Question

我正在阅读Peter Siebel的书Simple Database的Practical Common Lisp部分，想要维护一个包含大约50,000条记录的小型数据库。我认为在Emacs中这样做可能是一个有趣且有用的练习。除了少数notable differences之外，Emacs Lisp与CL有些兼容。上面示例中使用的格式函数是一个主要区别。

这是包含在CL中构建，保存和加载数据库所需的所有内容的代码。这可以修改为在Emacs中运行良好吗？我省略了选择和其中功能，但我想要包含它们。也许有更好的Emacs方式来构建和维护数据库？就个人而言，我将此作为练习来学习CL并解决现有问题。

;; Simple Common Lisp database
;; http://www.gigamonkeys.com/book/practical-a-simple-database.html
;;
(defvar *db* nil)

(defun make-cd (title artist rating ripped)
  (list :title title :artist artist :rating rating :ripped ripped))

(defun add-record (cd) (push cd *db*))

(defun dump-db ()
  (dolist (cd *db*)
    (format t "~{~a:~10t~a~%~}~%" cd)))

(defun save-db (filename)
  (with-open-file (out filename
                   :direction :output
                   :if-exists :supersede)
    (with-standard-io-syntax
      (print *db* out))))

(defun load-db (filename)
  (with-open-file (in filename)
    (with-standard-io-syntax
      (setf *db* (read in)))))
; ===
;
; Add some records
;
(add-record (make-cd "Roses" "Kathy Mattea" 7 t))
(add-record (make-cd "Fly" "Dixie Chicks" 8 t))
(add-record (make-cd "Home" "Dixie Chicks" 9 t))

; (dump-db)
; (save-db "cd.db")
; (load-db "cd.db")

Answer 1

这是我的解决方案：


(defvar *db* nil)

(setq *db* ())

(defun make-cd (title artist rating ripped)
  (list :title title :artist artist :rating rating :ripped ripped))

(defun add-record (cd) (push cd *db*))

(defun init ()
  (progn
    (add-record (make-cd "Roses" "Kathy Mattea" 7 t))
    (add-record (make-cd "Fly" "Dixie Chicks" 8 t))
    (add-record (make-cd "Home" "Dixie Chicks" 9 t))
    ))

(defun save-db (filename)
  (with-temp-buffer
    (print *db* (current-buffer))
    (write-file filename))
  (message "Saving database...done")
  )

(defun load-db (filename)
  (with-temp-buffer
    (insert-file-contents filename)
        (setq *db* (read (current-buffer)))))

(defun dump-db ()
  (dolist (cd *db*)
    (print cd)))


;; Test in M-x lisp-interaction-mode
;;(init)
;;(save-db "cd.db")
;*db*
;(add-record (make-cd "Born To Run" "Bruce Springsteen" 10 t))
;(add-record (make-cd "The River" "Bruce Springsteen" 10 t))
;(add-record (make-cd "Nebraska" "Bruce Springsteen" 10 t))
;(add-record (make-cd "Human Touch" "Bruce Springsteen" 10 nil))
;;(save-db "cd.db")
;(setq *db* ())
;;(load-db "cd.db")
;*db*

Answer 2

当我尝试为Emacs编写电子书库时，我将记录存储在列表中，并不时将其保存到磁盘。当列表长度超过大约五千条记录时，性能受到影响。

以下是代码中的一些函数：

(defun bread-library-load-db ()
 "Loads the list of books from disk file to the variable bread-library-db"
      (if (file-exists-p bread-library-file)
          (with-temp-buffer
        (insert-file-contents bread-library-file)
        (setq bread-library-db (read (current-buffer))))
        (setq bread-library-db '())))

(defun bread-library-add-book (file)
  "Attempts  to   get  metadata  from  file,   then  prompts  for
confirmation (or  modification) of these metadata,  then adds the
book to the database and saves it.  Intended use: from dired."
  (if (assoc file bread-library-db)
      (error "File is already in the database")
    (progn
      (let ((metadata (bread-get-metadata file)))
    (let ((filename (nth 0 metadata))
          (author (read-from-minibuffer 
               "Author: "
               (nth 1 metadata)))
          (title (read-from-minibuffer 
              "Title: "
              (nth 2 metadata)))
          (genre (read-from-minibuffer "Genre: " (nth 3 metadata)))
          (tags (read-from-minibuffer "Tags (separated and surrounded by colons): " ":"))
          (desc (nth 4 metadata)))
      (setq bread-library-db (cons 
                  (list filename author title tags "TOREAD" genre nil desc)
                  bread-library-db))))
      (bread-library-save-db bread-library-db))))

(defun bread-library-save-db (db)
    "Save the library database to a file."
    (message "Saving Bread library database...")
    (with-temp-buffer
      (insert "; 1.path 2.author 3.title 4.tags 5.state 6.genre 7.priority 8.description")
      (print db (current-buffer))
      (write-file bread-library-file))
    (message "Saving Bread library database...done"))

在Emacs中构建和维护数据库？

2 个答案: