A Redis server can handle multiple databases… which are numbered. I think it provides 32 of them by default; you can access them using the -n option to the redis-cli shell scripting command and by similar options to the connection arguments or using the “select()” method on its connection objects. (In this case .select() is … Read more
From the HBase shell you can use LIMIT: hbase> scan ‘test-table’, {‘LIMIT’ => 5} From the Java API you can use Scan.setMaxResultSize(N) or scan.setMaxResultsPerColumnFamily(N). HBase API docs – Scan.setMaxResultSize HBase API docs – Scan.setMaxResultsPerColumnFamily
So I’ve been trying to figure out the real bottom-line when it comes to NoSQL vs RDBMS myself, and always end up with a response that doesn’t quite cut it. In my search there are really 2 primary differences between NoSQL and SQL, with only 1 being a true advantage. ACID vs BASE – NoSQL … Read more
As a Cassandra developer, I’m better at answering the other side of the question: Cassandra scales better. Cassandra is known to scale to over 400 nodes in a cluster; when Facebook deployed Messaging on top of HBase they had to shard it across 100-node HBase sub-clusters. Cassandra supports hundreds, even thousands of ColumnFamilies. “HBase currently … Read more
At its most basic form NoSQL is really no more than a way of storing objects using some sort of key/value pairing system. You use this all the time already I assume. For instance. in javascript you can create an object named foo and then do foo[‘myobj’] = myobj; to store stuff in the object. … Read more
@Schildmeijer is largely right, however port 7001 is still used when using TLS Encrypted Internode communication So my complete list would be for current versions of Cassandra: 7199 – JMX (was 8080 pre Cassandra 0.8.xx) 7000 – Internode communication (not used if TLS enabled) 7001 – TLS Internode communication (used if TLS enabled) 9160 – … Read more
Redis Commander is great if you’re using node.js already. Super simple to get going with NPM: npm install -g redis-commander redis-commander Then point your browser at the address in the console
If you have virtual memory functionality turned on (EDIT: now deprecated), then Redis starts to store the “not-so-frequently-used” data to disk when memory runs out. If virtual memory in Redis is disabled (the default) and the maxmemory parameter is set (the default), Redis will not use any more memory than maxmemory allows. If you turn … Read more
All the answers for how to store many-to-many associations in the “NoSQL way” reduce to the same thing: storing data redundantly. In NoSQL, you don’t design your database based on the relationships between data entities. You design your database based on the queries you will run against it. Use the same criteria you would use … Read more
Eventual consistency: I watch the weather report and learn that it’s going to rain tomorrow. I tell you that it’s going to rain tomorrow. Your neighbor tells his wife that it’s going to be sunny tomorrow. You tell your neighbor that it is going to rain tomorrow. Eventually, all of the servers (you, me, your … Read more