With the advent of CQL3 the terminology has changed slightly from the old thrift terms. Basically Create Table foo (a int , b int, c int, d int, PRIMARY KEY ((a,b),c)) Will make a CQL3 table. The information in a and b is used to make the partition key, this describes which node the information … 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
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 rename the cluster without deleting data by updating it’s name in the system.local table (but you have to do this for each node…) cqlsh> UPDATE system.local SET cluster_name=”test” where key=’local’; # flush the sstables to persist the update. bash $ ./nodetool flush Finally you need to rename the cluster to the new name … Read more
In an effort to answer your questions, I did a little digging on this one. Does Cassandra capture microseconds with timestamp data type? Microseconds no, milliseconds yes. If I create your table, insert a row, and try to query it by the truncated time, it doesn’t work: aploetz@cqlsh:stackoverflow> INSERT INTO data (datetime, id, type, data) … Read more
You need to edit cassandra.yaml on the node you are trying to connect to and set the node ip address for rpc_address and listen_address and restart Cassandra. rpc_address is the address on which Cassandra listens to the client calls. listen_address is the address on which Cassandra listens to the other Cassandra nodes.
Short summary: Replication factor describes how many copies of your data exist. Consistency level describes the behavior seen by the client. Perhaps there’s a better way to categorize these. As an example, you can have a replication factor of 2. When you write, two copies will always be stored, assuming enough nodes are up. When … Read more
How about the following, using Cassandra’s Lightweight transactions 1 – Create IDs table: CREATE TABLE ids ( id_name varchar, next_id int, PRIMARY KEY (id_name) ) 2 – Insert every id you’d like to use a global sequence with For example: INSERT INTO ids (id_name, next_id) VALUES (‘person_id’, 1) 3 – Then, when inserting to a … Read more
Because of its distributed nature, Cassandra has no support for RDBMS style joins. You have a few options for when you want something like a join. One option perform separate queries and then have your application join the data itself. This makes sense if the data is relatively small and you only have to perform … 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