Oracle-L: RE: Performance/Design Advice or DBA vs. Developer

From: DENNIS WILLIAMS <DWILLIAMS_at_LIFETOUCH.COM>
Date: Tue, 20 May 2003 09:32:44 -0800
Message-ID: <F001.0059E08C.20030520093244@fatcity.com>

David

My thoughts are:

If he doesn't want to use a database, why make him use one. Maybe he should just create a file somewhere on the server. That way nobody will blame you.
He has a very shallow understanding of performance.
I'd like him to take a look at one of our systems that has a string like this at the heart of one of the main tables. The developers couldn't be bothered to do it "right", so we're stuck with a crippled design because so much has been built around this mistake that the only feasible way to fix it would be to rewrite the entire system.

Dennis Williams
DBA, 80%OCP, 100% DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com

-----Original Message-----
Sent: Tuesday, May 20, 2003 10:57 AM
To: Multiple recipients of list ORACLE-L

The developers have a new table that contains a varchar(2) column with multiple, space-separated values for backup targets on servers (I didn't do the modeling on this one). For example:

host_name       backup_target 
dbserver1       / /etc /oracle /scripts /any/other/long/directory/name

This column started out as varchar(2) 150, then grew to varchar(2) 250, and could potentially grow very long.

I recommended to the developers that we create a separate table to hold the separate values as individual rows, populated via trigger from a staging table during batch loads, something like this:

host_name       backup_target 
dbserver1       / 
dbserver1       /etc 
dbserver1       /oracle 
dbserver1       /scripts 
dbserver1       /any/other/long/directory/name

...

My reasoning is:

the backup_target column will not grow as long
reports from this table will not have to parse the data out by space-delimiters during execution
this also seems to correspond more towards 3rd Normal Form
I'm concerned about row-chaining on such a long column

Here is the response from one of the developers:

I can maybe be convinced otherwise, but here is my thinking in support of the "one big field" [varchar2(4000)?] theory:

Our database machines are not storage constrained, nor should they ever be, therefore, a varchar2(a bunch) field shouldn't be that much of a hardship. I'm unaware of performance issues that may arise by using a varchar2 field of this size. Anybody have any info on this?
Our batch loads are hulking processor hogs. When we look for changes to targets which we will probably do once per target list per load, we will need to compare an unparsed class config target list to one parsed out into 5 or 10 or 200 rows -- this is going to be very ugly, loopy, expensive. We will also need to parse out the individual entries and create a row for each.
The number of times that we will need to report a given target list in a parsed format should be small; some may never be displayed. When the time does come to report a target list, a java or perl (or even owa_pattern) regular expression replace operation is not all that expensive in terms of processing.

What do you guys think- anyone have experience with this type of situation?

PS- Environment is Oracle 9.2.0.2 on Sun Solaris; the database is hybrid OLTP and reporting.

Thanks for sharing,

David B. Wagoner
Database Administrator

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Author: DENNIS WILLIAMS
  INET: DWILLIAMS_at_LIFETOUCH.COM

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Received on Tue May 20 2003 - 12:32:44 CDT