Solved

Table locking with nested sets?

Posted on 2008-10-09
2
317 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

PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

Question has a verified solution.

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

Suggested Solutions

Title # Comments Views Activity
SQL Server 2012 Lag Function With Group Levels 1 27
Access SQL Server instance by NONE-admin Windows user 12 29
SQL, add where clause 5 24
SQLCMD Syntax 2 15
This article explains how to reset the password of the sa account on a Microsoft SQL Server.  The steps in this article work in SQL 2005, 2008, 2008 R2, 2012, 2014 and 2016.
For both online and offline retail, the cross-channel business is the most recent pattern in the B2C trade space.
This video shows, step by step, how to configure Oracle Heterogeneous Services via the Generic Gateway Agent in order to make a connection from an Oracle session and access a remote SQL Server database table.
Via a live example, show how to setup several different housekeeping processes for a SQL Server.

860 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