Automatizando a desfragmentação de índice no banco de dados MS SQL Server

Prefácio

Solução

1. Criando uma visualização mostrando quais índices foram fragmentados e a porcentagem dos índices fragmentados.
2. Criando uma tabela para armazenar os resultados da desfragmentação do índice.
3. Criando um procedimento armazenado para analisar e desfragmentar o índice selecionado.
4. Criando uma visualização para visualizar as estatísticas dos resultados da desfragmentação do índice.
5. Criando uma tarefa no Agente para executar o procedimento armazenado implementado.

USE [Database_Name]
GO

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE view [srv].[vIndexDefrag]
as
with info as 
(SELECT
	[object_id],
	database_id,
	index_id,
	index_type_desc,
	index_level,
	fragment_count,
	avg_fragmentation_in_percent,
	avg_fragment_size_in_pages,
	page_count,
	record_count,
	ghost_record_count
	FROM sys.dm_db_index_physical_stats
    (DB_ID(N'Database_Name')
	, NULL, NULL, NULL ,
	N'DETAILED')
	where index_level = 0
	)
SELECT
	b.name as db,
	s.name as shema,
	t.name as tb,
	i.index_id as idx,
	i.database_id,
	idx.name as index_name,
	i.index_type_desc,i.index_level as [level],
	i.[object_id],
	i.fragment_count as frag_num,
	round(i.avg_fragmentation_in_percent,2) as frag,
	round(i.avg_fragment_size_in_pages,2) as frag_page,
	i.page_count as [page],
	i.record_count as rec,
	i.ghost_record_count as ghost,
	round(i.avg_fragmentation_in_percent*i.page_count,0) as func
FROM Info as i
inner join [sys].[databases]	as b	on i.database_id = b.database_id
inner join [sys].[all_objects]	as t	on i.object_id = t.object_id
inner join [sys].[schemas]	as s	on t.[schema_id] = s.[schema_id]
inner join [sys].[indexes]	as idx on t.object_id = idx.object_id and idx.index_id = i.index_id
 where i.avg_fragmentation_in_percent >= 30 and i.index_type_desc <> 'HEAP';
GO

USE [Database_Name]
GO

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [srv].[Defrag](
	[ID] [bigint] IDENTITY(794,1) NOT NULL,
	[db] [nvarchar](100) NULL,
	[shema] [nvarchar](100) NULL,
	[table] [nvarchar](100) NULL,
	[IndexName] [nvarchar](100) NULL,
	[frag_num] [int] NULL,
	[frag] [decimal](6, 2) NULL,
	[page] [int] NULL,
	[rec] [int] NULL,
        [func] [int] NULL,
	[ts] [datetime] NULL,
	[tf] [datetime] NULL,
	[frag_after] [decimal](6, 2) NULL,
	[object_id] [int] NULL,
	[idx] [int] NULL,
	[InsertUTCDate] [datetime] NOT NULL,
 CONSTRAINT [PK_Defrag] PRIMARY KEY CLUSTERED 
(
	[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY];
GO

ALTER TABLE [srv].[Defrag] ADD  CONSTRAINT [DF_Defrag_InsertUTCDate]  DEFAULT (getutcdate()) FOR [InsertUTCDate];
GO

USE [Database_Name]
GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE PROCEDURE [srv].[AutoDefragIndex]
AS
BEGIN
	SET NOCOUNT ON;

	--declaring required variables
	declare @IndexName nvarchar(100) --index name
	,@db nvarchar(100)			 --database name
	,@Shema nvarchar(100)			 --schema name
	,@Table nvarchar(100)			 --table name
	,@SQL_Str nvarchar (2000)		 --string for command generation
	,@frag decimal(6,2)				 --fragmentation percentage before defragmentation
	,@frag_after decimal(6,2)		 --fragmentation percentage after defragmentation
        --Number of fragments at the final level of the IN_ROW_DATA allocation unit
        ,@frag_num int				 
	,@func int					 --round(i.avg_fragmentation_in_percent*i.page_count,0)
	,@page int					 --number of index pages  
	,@rec int						 --total number of records
	,@ts datetime					 --date and time of defragmentation start
	,@tf datetime					 --date and time of defragmenation finish
	--Table or view object ID for which the index was created
        ,@object_id int					 
	,@idx int;						 --index ID

