See you in Seattle!
My Summit abstract was accepted! I'm still a little surprised, but I'm also excited (okay, and a little nervous) to once more be presenting at the PASS Summit. If you'll be at Summit this year -- and I really hope you are, as it's well worth the time and cost -- then please make sure to say "hi" if you see me wandering around. Aside from the *excellent* content, my favorite thing about Summit is getting to meet so many great people. 
In other news, I've once more switched roles within GoDaddy. For the half dozen folks who've been following my blog from the beginning, you may remember that I originally started out on the traffic team working with tuning and VLDB's, then took an opportunity to switch to the BI team to learn more about OLAP. Recently, a new team has been formed under the BI branch that's tasked with developing a massive hybrid data warehouse (by hybrid, I mean half OLTP and half OLAP). "How massive is it?" Well, it's SO massive, we're expecting to be store petabytes of data when everything is said and done. I'm happy to say I'll be on this new team. So yes, that means we have an opening for an OLAP developer. We're also hiring SQL Server DBA's. We have offices in Cedar Rapids, Denver, and the Phoenix area. Send me an e-mail at michelle at sqlfool dot com if you're interested in learning more about this great job opportunity and company.
Lastly, I want to announce that SQL Saturday 50 is now open for registration! SQL Saturday 50 will be held in Iowa City, IA on Saturday, September 18th. We're almost at 50% of our attendance capacity, so if you're interested in attending, please register soon.
That's it for now. I promise that my next blog post will be uber technical.
SQL Saturday #50 – Call for Speakers
The Call for Speakers is now open for SQL Saturday #50, the East Iowa SQL Saturday event! This is our second time hosting a SQL Saturday, and we're hoping to build upon the success of last year's event. We're looking for a wide variety of topics on SQL Server and related technologies (i.e. PowerShell, R2, LINQ, etc.). We also have had several requests for intro-level topics, such as beginning disaster recovery and basic performance tuning. If you're even remotely thinking about speaking, please submit an abstract!
Last year we had about 100 folks attend from surrounding areas. This year, we're shooting for 125 attendees, which would max out our facility's capacity. Not sure how far away Iowa City is? It may be closer than you think. Allow me to rehash my travel times from last year's plea for speakers:
- Chicago – 3.5 hours
- Omaha – 3.5 hours
- Milwaukee – 4 hours
- Kansas City – 4.5 hours
- Minneapolis – 5 hours
- St. Louis – 5 hours
- Indianapolis – 6 hours
The event will be held on September 18th at the University of Iowa in Iowa City. You can find more information, including an abstract submission form, on our event website at http://sqlsaturday.com/50/eventhome.aspx.
Oh, and if you do make it to our SQL Saturday event, please make sure to stop me and say "hi!"
Summit 2010 Abstract Submission
Jeremiah Peschka just tweeted about the looming deadline to submit an abstract for Summit 2010. I've been trying to think of a good topic to present on, and this finally got my butt in gear to submit one! For those interested, here's what I submitted:
Heaps of Trouble, Clusters of Glory - A Look At Index Internals
Indexes are a crucial component of SQL Server, especially in performance tuning, yet many DBA's don't fully understand how indexes work. In this in-depth session, Michelle will examine the anatomy of indexes, from how they're stored to how they get fragmented. And to make our inner geeks happy, she'll look at page data to show you what's happening behind the scenes. Topics covered will include index structure, fragmentation and defragmentation, index partitioning, and index filtering. If you've ever wondered just *what* goes on in an index, don't miss this session!
Special thanks to Chris for help with the session title.
DELETE 5_Useless_Things FROM [SQL Server]
It's been a while since I've been caught up in a round of chainblogging, the blogosphere's version of a Facebook meme. This time, Denis Gobo tagged me in a post started by Paul Randal. Paul asked us to list the "top-5 things in SQL Server we all wish would just be removed from the product once and for all." I reviewed other posts, and the good and bad news is that they already listed several of the same things I would have. The good news is I'm apparently not alone; the bad news is that means I need to come up with something original! So while these wouldn't necessarily be the *first* 5 on my list, they'd still be on the list nevertheless:
Default Autogrowth Options
Okay, so I lied. I'm not completely original. Yes, I know Paul Randal also commented on this one. While I said I would try to come up with only original ones, this one just has to be repeated. I've actually this option overlooked in production environments, resulting in thousands of VLF's. It's just a terrible default, and it needs to be changed.
Edit Top 200 Rows
This "feature" is just asking for trouble. Any DBA who is managing a SQL Server database should understand how to actually write insert/update/delete statements. Maybe leave the option available in SQL Express, but please remove it from SQL Server Standard & Enterprise.
Debug
There's nothing wrong with the Debug option, but I think it should be removed as a default option for the toolbar. It's easily mistaken for "Execute," which I've seen more than one DBA do on occasion.
PIVOT
I understand the need to pivot your data, but let's face it. PIVOT is a clunky, expensive SQL operation. Let's move the presentation tasks to the presentation layer (.NET), and reserve the database layer for what it does best.
Update: By popular demand, I have removed PIVOT from this list. Who am I to argue with such fine folks?
Cursors
Okay, okay, I know I can't actually get rid of this, BUT I think it gets abused way too much. Set-based operations, anyone?
Alrighty, now it's my turn to tag! I'm not sure if they've already been hit, but I'm tagging:
Index Defrag Script, v4.0
In my blog post, "Index Defrag Script Updates - Beta Testers Needed", I stated "I'll hopefully have the new version online in just a few days." That was dated January 26th. I had every intention of following through with it, too, but something came up:
My daughter, Chloe Lynn, was born on February 10th. She's a happy, healthy baby girl who consumes all of my free time and already has both her parents wrapped around her adorable little finger. So while I apologize for the delay in posting the latest version, I hope you can understand and forgive me.
Alrighty, back to SQL stuff! This version of the script has been significantly overhauled from previous versions. Here's a full synopsis of the changes and enhancements:
- There's now a time limit option so you have more control over how long your defrags run. This time limit is checked *before* a defrag is begun, so it's still possible to have a defrag occur after the time limit is exceeded (i.e. a large index).
- I've added a static table for managing the index defrag scans. This way, you can start and stop the defrag process without the need to rescan. This is especially useful for VLDB's or any environment where you're unable to complete the defrags in one operation.
- Just in case you want to perform a rescan, even if there's still indexes left to defrag from your last rescan, there's a parameter to force it.
- There's now an option to sort by page count, range scan count, or fragmentation level. Range scan count is defaulted, as the indexes that have high amounts of range scans will benefit the most from having a defragged index. You can also specify whether you want to sort by ASC or DESC.
