Code to list potential cluster key space savings per table

Back in January I posted the results of the cluster key size survey I ran in 2011 and explained how the larger the cluster key is on your table, the more space is being wasted in all the nonclustered index rows. Check it out if you haven't already.

I've finally put together the code that will run through all your databases and give you a per-table indication of how much space is being taken up by cluster keys in nonclustered indexes, and the potential space savings if you converted the cluster key to a single 8-byte bigint. You can get it below or from here: KeySpaceSavingsSingleResultSet.zip (1.57 kb)

You can mess around with the code to do what you want. And I'm continuing to use sp_msforeachdb because it's the fastest way for me to knock out code for you, and it continues to irritate my good friend Aaron Bertrand :-)

Enjoy!

/*============================================================================
  File:     KeySpaceSavingsSingleResultSet.sql

  Summary:  Potential cluster key space savings

  SQL Server Versions: 2005 onwards
——————————————————————————
  Written by Paul S. Randal, SQLskills.com

  (c) 2012, SQLskills.com. All rights reserved.

  For more scripts and sample code, check out
    http://www.SQLskills.com

  You may alter this code for your own *non-commercial* purposes. You may
  republish altered code as long as you include this copyright and give due
  credit, but you must obtain prior permission before blogging this code.
 
  THIS CODE AND INFORMATION ARE PROVIDED "AS IS" WITHOUT WARRANTY OF
  ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED
  TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
  PARTICULAR PURPOSE.
============================================================================*/

IF EXISTS (SELECT * FROM msdb.sys.objects WHERE [name] = 'SQLskillsIKSpace')
    DROP TABLE msdb.dbo.SQLskillsIKSpace;
GO
CREATE TABLE msdb.dbo.SQLskillsIKSpace (
    DatabaseID SMALLINT,
 SchemaName SYSNAME,
 ObjectName SYSNAME,
    ObjectID INT,
    IndexCount SMALLINT DEFAULT (0),
    TableRows BIGINT DEFAULT (0),
    KeyCount SMALLINT DEFAULT (0),
    KeyWidth SMALLINT DEFAULT (0));
GO

EXEC sp_MSforeachdb
    N'IF EXISTS (SELECT 1 FROM (SELECT DISTINCT [name]
    FROM sys.databases WHERE [state_desc] = ''ONLINE''
        AND [database_id] > 4
        AND [name] != ''pubs''
        AND [name] != ''Northwind''
        AND [name] != ''distribution''
        AND [name] NOT LIKE ''ReportServer%''
        AND [name] NOT LIKE ''Adventure%'') AS names WHERE [name] = ''?'')
BEGIN
USE [?]

INSERT INTO msdb.dbo.SQLskillsIKSpace
(DatabaseID, SchemaName, ObjectName, ObjectID)
SELECT DB_ID (''?''), SCHEMA_NAME (o.[schema_id]), OBJECT_NAME (o.[object_id]), o.[object_id]
FROM sys.objects o
WHERE o.[type_desc] IN (''USER_TABLE'', ''VIEW'')
    AND o.[is_ms_shipped] = 0
    AND EXISTS (
        SELECT *
        FROM sys.indexes
        WHERE [index_id] = 1
            AND [object_id] = o.[object_id]);

UPDATE msdb.dbo.SQLskillsIKSpace
SET [TableRows] = (
    SELECT SUM ([rows])
    FROM sys.partitions p
    WHERE p.[object_id] = [ObjectID]
    AND p.[index_id] = 1)
WHERE [DatabaseID] = DB_ID (''?'');
 
UPDATE msdb.dbo.SQLskillsIKSpace
SET [IndexCount] = (
    SELECT COUNT (*)
    FROM sys.indexes i
    WHERE i.[object_id] = [ObjectID]
    AND i.[is_hypothetical] = 0
    AND i.[is_disabled] = 0
    AND i.[index_id] != 1)
WHERE [DatabaseID] = DB_ID (''?'');

UPDATE msdb.dbo.SQLskillsIKSpace
SET [KeyCount] = (
    SELECT COUNT (*)
    FROM sys.index_columns ic
    WHERE ic.[object_id] = [ObjectID]
    AND ic.[index_id] = 1)
WHERE [DatabaseID] = DB_ID (''?'');

UPDATE msdb.dbo.SQLskillsIKSpace
SET [KeyWidth] = (
    SELECT SUM (c.[max_length])
    FROM sys.columns c
    JOIN sys.index_columns ic
    ON c.[object_id] = ic.[object_id]
    AND c.[object_id] = [ObjectID]
    AND ic.[column_id] = c.[column_id]
    AND ic.[index_id] = 1)
WHERE [DatabaseID] = DB_ID (''?'');

DELETE msdb.dbo.SQLskillsIKSpace
WHERE
    ([KeyCount] = 1 AND [KeyWidth] < 9)
    OR [IndexCount] = 0 OR [TableRows] = 0;

END';
GO

SELECT
 DB_NAME ([DatabaseID]) AS [Database],
 [SchemaName] AS [Schema],
 [ObjectName] AS [Table],
    [IndexCount] AS [NCIndexes],
    [KeyCount] AS [ClusterKeys],
    [KeyWidth],
    [TableRows],
    [IndexCount] * [TableRows] * [KeyWidth] AS [KeySpaceInBytes],
    ([IndexCount] * [TableRows] * ([KeyWidth] – 8)) AS [PotentialSavings]
FROM msdb.dbo.SQLskillsIKSpace
ORDER BY [PotentialSavings] DESC;

DROP TABLE msdb.dbo.SQLskillsIKSpace;
GO