inefficient SQL detector

From: Charlie Mengler <charliem_at_mwh.com>
Date: Wed, 03 Oct 2001 13:05:37 -0700
Message-ID: <F001.003A1164.20011003132541@fatcity.com>

Yesterday while on a search for inefficient SQL I developed the following SQL; which did a decent job of highlighting 1 - 2 dozen SQL statements that were HIGHLY inefficient. The goal was to identify the SQL that did a "lot" of buffer_gets (> 2000000); that ran "frequently" (> 100 times); that only returned a "few" number of rows (1-2 per execution) and that did "many" (> 1000) buffer_gets for each execution. You should adjust these criteria to better match your own application & environment.

select disk_reads, buffer_gets, rows_processed, executions, (buffer_gets/executions) ratio, sql_text
from v$sql

where buffer_gets    > 2000000
 and  executions     > 100
 and  executions*2   > rows_processed

group by disk_reads, buffer_gets, rows_processed, executions, sql_text having (buffer_gets/executions) > 1000
order by 4
/

Alternatively this SQL can be order by 5

We are in the process of adding indexes that hopefully will GREATLY increase the selectivity of the SQL, rather than doing cartesian joins across tables.

HTH & YMMV!
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Charlie Mengler                            Maintenance Warehouse  
charliem_at_mwh.com                           10641 Scripps Summit Ct.
858-831-2229                               San Diego, CA 92131    
United WE Stand!                           Justice WILL Be Served!

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Author: Charlie Mengler
INET: charliem_at_mwh.com

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