Solved

Indexing on fact and dimension tables

Posted on 2014-11-11
6
103 Views
Last Modified: 2016-02-18
Will there be any benefit if I add index for all surrogate key in Fact tables and the primary key on all dimension tables ? What kinds of index key should be defined on each tables ? Please provide the TSQL that I need to run on dimenions and fact tables.

Currently, nothing is defined in the tables. Is there another way to increase the query for the SSAS ?

Tks

DIM_Customer (similar layout for other dimension tables)
---------------------
Customer_IDX
Customer
Name

FACT_SALES_INVOICE
------------------------------
CURRENTCY_IDX
REGION_COUNTRY_IDX
TRANSDATE
CUSTOMER_IDX
SALESMAN_IDX
:
:
0
Comment
Question by:AXISHK
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 3
6 Comments
 
LVL 48

Expert Comment

by:PortletPaul
ID: 40436728
Will there be any benefit if I add index for all surrogate key in Fact tables  ...?
YES

... and the primary key on all dimension tables ?
YES

I'm really rather surprised you have "dims & facts" without indexing.

In SQL Server the most important indexing decision is what will be the used for the clustered index as this shapes the physical means of storage on disk.

Are you absolutely certain there are no indexes on any of these tables?
0
 

Author Comment

by:AXISHK
ID: 40439094
Will it affect the processing speed of the cube, or affect the querying performance on the cube ?

Do I need to specify clustered index for primary key ?

Do I need to group any surrogate key in a single index, say

Current schema
DIM_CURRENCY (CURRENCY_IDX, CURRENCYCODE, NAME, SYMBOL, RATE)
FACT_SALES_INVOICE (CURRENCY_IDX, REGION_COUNTRY, TRANSDATE, CUSTOMER_IDX, SALESMAN_IDX, BASEAMOUNT, QTY, INVOICENO, COMPANY)

CREATE UNIQUE CLUSTERED INDEX PIndex
ON DIM_CURRENCY (CURRRENCY_IDX)

CREATE INDEX PIndex
ON FACT_SALES_INVOICE (CURRENTCY_IDX, REGION_COUNTRY_IDX, TRANSDATE, CUSTOMER_IDX, SALESMAN_IDX)

It seems that Fact Invoice doesn't have a primary key.

Any suggestion ?
0
 
LVL 48

Expert Comment

by:PortletPaul
ID: 40439100
It is not mandatory in database design that every table has a unique integer on every row,
it is extremely common but not mandatory.

It appears that the fact table DOES have a primary key, it just happens to involve multiple fields
(CURRENTCY_IDX, REGION_COUNTRY_IDX, TRANSDATE, CUSTOMER_IDX, SALESMAN_IDX)

However I doubt you can have so many indexes defined as "PIndex"

To second guess a database design from virtually no information or background is not a worthwhile activity and could be misleading for you. I would pose these questions to the database designer(s) or look for documentation on the design.
0
Free learning courses: Active Directory Deep Dive

Get a firm grasp on your IT environment when you learn Active Directory best practices with Veeam! Watch all, or choose any amount, of this three-part webinar series to improve your skills. From the basics to virtualization and backup, we got you covered.

 

Author Comment

by:AXISHK
ID: 40439217
Sorry, should create a single index with multiple fields, or create individual index for each surrogate (foreign key) ? Tks
0
 
LVL 48

Accepted Solution

by:
PortletPaul earned 500 total points
ID: 40439220
I do not know - with any certainty - through lack of knowledge - what your best options are.

Please discuss with the designer(s).
0
 

Author Closing Comment

by:AXISHK
ID: 40439332
Tks
0

Featured Post

Instantly Create Instructional Tutorials

Contextual Guidance at the moment of need helps your employees adopt to new software or processes instantly. Boost knowledge retention and employee engagement step-by-step with one easy solution.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This is basically a blog post I wrote recently. I've found that SARGability is poorly understood, and since many people don't read blogs, I figured I'd post it here as an article. SARGable is an adjective in SQL that means that an item can be fou…
Naughty Me. While I was changing the database name from DB1 to DB_PROD1 (yep it's not real database name ^v^), I changed the database name and notified my application fellows that I did it. They turn on the application, and everything is working. A …
With Secure Portal Encryption, the recipient is sent a link to their email address directing them to the email laundry delivery page. From there, the recipient will be required to enter a user name and password to enter the page. Once the recipient …

710 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question