- There's now min and max parameters for page counts. This is useful for a) ignoring indexes with less than 1 extent (as recommended by Microsoft) and b) for scheduling index operations by size. For instance, you may want to defrag your small indexes during business hours but leave your big indexes for evening or weekend hours.
- There's now a parameterized option for sorting in TEMPDB. This may reduce execution time and will prevent unnecessary database file size inflation during defrags. NOTE: Make sure you have enough free space in TEMPDB prior to enabling this option.
- I moved the SQL statement output to display before execution so you can see what's currently executing.
- I've added a debug output of the parameters selected. I've added additional validation to the start of the script, so this will help show you if an invalid value was submitted and overwritten.
- I've added new columns to the log table to show what command is being executed and what error, if any, occurred when trying to execute.
- I've added try/catch logic to handle errors during execution; this way, a single error will not prevent the whole script from terminating.
- The script will now force a rebuild for indexes with allow_page_locks = off.
- For those who use partitioning, you can now exclude the right-most populated partition from the defrag operation. This won't be applicable for all partitioning schemes, but for sliding-window scenarios (one of the most common schemes), it'll reduce contention on the partition that's being actively written to.
- I've fixed a bug where tables with LOB indexes may have more than one record returned from sys.dm_db_index_physical_stats.
- For various reasons, I've removed the option to rebuild stats.
Also, if you have a previous version of the script installed, this version will rename those tables, since there have been some changes made to them.
FAQ:
I often receive the same questions about this script, so allow me to answer them here:
"I keep running the script, but my index is still fragmented. Why?"
This is most likely a very small index. Here's what Microsoft has to say:
"In general, fragmentation on small indexes is often not controllable. The pages of small indexes are stored on mixed extents. Mixed extents are shared by up to eight objects, so the fragmentation in a small index might not be reduced after reorganizing or rebuilding the index. For more information about mixed extents, see Understanding Pages and Extents."
"What database should I create it in?" or "Can I create this in the MASTER database?"
It's up to you where you create it. You could technically create it in the MASTER database, but I recommend creating a utility database for your DBA administrative tasks.
"Can I run this againt a SharePoint database?"
I've never tried personally, but I've been told it runs just fine.
"What are the minimum requirements to run this script?" or "Will this run on SQL Server 2000 instances?"
You need to be on SQL Server 2005 SP2 or higher.
Without further ado, here's the script:
/* Scroll down to the see notes, disclaimers, and licensing information */ DECLARE @indexDefragLog_rename VARCHAR(128) , @indexDefragExclusion_rename VARCHAR(128) , @indexDefragStatus_rename VARCHAR(128); SELECT @indexDefragLog_rename = 'dba_indexDefragLog_obsolete_' + CONVERT(VARCHAR(10), GETDATE(), 112) , @indexDefragExclusion_rename = 'dba_indexDefragExclusion_obsolete_' + CONVERT(VARCHAR(10), GETDATE(), 112) , @indexDefragStatus_rename = 'dba_indexDefragStatus_obsolete_' + CONVERT(VARCHAR(10), GETDATE(), 112); IF Exists(SELECT [OBJECT_ID] FROM sys.tables WHERE [name] = 'dba_indexDefragLog') EXECUTE SP_RENAME dba_indexDefragLog, @indexDefragLog_rename; IF Exists(SELECT [OBJECT_ID] FROM sys.tables WHERE [name] = 'dba_indexDefragExclusion') EXECUTE SP_RENAME dba_indexDefragExclusion, @indexDefragExclusion_rename; IF Exists(SELECT [OBJECT_ID] FROM sys.tables WHERE [name] = 'dba_indexDefragStatus') EXECUTE SP_RENAME dba_indexDefragStatus, @indexDefragStatus_rename; Go CREATE TABLE dbo.dba_indexDefragLog ( indexDefrag_id INT IDENTITY(1,1) Not Null , databaseID INT Not Null , databaseName NVARCHAR(128) Not Null , objectID INT Not Null , objectName NVARCHAR(128) Not Null , indexID INT Not Null , indexName NVARCHAR(128) Not Null , partitionNumber SMALLINT Not Null , fragmentation FLOAT Not Null , page_count INT Not Null , dateTimeStart DATETIME Not Null , dateTimeEnd DATETIME Null , durationSeconds INT Null , sqlStatement VARCHAR(4000) Null , errorMessage VARCHAR(1000) Null CONSTRAINT PK_indexDefragLog_v40 PRIMARY KEY CLUSTERED (indexDefrag_id) ); PRINT 'dba_indexDefragLog Table Created'; CREATE TABLE dbo.dba_indexDefragExclusion ( databaseID INT Not Null , databaseName NVARCHAR(128) Not Null , objectID INT Not Null , objectName NVARCHAR(128) Not Null , indexID INT Not Null , indexName NVARCHAR(128) Not Null , exclusionMask INT Not Null /* 1=Sunday, 2=Monday, 4=Tuesday, 8=Wednesday, 16=Thursday, 32=Friday, 64=Saturday */ CONSTRAINT PK_indexDefragExclusion_v40 PRIMARY KEY CLUSTERED (databaseID, objectID, indexID) ); PRINT 'dba_indexDefragExclusion Table Created'; CREATE TABLE dbo.dba_indexDefragStatus ( databaseID INT , databaseName NVARCHAR(128) , objectID INT , indexID INT , partitionNumber SMALLINT , fragmentation FLOAT , page_count INT , range_scan_count BIGINT , schemaName NVARCHAR(128) Null , objectName NVARCHAR(128) Null , indexName NVARCHAR(128) Null , scanDate DATETIME , defragDate DATETIME Null , printStatus BIT DEFAULT(0) , exclusionMask INT DEFAULT(0) CONSTRAINT PK_indexDefragStatus_v40 PRIMARY KEY CLUSTERED(databaseID, objectID, indexID, partitionNumber) ); PRINT 'dba_indexDefragStatus Table Created'; IF OBJECTPROPERTY(OBJECT_ID('dbo.dba_indexDefrag_sp'), N'IsProcedure') = 1 BEGIN DROP PROCEDURE dbo.dba_indexDefrag_sp; PRINT 'Procedure dba_indexDefrag_sp dropped'; END; Go CREATE PROCEDURE dbo.dba_indexDefrag_sp /* Declare Parameters */ @minFragmentation FLOAT = 10.0 /* in percent, will not defrag if fragmentation less than specified */ , @rebuildThreshold FLOAT = 30.0 /* in percent, greater than @rebuildThreshold will result in rebuild instead of reorg */ , @executeSQL BIT = 1 /* 1 = execute; 0 = print command only */ , @defragOrderColumn NVARCHAR(20) = 'range_scan_count' /* Valid options are: range_scan_count, fragmentation, page_count */ , @defragSortOrder NVARCHAR(4) = 'DESC' /* Valid options are: ASC, DESC */ , @timeLimit INT = 720 /* defaulted to 12 hours */ /* Optional time limitation; expressed in minutes */ , @DATABASE VARCHAR(128) = Null /* Option to specify a database name; null will return all */ , @tableName VARCHAR(4000) = Null -- databaseName.schema.tableName /* Option to specify a table name; null will return all */ , @forceRescan BIT = 0 /* Whether or not to force a rescan of indexes; 1 = force, 0 = use existing scan, if available */ , @scanMode VARCHAR(10) = N'LIMITED' /* Options are LIMITED, SAMPLED, and DETAILED */ , @minPageCount INT = 8 /* MS recommends > 1 extent (8 pages) */ , @maxPageCount INT = Null /* NULL = no limit */ , @excludeMaxPartition BIT = 0 /* 1 = exclude right-most populated partition; 0 = do not exclude; see notes for caveats */ , @onlineRebuild BIT = 1 /* 1 = online rebuild; 0 = offline rebuild; only in Enterprise */ , @sortInTempDB BIT = 1 /* 1 = perform sort operation in TempDB; 0 = perform sort operation in the index's database */ , @maxDopRestriction TINYINT = Null /* Option to restrict the number of processors for the operation; only in Enterprise */ , @printCommands BIT = 0 /* 1 = print commands; 0 = do not print commands */ , @printFragmentation BIT = 0 /* 1 = print fragmentation prior to defrag; 0 = do not print */ , @defragDelay CHAR(8) = '00:00:05' /* time to wait between defrag commands */ , @debugMode BIT = 0 /* display some useful comments to help determine if/where issues occur */ AS /********************************************************************************* Name: dba_indexDefrag_sp Author: Michelle Ufford, http://sqlfool.com Purpose: Defrags one or more indexes for one or more databases Notes: CAUTION: TRANSACTION LOG SIZE SHOULD BE MONITORED CLOSELY WHEN DEFRAGMENTING. DO NOT RUN UNATTENDED ON LARGE DATABASES DURING BUSINESS HOURS. @minFragmentation defaulted to 10%, will not defrag if fragmentation is less than that @rebuildThreshold defaulted to 30% as recommended by Microsoft in BOL; greater than 30% will result in rebuild instead @executeSQL 1 = execute the SQL generated by this proc; 0 = print command only @defragOrderColumn Defines how to prioritize the order of defrags. Only used if @executeSQL = 1. Valid options are: range_scan_count = count of range and table scans on the index; in general, this is what benefits the most from defragmentation fragmentation = amount of fragmentation in the index; the higher the number, the worse it is page_count = number of pages in the index; affects how long it takes to defrag an index @defragSortOrder The sort order of the ORDER BY clause. Valid options are ASC (ascending) or DESC (descending). @timeLimit Optional, limits how much time can be spent performing index defrags; expressed in minutes. NOTE: The time limit is checked BEFORE an index defrag is begun, thus a long index defrag can exceed the time limitation. @database Optional, specify specific database name to defrag; If not specified, all non-system databases will be defragged. @tableName Specify if you only want to defrag indexes for a specific table, format = databaseName.schema.tableName; if not specified, all tables will be defragged. @forceRescan Whether or not to force a rescan of indexes. If set to 0, a rescan will not occur until all indexes have been defragged. This can span multiple executions. 1 = force a rescan 0 = use previous scan, if there are indexes left to defrag @scanMode Specifies which scan mode to use to determine fragmentation levels. Options are: LIMITED - scans the parent level; quickest mode, recommended for most cases. SAMPLED - samples 1% of all data pages; if less than 10k pages, performs a DETAILED scan. DETAILED - scans all data pages. Use great care with this mode, as it can cause performance issues. @minPageCount Specifies how many pages must exist in an index in order to be considered for a defrag. Defaulted to 8 pages, as Microsoft recommends only defragging indexes with more than 1 extent (8 pages). NOTE: The @minPageCount will restrict the indexes that are stored in dba_indexDefragStatus table. @maxPageCount Specifies the maximum number of pages that can exist in an index and still be considered for a defrag. Useful for scheduling small indexes during business hours and large indexes for non-business hours. NOTE: The @maxPageCount will restrict the indexes that are defragged during the current operation; it will not prevent indexes from being stored in the dba_indexDefragStatus table. This way, a single scan can support multiple page count thresholds. @excludeMaxPartition If an index is partitioned, this option specifies whether to exclude the right-most populated partition. Typically, this is the partition that is currently being written to in a sliding-window scenario. Enabling this feature may reduce contention. This may not be applicable in other types of partitioning scenarios. Non-partitioned indexes are unaffected by this option. 1 = exclude right-most populated partition 0 = do not exclude @onlineRebuild 1 = online rebuild; 0 = offline rebuild @sortInTempDB Specifies whether to defrag the index in TEMPDB or in the database the index belongs to. Enabling this option may result in faster defrags and prevent database file size inflation. 