queries
Longevity queries provide you with a way to retrieve multiple persistent objects. There are multiple
Repo methods for executing a query. Two of them, queryToVector and queryToIterator, are of
limited value, but depend only on Scala standard library classes. These are discussed in the
Retrieval by Query section. Other methods return streams for third-party
streaming libraries. These are discussed in the Stream by Query section.
To build queries, you can either use the query DSL, or you can assemble them by hand using the
classes and factory methods in package longevity.model.query. The query DSL is complete, so that
any query you can build by hand, you can also build with the DSL. We will focus our discussion here
on the DSL, since it is much more convenient to use. If you prefer to construct them by hand, please
refer to the ScalaDocs.
Please note that, due to the limited nature of Cassandra SELECT
statements, many of the queries discussed in this chapter will not
work when using a Cassandra back end. Please see the section on
Cassandra limitations for the details.
This chapter is organized as follows: