Object persistence API for Cassandra.
Category: JPQL
Cassandra primary key (a unique identifier for a row) is made up of two parts - 1) one or more partitioning columns and 2) zero or more clustering columns. To search a table without any indexes, all partitioning columns must be provided to avoid error message: Cannot execute this query as it might involve data filtering … Continue reading Cassandra Primary Key = ((Partitioning Key), Clustering Key): A simple explanation
Cassandra is a multi-node, peer-to-peer cluster/distributed system that distributes/stores data across all nodes in the cluster. Every table in Cassandra is physically stored in multiple SSTable files spread across one or multiple nodes. Rows are spread around the cluster based on a hash of the partition key, which is the first part of the primary key. … Continue reading How and when to index data in Cassandra for fast and efficient retrieval? – A simple explanation
Every time a record is inserted into Cassandra - it follows the write-path as per the diagram above. First, the record is written to a commit log (on disk). All records irrespective of schema tables are written to the commit log. The commit log enables recovery of memtable in case of hardware failure. Second, the … Continue reading How does Cassandra store data? – A simple explanation
#1. Cassandra allows creating a composite primary key (primary key consisting of more than one columns - first part being partition key and rest being clustering keys) For any queries using a composite pk column without including all of its partitioning key columns will require an index for lookup. For example: CREATE TABLE test.groupmechanism ( … Continue reading Cassandra Migration Tips
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