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Message-ID: <bf05e51c0607281206r3f568c08v6c173232a1fbd1e8@mail.gmail.com>
Date: Fri, 28 Jul 2006 14:06:21 -0500
From: "Aaron Bono" <postgresql@aranya.com>
To: "Michael Artz" <mlartz@gmail.com>
Subject: Re: Storing an ordered list
Cc: "Bruno Wolff III" <bruno@wolff.to>, pgsql-sql@postgresql.org
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On 7/26/06, Michael Artz <mlartz@gmail.com> wrote:
>
> On 7/26/06, Bruno Wolff III <bruno@wolff.to> wrote:
> > If you use numeric instead of int, then it is easy to insert new values.
>
> Hmm, hadn't thought about that.  How would you normally implement it?
> I'm thinking that, if I wanted to insert between A and B, I could take
> (A.order + B.order)/2, which would be pretty simple.  Is there a
> better way?


 This is a good idea.  Then you can add a scheduled process to read through
these values and turn them back to integer values on a regular basis (sort
of a reindexing) to keep your numbers from becoming small enough that you
start experiencing round off problems.  Perhaps you could add a trigger that
says if the value entered into the order field is going out to too many
decimal places, it renumbers everything. to keep the values clean.  Or
better yet, add a stored procedure you call to reorder the elements that
decides how to do it for you so you can easily rewrite the implementation
without having to change the application.

Just some ideas...

==================================================================
   Aaron Bono
   Aranya Software Technologies, Inc.
   http://www.aranya.com
==================================================================

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On 7/26/06, <b class="gmail_sendername">Michael Artz</b> &lt;<a href="mailto:mlartz@gmail.com">mlartz@gmail.com</a>&gt; wrote:<div><span class="gmail_quote"></span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
On 7/26/06, Bruno Wolff III &lt;<a href="mailto:bruno@wolff.to">bruno@wolff.to</a>&gt; wrote:<br>&gt; If you use numeric instead of int, then it is easy to insert new values.<br><br>Hmm, hadn't thought about that.&nbsp;&nbsp;How would you normally implement it?
<br>I'm thinking that, if I wanted to insert between A and B, I could take<br>(A.order + B.order)/2, which would be pretty simple.&nbsp;&nbsp;Is there a<br>better way?</blockquote><div><br>&nbsp;This is a good idea.&nbsp; Then you can add a scheduled process to read through these values and turn them back to integer values on a regular basis (sort of a reindexing) to keep your numbers from becoming small enough that you start experiencing round off problems.&nbsp; Perhaps you could add a trigger that says if the value entered into the order field is going out to too many decimal places, it renumbers everything. to keep the values clean.&nbsp; Or better yet, add a stored procedure you call to reorder the elements that decides how to do it for you so you can easily rewrite the implementation without having to change the application.
<br><br>Just some ideas...<br></div></div><br>==================================================================<br>&nbsp;&nbsp; Aaron Bono<br>&nbsp;&nbsp; Aranya Software Technologies, Inc.<br>&nbsp;&nbsp; <a href="http://www.aranya.com">http://www.aranya.com
</a><br>==================================================================

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