Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
?
Solved

Applying constraints to a large table

Posted on 2016-08-04
7
Medium Priority
?
40 Views
Last Modified: 2016-08-05
I Have had to rebuild a database for a customer and whilst most of this process has worked well I have come up against a problem.  On three tables when I run code similar to that below:

IF NOT EXISTS (SELECT * FROM sys.foreign_keys WHERE object_id = OBJECT_ID(N'[FK_GroupUserMap_User]') AND parent_object_id = OBJECT_ID(N'[GroupUserMap]'))
ALTER TABLE [GroupUserMap]  WITH NOCHECK ADD  CONSTRAINT [FK_GroupUserMap_User] FOREIGN KEY([UserInfoKey])
REFERENCES [UserInfo] ([UserInfoKey])

Open in new window


It is taking an inordinate amount of time to do 6 million rows.  Is there a way top improve this performance?

The SQL SERVER 2012 installation is on a virtual server which I have no administrative rights to and the customer has fairly limited IT resources too.
0
Comment
Question by:Alyanto
7 Comments
 
LVL 30

Expert Comment

by:Olaf Doschke
ID: 41741940
Why? The existence of the foreign key is not checked for 6 million rows but only a few rows of metadata in sys.foreign_keys and since your alter table adds a constraint with NOCHECK, this shouldn't take long, as it doesn't check the 6 million rows.

If anything does take long, then it's not this code but something else you don't show here.

Bye, Olaf.
1
 
LVL 1

Author Comment

by:Alyanto
ID: 41742202
Hey Olaf
That was my thoughts, but there is nothing else in the script that affects this code just more of the same.  and yet it runs for a weekend and no completion :(   I have pretty much read around the subject as completely is I think possible  I am hoping someone else has had a similar problem and found a solution.
0
 
LVL 30

Expert Comment

by:Olaf Doschke
ID: 41742284
Sure, you don't end with something like ALTER TABLE table WITH CHECK CHECK CONSTRAINT ALL?
I still stand to this, a constraint added with NOCHECK does not check rows, so the size of the table will not matter. You need to look for something else.

Bye, Olaf.
0
Granular recovery for Microsoft Exchange

With Veeam Explorer for Microsoft Exchange you can choose the Exchange Servers and restore points you’re interested in, and Veeam Explorer will present the contents of those mailbox stores for browsing, searching and exporting.

 
LVL 1

Author Comment

by:Alyanto
ID: 41742376
No Olaf I highlighted the code as written and execute it and I agree with you, I was hoping for someone to have had this experience and found a way around it.  That may never happen, I just need to give this a fair amount of time before I decide what to do next.
0
 
LVL 27

Accepted Solution

by:
Zberteoc earned 2000 total points
ID: 41742595
There must be a lock involved. I recommend you to install Adam Machanic's sp_whoisactive stored procedure and while you run that ALTER statement in a separate query window you will execute :

EXEC sp_whoisactive

and check for the blocking_session_id column. If there is a session_id in that column in the row that shows your ALTER statement then you will have to kill/terminate that process.

Here is the procedcure:

http://sqlblog.com/blogs/adam_machanic/archive/2012/03/22/released-who-is-active-v11-11.aspx

Download here: http://sqlblog.com/files/folders/beta/entry42453.aspx

It is free.
1
 
LVL 53

Expert Comment

by:Vitor Montalvão
ID: 41744006
A lock should be a good explanation but what make a table to be locked for a full weekend?
Do you have any job running? Something like an Import/Export or even a maintenance job scheduled for weekends?

Also if you don't want to use sp_WhoIsActive you can use the built in sp_who2 and check for the rows with blocked column <> 0.
1
 
LVL 1

Author Closing Comment

by:Alyanto
ID: 41744155
Well hats off to you,  Adam Mechanic tool soon found out that a user was simply ignoring the administrators instruction to cease and desist use.  Many thanks for the Cluedo tool.
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

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

I have a large data set and a SSIS package. How can I load this file in multi threading?
This article shows gives you an overview on SQL Server 2016 row level security. You will also get to know the usages of row-level-security and how it works
This video shows how to set up a shell script to accept a positional parameter when called, pass that to a SQL script, accept the output from the statement back and then manipulate it in the Shell.
Via a live example combined with referencing Books Online, show some of the information that can be extracted from the Catalog Views in SQL Server.
Suggested Courses

580 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