Two months ago I blogged about a procedure I wrote that, if you are using Ola Hallengren's index maintenance routine, can look for indexes that are being repeatedly defragged. This usually indicates that the fill factor can be adjusted downward so that the index doesn't need to be defragged every time your maintenance routine runs. Why do you care if indexes are being repeatedly defragged? For one, the defragmentation process is logged, so it generates lots of log records that need to be backed up, which increases your backup times, restore times, and backup file sizes. If you are using log shipping or any other high availability solution that utilizes the log file, it simply creates more work for that process.

Without covering all of that again, let me just point you to my previous post which not only talks about this in a bit more detail, but also features unicorns.

I've made some improvements to the code:

  1. The old version used to generate commands to rebuild indexes using the ONLINE = ON argument. This is an Enterprise-only feature and this new version is now smart enough to detect if you are running Enterprise edition or not and sets the option correctly. (ONLINE = ON should also be generated on SQL 2008 Datacenter edition, but I do not have a copy of that to test with. If someone can verify this works, please let me know.)
  2. The generated ALTER INDEX code used the PARTITION = ALL argument. This was not introduced until SQL 2008, so when running on a SQL 2005 server, the generated command would fail. Oops. The code now checks for this and will not include it on SQL 2005 machines.
  3. I've modified the subject line of the email that is generated to include the name of the database where excessive defragmentation was found. This is helpful when you are checking several databases on the same server.
  4. There were two locations where I forgot to put square brackets around the database name when generating commands, which caused errors when database name included a period. This has been fixed.

Be sure to revisit the original post for instructions on how to use this procedure. Pay special attention to the bits about how often to run this and how it needs to be correlated with how often you clear Ola's history table.

Known issues:

  1. The generated code will only work on non-partitioned indexes or indexes that are partitioned using aligned partitions (partitions that are based on equivalent partition functions). That's just how PARTITION = ALL works. However, even if you have non-aligned partitioned indexes, this routine will still identify them for you if they are being defragged constantly - you'll just have to write your own code to change the fill factor.
  2. This only examines one database at a time. Eventually, I want to modify this so it will look at all databases in Ola's log table at once, but that requires more coding than I have time to do right now. It's on the To Do list though.

Let me know if you find this useful or have any suggestions for improvements!

 


CREATE PROCEDURE [dbo].[up_IndexDefragFrequencyCheck]
       (
        @DatabaseToInvestigate VARCHAR(100) = NULL
       ,@CommandLogDatabase VARCHAR(100) = NULL
       ,@CountThreshold TINYINT = 4
       ,@OverRebuildThresholdNewFF TINYINT = 70
       ,@OverReorgThresholdNewFF TINYINT = 80
       ,@MailProfileName sysname
       ,@MailRecipients VARCHAR(MAX) = NULL
	   )
AS /*
	
	This procedure scans the CommandLog table of Ola Hallengren's index defrag script
		(http://ola.hallengren.com/) and identifies indexes that are being rebuilt or
		reorganized regularly. The original code comes courtesy of Tim Ford, who blogged
		this at http://thesqlagentman.com/2013/10/whats-the-frequency-kenneth/. This routine
		expands his work. The procedure is meant to be run on a regular basis and will send 
		an email when it finds indexes being defragged more than a specified number of times.
		It will also suggest rebuilding the index with a new fill factor to reduce the number
		of rebuilds or reorgs. The new fill factor recommended is one you specify, if the current
		fill factor of the index is 0 or 100%, otherwise it is 10% less than the current
		fill factor. It will not recommend anything less than 50%.

		IMPORTANT!!! This routine looks at the log table and the _current_ fill factor setting
		of the indexes. Therefore, in order to get appropriate fill factor recommendations,
		this routine should NOT be run more often than the log table is cleared. FOR EXAMPLE,
		IF YOU KEEP 30 DAYS WORTH OF LOG RECORDS IN YOUR TABLE, THIS ROUTINE SHOULD NOT BE RUN
		MORE OFTEN THAN EVERY 30 DAYS. This is because if you change the fill factor of an index
		it may result in stopping rebuilds, but the log table will still have the records of the
		prior rebuilds, which may trigger another recommendation to reduce the fill factor, which
		would then be 10% less than what you just changed it to.

		Do not blindly run the commands in the email notification! They are meant to make it easier
		for a DBA to change the fill factor, but they should be evaluated first to ensure they
		are appropriate for your situation.
		
