Solved

Table locking with nested sets?

Posted on 2008-10-09
2
319 Views
Last Modified: 2012-08-14
I'm attempting to use nested sets to represent a data hierarchy (see: http://dev.mysql.com/tech-resources/articles/hierarchical-data.html, except I'm doing it in SQL 2000, not MySQL).

I've written a stored procedure that handles an insert, it looks something like this the simplified code snippet I've attached.  It works fine, but my concern is about concurrent users (i.e. someone else updating/inserting and affecting the hierarchy at the same time).  The MySQL example uses a lock on the what I can only assume is the whole table before doing anything, but this seems like it might be
dangerous and/or overkill, especially if this data is ultimately being viewed a lot on a public web site.  I thought about just creating a seperate table with one field and one row to act as a lock in this stored procedure (and potentially a couple other related SPs), but that doesn't seem like a best practice.

Any thoughts?

CREATE PROCEDURE [dbo].[INSERT_NESTED_SET_WEBPAGE]
	@varTitle varchar(256),
	@parent int
AS
 
-- get the parent's rgt value
DECLARE @parentRight int;
SELECT @parentRight = rgt FROM my_data WHERE ID = @parent
 
-- make room for the new child (at the end of the nested set)
UPDATE my_data SET lft = lft + 2 WHERE lft >= @parentRight
UPDATE my_data SET rgt = rgt + 2 WHERE rgt >= @parentRight
 
-- insert the new child (at the end of the nested set)
INSERT INTO my_date (title, lft, rgt) VALUES (
	@varTitle,
	@parentRight,
	@parentRight + 1)
 
GO

Open in new window

0
Comment
Question by:saitwebdev
2 Comments
 
LVL 14

Accepted Solution

by:
puranik_p earned 250 total points
ID: 23054534
Just put the whole thing in a transaction. That's it!
The transactions are the simplest way to take care of the concurrency.
CREATE PROCEDURE [dbo].[INSERT_NESTED_SET_WEBPAGE]
        @varTitle varchar(256),
        @parent int
AS
 
-- get the parent's rgt value
DECLARE @parentRight int;
BEGIN TRANSACTION
SELECT @parentRight = rgt FROM my_data WHERE ID = @parent
 
-- make room for the new child (at the end of the nested set)
UPDATE my_data SET lft = lft + 2 WHERE lft >= @parentRight
UPDATE my_data SET rgt = rgt + 2 WHERE rgt >= @parentRight
 
-- insert the new child (at the end of the nested set)
INSERT INTO my_date (title, lft, rgt) VALUES (
        @varTitle,
        @parentRight,
        @parentRight + 1)
 
COMMIT TRANSACTION
GO

Open in new window

0
 

Author Closing Comment

by:saitwebdev
ID: 31504784
Thank you.  I came to that conclusion some time ago, but it's good to have confirmation.
0

Featured Post

Migrating Your Company's PCs

To keep pace with competitors, businesses must keep employees productive, and that means providing them with the latest technology. This document provides the tips and tricks you need to help you migrate an outdated PC fleet to new desktops, laptops, and tablets.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Nowadays, some of developer are too much worried about data. Who is using data, who is updating it etc. etc. Because, data is more costlier in term of money and information. So security of data is focusing concern in days. Lets' understand the Au…
Introduction In my previous article (http://www.experts-exchange.com/Microsoft/Development/MS-SQL-Server/SSIS/A_9150-Loading-XML-Using-SSIS.html) I showed you how the XML Source component can be used to load XML files into a SQL Server database, us…
Familiarize people with the process of utilizing SQL Server functions from within Microsoft Access. Microsoft Access is a very powerful client/server development tool. One of the SQL Server objects that you can interact with from within Microsoft Ac…
Via a live example, show how to backup a database, simulate a failure backup the tail of the database transaction log and perform the restore.

749 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question