1 = perform sort operation in TempDB 0 = perform sort operation in the index's database @maxDopRestriction Option to specify a processor limit for index rebuilds @printCommands 1 = print commands to screen; 0 = do not print commands @printFragmentation 1 = print fragmentation to screen; 0 = do not print fragmentation @defragDelay Time to wait between defrag commands; gives the server a little time to catch up @debugMode 1 = display debug comments; helps with troubleshooting 0 = do not display debug comments Called by: SQL Agent Job or DBA ---------------------------------------------------------------------------- DISCLAIMER: This code and information are provided "AS IS" without warranty of any kind, either expressed or implied, including but not limited to the implied warranties or merchantability and/or fitness for a particular purpose. ---------------------------------------------------------------------------- LICENSE: This index defrag script is free to download and use for personal, educational, and internal corporate purposes, provided that this header is preserved. Redistribution or sale of this index defrag script, in whole or in part, is prohibited without the author's express written consent. ---------------------------------------------------------------------------- Date Initials Version Description ---------------------------------------------------------------------------- 2007-12-18 MFU 1.0 Initial Release 2008-10-17 MFU 1.1 Added @defragDelay, CIX_temp_indexDefragList 2008-11-17 MFU 1.2 Added page_count to log table , added @printFragmentation option 2009-03-17 MFU 2.0 Provided support for centralized execution , consolidated Enterprise & Standard versions , added @debugMode, @maxDopRestriction , modified LOB and partition logic 2009-06-18 MFU 3.0 Fixed bug in LOB logic, added @scanMode option , added support for stat rebuilds (@rebuildStats) , support model and msdb defrag , added columns to the dba_indexDefragLog table , modified logging to show "in progress" defrags , added defrag exclusion list (scheduling) 2009-08-28 MFU 3.1 Fixed read_only bug for database lists 2010-04-20 MFU 4.0 Added time limit option , added static table with rescan logic , added parameters for page count & SORT_IN_TEMPDB , added try/catch logic and additional debug options , added options for defrag prioritization , fixed bug for indexes with allow_page_lock = off , added option to exclude right-most partition , removed @rebuildStats option , refer to http://sqlfool.com for full release notes ********************************************************************************* Example of how to call this script: Exec dbo.dba_indexDefrag_sp @executeSQL = 1 , @printCommands = 1 , @debugMode = 1 , @printFragmentation = 1 , @forceRescan = 1 , @maxDopRestriction = 1 , @minPageCount = 8 , @maxPageCount = Null , @minFragmentation = 1 , @rebuildThreshold = 30 , @defragDelay = '00:00:05' , @defragOrderColumn = 'page_count' , @defragSortOrder = 'DESC' , @excludeMaxPartition = 1 , @timeLimit = Null; *********************************************************************************/ SET NOCOUNT ON; SET XACT_Abort ON; SET Quoted_Identifier ON; BEGIN BEGIN Try /* Just a little validation... */ IF @minFragmentation IS Null Or @minFragmentation Not Between 0.00 And 100.0 SET @minFragmentation = 10.0; IF @rebuildThreshold IS Null Or @rebuildThreshold Not Between 0.00 And 100.0 SET @rebuildThreshold = 30.0; IF @defragDelay Not Like '00:[0-5][0-9]:[0-5][0-9]' SET @defragDelay = '00:00:05'; IF @defragOrderColumn IS Null Or @defragOrderColumn Not In ('range_scan_count', 'fragmentation', 'page_count') SET @defragOrderColumn = 'range_scan_count'; IF @defragSortOrder IS Null Or @defragSortOrder Not In ('ASC', 'DESC') SET @defragSortOrder = 'DESC'; IF @scanMode Not In ('LIMITED', 'SAMPLED', 'DETAILED') SET @scanMode = 'LIMITED'; IF @debugMode IS Null SET @debugMode = 0; IF @forceRescan IS Null SET @forceRescan = 0; IF @sortInTempDB IS Null SET @sortInTempDB = 1; IF @debugMode = 1 RAISERROR('Undusting the cogs and starting up...', 0, 42) WITH NoWait; /* Declare our variables */ DECLARE @objectID INT , @databaseID INT , @databaseName NVARCHAR(128) , @indexID INT , @partitionCount BIGINT , @schemaName NVARCHAR(128) , @objectName NVARCHAR(128) , @indexName NVARCHAR(128) , @partitionNumber SMALLINT , @fragmentation FLOAT , @pageCount INT , @sqlCommand NVARCHAR(4000) , @rebuildCommand NVARCHAR(200) , @dateTimeStart DATETIME , @dateTimeEnd DATETIME , @containsLOB BIT , @editionCheck BIT , @debugMessage NVARCHAR(4000) , @updateSQL NVARCHAR(4000) , @partitionSQL NVARCHAR(4000) , @partitionSQL_Param NVARCHAR(1000) , @LOB_SQL NVARCHAR(4000) , @LOB_SQL_Param NVARCHAR(1000) , @indexDefrag_id INT , @startDateTime DATETIME , @endDateTime DATETIME , @getIndexSQL NVARCHAR(4000) , @getIndexSQL_Param NVARCHAR(4000) , @allowPageLockSQL NVARCHAR(4000) , @allowPageLockSQL_Param NVARCHAR(4000) , @allowPageLocks INT , @excludeMaxPartitionSQL NVARCHAR(4000); /* Initialize our variables */ SELECT @startDateTime = GETDATE() , @endDateTime = DATEADD(MINUTE, @timeLimit, GETDATE()); /* Create our temporary tables */ CREATE TABLE #databaseList ( databaseID INT , databaseName VARCHAR(128) , scanStatus BIT ); CREATE TABLE #processor ( [INDEX] INT , Name VARCHAR(128) , Internal_Value INT , Character_Value INT ); CREATE TABLE #maxPartitionList ( databaseID INT , objectID INT , indexID INT , maxPartition INT ); IF @debugMode = 1 RAISERROR('Beginning validation...', 0, 42) WITH NoWait; /* Make sure we're not exceeding the number of processors we have available */ INSERT INTO #processor EXECUTE XP_MSVER 'ProcessorCount'; IF @maxDopRestriction IS Not Null And @maxDopRestriction > (SELECT Internal_Value FROM #processor) SELECT @maxDopRestriction = Internal_Value FROM #processor; /* Check our server version; 1804890536 = Enterprise, 610778273 = Enterprise Evaluation, -2117995310 = Developer */ IF (SELECT SERVERPROPERTY('EditionID')) In (1804890536, 610778273, -2117995310) SET @editionCheck = 1 -- supports online rebuilds ELSE SET @editionCheck = 0; -- does not support online rebuilds /* Output the parameters we're working with */ IF @debugMode = 1 BEGIN SELECT @debugMessage = 'Your selected parameters are... Defrag indexes with fragmentation greater than ' + CAST(@minFragmentation AS VARCHAR(10)) + '; Rebuild indexes with fragmentation greater than ' + CAST(@rebuildThreshold AS VARCHAR(10)) + '; You' + CASE WHEN @executeSQL = 1 THEN ' DO' ELSE ' DO NOT' END + ' want the commands to be executed automatically; You want to defrag indexes in ' + @defragSortOrder + ' order of the ' + UPPER(@defragOrderColumn) + ' value; You have' + CASE WHEN @timeLimit IS Null THEN ' not specified a time limit;' ELSE ' specified a time limit of ' + CAST(@timeLimit AS VARCHAR(10)) END + ' minutes; ' + CASE WHEN @DATABASE IS Null THEN 'ALL databases' ELSE 'The ' + @DATABASE + ' database' END + ' will be defragged; ' + CASE WHEN @tableName IS Null THEN 'ALL tables' ELSE 'The ' + @tableName + ' table' END + ' will be defragged; We' + CASE WHEN Exists(SELECT TOP 1 * FROM dbo.dba_indexDefragStatus WHERE defragDate IS Null) And @forceRescan <> 1 THEN ' WILL NOT' ELSE ' WILL' END + ' be rescanning indexes; The scan will be performed in ' + @scanMode + ' mode; You want to limit defrags to indexes with' + CASE WHEN @maxPageCount IS Null THEN ' more than ' + CAST(@minPageCount AS VARCHAR(10)) ELSE ' between ' + CAST(@minPageCount AS VARCHAR(10)) + ' and ' + CAST(@maxPageCount AS VARCHAR(10)) END + ' pages; Indexes will be defragged' + CASE WHEN @editionCheck = 0 Or @onlineRebuild = 0 THEN ' OFFLINE;' ELSE ' ONLINE;' END + ' Indexes will be sorted in' + CASE WHEN @sortInTempDB = 0 THEN ' the DATABASE' ELSE ' TEMPDB;' END + ' Defrag operations will utilize ' + CASE WHEN @editionCheck = 0 Or @maxDopRestriction IS Null THEN 'system defaults for processors;' ELSE CAST(@maxDopRestriction AS VARCHAR(2)) + ' processors;' END + ' You' + CASE WHEN @printCommands = 1 THEN ' DO' ELSE ' DO NOT' END + ' want to print the ALTER INDEX commands; You' + CASE WHEN @printFragmentation = 1 THEN ' DO' ELSE ' DO NOT' END + ' want to output fragmentation levels; You want to wait ' + @defragDelay + ' (hh:mm:ss) between defragging indexes; You want to run in' + CASE WHEN @debugMode = 1 THEN ' DEBUG' ELSE ' SILENT' END + ' mode.'; RAISERROR(@debugMessage, 0, 42) WITH NoWait; END; IF @debugMode = 1 RAISERROR('Grabbing a list of our databases...', 0, 42) WITH NoWait; /* Retrieve the list of databases to investigate */ INSERT INTO #databaseList SELECT database_id , name , 0 -- not scanned yet for fragmentation FROM sys.databases WHERE name = IsNull(@DATABASE, name) And [name] Not In ('master', 'tempdb')-- exclude system databases And [STATE] = 0 -- state must be ONLINE And is_read_only = 0; -- cannot be read_only /* Check to see if we have indexes in need of defrag; otherwise, re-scan the database(s) */ IF Not Exists(SELECT TOP 1 * FROM dbo.dba_indexDefragStatus WHERE defragDate IS Null) Or @forceRescan = 1 BEGIN /* Truncate our list of indexes to prepare for a new scan */ TRUNCATE TABLE dbo.dba_indexDefragStatus; IF @debugMode = 1 RAISERROR('Looping through our list of databases and checking for fragmentation...', 0, 42) WITH NoWait; /* Loop through our list of databases */ WHILE (SELECT COUNT(*) FROM #databaseList WHERE scanStatus = 0) > 0 BEGIN SELECT TOP 1 @databaseID = databaseID FROM #databaseList WHERE scanStatus = 0; SELECT @debugMessage = ' working on ' + DB_NAME(@databaseID) + '...'; IF @debugMode = 1 RAISERROR(@debugMessage, 0, 42) WITH NoWait; /* Determine which indexes to defrag using our user-defined parameters */ INSERT INTO dbo.dba_indexDefragStatus ( databaseID , databaseName , objectID , indexID , partitionNumber , fragmentation , page_count , range_scan_count , scanDate ) SELECT ps.database_id AS 'databaseID' , QUOTENAME(DB_NAME(ps.database_id)) AS 'databaseName' , ps.OBJECT_ID AS 'objectID' , ps.index_id AS 'indexID' , ps.partition_number AS 'partitionNumber' , SUM(ps.avg_fragmentation_in_percent) AS 'fragmentation' , SUM(ps.page_count) AS 'page_count' , os.range_scan_count , GETDATE() AS 'scanDate' FROM sys.dm_db_index_physical_stats(@databaseID, OBJECT_ID(@tableName), Null , Null, @scanMode) AS ps Join sys.dm_db_index_operational_stats(@databaseID, OBJECT_ID(@tableName), Null , Null) AS os ON ps.database_id = os.database_id And ps.OBJECT_ID = os.OBJECT_ID and ps.index_id = os.index_id And ps.partition_number = os.partition_number WHERE avg_fragmentation_in_percent >= @minFragmentation And ps.index_id > 0 -- ignore heaps And ps.page_count > @minPageCount And ps.index_level = 0 -- leaf-level nodes only, supports @scanMode GROUP BY ps.database_id , QUOTENAME(DB_NAME(ps.database_id)) , ps.OBJECT_ID , ps.index_id , ps.partition_number , os.range_scan_count OPTION (MaxDop 2); /* Do we want to exclude right-most populated partition of our partitioned indexes? */ IF @excludeMaxPartition = 1 BEGIN SET @excludeMaxPartitionSQL = ' Select ' + CAST(@databaseID AS VARCHAR(10)) + ' As [databaseID] , [object_id] , index_id , Max(partition_number) As [maxPartition] From ' + DB_NAME(@databaseID) + '.sys.partitions Where partition_number > 1 And [rows] > 0 Group By object_id , index_id;'; INSERT INTO #maxPartitionList EXECUTE SP_EXECUTESQL @excludeMaxPartitionSQL; END; /* Keep track of which databases have already been scanned */ UPDATE #databaseList SET scanStatus = 1 WHERE databaseID = @databaseID; END /* We don't want to defrag the right-most populated partition, so delete any records for partitioned indexes where partition = Max(partition) */ IF @excludeMaxPartition = 1 BEGIN DELETE ids FROM dbo.dba_indexDefragStatus AS ids Join #maxPartitionList AS mpl ON ids.databaseID = mpl.databaseID And ids.objectID = mpl.objectID And ids.indexID = mpl.indexID And ids.partitionNumber = mpl.maxPartition; END; /* Update our exclusion mask for any index that has a restriction on the days it can be defragged */ UPDATE ids SET ids.exclusionMask = ide.exclusionMask FROM