Comments on: Hints on Hints http://jonathanlewis.wordpress.com/2009/05/09/hints-on-hints/ Just another Oracle weblog Sat, 18 May 2013 11:04:10 +0000 hourly 1 http://wordpress.com/ By: Enabling constraint in parallel « Timur Akhmadeev's blog http://jonathanlewis.wordpress.com/2009/05/09/hints-on-hints/#comment-39597 Wed, 16 Feb 2011 19:05:42 +0000 http://jonathanlewis.wordpress.com/?p=1145#comment-39597 [...] current best cost. It is the same issue as with PARALLEL hint explained by Jonathan Lewis in his Hints on Hints paper: single PARALLEL hint is not enough to make the plan go parallel. So how to make sure the [...]

]]> By: Does the Optimizer Need a Hint? « So Many Oracle Manuals, So Little Time http://jonathanlewis.wordpress.com/2009/05/09/hints-on-hints/#comment-33460 Sun, 14 Jun 2009 18:19:57 +0000 http://jonathanlewis.wordpress.com/?p=1145#comment-33460 [...] optimizer completely if you want it to do precisely what you want. Jonathan’s recent presentation Hints on Hints provides more information on the subject. If you tell your son not to touch the cookie jar, you [...]

]]> By: Hemant K Chitale http://jonathanlewis.wordpress.com/2009/05/09/hints-on-hints/#comment-33059 Wed, 20 May 2009 07:18:32 +0000 http://jonathanlewis.wordpress.com/?p=1145#comment-33059 MetaLink Note#826893.1 contains a change of behaviour in handling invalid hints if such invalid hints include Keywords.
Parsing of Hints has been (slightly) changed in 10g such that if an invalid hint includes a Keyword, any hint after that (even if valid) is ignored.

]]> By: Jonathan Lewis http://jonathanlewis.wordpress.com/2009/05/09/hints-on-hints/#comment-32956 Mon, 11 May 2009 18:17:15 +0000 http://jonathanlewis.wordpress.com/?p=1145#comment-32956 Hemant,

The “joy” of that particular hint is that you can put it into a piece of code and it produces a parallel tablescan for months – but as the data size grows bigger Oracle suddenly finds a serial indexed access path that costs less – and changes plans for “no apparent reason”.

]]> By: Hemant K Chitale http://jonathanlewis.wordpress.com/2009/05/09/hints-on-hints/#comment-32949 Mon, 11 May 2009 05:11:25 +0000 http://jonathanlewis.wordpress.com/?p=1145#comment-32949 Aah ! “The parallel hint tells Oracle to change the arithmetic – it doesn’t force Oracle to run parallel and it isn’t supposed to force Oracle to run parallel.”
is *most* interesting.

It wasn’t clear to me why sometimes I would see differences in behaviour when using FULL and PARALLEL together. I now have something to go on and test test test ! (And also validate if I hadn’t had syntax errors in my Hints !)

]]> By: Ben Prusinski http://jonathanlewis.wordpress.com/2009/05/09/hints-on-hints/#comment-32945 Sun, 10 May 2009 15:49:59 +0000 http://jonathanlewis.wordpress.com/?p=1145#comment-32945 Hi Jonathan,

I look forward to meeting you at OpenWorld this year.

Cheers,
Ben

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