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Re: Can Perf. Hints Change Result Set

From: Ralph Ganszky <ralph.ganszky_at_sap.com>
Date: Sat, 27 Nov 1999 19:46:11 +0100
Message-ID: <384026F3.CEC6640D@sap.com>


Hi Buck,

I agree with all other replys, that hints shouldn't change the result set of a query
and that there are some bugs which change the result set either. I also want to add one
bug to the list. If You enable Complex_View_Merging with the MERGE hint in Oracle
8.0.4, 8.0.5 You can get wrong result sets. But it don't depends on using hints or not,
the same error occurs if You set the Oracle Parameter in the Session or in the init.ora.

But I think that I should mention that if You use Hints You need statistics on the
tables in the query. If You don't have statistics Oracle will estimate the statistics
of the table and I would expect that in almost all cases Oracle will guess wrong.

--
Best regards

Ralph Ganszky

Buck Turgidson wrote:

> I need to do some tuning of some PeopleSoft Payroll SQL statements, and it
> will probably involve adding some hints to some stored SQL statements. We
> run the instance in RULE.
>
> Could a hint ever change the data returned from a SQL statement? If there
> is a risk of that, then we will obviously need to do some level of
> application testing in parallel to make sure we generate the same paychecks
> with and without the hints.
Received on Sat Nov 27 1999 - 12:46:11 CST

Original text of this message

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