Re: Questions about SQL Plan Management
- From: Wolfgang Breitling <breitliw@xxxxxxxxxxxxx>
- To: iggy_fernandez@xxxxxxxxxxx
- Date: Thu, 3 Jul 2014 13:49:56 -0600
By going through the full optimization exercise the CBO makes sure that the
conditions are such that it CAN come up with the same plan as in SPM. ONLY then
does it check if it is "allowed" to use this plan.
Wolfgang Breitling
breitliw@xxxxxxxxxxxxx
On 2014-07-03, at 1:27 PM, Iggy Fernandez <iggy_fernandez@xxxxxxxxxxx> wrote:
> Thanks for all the insights.
>
> If SPM stores the approved plan in the SPM baseline, then why are the
> transformation and optimization procedures invoked (the 10053 trace proves
> this) every time the query is hard-parsed? Why not simply reuse the approved
> plan; in other words, why not bypass the transformation and optimization
> procedures? (The same question might be asked about stored outlines.)
>
> This suggests that the SPM baseline does not contain all elements of the
> approved plan. If SPM baselines are basically stored outlines, then they
> don't contain access and filter predicates; this could cause the stability
> guarantee to fail. There may be other scenarios which lead to a failure of
> the stability guarantee.
>
> Iggy
>
> P.S. I could not figure out where SPM stores plan details.
>
Other related posts:
