web4r uses a persistent object database named Elephant.
web4r depends on Elephant. If you haven't downloaded or installed it, download and configure Elephant. (currently only works with v0.9)
See the Elephant user manual for detail.
(eval-when (:compile-toplevel :load-toplevel :execute)
(asdf:oos 'asdf:load-op :elephant))
(use-package :elephant)
; Opening a store
(open-store '(:BDB "/path/to/db"))
; Defining a persistent class
(defpclass blog ()
((title :initarg :title :accessor title :index t)
(body :initarg :body)))
; An instance of a persistent class is permanently stored in the data store.
(dotimes (x 10)
(make-instance 'blog :title x :body x))
(let ((all (get-instances-by-class 'blog))) ; getting all instances by a class
(print (subseq all 0 3)) ; getting the first three
(print (sort all #'< :key 'title))) ; sorting instances by a slot
; Retrieving an instance from a slot index by value
(get-instances-by-value 'blog 'title 5)
; Getting all instances that match values between start and end
(get-instances-by-range 'blog 'title 2 4)
; updating an instance
(let ((i (get-instance-by-value 'blog 'title 5)))
(setf (title i) 0))
; Removing all instances by a class
(drop-instances (get-instances-by-class 'blog))