Feb 01 2008

Using Shortcut Joins The Right Way

Categories: Universe Design Dave Rathbun @ 10:48 am

Better, Faster, Cheaper?

Shortcut joins seem to be one of the more misunderstood features of Designer. They should not be used to resolve loops; that is not their function. They are supposed to be used to take shortcuts, thus the name. 🙂 They can make your queries faster, certainly, as they allow you to drop tables from the query. But there are limits as to how they can be used.

As a designer I almost always wait to the last step (or nearly so) to add shortcut joins. Here is the most important point about shortcut joins, in my opinion: If a universe isn’t working without them, adding shortcut joins does not fix any problems. In fact, it may only make them worse. I covered shortcut joins in a fairly detailed fashion in my most recent conference presentation. I am working on a series of posts to supplement the presentation slides and those will hopefully be ready soon.

5 Responses to “Using Shortcut Joins The Right Way”

  1. Comment by Indu February 4th, 2008 at 8:31 am

    Hi Dave,

    Good morning to you. That topics on Index Awareness and short cut joins are very nice and useful. It cleared many of my doubts.

    When you are talking abt Univ Design. Just thought would check with you, since i am not finding any link to put some new posts on your site.

    1) Are there any known restrictions/limitations in BO Designer with regard to number of tables/views, etc. a particular schema can have and be able to access via the tool?

    2) Or Is there a known limitation in BO Designer which you have come across which would make you feel that if i have a schema that has over say 20,000 views – then it will not work? And that is the limitation ?

    3) Also is there a limitation of the number of objects – we can have in a Universe ?

    Could you please advise on this ?

    Thanks

    Kind regards
    indu

  2. Comment by Indu February 4th, 2008 at 8:33 am

    Hi Dave,

    Another request if you could please help :

    If you could also talk about Contexts And Aliases and their use with examples that would be very helpful for learners like me – of universe design.

    Although i somehow figured out : when to use aliases and when to use contexts. But still i think some more clarity is required.

    I have an understanding that :

    (i) when you have only ONE Look up table (fact table) and other tables as dimension tables then it is suggested that you create Alias and break the loop.

    (ii) And that if there are MORE THAN ONE LOOK UP Table, then for each fact table, you create a context with all the other dimension tables.

    Is this understanding of mine correct ?

    But i would appreciate if you could put in some examples with complex tables / views / derived tables and help in better understanding.

    Thanks again in advance.

    Kind regards
    indu

  3. Comment by Dave Rathbun February 4th, 2008 at 10:31 am

    Hi, indu, thanks for your comments. I do intend to cover contexts and aliases in various posts but have not taken time to do so yet. The reason they are lower on my priority list is I have already written a number of presentations on these concepts; please check the presentations page here on my blog.

    Also please note that while I appreciate the time you took to post your comments, I only intend to respond to comments that are “on topic” with the blog posts. Questions that are not related to the post are better posted on BOB. I set that policy in place when I started my blog; more details. Thanks for understanding.

  4. Comment by Indu February 4th, 2008 at 2:21 pm

    Thanks Dave

    I understand and agree to what you say.

    Also all your downloads from Integra are interesting and informative too.
    As regards my posts on contexts. It was out of curiosity while i am learning something.

    As regards the other question on views, one of my friends told me that they are looking at some huge datamart and for building universes.
    I told him that Univ designer would crash. And that question too was out of curiosity, while i happened to see your blog today.

    I fully understand how you must be hard pressed for time.

    And i very much appreciate your response.

    Thanks once again.

    Kind regards
    indu

  5. Comment by Dave Rathbun February 4th, 2008 at 9:32 pm

    You make me sound so harsh. 🙂 It was not my intention, my apologies if that’s how it seemed. I am behind on a number of projects and while I enjoy reading comments I just don’t have time to respond unless it is to clarify a point that I’ve already written about.

    Stay tuned. Once I get things back under control I will be back. 🙂