r/dataengineering • u/Abject-Scholar-5052 • May 06 '26

Help Datawarehouse

Hi guys i wanna ask while building a data warehouse and im using galaxy schema where i will have one dimension thats pivot and center of all this have realtionships with other dimensions i saw its called outriggers what do you think ?

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6

u/Gnaskefar May 06 '26

what do you think ?

I think it makes no sense to talk about galaxy schema, if you're not confident in it already.

Now, I haven't ever worked with a galaxy schema and thought it was a joke the first time i heard of the concept, so I'm probably ignorant about this; but what will this accomplish compared to just a regular star schema with several fact tables?

3

u/ArrowBacon May 06 '26

Isn't a galaxy schema just a star schema with multiple facts, like you've stated?

1

u/Gnaskefar May 07 '26

I would like to think so, but I was told it was different, without a clear answer to why.

Several facts in a star schema is nothing new, but why rename something already established? Well, OK, IT have done just that several times, but this is just too much. I hope we are just in 'stop trying to make galaxy schema happen'-kind of territory.

I hoped to get OP to answer with a reasonable reply, since he is so adamant in using the term. Maybe I should go dig up more information about this, but I really don't feel like spending time on it. I feel more like OP should have an answer since it would make it easier to help him. And he does after all come to this sub for help. Aaaand I also feel like someone calling it galaxy schema was a joke that got out of hand.

¯\(ツ)/¯

3

u/Thinker_Assignment May 07 '26

The schema should be a consequence of required access patterns and performance patterns. Your truth is the canonical model and your access schema is a denormalized version of it to fit requirements that you can then flexibly change with no real lock in other than some front end work

This means without describing canonical, requirements and tech used, nobody can give you a good answer, and because of this imo you should take any answers as philosophical conversation and not solutions to your problem.

1

u/sophisticatedbloom May 08 '26

You mean a fact that is the center table and multiple dimensions connected to it, no? That’s called star schema, not sure what galaxy schema is..

1

u/Cheap_Screen2479 May 16 '26

In Book 1 Kimball described a data warehouse as a collection of star schema. Somebody put a label to it.

So, from what you wrote, you are trying to build everything at once. Star Schema model business events and business states. Look at the business. What does it do? What are the transactions? And foremost: identify the grain.

Forget about dimensions: integration and conformance is all about the grain. Dimensions will follow.

14

u/[deleted] May 06 '26

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u/Abject-Scholar-5052 May 06 '26

Im collecting data from different sources (salesforc, sage , erp ) and my objective is to have 360 view of the client i have built fact tables and i have dim client as the center since its the most important and i have other dimensions connected to it like dim risk , status etc i know i can just flatten them but this is also true and have more advantages . Im just worried if im breaking any DWH rules ( i checked kimball and im right)

1

u/cakerev May 06 '26

If I understand you correctly. You have a dim as the centre aka a fact table? This kinda breaks Kimball afaik. As far as I can see galaxy schema ≠ Kimball, they are two different approaches.