		Input parameters:

		@DatabaseToInvestigate - The database to scan for excessive defrags
		@CommandLogDatabase - Database holding the CommandLog table of Ola's routine
		@CountThreshold - indexes being defragged equal to or greater this number of times
							are flagged as being excessively defragged
		@OverRebuildThresholdNewFF - Initial starting fill factor suggestion for indexes that
							are being rebuilt more than @CountThreshold times. Only used when
							current fill factor is 0 or 100
		@OverReorgThresholdNewFF - Initial starting fill factor suggestion for indexes that
							are being reorganized more than @CountThreshold times. Only used when
							current fill factor is 0 or 100
		@MailProfileName - name of mail profile the routine can use to send email
		@MailRecipients - list of email addresses the notification will be sent to. Must be of
							the form xxx@xxx.xxx  Multiple addresses should be separated by a ;


		Shaun J. Stuart
		shaunjstuart.com

		v1.0 - 10/8/13
		v1.1 - 10/13/13 - SJS - Added support for case where current fill factor between 100 and the
								min thresholds passed in.
		v1.2 - 1/16/14  - SJS - Added check for SQL 2005, which does not support the PARTITION = ALL option
							  - Added check for Enterprise edition to set ONLINE = ON or OFF
							  - Added square brackets around DB name where they were not before to
									handle db names with periods in them
							  - Added database name to email subject line

*/




       DECLARE @SQLstr VARCHAR(2000)
       DECLARE @EmailBody VARCHAR(MAX)
       DECLARE @CRLF CHAR(2)
       DECLARE @EmailSubject VARCHAR(200)
	   DECLARE @SQLVersion TINYINT
	   DECLARE @SupportsOnlineRebuilds BIT

       SET @CRLF = CHAR(13) + CHAR(10)
	   SET @SQLVersion = LEFT(CAST(SERVERPROPERTY('productversion') AS VARCHAR(15)),
                        CHARINDEX('.',
                                CAST(SERVERPROPERTY('productversion') AS VARCHAR(15)))
                        - 1)
	/* SQLVersion: 9 = SQL 2005, 10 = SQL 2008 or 2008 R2, 11 = 2012 */

	IF LEFT(CAST(SERVERPROPERTY ('edition')AS VARCHAR(50)),10) = 'Enterprise'
		OR LEFT(CAST(SERVERPROPERTY ('edition')AS VARCHAR(50)),10) = 'Datacenter'
	BEGIN
		SET @SupportsOnlineRebuilds = 1
	END
	ELSE
	BEGIN
		SET @SupportsOnlineRebuilds = 0
	END

/* Data validation */

       IF @DatabaseToInvestigate IS NULL
          OR @DatabaseToInvestigate = ''
          BEGIN
                SELECT  'A database to investigate must be specified.'
                RETURN
          END

       IF @CommandLogDatabase IS NULL
          OR @CommandLogDatabase = ''
          BEGIN
                SELECT  'A database holding the CommandLog table must be specified.'
                RETURN
          END

       IF @MailRecipients IS NULL
          OR @MailRecipients = ''
          BEGIN
                SELECT  'At least one email recipient must be specified.'
                RETURN
          END

       IF @MailRecipients NOT LIKE '%@%.%'
          BEGIN
                SELECT  'Email recipient not valid address format.'
                RETURN
          END



--============================================================================
-- INDEX REBUILD COUNT 
--============================================================================

       IF EXISTS ( SELECT   name
                   FROM     tempdb.sys.objects
                   WHERE    name = '##Recommendations' )
          BEGIN
                DROP TABLE ##Recommendations
          END

       IF EXISTS ( SELECT   name
                   FROM     tempdb.sys.objects
                   WHERE    name = '##Index_History' )
          BEGIN
                DROP TABLE ##Index_History
          END
 
       IF EXISTS ( SELECT   name
                   FROM     tempdb.sys.objects
                   WHERE    name = '##Indexes' )
          BEGIN
                DROP TABLE ##Indexes
          END

       CREATE TABLE ##Recommendations
              (
               CommandLine VARCHAR(MAX)
              );



       CREATE TABLE ##Index_History
              (
               the_database sysname
              ,the_schema sysname
              ,the_object sysname
              ,the_index sysname
              ,index_type VARCHAR(13)
              ,fill_factor TINYINT
              ,rebuild_count INT NULL
              ,reorg_count INT NULL
              );
 
       CREATE TABLE ##Indexes
              (
               the_schema sysname
              ,the_object sysname
              ,the_index sysname
              ,fill_factor TINYINT
              );
 
