Hints used most often?
- From: "kyle Hailey" <kylelf@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Mon, 31 Mar 2008 15:46:29 -0700
I'm curious what hints people use the most often tuning SQL statements and why.
I'm been working on monitoring tools such as my free ASHMON sort of an
OEM-lite and S-ASH packages and Acitve Session History Simulator (see
http://perfvision.com/ashmon.php and http://perfvision.com/ash.php),
but now I'm shifting gears and starting to concentrate more on SQL
tuning. My goal is a sql tuning workbench (see Dan Tow's appendix B in
O'Reilly "SQL Tuning" for an example) but for starters I'm going to
play around with brute force SQL hint injection, which yes, is a wacky
idea, with limited use, but its the first step towards the ultimate
goal, thus I'm curious what hints are most used by people and why they
use them in order to set up some initial hint injection code with
appropriate heuristics.
For example:
NO_INDEX - setting indexes off I know aren't appropriate
INDEX_COMBINE - merging bitmap indexes, I've run into a number of
cases where Oracle for some reason seems not to merge bitmap indexes
FIRST_ROWS(n) - of course when I only want the first few rows
PARALLEL - to force parallel query on certain specific queries
There is an almost overwhelming list of hints thus know what is
actually the most used would be a good starting point for writing some
test code.
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