Solved

Indexing on fact and dimension tables

Posted on 2014-11-11
6
88 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
  • 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
Control application downtime with dependency maps

Visualize the interdependencies between application components better with Applications Manager's automated application discovery and dependency mapping feature. Resolve performance issues faster by quickly isolating problematic components.

 

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

Best Practices: Disaster Recovery Testing

Besides backup, any IT division should have a disaster recovery plan. You will find a few tips below relating to the development of such a plan and to what issues one should pay special attention in the course of backup planning.

Question has a verified solution.

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

After restoring a Microsoft SQL Server database (.bak) from backup or attaching .mdf file, you may run into "Error '15023' User or role already exists in the current database" when you use the "User Mapping" SQL Management Studio functionality to al…
In this article we will get to know that how can we recover deleted data if it happens accidently. We really can recover deleted rows if we know the time when data is deleted by using the transaction log.
Windows 10 is mostly good. However the one thing that annoys me is how many clicks you have to do to dial a VPN connection. You have to go to settings from the start menu, (2 clicks), Network and Internet (1 click), Click VPN (another click) then fi…
Internet Business Fax to Email Made Easy - With  eFax Corporate (http://www.enterprise.efax.com), you'll receive a dedicated online fax number, which is used the same way as a typical analog fax number. You'll receive secure faxes in your email, f…

895 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

Need Help in Real-Time?

Connect with top rated Experts

12 Experts available now in Live!

Get 1:1 Help Now