Re: Looking for notes / examples where OFE doesn't help

From: Mohamed Houri <mohamed.houri_at_gmail.com>
Date: Thu, 27 Nov 2014 16:30:16 +0100
Message-ID: <CAJu8R6heWj-WSGsCZaA5nFGgFdJkZSt-eVdedkV_wQVn+Qh99Q_at_mail.gmail.com>

In the following blog article in response to my comment Jonathan Lewis wrote this

*"Although optimizer_features_enable will make the optimizer revert to earlier behaviour, I don’t think there’s any guarantee that it will re-introduce bugs that were present in earlier versions"*

http://jonathanlewis.wordpress.com/2011/03/02/first_rows/#comments

Best regards
Mohamed Houri

2014-11-27 13:13 GMT+01:00 Mauro Pagano <mauro.pagano_at_gmail.com>:

> I don't have any example handy but any CBO fix that is not under a
> fix_contol (ie. fix for wrong result bugs or ora-600/7445) would not be
> disabled by an older OFE and so if such fix is responsible for a plan
> change then changing OFE param will not revert to the old plan
>
> Sent from my iPhone
>
> On Nov 27, 2014, at 3:32 AM, Chitale, Hemant K <Hemant-K.Chitale_at_sc.com>
> wrote:
>
> I am looking for notes and/or examples that show that, after an upgrade
> and execution plan changes, even resetting OFE doesn’t always help. That
> is : OFE set to the previous version doesn’t guarantee that execution
> plan and runtime will be exactly as it was in the earlier version.
>
> One example I find is at
> *http://jonathanlewis.wordpress.com/2014/11/03/upgrades-4/*
> <http://jonathanlewis.wordpress.com/2014/11/03/upgrades-4/>
>
> Any more would help me.
>
> Hemant K Chitale
>
>
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Received on Thu Nov 27 2014 - 16:30:16 CET