You can use the TimeUUID type in Cassandra, which backs a Type 1 UUID. This uses the current time and the creator’s MAC address and a sequence number. If the TimeUUID number is generated correctly this can be done with zero collisions (you can use the CQL now() method or insert your own, the java … Read more
cqlsh -e “select * from ks.table limit 1;” > ~/output
There are a couple of ways to go about this. From within cqlsh, you can simply show version. aploetz@cqlsh> show version [cqlsh 5.0.1 | Cassandra 2.1.8 | CQL spec 3.2.0 | Native protocol v3] However, that only works from within cqlsh. Fortunately, you can also query system.local for that information as well. aploetz@cqlsh> SELECT cql_version … Read more
The timeout is because Cassandra is taking longer than the timeout (default is 10 seconds) to return the data. For your query, Cassandra will attempt to fetch the entire dataset before returning. For more than a few records this can easily take longer than the timeout. For queries that are producing lots of data you … Read more
Cassandra = No Joins. Your model is 100% relational. You need to rethink it for Cassandra. I would advice you take a look at these slides. They dig deep into how to model data for cassandra. Also here is a webinar covering the topic. But stop thinking foreign keys and joining tables, because if you … 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
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
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’);