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SQL Tuning via Throwaway Method
February 10, 2004

Martin Berg of Oracle Denmark has recently published a methodology for tuning SQL via his "throwaway" method.

 According to Berg:

 Basically tuning of queries can be done by following high level method:

1. Set goals

2. Identify queries to be tuned

3. For every query identified:

        4. Analyze query

       5. Suggest changes to improve performance

        6. Implement changes

       7. Test improvement

       8. Repeat until goal reached (or time spend)

Traditionally the hardest part of this is to get from step 4 (‘analyze’) to step 5 (‘suggest changes’) and has - as described in the introduction - been up to the guesswork and/or experience of the statement tuner.

The concept of tuning by eliminating throwaway is meant to directly address this part of the tuning method by quantifying the work done in each of the execution steps a query is build upon.

Berg identifies two types of throwaway:

Primary throwaway is the amount of rows from the input to a row source that cannot be found in the output from that particular row source.

Secondary throwaway is the amount of rows generated as output from a row source which are then thrown away in a following row source with primary throwaway.


This is a heavy read, and not for beginner DBAs, but quite interesting.

http://miracleas.dk/tools/throwaway2.pdf
 


 

 

 
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