RE: inefficient sql

  • From: "Iotzov, Iordan" <IIotzov@xxxxxxxxxxxxxxx>
  • To: "'Chris.Stephens@xxxxxxx'" <Chris.Stephens@xxxxxxx>, "'oracle-l@xxxxxxxxxxxxx'" <oracle-l@xxxxxxxxxxxxx>
  • Date: Wed, 30 May 2012 10:05:22 -0400

LIO to rows is indeed a good ratio to monitor. This ratio is, however, 
practically meaningless for SQLs that do aggregates, such as COUNT, SUM, AVG, 
etc.  Separating aggregate from regular SQLs would be the biggest challenge for 
an automated report.

Iordan Iotzov

-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On 
Behalf Of Stephens, Chris
Sent: Tuesday, May 29, 2012 4:15 PM
To: 'oracle-l@xxxxxxxxxxxxx'
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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