How does a derived attribute view work technically?

[i033659]

Hi all,

I know what a derived attribute view is and how it is used and how it works. But what actually is going on behind the scenes, when I e.g. add an additional field to the base view and the change is propagated to  the referencing view after activating the referenced view?

I could not find a difference in the creating SQL neither.

Thanks,

Ingo

[lbreddemann]

Hi Ingo,

not really sure what you're after.

But derived attribute views really are treated as if you include a table a second time into an SQL statement. In this case you have to provide an alias for the second usage - that's pretty much what you do when you setup the derived attribute view and drag it into the logical join node of an analytical view.

During query processing, the OLAP engine "knows" that although this is the same attribute view it should deal with it as if it was a separate one.

That's really all what's about that this

- Lars

[i033659]

Hi Lars,

Thanks for your answer, however it was not quite what I am interested in:

What I want to know is: How does the referenced view know, that there is another (derived) view referencing it? I want to understand the mechanism which makes changes done with the referenced view immediately visible in the referencing views.

Regards,

Ingo

[sagarjoshi]

Hi Ingo,

This is what I had observed. In the derived view repository XML there is a reference to base view and this is what connects both. Not sure how during activation time of reference view all derived views are determined internally. I thought that there should be connection in object_dependencies table but surprisingly it is no there for derived view and reference view. Not sure if there are other system tables for view dependency.

<baseDimensionUri>/<Package>/attributeviews/AT_TEST</baseDimensionUri>

Thanks, Sagar

[lbreddemann]

Correct!

Derived views work by reference and only upon access of either the runtime or the design object, SAP HANA looks up the original object.