dbo.dba_indexDefragStatus AS ids Join dbo.dba_indexDefragExclusion AS ide ON ids.databaseID = ide.databaseID And ids.objectID = ide.objectID And ids.indexID = ide.indexID; END SELECT @debugMessage = 'Looping through our list... there are ' + CAST(COUNT(*) AS VARCHAR(10)) + ' indexes to defrag!' FROM dbo.dba_indexDefragStatus WHERE defragDate IS Null And page_count Between @minPageCount And IsNull(@maxPageCount, page_count); IF @debugMode = 1 RAISERROR(@debugMessage, 0, 42) WITH NoWait; /* Begin our loop for defragging */ WHILE (SELECT COUNT(*) FROM dbo.dba_indexDefragStatus WHERE ( (@executeSQL = 1 And defragDate IS Null) Or (@executeSQL = 0 And defragDate IS Null And printStatus = 0) ) And exclusionMask & POWER(2, DATEPART(weekday, GETDATE())-1) = 0 And page_count Between @minPageCount And IsNull(@maxPageCount, page_count)) > 0 BEGIN /* Check to see if we need to exit our loop because of our time limit */ IF IsNull(@endDateTime, GETDATE()) < GETDATE() BEGIN RAISERROR('Our time limit has been exceeded!', 11, 42) WITH NoWait; END; IF @debugMode = 1 RAISERROR(' Picking an index to beat into shape...', 0, 42) WITH NoWait; /* Grab the index with the highest priority, based on the values submitted; Look at the exclusion mask to ensure it can be defragged today */ SET @getIndexSQL = N' Select Top 1 @objectID_Out = objectID , @indexID_Out = indexID , @databaseID_Out = databaseID , @databaseName_Out = databaseName , @fragmentation_Out = fragmentation , @partitionNumber_Out = partitionNumber , @pageCount_Out = page_count From dbo.dba_indexDefragStatus Where defragDate Is Null ' + CASE WHEN @executeSQL = 0 THEN 'And printStatus = 0' ELSE '' END + ' And exclusionMask & Power(2, DatePart(weekday, GetDate())-1) = 0 And page_count Between @p_minPageCount and IsNull(@p_maxPageCount, page_count) Order By + ' + @defragOrderColumn + ' ' + @defragSortOrder; SET @getIndexSQL_Param = N'@objectID_Out int OutPut , @indexID_Out int OutPut , @databaseID_Out int OutPut , @databaseName_Out nvarchar(128) OutPut , @fragmentation_Out int OutPut , @partitionNumber_Out int OutPut , @pageCount_Out int OutPut , @p_minPageCount int , @p_maxPageCount int'; EXECUTE SP_EXECUTESQL @getIndexSQL , @getIndexSQL_Param , @p_minPageCount = @minPageCount , @p_maxPageCount = @maxPageCount , @objectID_Out = @objectID OUTPUT , @indexID_Out = @indexID OUTPUT , @databaseID_Out = @databaseID OUTPUT , @databaseName_Out = @databaseName OUTPUT , @fragmentation_Out = @fragmentation OUTPUT , @partitionNumber_Out = @partitionNumber OUTPUT , @pageCount_Out = @pageCount OUTPUT; IF @debugMode = 1 RAISERROR(' Looking up the specifics for our index...', 0, 42) WITH NoWait; /* Look up index information */ SELECT @updateSQL = N'Update ids Set schemaName = QuoteName(s.name) , objectName = QuoteName(o.name) , indexName = QuoteName(i.name) From dbo.dba_indexDefragStatus As ids Inner Join ' + @databaseName + '.sys.objects As o On ids.objectID = o.object_id Inner Join ' + @databaseName + '.sys.indexes As i On o.object_id = i.object_id And ids.indexID = i.index_id Inner Join ' + @databaseName + '.sys.schemas As s On o.schema_id = s.schema_id Where o.object_id = ' + CAST(@objectID AS VARCHAR(10)) + ' And i.index_id = ' + CAST(@indexID AS VARCHAR(10)) + ' And i.type > 0 And ids.databaseID = ' + CAST(@databaseID AS VARCHAR(10)); EXECUTE SP_EXECUTESQL @updateSQL; /* Grab our object names */ SELECT @objectName = objectName , @schemaName = schemaName , @indexName = indexName FROM dbo.dba_indexDefragStatus WHERE objectID = @objectID And indexID = @indexID And databaseID = @databaseID; IF @debugMode = 1 RAISERROR(' Grabbing the partition count...', 0, 42) WITH NoWait; /* Determine if the index is partitioned */ SELECT @partitionSQL = 'Select @partitionCount_OUT = Count(*) From ' + @databaseName + '.sys.partitions Where object_id = ' + CAST(@objectID AS VARCHAR(10)) + ' And index_id = ' + CAST(@indexID AS VARCHAR(10)) + ';' , @partitionSQL_Param = '@partitionCount_OUT int OutPut'; EXECUTE SP_EXECUTESQL @partitionSQL, @partitionSQL_Param, @partitionCount_OUT = @partitionCount OUTPUT; IF @debugMode = 1 RAISERROR(' Seeing if there are any LOBs to be handled...', 0, 42) WITH NoWait; /* Determine if the table contains LOBs */ SELECT @LOB_SQL = ' Select @containsLOB_OUT = Count(*) From ' + @databaseName + '.sys.columns With (NoLock) Where [object_id] = ' + CAST(@objectID AS VARCHAR(10)) + ' And (system_type_id In (34, 35, 99) Or max_length = -1);' /* system_type_id --> 34 = image, 35 = text, 99 = ntext max_length = -1 --> varbinary(max), varchar(max), nvarchar(max), xml */ , @LOB_SQL_Param = '@containsLOB_OUT int OutPut'; EXECUTE SP_EXECUTESQL @LOB_SQL, @LOB_SQL_Param, @containsLOB_OUT = @containsLOB OUTPUT; IF @debugMode = 1 RAISERROR(' Checking for indexes that do not allow page locks...', 0, 42) WITH NoWait; /* Determine if page locks are allowed; for those indexes, we need to always rebuild */ SELECT @allowPageLockSQL = 'Select @allowPageLocks_OUT = Count(*) From ' + @databaseName + '.sys.indexes Where object_id = ' + CAST(@objectID AS VARCHAR(10)) + ' And index_id = ' + CAST(@indexID AS VARCHAR(10)) + ' And Allow_Page_Locks = 0;' , @allowPageLockSQL_Param = '@allowPageLocks_OUT int OutPut'; EXECUTE SP_EXECUTESQL @allowPageLockSQL, @allowPageLockSQL_Param, @allowPageLocks_OUT = @allowPageLocks OUTPUT; IF @debugMode = 1 RAISERROR(' Building our SQL statements...', 0, 42) WITH NoWait; /* If there's not a lot of fragmentation, or if we have a LOB, we should reorganize */ IF (@fragmentation < @rebuildThreshold Or @containsLOB >= 1 Or @partitionCount > 1) And @allowPageLocks = 0 BEGIN SET @sqlCommand = N'Alter Index ' + @indexName + N' On ' + @databaseName + N'.' + @schemaName + N'.' + @objectName + N' ReOrganize'; /* If our index is partitioned, we should always reorganize */ IF @partitionCount > 1 SET @sqlCommand = @sqlCommand + N' Partition = ' + CAST(@partitionNumber AS NVARCHAR(10)); END /* If the index