SQL: Cleaning Up After the Database Tuning Engine Advisor

I’ve recently had to do a quick bit of DB performance analysis work on a 3rd Party database to see if I can improve performance(without being too invasive).  The quickest way to do this, is using the Database Tuning Engine Advisor tool that comes with SQL 2008 (the best way is to have loads of experience and a tonne of time to properly analyse the database).

Part of my analysis procedure was to make a script of queries that I could run with and without the DTA recommended indexes to evaluate any real world improvement.  This meant I needed to be able to roll back any indexes created by DTA.  Unfortunately, DTA gives you and install script for the new indexes but not a removal script.  I needed to write something myself.

Fortunately, the DTA created indexes and statistics are all prefixed with _dta_ so it’s relatively easy to write a query to remove the automatically created scripts:

First to drop the generated statistics:

   1: DECLARE @dtaStats AS TABLE(Id INT IDENTITY(1,1), StatName VARCHAR(255), TableName VARCHAR(255))

   2: DECLARE @currentId AS INT

   3: DECLARE @lastId AS INT

   4:  

   5: DECLARE @statName VARCHAR(255)

   6: DECLARE @tableName VARCHAR(255)

   7:  

   8: INSERT INTO @dtaStats(StatName,TableName)

   9:     SELECT name, OBJECT_NAME(OBJECT_ID) AS TABLENAME

  10:     FROM sys.stats

  11:     WHERE name like '_dta_stat_%'

  12:  

  13: SET @currentId=NULL

  14: SET @lastId=0

  15:  

  16: SELECT @currentId=MIN(Id)

  17: FROM @dtaStats 

  18: WHERE Id>@LastId

  19:  

  20: WHILE (@currentId IS NOT NULL)

  21: BEGIN

  22:  

  23:     SELECT @statName=StatName, @tableName=TableName FROM @dtaStats WHERE Id=@currentId

  24:     

  25:     PRINT 'DROP STATISTICS ' + @tableName + '.' + @statName

  26:     

  27:     EXEC('DROP STATISTICS ' + @tableName + '.' + @statName)

  28:     

  29:     SET @lastId = @currentId 

  30:     SET @currentId=null

  31:  

  32:     SELECT @currentId=MIN(Id)

  33:     FROM @dtaStats 

  34:     WHERE Id>@LastId

  35:  

  36: END

  37:  

  38:  

Then drop the generated indexes:

   1:  

   2: DECLARE @dtaIndex AS TABLE(Id INT IDENTITY(1,1), IndexName VARCHAR(255), TableName VARCHAR(255))

   3: DECLARE @currentId AS INT

   4: DECLARE @lastId AS INT

   5:  

   6: DECLARE @IndexName VARCHAR(255)

   7: DECLARE @tableName VARCHAR(255)

   8:  

   9: INSERT INTO @dtaIndex(IndexName,TableName)

  10:     SELECT name, OBJECT_NAME(OBJECT_ID) AS TABLENAME

  11:     FROM sys.indexes

  12:     WHERE name like '_dta_index_%'

  13:     

  14: SET @lastId=0

  15: SET @currentId=NULL

  16:  

  17: SELECT @currentId=MIN(Id)

  18: FROM @dtaIndex 

  19: WHERE Id>@LastId

  20:  

  21: PRINT @currentId

  22:  

  23: WHILE (@currentId IS NOT NULL)

  24: BEGIN

  25:  

  26:     SELECT @IndexName=IndexName, @tableName=TableName FROM @dtaIndex WHERE Id=@currentId

  27:     

  28:     PRINT 'DROP INDEX ' + @IndexName + ' ON ' + @tableName

  29:     

  30:     EXEC('DROP INDEX ' + @IndexName + ' ON ' + @tableName)

  31:     

  32:     SET @lastId = @currentId 

  33:     SET @currentId=NULL

  34:  

  35:     SELECT @currentId=MIN(Id)

  36:     FROM @dtaIndex 

  37:     WHERE Id>@LastId

  38:  

  39: END

  40:  

  41:  

The database is now back to a pre-DTA’ed state!