Question

我有一个图书馆管理应用程序。我没有使用ORM（这是用于数据库项目，不允许使用ORM）要签出我正在进行表单验证的书。像这样：

class CheckoutForm(Form):
    book_id = TextField('book_id', validators = [Required()])
    branch_id = TextField('branch_id', validators = [Required()])
    card_no = TextField('card_no',validators = [Required()])

    def __init__(self, *args, **kwargs):
        Form.__init__(self, *args, **kwargs)

    def validate(self):
        rv = Form.validate(self)
        if not rv:
            return False

       # Get total copies of the book check if not 0
       cur.execute("""select SUM(No_of_copies) from book b, book_copies c where     b.Book_id = c.Book_id and
       b.Book_id = %s and c.Branch_id = %s""",\
            (self.book_id.data.strip(), self.branch_id.data.strip()))
        copies = cur.fetchone()[0]
        if copies == 0:
            self.branch_id.errors.append("Book not at this Branch.")
            return False

        # Get total available copies of the book in given branch check if not 0
        cur.execute("""select count(*) from book_loans l, book b, book_copies c where    b.Book_id = l.Book_id  and b.Book_id = c.Book_id and Date_in is NULL and b.Book_id = %s and c.Branch_id = %s""",(self.book_id.data.strip(),self.branch_id.data.strip()) )
        checked_out = cur.fetchone()[0]
        print checked_out
        avail_copies = copies - checked_out
        print avail_copies
        if avail_copies <= 0:
            self.branch_id.errors.append("No copies available right now.")
            return False

现在，如果我手动删除book_loans表中的行，如果我不重新启动应用程序，我会继续看到avail_copies和副本的旧值（在db更改之前）。为什么会这样？

db更改后，Flask app需要重新启动吗？

0 个答案: