r9336: 12 May 2004 Kevin Rosenberg (kevin@rosenberg.net)

[clsql.git] / sql / transaction.lisp

diff --git a/sql/transaction.lisp b/sql/transaction.lisp
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+++ b/sql/transaction.lisp
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+;;;; -*- Mode: LISP; Syntax: ANSI-Common-Lisp; Base: 10 -*-
+;;;; *************************************************************************
+;;;;
+;;;; $Id$
+;;;;
+;;;; Transaction support
+;;;;
+;;;; This file is part of CLSQL.
+;;;;
+;;;; CLSQL users are granted the rights to distribute and use this software
+;;;; as governed by the terms of the Lisp Lesser GNU Public License
+;;;; (http://opensource.franz.com/preamble.html), also known as the LLGPL.
+;;;; *************************************************************************
+
+(in-package #:clsql-sys)
+
+(defclass transaction ()
+  ((commit-hooks :initform () :accessor commit-hooks)
+   (rollback-hooks :initform () :accessor rollback-hooks)
+   (status :initform nil :accessor transaction-status))) ; nil or :committed
+
+(defun commit-transaction (database)
+  (when (and (transaction database)
+             (not (transaction-status (transaction database))))
+    (setf (transaction-status (transaction database)) :committed)))
+
+(defun add-transaction-commit-hook (database commit-hook)
+  (when (transaction database)
+    (push commit-hook (commit-hooks (transaction database)))))
+
+(defun add-transaction-rollback-hook (database rollback-hook)
+  (when (transaction database)
+    (push rollback-hook (rollback-hooks (transaction database)))))
+
+(defmethod database-start-transaction (database)
+  (unless database (error 'clsql-no-database-error))
+  (unless (transaction database)
+    (setf (transaction database) (make-instance 'transaction)))
+  (when (= (incf (transaction-level database) 1))
+    (let ((transaction (transaction database)))
+      (setf (commit-hooks transaction) nil
+            (rollback-hooks transaction) nil
+            (transaction-status transaction) nil)
+      (execute-command "BEGIN" :database database))))
+
+(defmethod database-commit-transaction (database)
+    (if (> (transaction-level database) 0)
+        (when (zerop (decf (transaction-level database)))
+          (execute-command "COMMIT" :database database)
+          (map nil #'funcall (commit-hooks (transaction database))))
+        (warn 'clsql-simple-warning
+              :format-control "Cannot commit transaction against ~A because there is no transaction in progress."
+              :format-arguments (list database))))
+
+(defmethod database-abort-transaction (database)
+    (if (> (transaction-level database) 0)
+        (when (zerop (decf (transaction-level database)))
+          (unwind-protect 
+               (execute-command "ROLLBACK" :database database)
+            (map nil #'funcall (rollback-hooks (transaction database)))))
+        (warn 'clsql-simple-warning
+              :format-control "Cannot abort transaction against ~A because there is no transaction in progress."
+              :format-arguments (list database))))
+
+
+(defmacro with-transaction ((&key (database '*default-database*)) &rest body)
+  "Executes BODY within a transaction for DATABASE (which defaults to
+*DEFAULT-DATABASE*). The transaction is committed if the body finishes
+successfully (without aborting or throwing), otherwise the database is
+rolled back."
+  (let ((db (gensym "db-")))
+    `(let ((,db ,database))
+      (unwind-protect
+           (progn
+             (database-start-transaction ,db)
+             ,@body
+             (commit-transaction ,db))
+        (if (eq (transaction-status (transaction ,db)) :committed)
+            (database-commit-transaction ,db)
+            (database-abort-transaction ,db))))))
+
+(defun commit (&key (database *default-database*))
+  "Commits changes made to DATABASE which defaults to *DEFAULT-DATABASE*."
+  (database-commit-transaction database))
+
+(defun rollback (&key (database *default-database*))
+  "Rolls back changes made in DATABASE, which defaults to
+*DEFAULT-DATABASE* since the last commit, that is changes made since
+the last commit are not recorded."
+  (database-abort-transaction database))
+
+(defun start-transaction (&key (database *default-database*))
+  "Starts a transaction block on DATABASE which defaults to
+*default-database* and which continues until ROLLBACK or COMMIT are
+called."
+  (unless (in-transaction-p :database database)
+    (database-start-transaction database)))
+
+(defun in-transaction-p (&key (database *default-database*))
+  "A predicate to test whether we are currently within the scope of a
+transaction in DATABASE."
+  (and database (transaction database) (= (transaction-level database) 1)))