Choosing between Cassandra and Aerospike really depends on your use case more than anything. I have personally used both as a production system for the same project and for me Aerospike was the clear winner but that’s because our use case is to have highly concurrent, low latency, transactional, small updates to billions of entries … Read more
You don’t need to use tokens, if you are using Cassandra 2.0+. Cassandra 2.0 has auto paging. Instead of using token function to create paging, it is now a built-in feature. Now developers can iterate over the entire result set, without having to care that it’s size is larger than the memory. As the client … Read more
The hierarchy of elements in Cassandra is: Cluster Data center(s) Rack(s) Server(s) Node (more accurately, a vnode) A Cluster is a collection of Data Centers. A Data Center is a collection of Racks. A Rack is a collection of Servers. A Server contains 256 virtual nodes (or vnodes) by default. A vnode is the data … Read more
Very simple. Just enter this command in your cqlsh shell and enjoy select * from system.schema_keyspaces; In C*3.x, we can simply use describe keyspaces
You can think of the commit log as an optimization, but Cassandra would be unusably slow without it. When MemTables get written to disk we call them SSTables. SSTables are immutable, meaning once Cassandra writes them to disk it does not update them. So when a column changes Cassandra needs to write a new SSTable … Read more
There is a subtle difference. Inserted records via INSERT remain if you set all non-key fields to null. Records inserted via UPDATE go away if you set all non-key fields to null. Try this: CREATE TABLE T ( pk int, f1 int, PRIMARY KEY (pk) ); INSERT INTO T (pk, f1) VALUES (1, 1); UPDATE … Read more
You shouldn’t put the quotes around the UUID to stop it being interpreted as a string i.e. insert into devices (device_id, geohash,name, external_identifier, measures, tags) values (c37d661d-7e61-49ea-96a5-68c34e83db3a,’9q9p3yyrn1′, ‘Acme1’, ‘936’, {‘aparPower’,’actPower’,’actEnergy’},{‘make’:’Acme’});
As of Cassandra 2.0.7 you can just use uuid(), which generates a random type 4 UUID: INSERT INTO users(uid, name) VALUES(uuid(), ‘my name’);
select * from update_audit where scopeid=35 and formid=78005 and record_link_id=9897; How the above query will work internally in cassandra? Essentially, all data for partition scopeid=35 and formid=78005 will be returned, and then filtered by the record_link_id index. It will look for the record_link_id entry for 9897, and attempt to match-up entries that match the rows … Read more
You can use the truncate thrift call, or the TRUNCATE <table> command in CQL. http://www.datastax.com/docs/1.0/references/cql/TRUNCATE