Tag Archives: Indexes

Script to find the size of all Indexes in a database

Continuing with my interest with Indexes, i wrote this script that finds the size of all indexes in a database along with the table and the filegroup on which the index resides. I have used the AdventureWorks2012 database as an example. Please replace the DB name for which you want to find the information.

USE AdventureWorks2012
go
IF OBJECT_ID('tempdb..#Indexdata', 'U') IS NOT NULL
DROP TABLE #Indexdata

DECLARE
@SizeofIndex BIGINT, @IndexID INT,
@NameOfIndex nvarchar(200),@TypeOfIndex nvarchar(50),
@ObjectID INT,@IsPrimaryKey INT,
@FGroup VARCHAR(20)

create table #Indexdata (name nvarchar(50),
IndexID int, IndexName nvarchar(200),
SizeOfIndex int, IndexType nvarchar(50),
IsPrimaryKey INT,FGroup VARCHAR(20))
DECLARE Indexloop CURSOR FOR
SELECT idx.object_id, idx.index_id, idx.name, idx.type_desc
,idx.is_primary_key,fg.name
FROM sys.indexes idx
join sys.objects so
on idx.object_id = so.object_id JOIN sys.filegroups fg
ON idx.data_space_id = fg.data_space_id
where idx.type_desc != 'Heap'
and so.type_desc not in ('INTERNAL_TABLE','SYSTEM_TABLE')

OPEN Indexloop

FETCH NEXT FROM Indexloop
INTO @ObjectID, @IndexID, @NameOfIndex,
@TypeOfIndex,@IsPrimaryKey,@FGroup

WHILE (@@FETCH_STATUS = 0)
BEGIN
SELECT @SizeofIndex = sum(avg_record_size_in_bytes * record_count)
FROM sys.dm_db_index_physical_stats(DB_ID(),@ObjectID,
@IndexID, NULL, 'detailed')

insert into #Indexdata(name, IndexID, IndexName, SizeOfIndex,
IndexType,IsPrimaryKey,FGroup)
SELECT TableName = OBJECT_NAME(@ObjectID),
IndexID = @IndexID,
IndexName = @NameOfIndex,
SizeOfIndex = CONVERT(DECIMAL(16,1),(@SizeofIndex/(1024.0 * 1024))),
IndexType = @TypeOfIndex,
IsPrimaryKey = @IsPrimaryKey,
FGroup = @FGroup

FETCH NEXT FROM Indexloop
INTO @ObjectID, @IndexID, @NameOfIndex,
 @TypeOfIndex,@IsPrimaryKey,@FGroup
END
CLOSE Indexloop
DEALLOCATE Indexloop

select name as TableName, IndexName, IndexType,
SizeOfIndex AS [Size of index(MB)],
case when IsPrimaryKey = 1 then 'Yes' else 'No' End as [IsPrimaryKey]
,FGroup AS [File Group]
from #Indexdata order by SizeOfIndex DESC

Snapshot of the output below:
Indexsize

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Find all unused indexes in a database

While doing an index analysis activity i had to find the indexes are hardly being used in our production DB’s. I wrote this script to acheive the same

SELECT case when os.is_published = 1 then 'Replicated' else 'Not Replicated'
end as ReplicatedorNot,
OBJECT_NAME(idx.object_id) AS TableName ,
idx.name as Index_name,
istat.user_lookups,
istat.user_scans,
istat.user_seeks,
istat.user_updates
FROM sys.dm_db_index_usage_stats AS istat
JOIN sys.indexes AS idx ON idx.index_id = istat.index_id
join sys.objects os
on idx.object_id = os.object_id
AND idx.object_id = istat.object_id
WHERE
istat.database_id = DB_ID('databasename') -- type the name of the Db
and object_name(idx.object_id) not like 'Ms%'
and object_name(idx.object_id) not like 'sys%'
and object_name(idx.object_id) not like 'id_%'
and object_name(idx.object_id) not like 'conflict%'
and object_name(idx.object_id) not like 'Any other tables that you like to avoid%'
AND idx.is_unique_constraint = 0 -- no unique indexes
AND idx.is_primary_key = 0
AND idx.is_disabled = 0
AND idx.type > 1 -- don't consider heaps/clustered index
AND ( ( istat.user_seeks + istat.user_scans +istat.user_lookups )  <  istat.user_updates
or (istat.user_seeks = 0 AND istat.user_scans = 0 AND istat.user_lookups = 0))
order by (istat.user_seeks + istat.user_scans +
istat.user_lookups)

What is the difference between Unique Index and Unique Constraint

There is no difference between a unique constraint and a unique index other than the fact that the unique constraint is listed as a constraint in the database. A unique constraint cannot be disabled.The status of a constraint does not allow the unique constraint any additional functionality over a unique index. Even though the syntax for both are different the effect is the same. Unique Constraint creates Unique Index to maintain the constraint to prevent duplicate keys. Unique Index or Primary Key Index are physical structure that maintain uniqueness over some combination of columns across all rows of a table.

Let us start by building and example:
USE AdventureWorks
go
CREATE TABLE dbo.Test
( ID int NULL
) ON [PRIMARY]
GO
ALTER TABLE [dbo].[Test] ADD CONSTRAINT [CK_Test] UNIQUE
(
[ID] ASC
) ON [PRIMARY]
GO
CREATE UNIQUE NONCLUSTERED INDEX [IDX_Test_ID] ON [dbo].[Test]
(
[ID] ASC
)
GO
exec sp_helpconstraint Test
exec sp_helpindex Test

Snapshot of the output can been seen below.

Unique Index

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