What is the most efficient way to allow users to order a model?

I have a note model. A user has many notes. At the moment, the notes are ordered by date, and then by created_at.

I would like to give users the ability to order the notes (within a date) themselves.

For instance, if this is how they are currently displayed:

Date1
    note1,note2,note3
Date2
    note4
Date3
    note5,note6

The user could reorder them as follows:

Date1
    note3,note1,note2
开发者_运维百科Date2
    note4
Date3
    note6,note5

What is the most efficient way to implement this in Rails? Should I used a linked list? Or something else?

I'm using Rails 3.0.1 and Ruby 1.9.2

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My preference is to do this directly in the Model and let the database handle the ordering so I usually add a order_by field. When the user reorders the list the code simply tweaks the order_by field to reflect the new ordering.

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I think that i would give it a position attribute. Thus, initially :

note1 -> 1 note2 -> 2 note3 -> 3 note4 -> 4 note5 -> 5

If i want note5 to get a position of 2, i would just need to exchange the position attributes.