       SET @SQLstr = 'INSERT  INTO ##Indexes
        (the_schema
        ,the_object
        ,the_index
        ,fill_factor)
        SELECT  OBJECT_SCHEMA_NAME(SO.object_id, DB_ID('''
           + @DatabaseToInvestigate + ''')) AS the_schema
               ,SO.name AS the_object
               ,SI.name AS the_index
               ,SI.fill_factor
        FROM    [' + @DatabaseToInvestigate + '].sys.objects SO
                INNER JOIN [' + @DatabaseToInvestigate
           + '].sys.indexes SI ON SO.object_id = SI.object_id
        WHERE   SI.index_id > 0;'
		--PRINT @SQLstr
       EXEC (@SQLstr)
 
       SET @SQLstr = 'INSERT  INTO ##Index_History
        (the_database
        ,the_schema
        ,the_object
        ,the_index
        ,index_type
        ,fill_factor
        ,rebuild_count
        ,reorg_count)
        SELECT  C.DatabaseName
               ,C.SchemaName
               ,C.ObjectName
               ,C.IndexName
               ,CASE C.IndexType
                  WHEN 1 THEN ''Clustered''
                  ELSE ''Non-Clustered''
                END AS IndexType
               ,IX.fill_factor
               ,COUNT(C.ID) AS rebuild_count
               ,0 AS reorg_count
        FROM    [' + @CommandLogDatabase + '].dbo.CommandLog C
                LEFT JOIN ##Indexes IX ON C.SchemaName = IX.the_schema
                                          AND C.ObjectName = IX.the_object
                                          AND C.IndexName = IX.the_index
        WHERE   C.CommandType = ''ALTER_INDEX''
                AND C.ObjectType = ''U''
                AND C.Command LIKE ''%REBUILD%''
                AND C.DatabaseName = ''' + @DatabaseToInvestigate + '''
        GROUP BY C.DatabaseName
               ,C.SchemaName
               ,C.ObjectName
               ,C.IndexName
               ,IndexType
               ,IX.fill_factor;'
		--PRINT @SQLstr
       EXEC (@SQLstr) 
--============================================================================
-- INDEX REORGANIZE (ONLY) COUNT 
--============================================================================
       SET @SQLstr = 'INSERT  INTO ##Index_History
        (the_database
        ,the_schema
        ,the_object
        ,the_index
        ,index_type
        ,fill_factor
        ,rebuild_count
        ,reorg_count)
        SELECT  C.DatabaseName
               ,C.SchemaName
               ,C.ObjectName
               ,C.IndexName
               ,CASE C.IndexType
                  WHEN 1 THEN ''Clustered''
                  ELSE ''Non-Clustered''
                END AS IndexType
               ,IX.fill_factor
               ,0 AS rebuild_count
               ,COUNT(C.ID) AS reorg__count
        FROM    [' + @CommandLogDatabase
           + '].dbo.CommandLog C
                LEFT JOIN ##Indexes IX ON C.SchemaName = IX.the_schema
                                          AND C.ObjectName = IX.the_object
                                          AND C.IndexName = IX.the_index
                LEFT JOIN ##Index_History IH ON C.DatabaseName = IH.the_database
                                                AND C.SchemaName = IH.the_schema
                                                AND C.ObjectName = IH.the_object
                                                AND C.IndexName = IH.the_index
        WHERE   C.CommandType = ''ALTER_INDEX''
                AND C.ObjectType = ''U''
                AND C.Command LIKE ''%REORGANIZE%''
                AND C.DatabaseName = ''' + @DatabaseToInvestigate + '''
                AND IH.the_database IS NULL
        GROUP BY C.DatabaseName
               ,C.SchemaName
               ,C.ObjectName
               ,C.IndexName
               ,IndexType
               ,IX.fill_factor;'
		--PRINT @SQLstr
       EXEC (@SQLstr)
--========================================================
-- ACCOUNT FOR INDEXES BOTH REBUILT AND REORGANIZED
--========================================================
       SET @SQLstr = 'UPDATE  ##Index_History
					  SET     reorg_count = C2.reorganize_count
					  FROM    ##Index_History IH
					  INNER JOIN (SELECT  C.DatabaseName
						     ,C.SchemaName
							   ,C.ObjectName
							,C.IndexName
                           ,	COUNT(C.ID) AS reorganize_count
                      FROM    [' + @CommandLogDatabase + '].dbo.CommandLog C
                      WHERE   C.CommandType = ''ALTER_INDEX''
                              AND C.ObjectType = ''U''
                              AND C.Command LIKE ''%REORGANIZE%''
                              AND C.DatabaseName = ''' + @DatabaseToInvestigate
           + '''
			          GROUP BY C.DatabaseName
                            ,C.SchemaName
                            ,C.ObjectName
                            ,C.IndexName
                    ) C2 ON IH.the_database = C2.DatabaseName
                            AND IH.the_schema = C2.SchemaName
                            AND IH.the_object = C2.ObjectName
                            AND IH.the_index = C2.IndexName
					  WHERE   IH.rebuild_count > 0'
--print @SQLstr
       EXEC (@SQLstr) 
--============================================================================
-- RETURN THE RESULTS
--============================================================================
 
