Disadvantages of navigational attributes on query performance

[Former Member]

Hi all,

Can anybody tell me what are the disadvantages of navigational attributes on query performance. Maximum how many Navigational Attributes should we use in a Query?

Thanks.

[Former Member · Accepted solution]

HI sudhakar

Almost everyone has mentioned the impact to the query being extra joins, e.g. 5 Nav Attr in the query ==> 5 more tables.

I don't think you can make a generalization that you should not have more than X Nav Attr in a query - there are just too many other variables:

How big are the fact tables?

How big are the master data tables of the Nav Attr?

Are there appropriate indices on the master data tables?

How often will this query be run - 1000 times a day or 5 times a day?

Are the Nav Attr in the initial view, or are they only going to be drilled into occasionally?

Are ther aggregates for the cube?

Bottomline - I don't think there's a simple answer to the question. It can certainly help to bringa DBA into the loop to review the SQL that is generated to see where additional indices might help.

Cheers

Sunil Reddy LCP

[Former Member · Accepted solution]

I dont know its a Coincidence or fake ( Please excuess me if i am mistaken ) i strongly feel sunil and sudhakar are same.... i got this doubt when sudharkar wrote question and the signature was sunil reddy LCP and when i check Sudhakar questions which he wrote in this forums all answers and points awared to SUnil strange...........

sharp deep

[Former Member]

Hi

Navigation attributes are joins that need to be performed at query execution. There is no limit that I know of for navigational attributes but for large queries , it is desirable to minimize navigational attributes.

Joins at runtime for query generation are very expensive and should be minimized.

Cheers

Sunil Reddy LCP

[Former Member]

Hi ,

pls do this fast

Message was edited by:

sudhakar reddy

[Former Member]

Hi ,

Navigational attributes are part of the “extended star schema”. Navigational attributes require additional table joins at runtime (in comparison to dimension characteristics) so having an impact on performance.

– but usually the decision for dimension characteristics or navigational attributes is based on business requirements rather than on performance considerations.

I am not sure there is any reccommendation on no of navigational attributes etc.

Is it correct

Message was edited by:

sudhakar reddy

[Former Member]

http://help.sap.com/saphelp_nw04/helpdata/en/2e/caceae8dd08e48a63c2da60c8ffa5e/content.htm

read this Link

[Former Member]

Hi

Ya thats correct

Cheers

Sunil Reddy LCP