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ce2qo_disable_unfolding execution hint

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Hi ,

I want to understand on ce2qo_disable_unfolding execution hint. Can some one explain the same in detail.


Thank You,

Raviteja Purama

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lbreddemann
Active Contributor

After you've read

SAP note 2291812 - SAP HANA DB: Disable/Enable CalculationEngine Feature - CalcView Unfolding

what questions do you have specifically?

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Hi Lars,

Thanks for your reply. However, i dont have access to view the SAP note.

Could you please in brief about this execution hint and how does it will be helpful by using in the CV View.

Thank You,

Raviteja Purama

lbreddemann
Active Contributor
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I'm probably not going to repeat a document that has been released as a SAP note here.

Maybe this way around: what do you understand that "unfolding" means in the context of SAP HANA calculation views?

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I have no idea on how unfolding works. It would be great if you can share any information on this.

Thank You,

Raviteja Purama

lbreddemann
Active Contributor
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In very short form: "unfolding" is the translation of calc engine constructs into relational constructs. The idea here is, that if the complete hierarchy of calculation views can be "translated" into relational constructs, then the whole query plus the view definition can be processed by the relational query transformation and optimisation stack (which is what happens to "normal" SQL statements).

As some of the calc engine constructs cannot be translated into relational operations, the "unfolding" may only be partial. That's when you see a "CALC VIEW" in the EXPLAIN PLAN of a query.

The hint you mentioned is there to prevent the unfolding, as in some situations it might be better to not go with a partially unfolded view hierarchy. This of course has to be checked and analysed for each case individually and should be considered the rare exception that mostly applies when dealing with rather old HANA information models.

Basically, whenever you build new views nowadays, this hint should not be required and the views should gain best performance with complete unfolding.