	--getting current date and time
	set @ts = getdate();
	
	--getting next index for defragmenation
	--Here the important index is selected. At that, a situation when one index is defragmented regularly, while other indexes are not selected for defragmentation is unlikely.
	select top 1
		@IndexName = index_name,
		@db=db,
		@Shema = shema,
		@Table = tb,
		@frag = frag,
		@frag_num = frag_num,
		@func=func,
		@page =[page],
		@rec = rec,
		@object_id = [object_id],
		@idx = idx 
	from  [srv].[vIndexDefrag]
	order by func*power((1.0-
	  convert(float,(select count(*) from SRV.[srv].[Defrag] vid where vid.db=db 
														 and vid.shema = shema
														 and vid.[table] = tb
														 and vid.IndexName = index_name))
	 /
	 convert(float,
                  case  when (exists (select top 1 1 from SRV.[srv].[Defrag] vid1 where vid1.db=db))
                            then (select count(*) from  SRV.[srv].[Defrag] vid1 where vid1.db=db)
                            else 1.0 end))
                    ,3) desc

	--if we get such index
	if(@db is not null)
	begin
	   --index reorganization
	   set @SQL_Str = 'alter index ['[email protected]+'] on ['[email protected]+'].['[email protected]+'] Reorganize';

		execute sp_executesql  @SQL_Str;

		--getting current date and time
		set @tf = getdate()

		--getting fragmentation percentage after defragmentation
		SELECT @frag_after = avg_fragmentation_in_percent
		FROM sys.dm_db_index_physical_stats
			(DB_ID(@db), @object_id, @idx, NULL ,
			N'DETAILED')
		where index_level = 0;

		--writing the result of work
		insert into SRV.srv.Defrag(
									[db],
									[shema],
									[table],
									[IndexName],
									[frag_num],
									[frag],
									[page],
									[rec],
									ts,
									tf,
									frag_after,
									object_id,
									idx
								  )
						select
									@db,
									@shema,
									@table,
									@IndexName,
									@frag_num,
									@frag,
									@page,
									@rec,
									@ts,
									@tf,
									@frag_after,
									@object_id,
									@idx;
		
		--upating statistics for index
		set @SQL_Str = 'UPDATE STATISTICS ['[email protected]+'].['[email protected]+'] ['[email protected]+']';

		execute sp_executesql  @SQL_Str;
	end
END

USE [Database_Name]
GO

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE view [srv].[vStatisticDefrag] as
SELECT top 1000
	  [db]
	  ,[shema]
          ,[table]
          ,[IndexName]
          ,avg([frag]) as AvgFrag
          ,avg([frag_after]) as AvgFragAfter
	  ,avg(page) as AvgPage
  FROM [srv].[Defrag]
  group by [db], [shema], [table], [IndexName]
  order by abs(avg([frag])-avg([frag_after])) desc;
GO

1. A desfragmentação simultânea de todos os índices durante a carga mínima do banco de dados é inaceitável para os sistemas 24 horas por dia, 7 dias por semana, pois os índices são constantemente fragmentados e quase não há tempo em que o banco de dados permaneça ocioso.
2. Reorganização de índice do SQL Server – esta operação bloqueia uma tabela ou partição (no caso de um índice particionado), o que não é bom para os sistemas 24 horas por dia, 7 dias por semana. Em seguida, a reconstrução do índice no modo em tempo real é suportada apenas na solução Enterprise e também pode causar danos aos dados.

Referências

• Reorganizar e reconstruir índices
• sys.dm_db_index_physical_stats

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