RE: Hints used most often?
- From: "Milen Kulev" <makulev@xxxxxxx>
- To: <kylelf@xxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 1 Apr 2008 23:03:04 +0200
... And hints controlling subquery processing (push/unnest) shouldn't be
forgotten, especially
when used in combination with QB_NAME (for finer control):
- PUSH_SUBQ
- NO_PUSH_SUBQ
- NO_MERGE
- NO_UNNEST
HTH.Milen
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of kyle Hailey
Sent: Tuesday, April 01, 2008 12:46 AM
To: oracle-l@xxxxxxxxxxxxx
Subject: Hints used most often?
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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