RE: inefficient sql

From: Ric Van Dyke <>
Date: Tue, 29 May 2012 15:39:14 -0500
Message-ID: <>

Generally speaking for each row returned you shouldn't do more than 10 LIOs per table.

Sooooo... <number of rows in result set> * <tables> * 10 = Max tolerated LIOs

Of course you could just start with <number of rows in result set> / LIOs. If this is 10 or less then you it's likely alright, anything over certainly needs to be looked at.

Ric Van Dyke
Education Director
Hotsos Ltd

-----Original Message-----

[] On Behalf Of Stephens, Chris Sent: Tuesday, May 29, 2012 4:15 PM
To: ''
Subject: inefficient sql

I'm interested in creating a daily report to run in our development environments to spot inefficient SQL early in the process. I've already got one that lists top ten highest elapsed time and top ten most frequently executed. They have helped tremendously in focusing on the right SQL. However, there is often SQL here that makes its way into integration and production that could be improved upon. (Yes I know where SQL falls in the optimization hierarchy and am well aware that business tasks are what are important but these reports have proved their value over and over.)

I'm pretty confident that a ratio of LIO's to rows returned by each row operation in an SQL execution plan is a good indicator of SQL efficiency. I think I've heard this in a few different presentations. I don't, however, recall what that ratio should be or if I'm misremembering completely.

What do you all consider good indicators of inefficient SQL and how to you identify those statements?


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-- Received on Tue May 29 2012 - 15:39:14 CDT

Original text of this message