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One solution to this might be to store the table contents 3 times with the 3 different triangle levels, but, of course, that means the data has to be written 3 times on ingest! (Likewise all crossmatch catalogues would need to be written 3 times.) Note, however, that Cassandra positively encourages this practice.
Let’s take a closer look at Cassandra. The following information is based on this tutorial. Cassandra is a key-value store and doesn’t quite work like normal relational databases. For a start, they are NOT relational. “Tables” are groups (“families”) of columns and Cassandra encourages you to flatten your schema down into giant groups of columns. Here’s some terminology:
Cassandra Data Model | Relational Data Model |
|---|---|
Keyspace | Database |
Column Family | Table |
Partition Key | Primary Key |
Column Name/Key | Column Name |
Column Value | Column Value |
Note the “partition key” terminology - we’ll come back to that. The partition key determines how the data is distributed across multiple nodes. In Cassandra, replication is built in, and the replication factor determines how many other nodes the data is copied to.