is heavily fragmented and doesn't contain any partitions or LOB's, or if the index does not allow page locks, rebuild it */ ELSE IF (@fragmentation >= @rebuildThreshold Or @allowPageLocks <> 0) And IsNull(@containsLOB, 0) != 1 And @partitionCount <= 1 BEGIN /* Set online rebuild options; requires Enterprise Edition */ IF @onlineRebuild = 1 And @editionCheck = 1 SET @rebuildCommand = N' Rebuild With (Online = On'; ELSE SET @rebuildCommand = N' Rebuild With (Online = Off'; /* Set sort operation preferences */ IF @sortInTempDB = 1 SET @rebuildCommand = @rebuildCommand + N', Sort_In_TempDB = On'; ELSE SET @rebuildCommand = @rebuildCommand + N', Sort_In_TempDB = Off'; /* Set processor restriction options; requires Enterprise Edition */ IF @maxDopRestriction IS Not Null And @editionCheck = 1 SET @rebuildCommand = @rebuildCommand + N', MaxDop = ' + CAST(@maxDopRestriction AS VARCHAR(2)) + N')'; ELSE SET @rebuildCommand = @rebuildCommand + N')'; SET @sqlCommand = N'Alter Index ' + @indexName + N' On ' + @databaseName + N'.' + @schemaName + N'.' + @objectName + @rebuildCommand; END ELSE /* Print an error message if any indexes happen to not meet the criteria above */ IF @printCommands = 1 Or @debugMode = 1 RAISERROR('We are unable to defrag this index.', 0, 42) WITH NoWait; /* Are we executing the SQL? If so, do it */ IF @executeSQL = 1 BEGIN SET @debugMessage = 'Executing: ' + @sqlCommand; /* Print the commands we're executing if specified to do so */ IF @printCommands = 1 Or @debugMode = 1 RAISERROR(@debugMessage, 0, 42) WITH NoWait; /* Grab the time for logging purposes */ SET @dateTimeStart = GETDATE(); /* Log our actions */ INSERT INTO dbo.dba_indexDefragLog ( databaseID , databaseName , objectID , objectName , indexID , indexName , partitionNumber , fragmentation , page_count , dateTimeStart , sqlStatement ) SELECT @databaseID , @databaseName , @objectID , @objectName , @indexID , @indexName , @partitionNumber , @fragmentation , @pageCount , @dateTimeStart , @sqlCommand; SET @indexDefrag_id = SCOPE_IDENTITY(); /* Wrap our execution attempt in a try/catch and log any errors that occur */ BEGIN Try /* Execute our defrag! */ EXECUTE SP_EXECUTESQL @sqlCommand; SET @dateTimeEnd = GETDATE(); /* Update our log with our completion time */ UPDATE dbo.dba_indexDefragLog SET dateTimeEnd = @dateTimeEnd , durationSeconds = DATEDIFF(SECOND, @dateTimeStart, @dateTimeEnd) WHERE indexDefrag_id = @indexDefrag_id; END Try BEGIN Catch /* Update our log with our error message */ UPDATE dbo.dba_indexDefragLog SET dateTimeEnd = GETDATE() , durationSeconds = -1 , errorMessage = Error_Message() WHERE indexDefrag_id = @indexDefrag_id; IF @debugMode = 1 RAISERROR(' An error has occurred executing this command! Please review the dba_indexDefragLog table for details.' , 0, 42) WITH NoWait; END Catch /* Just a little breather for the server */ WAITFOR Delay @defragDelay; UPDATE dbo.dba_indexDefragStatus SET defragDate = GETDATE() , printStatus = 1 WHERE databaseID = @databaseID And objectID = @objectID And indexID = @indexID And partitionNumber = @partitionNumber; END ELSE /* Looks like we're not executing, just printing the commands */ BEGIN IF @debugMode = 1 RAISERROR(' Printing SQL statements...', 0, 42) WITH NoWait; IF @printCommands = 1 Or @debugMode = 1 PRINT IsNull(@sqlCommand, 'error!'); UPDATE dbo.dba_indexDefragStatus SET printStatus = 1 WHERE databaseID = @databaseID And objectID = @objectID And indexID = @indexID And partitionNumber = @partitionNumber; END END /* Do we want to output our fragmentation results? */ IF @printFragmentation = 1 BEGIN IF @debugMode = 1 RAISERROR(' Displaying a summary of our action...', 0, 42) WITH NoWait; SELECT databaseID , databaseName , objectID , objectName , indexID , indexName , partitionNumber , fragmentation , page_count , range_scan_count FROM dbo.dba_indexDefragStatus WHERE defragDate >= @startDateTime ORDER BY defragDate; END; END Try BEGIN Catch SET @debugMessage = Error_Message() + ' (Line Number: ' + CAST(Error_Line() AS VARCHAR(10)) + ')'; PRINT @debugMessage; END Catch; /* When everything is said and done, make sure to get rid of our temp table */ DROP TABLE #databaseList; DROP TABLE #processor; DROP TABLE #maxPartitionList; IF @debugMode = 1 RAISERROR('DONE! Thank you for taking care of your indexes! :)', 0, 42) WITH NoWait; SET NOCOUNT OFF; RETURN 0 END
You can also download it here: dba_indexDefrag_sp_v40_public.txt
I've had this latest version in production on terabyte-size databases running SQL Server 2005 and 2008 Enterprise editions for the last 3 months, where it runs nightly without issue. I've also had numerous beta testers report success in their environments, too. But to be safe, make sure to keep an eye on it the first time it runs to ensure you understand the impact on your server.
Enjoy!
Michelle
Filtered Indexes Work-Around
Recently, I needed to create a stored procedure that queried a rather large table. The table has a filtered index on a date column, and it covers the query. However, the Query Optimizer was not using the index, which was increasing the execution time (not to mention IO!) by at least 10x. This wasn't the first time I've had the Optimizer fail to use a filtered index. Normally when this happens, I use a table hint to force the filtered index -- after I verify that it is indeed faster, of course. However, since this was a stored procedure, I was receiving the following error message whenever I tried to execute the proc:
Query processor could not produce a query plan because of the hints defined in this query. Resubmit the query without specifying any hints and without using SET FORCEPLAN.
SQL Server would not allow me to execute the stored procedure using the filtered index hint. If I removed the hint, it executed, but it used a different, non-covering and far more expensive index. For those of you not familiar with this issue, allow me to illustrate the problem.
