This section describes how to store Cassandra rows in Scala tuples or objects of your own classes.
Instead of mapping your Cassandra rows to objects of the CassandraRow class, you can directly
unwrap column values into tuples of desired type.
sc.cassandraTable[(String, Int)]("test", "words").select("word", "count").toArray
// Array((bar,20), (foo,10))
sc.cassandraTable[(Int, String)]("test", "words").select("count", "word").toArray
// Array((20,bar), (10,foo))Define a case class with properties named the same as the Cassandra columns.
For multi-word column identifiers, separate each word by an underscore in Cassandra,
and use the camel case convention on the Scala side. Then provide the explicit class name
when invoking cassandraTable:
case class WordCount(word: String, count: Int)
sc.cassandraTable[WordCount]("test", "words").toArray
// Array(WordCount(bar,20), WordCount(foo,10))The column-property naming convention is:
| Cassandra column name | Scala property name |
|---|---|
count |
count |
column_1 |
column1 |
user_name |
userName |
Using the same property names as columns also works:
| Cassandra column name | Scala property name |
|---|---|
COUNT |
COUNT |
column_1 |
column_1 |
user_name |
user_name |
The class doesn't necessarily need to be a case class. The only requirements are:
- it must be
Serializable - it must have a constructor with parameter names and types matching the columns
- it must be compiled with debug information, so it is possible to read parameter names at runtime
Property values might be also set by Scala-style setters. The following class is also compatible:
class WordCount extends Serializable {
var word: String = ""
var count: Int = 0
}