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

x
?
Solved

How to speed up deleting rows, when there are child tables?

Posted on 2013-06-11
8
Medium Priority
?
528 Views
Last Modified: 2013-06-13
Hi,

I want to delete nearly 9000 rows from a table of 4 million rows.

The table is having two child tables.
The table is having primary key.
primary key is used when deleting.

I tried the following, but still it is taking 3 hours
Forall statement.
Nologging.
Delete using ROWID.

Please let me know is there any other  general approach, I can try.

If you want I want, I can post more details tomorrow.
0
Comment
Question by:sakthikumar
8 Comments
 
LVL 74

Expert Comment

by:sdstuber
ID: 39239024
How many total rows are you deleting?  parent + child?

Based on 9000/4000000,  that's should be quick.
Less than a minute even with full table scans.

Any triggers firing?

And the most likely cause - any blocking locks from other sessions on the parent or any of the children?
0
 
LVL 35

Expert Comment

by:johnsone
ID: 39239087
I assume you have cascading constraints.  If that is the case, don't use the constraints to do the deletes of the child tables.  Delete them yourself.  Locking down the parent child tree and then deleting back up the tree takes a lot of time.  We have found that deleting children first, then parents is much faster.
0
 
LVL 21

Expert Comment

by:flow01
ID: 39239432
Does the child table have an index on the foreign_key columns referring to the parent table ?
0
Get free NFR key for Veeam Availability Suite 9.5

Veeam is happy to provide a free NFR license (1 year, 2 sockets) to all certified IT Pros. The license allows for the non-production use of Veeam Availability Suite v9.5 in your home lab, without any feature limitations. It works for both VMware and Hyper-V environments

 
LVL 15

Expert Comment

by:Franck Pachot
ID: 39240218
Hi,

The forall approach is ok if you want to do it online. You can do intermediate commits and run it ad several times for few rows. And as you can do it online, the duration should not matter.

Note that NOLOGGING has no meaning here for the delete statement.

Regards,
Franck.
0
 

Author Comment

by:sakthikumar
ID: 39241388
If I disable the constraints, it is very fast. let me check the other things.
0
 
LVL 35

Accepted Solution

by:
johnsone earned 2000 total points
ID: 39241558
Disable which constraints?  The foreign key constraints?  If so, were they cascade delete constraints?  If they are not cascading constraints, then I would venture a guess that the key field of the parent table is not indexed in the child table.  That would cause a significant slow down in deletes.
0
 
LVL 23

Expert Comment

by:David
ID: 39243130
Please post the entire SQL statement, changing names as necessary.
0
 

Author Closing Comment

by:sakthikumar
ID: 39244753
Correct. It was not indexed, When it is indexed, it is fast.

Thank you very much.
0

Featured Post

Free Tool: IP Lookup

Get more info about an IP address or domain name, such as organization, abuse contacts and geolocation.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

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

How to Create User-Defined Aggregates in Oracle Before we begin creating these things, what are user-defined aggregates?  They are a feature introduced in Oracle 9i that allows a developer to create his or her own functions like "SUM", "AVG", and…
When it comes to protecting Oracle Database servers and systems, there are a ton of myths out there. Here are the most common.
This video shows setup options and the basic steps and syntax for duplicating (cloning) a database from one instance to another. Examples are given for duplicating to the same machine and to different machines
This video shows how to Export data from an Oracle database using the Datapump Export Utility.  The corresponding Datapump Import utility is also discussed and demonstrated.
Suggested Courses
Course of the Month13 days, 11 hours left to enroll

581 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