Index Seek not happening

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Index Seek not happening

vignesh.ms

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December 3, 2014 at 11:29 pm

#313522

Hi There,
I'm having a table to hold the photo details of a business, BusinessPhotoId is the primary key column.
Now I require to find photos of a business so I used the following query,

select * from businessphoto where businessid = 2

CI - Clutered Index
NCI - Non-Clutered Index
It leads a CI scan, So I decided to create an NCI on BusinessId column
Though I created a NCI, execution plan shows only CI scan.
1. What is the problem, why the optimizer goes with the index seek?
2. Do you need any other Info from me about the table to ans ?
Thanks

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viggneshwar Newbie Points: 6 More actions · Answer 1

Hi,

It's not necessary, plan always should be index seek. Based on volume of table data, index scan will be considered as best plan by the compiler.

Gail Shaw SSC Guru Points: 1004504 More actions · Answer 2

Without seeing the execution plan, vague guess. Index is not covering and too many rows are being returned to make index seek + all the key lookups efficient.

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Koen Verbeeck SSC Guru Points: 259115 More actions · Answer 3

vignesh.ms (12/3/2014)
Though I created a NCI, execution plan shows only CI scan.
1. What is the problem, why the optimizer goes with the index seek?
2. Do you need any other Info from me about the table to ans ?
Thanks

You are doing a SELECT *. Chances are very big your index is not covering.

Table definition, index definition and execution plan might be a help to troubleshoot this.

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Grant Fritchey SSC Guru Points: 398909 More actions · Answer 4

And because you're selecting everything, that's all stored with the clustered index, hence the scan.

How many rows is it returning out of how many rows in the database?

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ScottPletcher SSC Guru Points: 101120 More actions · Answer 5

If you (almost) always do lookups on the table based on "businessid", then cluster the table on businessid. If you need to keep the PK, make the PK nonclustered .

ALTER TABLE businessphoto DROP CONSTRAINT [PK_businessphoto]

--chg fillfactor and filegroup name as needed

CREATE CLUSTERED INDEX CL_businessphoto ON dbo.businessphoto ( businessid ) WITH ( FILLFACTOR = 98 ) ON [PRIMARY]

ALTER TABLE businessphoto ADD CONSTRAINT [PK_businessphoto] PRIMARY KEY NONCLUSTERED ( BusinessPhotoId ) WITH ( FILLFACTOR = 100 ) ON [PRIMARY]

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vignesh.ms Hall of Fame Points: 3456 More actions · Answer 6

ScottPletcher (12/4/2014)
If you (almost) always do lookups on the table based on "businessid", then cluster the table on businessid. If you need to keep the PK, make the PK nonclustered .
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Thanks dude.. it works. good thinking