       SELECT   the_database
               ,the_schema
               ,the_object
               ,the_index
               ,index_type
               ,ISNULL(CONVERT(VARCHAR(20), fill_factor), 'No longer exists') AS fill_factor
               ,rebuild_count
               ,reorg_count
       FROM     ##Index_History
       WHERE    rebuild_count >= @CountThreshold
                OR reorg_count >= @CountThreshold
       ORDER BY the_database
               ,rebuild_count DESC
               ,reorg_count DESC
               ,the_object
               ,the_index
 
       INSERT   INTO ##Recommendations
                (CommandLine)
                SELECT  'USE [' + the_database + ']; ' + @CRLF
                        + 'ALTER INDEX [' + the_index + '] ON [' + the_schema
                        + '].[' + the_object + '] ' + @CRLF
                        + 'REBUILD ' + 
							CASE 
								WHEN @SQLVersion = 9 THEN ' '
								WHEN @SQLVersion > 9 THEN  'PARTITION = ALL '
							END
						+ 'WITH (PAD_INDEX = OFF, '
                        + 'STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = ON, ' +
							CASE @SupportsOnlineRebuilds 
								WHEN 1 THEN 'ONLINE = ON, '
								WHEN 0 THEN 'ONLINE = OFF, '
							END
                        + @CRLF
                        + 'ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = '
                        + CASE WHEN fill_factor = '0'
                               THEN CAST(@OverRebuildThresholdNewFF AS VARCHAR(3))
                               WHEN fill_factor = '100'
                               THEN CAST(@OverRebuildThresholdNewFF AS VARCHAR(3))
                               WHEN fill_factor <= @OverRebuildThresholdNewFF
                               THEN CAST(@OverRebuildThresholdNewFF - 10 AS VARCHAR(3))
							   WHEN (fill_factor > @OverRebuildThresholdNewFF AND 
								fill_factor <100)
                               THEN CAST(@OverRebuildThresholdNewFF AS VARCHAR(3))
                               ELSE NULL /* unknown case */
                          END + '); '  + @CRLF AS RebuildCommand
                FROM    ##Index_History
                WHERE   rebuild_count >= @CountThreshold
                        AND (fill_factor = 0
                             OR fill_factor >= 60)
                UNION ALL
                SELECT  'USE [' + the_database + ']; ' + @CRLF
                        + 'ALTER INDEX [' + the_index + '] ON [' + the_schema
                        + '].[' + the_object + '] ' + @CRLF
                        + 'REBUILD ' +
							CASE 
								WHEN @SQLVersion = 9 THEN ' '
								WHEN @SQLVersion > 9 THEN  'PARTITION = ALL '
							END
						+ 'WITH (PAD_INDEX = OFF, '
                        + 'STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = ON, ' +
							CASE @SupportsOnlineRebuilds 
								WHEN 1 THEN 'ONLINE = ON, '
								WHEN 0 THEN 'ONLINE = OFF, '
							END						
                        + @CRLF
                        + 'ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = '
                        + CASE WHEN fill_factor = '0'
                               THEN CAST(@OverReorgThresholdNewFF AS VARCHAR(3))
                               WHEN fill_factor = '100'
                               THEN CAST(@OverReorgThresholdNewFF AS VARCHAR(3))
                               WHEN fill_factor <= @OverReorgThresholdNewFF
                               THEN CAST(@OverReorgThresholdNewFF - 10 AS VARCHAR(3))
							   WHEN (fill_factor > @OverReorgThresholdNewFF AND 
								fill_factor <100)
                               THEN CAST(@OverReorgThresholdNewFF AS VARCHAR(3))
                               ELSE NULL /* unknown case */
                          END + '); ' + @CRLF AS RebuildCommand
                FROM    ##Index_History
                WHERE   reorg_count >= @CountThreshold
                        AND (fill_factor = 0
                             OR fill_factor >= 60)

