advance for all the inputs. EDIT: It doesn't necessarily need to be a hash table, whatever key-value pair table would probably do. On a unix system I'd probably utilise a shared memory buffer (see shm_open() ), or if that's not available a memory-mapped file with the MAP_SHARED flag, see the OS-specific differences

reading value in CFDictionary with swift

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问题 I'm just starting with swift and cocoa. I'm trying to create a basic app that does image manipulation. I've allready got all information of the image with this: let imageRef:CGImageSourceRef = CGImageSourceCreateWithURL(url, nil).takeUnretainedValue() let imageDict:CFDictionaryRef = CGImageSourceCopyPropertiesAtIndex(imageRef, 0, nil).takeUnretainedValue() the dictionary contains following information: { ColorModel = Gray; DPIHeight = 300; DPIWidth = 300; Depth = 1; Orientation = 1;

Mapper input Key-Value pair in Hadoop

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问题 Normally, we write the mapper in the form : public static class Map extends Mapper<**LongWritable**, Text, Text, IntWritable> Here the input key-value pair for the mapper is <LongWritable, Text> - as far as I know when the mapper gets the input data its goes through line by line - so the Key for the mapper signifies the line number - please correct me if I am wrong. My question is : If I give the input key-value pair for mapper as <Text, Text> then it is giving the error java.lang

store known key/value pairs in c

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问题 I'm currently learning c. I'm writing a web server as an exercise. Now i have to store the status codes and reason phrases. What is the best way to store those key/value pairs? My first bet was a hashmap. But there is no native implementation in c. So i would have to use a library. 回答1: Like other answers, I would also recommend just using an array of strings as a lookup table. If you assume all the status codes are unique, an array of strings is by far the easiest implementation for a

Java中HashMap的实现原理

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一、Java中的hashCode和equals 1、关于hashCode hashCode的存在主要是用于查找的快捷性，如Hashtable，HashMap等，hashCode是用来在散列存储结构中确定对象的存储地址的如果两个对象相同，就是适用于equals(java.lang.Object) 方法，那么这两个对象的hashCode一定要相同如果对象的equals方法被重写，那么对象的hashCode也尽量重写，并且产生hashCode使用的对象，一定要和equals方法中使用的一致，否则就会违反上面提到的第2点两个对象的hashCode相同，并不一定表示两个对象就相同，也就是不一定适用于equals(java.lang.Object) 方法，只能够说明这两个对象在散列存储结构中，如Hashtable，他们“存放在同一个篮子里“ 再归纳一下就是hashCode是用于查找使用的，而equals是用于比较两个对象的是否相等的。以下对hashCode的解读摘自其他博客： 1.hashcode是用来查找的，如果你学过数据结构就应该知道，在查找和排序这一章有例如内存中有这样的位置 0 1 2 3 4 5 6 7 而我有个类，这个类有个字段叫ID,我要把这个类存放在以上8个位置之一，如果不用hashcode而任意存放，那么当查找时就需要到这八个位置里挨个去找，或者用二分法一类的算法。

Key Value Database For Windows?

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问题 Other than MongoDB and Memcached, what key-value stores run on Windows? Most of the ones I've seen seem to only run on Linux (Hypertable, Redis, Lightcloud). Related links: Is there a business proven cloud store / Key=>Value Database? (Open Source) http://www.metabrew.com/article/anti-rdbms-a-list-of-distributed-key-value-stores/ 回答1: I would take a look at this article from highscalability.com. It describes a few options that you may want to consider, including Tokyo Cabinet/Tyrant, CouchDB

Key: value store in Python for possibly 100 GB of data, without client/server [closed]

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问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed last year . There are many solutions to serialize a small dictionary: json.loads / json.dumps , pickle , shelve , ujson , or even by using sqlite . But when dealing with possibly 100 GB of data, it's not possible anymore to use such modules that would possibly rewrite the whole data when

微软并发Key-Value存储库FASTER介绍

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微软支持并发的Key-Value 存储库有C++与C#两个版本。号称迄今为止最快的并发键值存储。下面是C#版本翻译： FASTER C＃可在.NET Framework和.NET Core中运行，并且可以在单线程和并发设置中使用。经过测试，可以在Windows和Linux上使用。它公开了一种API，该API可以执行读取，盲更新（Upserts）和读取-修改-写入(RMW)操作的混合。它支持大于内存的数据，并接受IDevice将日志存储在文件中的实现。提供了IDevice本地文件系统的实现，也可以写入远程文件系统。或者将远程存储映射到本地文件系统中。FASTER可以用作传统并发数据结构类似ConcurrentDictionary的高性能替代品，并且还支持大于内存的数据。它支持增量或非增量数据结构类型的检查点。 FASTER支持三种基本操作： Read：从键值存储中读取数据 Upsert：将值盲目向上插入到存储中（不检查先前的值） Read-Modify-Write：更新存储区中的值，用于实现“求和”和“计数”之类的操作。构建在实例化FASTER之前，您需要创建FASTER将使用的存储设备。如果使用的是可移植类型（byte、int、double）类型，则仅需要混合日志设备。如果使用对象，则需要创建一个单独的对象日志设备。 IDevice log = Devices