Technical Article

Flexible Statistics Update

,

  1. Please create the stored procedure
  2. Execute the procedure in debug mode first: EXEC sp_FlexibleUpdateStatistics @Debug=1  this will not do anything except listing the statistics to update.
  3. Please execute the procedure with the parameters that satisfy your needs
CREATE PROCEDURE [dbo].[sp_FlexibleUpdateStatistics] 
@MaxExecutionTime int = 10, -- Script will stop if execution time exceeds this parameter (in minutes)
@Debug tinyint = 1, -- Debug mode = 1, execution mode = 0... It only prints the statements in debug mode
@ConsoleMode tinyint = 1, -- If 1, It will also print additional messages at execution mode. It should be better to set as 0 when running with SQL Agent Job.
@MinModificationCount int = 10000, -- Script will update statistics only if the statistics modified rowscount is greater than @MinModificationCount
@OnlyIndexStats tinyint = 0 -- If you want to ignore auto created statistics (WA_Sys*) , set this parameter to 1
AS
BEGIN

SET NOCOUNT ON;

-- Internal variables
DECLARE @Counter int = 0
DECLARE @DatabaseId int 
DECLARE @DatabaseName sysname 
DECLARE @AllStartTime datetime = GETDATE()
DECLARE @UpdateStatStartTime datetime 
DECLARE @ObjectNameNVARCHAR(500)
DECLARE @StatisticsNameNVARCHAR(500)
DECLARE @SQL NVARCHAR(MAX)
DECLARE @StatisticsSQL NVARCHAR(MAX)

CREATE TABLE #Statistics(
Id int IDENTITY PRIMARY KEY,
DatabaseName varchar(100) NOT NULL,
SchemaName varchar(255) NOT NULL,
TableName varchar(255) NOT NULL,
StatisticsName nvarchar(255) NOT NULL,
LastUpdated datetime,
DaysBefore bigint,
ActualRows bigint,
ModificationCount bigint,
ObjectName AS ('[' + DatabaseName + '].[' + SchemaName + '].[' + TableName + ']') PERSISTED,
StatisticsSQL AS ('UPDATE STATISTICS ' + '[' + DatabaseName + '].[' + SchemaName + '].[' + TableName + ']' + ' [' + StatisticsName + '];' )  PERSISTED
)

-- Here we can alter the query to fetch the only databases which we want to alter their indexes
DECLARE Db_Cursor CURSOR FOR  
SELECT database_id, name FROM sys.databases WHERE name NOT IN ('master','model', 'tempdb', 'distribution' ) AND is_read_only <> 1


OPEN Db_Cursor  
FETCH NEXT FROM Db_Cursor INTO @DatabaseId, @DatabaseName  

WHILE @@FETCH_STATUS = 0  
BEGIN  

SET @SQL = '
USE ' + @DatabaseName + ';

INSERT #Statistics(DatabaseName, SchemaName, TableName,  StatisticsName, LastUpdated, DaysBefore, ActualRows, ModificationCount)
SELECT
DatabaseName = ''' + @DatabaseName + ''' ,
SchemaName = sch.name,
TableName = o.name,
StatisticsName = [s].[name],
LastUpdated = [sp].[last_updated],
DaysBefore = DATEDIFF(day, [sp].[last_updated], GETDATE()),
ActualRows = [sp].[rows],
ModificationCount = [sp].[modification_counter] 
FROM [sys].[stats] AS [s] 
inner join sys.stats_columns sc
on s.stats_id=sc.stats_id and s.object_id=sc.object_id
inner join sys.columns c
on c.object_id=sc.object_id and c.column_id=sc.column_id
inner join sys.objects o
on s.object_id=o.object_id
inner join sys.schemas sch
on o.schema_id=sch.schema_id
OUTER APPLY sys.dm_db_stats_properties ([s].[object_id],[s].[stats_id]) AS [sp]
WHERE [sp].[modification_counter] > ' + CONVERT(NVARCHAR(20), @MinModificationCount) + CASE WHEN @OnlyIndexStats=1 THEN 'AND [s].[name] NOT LIKE ''_WA_Sys_%'' ' ELSE ' '  END + '
 OPTION (MAXDOP 1)'

EXECUTE sp_executesql  @SQL
FETCH NEXT FROM Db_Cursor INTO @DatabaseId, @DatabaseName  
END  

CLOSE Db_Cursor  
DEALLOCATE Db_Cursor 

CREATE NONCLUSTERED INDEX IX_Statistics_tmp_ObjectName ON #Statistics
(
ObjectName ASC
)
INCLUDE
(
StatisticsName,
LastUpdated,
DaysBefore,
ActualRows,
ModificationCount,
StatisticsSQL
)

SELECT ObjectName, StatisticsName
INTO #Multiple
FROM #Statistics s
GROUP BY ObjectName, StatisticsName
HAVING COUNT(*) > 1

DELETE
FROM #Statistics 
WHERE Id IN
(
SELECT Id
FROM #Statistics s
INNER JOIN #Multiple m ON m.ObjectName = s.ObjectName AND m.StatisticsName = s.StatisticsName
WHERE s.Id Not IN 
(
SELECT TOP 1 s1.Id
FROM #Multiple m1 
INNER JOIN #Statistics s1 ON m1.ObjectName = s1.ObjectName AND m1.StatisticsName = s1.StatisticsName ORDER BY s1.LastUpdated 
)
)

IF @OnlyIndexStats = 1
BEGIN
DELETE FROM #Statistics WHERE StatisticsName LIKE '_WA_Sys_%'
END


IF @Debug = 1 OR @ConsoleMode=1
BEGIN
SELECT *FROM #Statistics S
ORDER BY  (((ModificationCount / 100)+1) * (DaysBefore + 1)) DESC
END

-- Reorganize the indexes by the most fragmented and most accessed
DECLARE Stats_Cursor CURSOR FOR  
SELECT 
ObjectName,
StatisticsName,
StatisticsSQL 
FROM #Statistics S
ORDER BY (((ModificationCount / 100)+1) * (DaysBefore + 1)) DESC
OPEN Stats_Cursor
FETCH NEXT FROM Stats_Cursor INTO @ObjectName, @StatisticsName, @StatisticsSQL


WHILE @@FETCH_STATUS = 0  
BEGIN  

IF DATEDIFF(second, @AllStartTime, GETDATE()) >= (@MaxExecutionTime * 60)
BEGIN
BREAK;
END

SET @Counter += 1;

IF @Debug = 1
BEGIN
PRINT @StatisticsSQL
PRINT '---------------------------------'
PRINT ''
END
ELSE
BEGIN
SET @UpdateStatStartTime = GETDATE()
IF @ConsoleMode = 1 OR @Debug=1
BEGIN
PRINT CONVERT(VARCHAR(23), @UpdateStatStartTime, 120) + ' Updating stats ' + @ObjectName
PRINT 'Update stats statement: ' + @StatisticsSQL
END

EXECUTE sp_executesql  @StatisticsSQL;


IF @ConsoleMode = 1 OR @Debug=1
BEGIN
PRINT CONVERT(VARCHAR(23), GETDATE(), 120) + ' stats updated in ' + CONVERT(VARCHAR(10), DATEDIFF(second, @UpdateStatStartTime, GETDATE())) + ' seconds'
PRINT '---------------------------------------------------------------------------------------'
PRINT ''
END

END

FETCH NEXT FROM Stats_Cursor INTO  @ObjectName, @StatisticsName, @StatisticsSQL

END  
CLOSE Stats_Cursor
DEALLOCATE Stats_Cursor

DROP TABLE #Multiple
DROP TABLE #Statistics;
END
GO

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