       IF EXISTS ( SELECT   1
                   FROM     ##Recommendations )
          BEGIN
                SET @EmailBody = @CRLF
                    + 'Analysis of the index defrag log table has been performed and it appears '
                    + 'there are indexes that are being repeatedly defragged. Repeated defragging may '
                    + 'indicate the indexes need a lower fill factor to reduce page splits. Repeated '
                    + 'defragging also wastes resources and generates large amounts of potentially '
                    + 'unnecessary transaction log entries. The parameters used to generate this report '
                    + 'are: ' + @CRLF + @CRLF + 'Server: ' + @@SERVERNAME
                    + @CRLF + 'Database: ' + @DatabaseToInvestigate + @CRLF
                    + 'Min number of rebuilds / reorgs flagged as excessive: '
                    + CAST(@CountThreshold AS VARCHAR(3)) + '. ' + @CRLF
                    + 'Starting suggested fill factor for excessive rebuilds: '
                    + CAST(@OverRebuildThresholdNewFF AS VARCHAR(3)) + '. '
                    + @CRLF
                    + 'Starting suggested fill factor for excessive reorgs: '
                    + CAST(@OverReorgThresholdNewFF AS VARCHAR(3)) + '. '
                    + @CRLF + @CRLF + @CRLF
                    + 'Below are the suggested commands to change the fill factor on the indexes in question. '
                    + 'These commands should be carefully evaluated before being run to ensure they are '
                    + 'appropriate for the situation! In particular, if this routine is run more frequently '
                    + 'than the defrag log table is cleared, it may result in inappropriate fill factor '
                    + 'recommendations.' + @CRLF + @CRLF + @CRLF


                IF EXISTS ( SELECT  1
                            FROM    ##Index_History
                            WHERE   (rebuild_count >= @CountThreshold
                                     OR reorg_count >= @CountThreshold)
                                    AND fill_factor <= 50 
									AND fill_factor > 0)
                   BEGIN
                         SET @EmailBody = @EmailBody + @CRLF + @CRLF
                             + 'Note: Some indexes were found that are being defragged regularly and have a fill factor '
                             + 'setting of 50 or less. Reducing the fill factor further is not generally recommended '
                             + 'and further investigation is warranted.'
                             + @CRLF + @CRLF

                         INSERT INTO ##Recommendations
                                (CommandLine)
                                SELECT  '/* Database [' + the_database
                                        + '], index [' + the_index + ']'
                                        + ' on [' + the_schema + '].['
                                        + the_object + '] '
                                        + 'is being repeatedly rebuilt and its fill factor '
                                        + 'is already set to 50 or less. This likely is worth a deeper '
                                        + 'investigation. */' AS RebuildCommand
                                FROM    ##Index_History
                                WHERE   rebuild_count >= @CountThreshold
                                        AND fill_factor <= 50
										AND fill_factor > 0 
                                UNION ALL
                                SELECT  '/* Database [' + the_database
                                        + '], index [' + the_index + ']'
                                        + ' on [' + the_schema + '].['
                                        + the_object + '] '
                                        + 'is being repeatedly reorganized and its fill factor '
                                        + 'is already set to 50 or less. This likely is worth a deeper '
                                        + 'investigation. */' AS RebuildCommand
                                FROM    ##Index_History
                                WHERE   reorg_count >= @CountThreshold
                                        AND fill_factor <= 50
										AND fill_factor > 0

                   END
                SET @EmailSubject = 'Excessive Index Defragmenting found on '
                    + @@Servername + ', database ' + @DatabaseToInvestigate

                EXEC msdb.dbo.sp_send_dbmail
                    @profile_name = @MailProfileName
                   ,@recipients = @MailRecipients
                   ,@subject = @EmailSubject
                   ,@body = @EmailBody
                   ,@query = 'SELECT * FROM ##Recommendations'
                   ,@query_result_width = 32767
                   ,@query_no_truncate = 1


          END

--============================================================================
-- CLEANUP THE MESS
--============================================================================

IF EXISTS ( SELECT  name
            FROM    tempdb.sys.objects
            WHERE   name = '##Index_History' )
   BEGIN
         DROP TABLE ##Index_History
   END
 
IF EXISTS ( SELECT  name
            FROM    tempdb.sys.objects
            WHERE   name = '##Indexes' )
   BEGIN
         DROP TABLE ##Indexes
   END

IF EXISTS ( SELECT  name
            FROM    tempdb.sys.objects
            WHERE   name = '##Recommendations' )
   BEGIN
         DROP TABLE ##Recommendations
   END

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