a cassandra connector
- migrations (from drift)
- low-level async API (built on alia)
- higher-level async API dealing with unique keys, secondary and lookup tables
To use drift migrations you will need to install er-cassandra as a dependency and the drift plugin into your project
{:dependencies [...
[employeerepublic/er-cassandra "0.3.0" ]
...}
{:plugins [...
[drift "1.5.3"]
...}
and create a drift config namespace like this one, which puts the migrations in
src/api/migrations_cassandra
(ns api.migrate-config
(:require [er-cassandra.drift.migrate-config :as mc]
[api.main :as a]))
(defn cassandra []
(mc/cassandra {:alia-session (s/get-an-er-cassandra-session)
:keyspace "a_keyspace"
:namespace "api.migrate-config/cassandra"
:directory "src/api/migrations_cassandra"}))
then migrations can be created and run like this :
lein create-migration -c api.migrate-config/cassandra create-migration create-users
lein migrate -c api.migrate-config/cassandra
lein migrate -c api.migrate-config/cassandra --version 20150804151456
migrations are created with empty up and down functions - fill
these in to implement the migration like this -
(ns api.migrations-cassandra.20150804151456-create-users
(:require [qbits.alia :as alia]
[qbits.hayt :as h]
[er-cassandra.drift.migration-helpers :refer :all]))
(defn up
"Migrates the database up to version 20150804151456."
[]
(println "er-api.migrations-cassandra.20150804151456-create-users up...")
(execute
"create table users (id timeuuid,
username text,
name text,
created_at timestamp,
email set<text>,
primary key (id))")
(execute
"create table users_by_username (id timeuuid,
username text,
name text,
created_at timestamp,
email set<text>,
primary key (username))")
(execute
"create table users_by_email (email varchar,
id timeuuid,
primary key (email))"))
(defn down
"Migrates the database down from version 20150804151456."
[]
(println "er-api.migrations-cassandra.20150804151456-create-users down...")
(execute "drop table users")
(execute "drop table users_by_username")
(execute "drop table users_by_email"))
The simple API is simple
(require '[er-cassandra.session.alia :as alia-session])
(require '[er-cassandra.record :as r])
(def session (alia-session/create-session {:contact-points ["localhost"]
:keyspace "a_keyspace"}))
(r/insert session :users {:id #uuid "f11c0190-40de-11e5-bb66-c37b19130f2f"
:username "foo"
:name "Foo McFoo"
:email #{"foo@foo.com" "foo.mcfoo@foo.com"}})
@(r/select session :users :id #uuid "f11c0190-40de-11e5-bb66-c37b19130f2f")
;; => ({:id #uuid "f11c0190-40de-11e5-bb66-c37b19130f2f",
;; :created_at nil, :device_id #{}, :email #{"foo.mcfoo@foo.com" "foo@foo.com"},
;; :name "Foo McFoo", :username "foo"})
@(r/select-one session :users :id #uuid "f11c0190-40de-11e5-bb66-c37b19130f2f")
;; => {:id #uuid "f11c0190-40de-11e5-bb66-c37b19130f2f", :created_at nil,
;; :device_id #{}, :email #{"foo.mcfoo@foo.com" "foo@foo.com"},
;; :name "Foo McFoo", :username "foo"}
(r/update session :users :id {:username "foo.mcfoo"} {:key-value #uuid "f11c0190-40de-11e5-bb66-c37b19130f2f"})
(r/delete session :users :id #uuid "f11c0190-40de-11e5-bb66-c37b19130f2f")
The higher-level API requires a model to be defined, and manages unique-keys, secondary tables and lookup tables
A model must be defined, and then the high-level API will look after secondary tables, lookup tables and unique-key acquisition with lightweight-transactions
(require '[er-cassandra.model :as m])
(m/defmodel Users
{:primary-table {:name :users
:key :id}
:secondary-tables [{:name :users_by_username
:key :username}]
:unique-key-tables [{:name :users_by_email
:key :email
:collection :set}]})
@(m/upsert session Users {:id #uuid "f11c0190-40de-11e5-bb66-c37b19130f2f"
:username "foo"
:name "Foo McFoo"
:email #{"foo@foo.com" "foo.mcfoo@foo.com"}})
;; => #object[cats.monad.either.Right 0xd4e215c {:status :ready,
;; :val [{:id #uuid "f11c0190-40de-11e5-bb66-c37b19130f2f",
;; :created_at nil, :device_id #{},
;; :email #{"foo.mcfoo@foo.com" "foo@foo.com"},
;; :name "Foo McFoo", :username "foo"}
;; nil]}]
@(m/upsert session Users {:id #uuid "47d3a3a0-40ec-11e5-84fa-b7ba3fcfbef9"
:username "foo-too"
:name "Foo Too McFoo"
:email #{"foo@foo.com" "foo.too.mcfoo@foo.com"}})
;; -> #object[cats.monad.either.Right 0x1b5c287f {:status :ready,
;; :val [{:id #uuid "47d3a3a0-40ec-11e5-84fa-b7ba3fcfbef9",
;; :created_at nil, :device_id #{},
;; :email #{"foo.too.mcfoo@foo.com"},
;; :name "Foo Too McFoo", :username "foo-too"}
;; {[:email] [#{"foo@foo.com"}]}]}]
;; shows that the second upsert failed to acquire the
;; "foo@foo.com" [:email] unique key
;; select automatically uses lookup or secondary tables
@(m/select-one session Users :email "foo@foo.com")
@(m/select-one session Users :email "foo.too.mcfoo@foo.com")
@(m/select-one session Users :username "foo")
The high-level API calls are processed within the manifold monad from
cats
and all return a Deferred result.
Copyright © 2015 Employee Republic Limited
Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.