Oracle Scratchpad

January 3, 2007

Hints and Guesses

Filed under: Hints,Ignoring Hints,Indexing — Jonathan Lewis @ 8:45 pm GMT Jan 3,2007

If you go to this URL, you will find a discussion about the index_ss() hint. It’s an interesting example of how (a) you could argue that Oracle is ignoring hints until (b) you realise that we really can’t tell what’s going on because we don’t know what a hint is supposed to do.


October 28, 2006

Taking a Hint

Filed under: CBO,Execution plans,Hints,Ignoring Hints,Indexing — Jonathan Lewis @ 10:32 pm GMT Oct 28,2006

It seems the word is gradually getting around the Oracle world that “hints” are really absolute directives to the optimizer that cannot be ignored – if they are correctly used.

Unfortunately the documentation on hints is far from complete, so it is very easy to produce examples that suggest that a hint has been ignored. Here’s one I came across recently in a note about 10g.


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