key-value-store | 易学教程

iCloud KeyValue store not recognized on first launch

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问题 My app uses iCloud (key-value store) to sync an unique id between multiple devices. This works accept at the point were it really has to work, at the first launch of the app. It looks like the device isn't yet familiar with the values from iCloud at first launch, only after the app is installed and has been running for a while. I check for the iCloud value in the viewDidLoad function on main view of the app. So, my questions: Is this the expected behavior? If yes, is there another solution?

What's the difference between ZooKeeper and any distributed Key-Value stores?

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I am new to zookeeper and distributed systems, and am learning it myself. From what I understand for now, it seems that ZooKeeper is simply a key-value store whose keys are paths and values are strings, which is nothing different from, say, Redis. (And apparently we can use slash-separated path as keys in redis as well.) So my question is, what is the essential difference between ZooKeeper and other distributed KV store? Why is ZooKeeper using so called "paths" as keys, instead of simple strings? kuujo You're comparing the high level data model of ZooKeeper to other key value stores, but that

How to store array of hashes in redis

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I want to store array of hashes in redis , what is best way to code it ? The only way AFAIK is to de-reference them. Say you have an array of 2 hashes like: {foo: 'bar', baz: 'qux'} . You'd store them separately, and then create a SET that references them all: HMSET myarr:0 foo bar baz qux SADD myarr myarr:0 HMSET myarr:1 foo bar baz qux SADD myarr myarr:1 Then you can retrieve them all by querying the set: SMEMBERS myarr and then call HGETALL <key> on all the returned keys to rebuild your original array of hashes. I hope this makes sense. And if you find a smarter way I'd be happy to hear it.

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

How to separate redis database for same two app in node.js

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问题 I have two same app running on different one for demo and one for developement .and m using the redis database to store key value, how can i seperate redis database for these two different app. m using node.js for redis client. and m using this https://github.com/mranney/node_redis/ redis client. how to seperate redis database for same app in node. 回答1: You can use the .select(db, callback) function in node_redis. var redis = require('redis'), db = redis.createClient(); db.select(1, function

Looking for a lightweight java-compatible in-memory key-value store [closed]

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问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 4 years ago . Berkeley DB would be the best choice probably but I can't use it due to licensing issues. Are there any alternatives? 回答1: You can try Hazelcast. Just add hazelcast.jar to your classpath. And start coding java.util.Map map = Hazelcast.getMap("myMap"); You'll get an in-memory, distributed, dynamically scalable

Writing a key-value store

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问题 I am looking to write a Key/value store (probably in python) mostly just for experience, and because it's something I think that is a very useful product. I have a couple of questions. How, in general, are key/value pairs normally stored in memory and on disk? How would one go about loading the things stored on disk, back into memory? Do key/value stores keep all the key/value pairs in memory at once? or is it read from the disk? I tried to find some literature on the subject, but didn't get

Leader election for paxos-based replicated key value store

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I am going to implement a key value store with multi Paxos. I would have several nodes, one of which is the primary node. This primary node receive update requests and replicate values to slave nodes. My question is how the primary node (or leader) is selected? Can I still use the Paxos algorithm? If so, do you think it is necessary to abstract the paxos implementation to a single unit that could be used not only by the replication unit but also the leader election unit？ If I use the node with the least id to be the leader? How can I implement the master lease? Thanks for any answers. Before I

Need a distributed key-value lookup system

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问题 I need a way to do key-value lookups across (potentially) hundreds of GB of data. Ideally something based on a distributed hashtable, that works nicely with Java. It should be fault-tolerant, and open source. The store should be persistent, but would ideally cache data in memory to speed things up. It should be able to support concurrent reads and writes from multiple machines (reads will be 100X more common though). Basically the purpose is to do a quick initial lookup of user metadata for a

What is the purpose of colons within Redis keys

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问题 I'm learning how to use Redis for a project of mine. One thing I haven't got my head around is what exactly the colons are used for in the names of keys. I have seen names of key such as these: users:bob color:blue item:bag Does the colon separate keys into categories and make finding the keys faster? If so can you use multiple colons when naming keys to break them down into sub categories? Lastly do they have anything to do with defining different databases within the Redis server? I have