Script to UPDATE STATISTICS with time window

Bill Graziano |

I recently spent some time troubleshooting odd query plans and came to the conclusion that we needed better statistics.  We’ve been running sp_updatestats but apparently it wasn’t sampling enough of the table to get us what we needed.  I have a pretty limited window at night where I can hammer the disks while this runs. 

The script below just calls UPDATE STATITICS on all tables that “need” updating.  It defines need as any table whose statistics are older than the number of days you specify (30 by default).  It also has a throttle so it breaks out of the loop after a set amount of time (60 minutes).  That means it won’t start processing a new table after this time but it might take longer than this to finish what it’s doing.  It always processes the oldest statistics first so it will eventually get to all of them.  It defaults to sample 25% of the table.  I’m not sure that’s a good default but it works for now.  I’ve tested this in SQL Server 2005 and SQL Server 2008.  I liked the way Michelle parameterized her re-index script and I took the same approach.

CREATE PROCEDURE dbo.UpdateStatistics
  (

    @timeLimit smallint = 60
    ,@debug bit = 0
    ,@executeSQL bit = 1
    ,@samplePercent tinyint = 25
    ,@printSQL bit = 1
    ,@minDays tinyint = 30
  )
AS
/*****************************************************************
*
* Copyright Bill Graziano 2010
*
******************************************************************/

SET NOCOUNT ON;

PRINT '[ ' + CAST(GETDATE() AS VARCHAR(100)) + ' ] ' + 'Launching...'


IF OBJECT_ID('tempdb..#status') IS NOT NULL
    DROP TABLE #status;

CREATE TABLE #status
(
      databaseID        INT
    , databaseName      NVARCHAR(128)
    , objectID          INT
    , page_count        INT
    , schemaName        NVARCHAR(128)   Null
    , objectName        NVARCHAR(128)   Null
    , lastUpdateDate    DATETIME
    , scanDate          DATETIME        
 
    CONSTRAINT PK_status_tmp
        PRIMARY KEY CLUSTERED(databaseID, objectID)
);

DECLARE @SQL NVARCHAR(MAX);
DECLARE @dbName nvarchar(128);


DECLARE @databaseID INT;
DECLARE @objectID INT;
DECLARE @schemaName NVARCHAR(128);
DECLARE @objectName NVARCHAR(128);

DECLARE @lastUpdateDate DATETIME;
DECLARE @startTime DATETIME;

SELECT @startTime = GETDATE();

DECLARE cDB CURSOR
READ_ONLY
FOR select [name] from master.sys.databases where database_id > 4


OPEN cDB

FETCH NEXT FROM cDB INTO @dbName
WHILE (@@fetch_status <> -1)
BEGIN
    IF (@@fetch_status <> -2)
    BEGIN

        SELECT @SQL = '
            use ' + QUOTENAME(@dbName) + '

            select
                DB_ID() as databaseID 
                , DB_NAME() as databaseName
                ,t.object_id
                ,sum(used_page_count) as page_count
                ,s.[name] as schemaName
                ,t.[name] AS objectName
                , COALESCE(d.stats_date, ''1900-01-01'')
                , GETDATE() as scanDate
            from sys.dm_db_partition_stats ps
            join sys.tables t on t.object_id = ps.object_id
            join sys.schemas s on s.schema_id = t.schema_id
            join (
                    SELECT
                        object_id,
                        MIN(stats_date) as stats_date
                    FROM (
                        select
                            object_id,
                            stats_date(object_id, stats_id) as stats_date
                        from
                            sys.stats) as d
                    GROUP BY object_id
                        ) as d ON d.object_id = t.object_id
            where ps.row_count > 0
            group by s.[name], t.[name], t.object_id, 
                COALESCE(d.stats_date, ''1900-01-01'')
            '
            
            SET ANSI_WARNINGS OFF;

            Insert #status
            EXEC ( @SQL);
            
            SET ANSI_WARNINGS ON; 


    END
    FETCH NEXT FROM cDB INTO @dbName
END

CLOSE cDB
DEALLOCATE cDB




DECLARE cStats CURSOR
READ_ONLY
FOR SELECT 
          databaseID       
        , databaseName     
        , objectID         
        , schemaName       
        , objectName  
        , lastUpdateDate     
    FROM #status
    WHERE DATEDIFF(dd, lastUpdateDate, GETDATE()) >= @minDays
    ORDER BY lastUpdateDate ASC, page_count desc, [objectName] ASC
    

OPEN cStats

FETCH NEXT FROM cStats INTO @databaseID, @dbName, @objectID, 
    @schemaName, @objectName, @lastUpdateDate

WHILE (@@fetch_status <> -1)
BEGIN
    IF (@@fetch_status <> -2)
    BEGIN

        IF DATEDIFF(mi, @startTime, GETDATE()) > @timeLimit
          BEGIN
            PRINT '[ ' + CAST(GETDATE() AS VARCHAR(100)) + ' ] ' +
                 '*** Time Limit Reached ***';
            GOTO __DONE;
          END

        SELECT @SQL = 'UPDATE STATISTICS ' +
            QUOTENAME(@dBName) + '.' +
            QUOTENAME(@schemaName) + '.' +
            QUOTENAME(@ObjectName) +
            ' WITH SAMPLE ' + CAST(@samplePercent AS NVARCHAR(100)) + ' PERCENT;';
        
        IF @printSQL = 1
            PRINT '[ ' + CAST(GETDATE() AS VARCHAR(100)) + ' ] ' + 
                @SQL + 
                '  (Last Updated: ' + CAST(@lastUpdateDate AS VARCHAR(100)) + ')'
            
        IF @executeSQL = 1
          BEGIN
            EXEC (@SQL);
          END
        
        
    END
    FETCH NEXT FROM cStats INTO @databaseID, @dbName, @objectID, 
        @schemaName, @objectName, @lastUpdateDate
END

__DONE:

CLOSE cStats
DEALLOCATE cStats

PRINT '[ ' + CAST(GETDATE() AS VARCHAR(100)) + ' ] ' + 'Completed.'
GO
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