Hayt

CQL3 DSL for Clojure.

What?

Hayt is a thin query DSL for CQL.

It works in 2 simple steps, first the query api generates a map (AST) representation of the query, allowing you to compose/modify it at will, then there's a compilation step that will generate a raw string for you to use in prepared statements or normal queries.

Both are decoupled, so you can just use the AST directly and make your own api on top of it if that's what you like.

What's in the box?

• Complete CQL 3.1.1+ coverage including some features in Cassandra trunk, DDL, CQL Functions, counter , triggers and collections operations
• Support for both Raw queries and Prepared Statements generation
• Great performance (lots of transducing and fiddling with StringBuilder)
• Extensive test coverage
• Decoupled query compiler, allowing you to build your own DSL in minutes
• Highly composable using simple maps or the functions provided
• Extensible Clojure data types support
• Constantly kept up to date with Cassandra changes, almost daily
• No (exposed) macros

Installation

Please check the Changelog first if you are upgrading.

Note: while in beta the API is still subject to changes.

Usage

This should be familiar if you know Korma or ClojureQL. One of the major differences is that Hayt doesn't expose macros.

(use 'qbits.hayt)

(select :foo
        (where {:bar 2}))

(update :some-table
         (set-columns {:bar 1
                       :baz (inc-by 2)})
         (where [[= :foo :bar]
                 [> :moo 3]
                 [:> :meh 4]
                 [:in :baz [5 6 7]]]))

All these functions do is generate maps, if you want to build your own DSL on top of it or use maps directly, feel free to do so.

(select :users
        (columns :a :b)
        (where [[= :foo :bar]
                [> :moo 3]
                [:> :meh 4]
                [:in :baz [5 6 7]]])})

;; generates the following

>> {:select :users
    :columns [:a :b]
    :where [[= :foo :bar]
            [> :moo 3]
            [:> :meh 4]
            [:in :baz [5 6 7]]]}

Since Queries are just maps they are composable using the usual merge into assoc etc.

(def base (select :foo (where {:foo 1})))

(merge base
       (columns :bar :baz)
       (where {:bar 2})
       (order-by [:bar :asc])
       (using :ttl 10000))

To compile the queries just use ->raw

(->raw (select :foo))
> "SELECT * FROM foo;"


(->raw {:select :foo :columns [:a :b]})
> "SELECT a, b FROM foo;"

;; or if you want full control of what's prepared you can use
;; `cql-raw` with ->raw compilation:


;; here `?` is an alias to `(cql-raw "?")`

(->raw (select :foo (where {:bar 1 :baz ?})))
> "SELECT * FROM foo WHERE bar = 1 AND baz = ?;"


;; and named parameters using keywords

(->raw (select :foo (where {:bar 1 :baz :named)}))
> "SELECT * FROM foo WHERE bar = 1 AND baz = :named;"

When compiling with ->raw we take care of the encoding/escaping required by CQL. This process is also open via the qbits.hayt.CQLEntities protocol for both values and identifiers. We also supply a joda-time codec for you to use if you require to in qbits.hayt.codec.joda-time. This codec is a good example of how to handle custom type encoding.

If you are curious about what else it can do, head to the codox documentation or the tests.

License

Copyright @Max Penet

Distributed under the Eclipse Public License, the same as Clojure.