First, create a table to play with and populate it with some bogus data:
CREATE TABLE dbo.filteredIndexTest ( myID INT IDENTITY(1,3) , myDate SMALLDATETIME , myData CHAR(100) CONSTRAINT PK_filteredIndexTest PRIMARY KEY CLUSTERED(myID) ); SET NOCOUNT ON; DECLARE @DATE SMALLDATETIME = '2010-01-01'; WHILE @DATE < '2010-02-01' BEGIN INSERT INTO dbo.filteredIndexTest ( myDate , myData ) SELECT @DATE , 'Date: ' + CONVERT(VARCHAR(20), @DATE, 102); SET @DATE = DATEADD(MINUTE, 1, @DATE); END; SELECT COUNT(*) FROM dbo.filteredIndexTest;
It looks like this will generate 44,640 rows of test data... plenty enough for our purposes. Now, let's create our filtered index and write a query that will use it:
CREATE NONCLUSTERED INDEX IX_filteredIndexTest_1 ON dbo.filteredIndexTest(myDate) Include (myData) WHERE myDate >= '2010-01-27'; SELECT DISTINCT myData FROM dbo.filteredIndexTest WHERE myDate >= '2010-01-28';
If you look at the execution plan for this query, you'll notice that the Optimizer is using the filtered index. Perfect! Now let's parameterize it.
DECLARE @myDate1 SMALLDATETIME = '2010-01-28'; SELECT DISTINCT myData FROM dbo.filteredIndexTest WHERE myDate >= @myDate1;
Uh oh. Looking at the execution plan, we see that SQL Server is no longer using the filtered index. Instead, it's scanning the clustered index! Why is this? There's actually a good explanation for it. The reason is that I could, in theory, pass a date to my parameter that fell outside of the filtered date range. If that's the case, then SQL Server could not utilize the filtered index. Personally, I think it's a bug and SQL Server should identify whether or not a filtered index could be used based on the actual value submitted, but... that's a whole other blog post.
So what can we do? Well, dynamic SQL may be able to help us out in this case. Let's give it a go. First, let's try parameterized dynamic SQL.
DECLARE @mySQL1 NVARCHAR(2000) , @myParam NVARCHAR(2000) = '@p_myDate2 smalldatetime' , @myDate2 SMALLDATETIME = '2010-01-28'; SET @mySQL1 = 'Select Distinct myData From dbo.filteredIndexTest Where myDate >= @p_myDate2'; EXECUTE SP_EXECUTESQL @mySQL1, @myParam, @p_myDate2 = @myDate2;
Looking at the execution plan, we see we're still scanning on the clustered index. This is because the parameterized dynamic SQL resolves to be the exact same query as the one above it. Let's try unparameterized SQL instead:
DECLARE @mySQL2 NVARCHAR(2000) , @myDate3 SMALLDATETIME = '2010-01-28'; SET @mySQL2 = 'Select Distinct myData From dbo.filteredIndexTest Where myDate >= ''' + CAST(@myDate3 AS VARCHAR(20)) + ''''; EXECUTE SP_EXECUTESQL @mySQL2; -- Drop Table dbo.filteredIndexTest;
Voila! We have a seek on our filtered index. Why? Because the statement resolves to be identical to our first query, where we hard-coded the date value in the WHERE clause.
Now, I want to stress this fact: you should always, ALWAYS use parameterized dynamic SQL whenever possible. Not only is it safer, but it's also faster, because it can reuse cached plans. But sometimes you just cannot accomplish the same tasks with it. This is one of those times. If you do end up needing to use unparameterized dynamic SQL as a work-around, please make sure you're validating your input, especially if you're interfacing with any sort of external source.
There's an even easier work-around for this problem that Dave (http://www.crappycoding.com) shared with me: recompile.
Adding "Option (Recompile)" to the end of your statements will force the Optimizer to re-evaluate which index will best meet the needs of your query every time the statement is executed. More importantly, it evaluates the plan based on the actual values passed to the parameter... just like in our hard-coded and dynamic SQL examples. Let's see it in action:
DECLARE @myDate4 SMALLDATETIME = '2010-01-28'; SELECT DISTINCT myData FROM dbo.filteredIndexTest WHERE myDate >= @myDate4 OPTION (RECOMPILE); DECLARE @myDate5 SMALLDATETIME = '2010-01-20'; SELECT DISTINCT myData FROM dbo.filteredIndexTest WHERE myDate >= @myDate5 OPTION (RECOMPILE);
If we look at the execution plans for the 2 queries above, we see that the first query seeks on the filtered index, and the second query scans on the clustered index. This is because the second query cannot be satisfied with the filtered index because we initially limited our index to dates greater than or equal to 1/27/2010.
There are, of course, trade-offs associated with each approach, so use whichever one best meets your needs. Do you have another work-around for this issue? If so, please let me know.
Update:
Alex Kuznetsov (http://www.simple-talk.com/author/alex-kuznetsov/) shared this method too:
DECLARE @myDate1 SMALLDATETIME = '2010-01-28'; SELECT DISTINCT myData FROM dbo.filteredIndexTest WHERE myDate = @myDate1 AND myDate >= '2010-01-27';
Like the other examples, this will result in an index seek on the filtered index. Basically, by explicitly declaring the start date of your filter, you're letting the Optimizer know that the filtered index can satisfy the request, regardless of the parameter value passed. Thanks for the tip, Alex!
Index Defrag Script Updates – Beta Testers Needed
Update: Wow! I've received a ton of responses to my request for beta testers. Thank you all! The SQL Community is really amazing. I'll hopefully have the new version online in just a few days.
Over the last few months, I've received many great comments and suggestions regarding my Index Defrag Script v3.0. I've just recently had time to implement most of these suggestions, plus some other things that I thought would be useful.
Here's some of what you can look forward to shortly:
- Probably the single most requested feature, the new version of the script allows you to set a time limit for index defrags.
- There's now a static table for managing the status of index defrags. This way, when your time limit is reached, you can pick up where you left off the next day, without the need to rescan indexes.
- There's now an option to prioritize defrags by range scan counts, fragmentation level, or page counts.
- For those using partitioning, there is now an option to exclude the right-most populated partition from defrags (in theory, the one you're writing to in a sliding-window scenario).
- Options such as page count limits and SORT_IN_TEMPDB are now parameterized.
- I've enhanced error logging.
- ... and more!
Right now, I'm looking for a few folks who are willing to beta test the script. If you're interested, please send me an e-mail at michelle at sqlfool dot com with the editions of SQL Server you can test this on (i.e. 2005 Standard, 2008 Enterprise, etc.).
Thank you!
Replication Bug with Partitioned Tables
Recently, we came across a bug in SQL Server 2005 on one of our production servers. Apparently, if you execute an ALTER TABLE statement on a replicated table with more than 128 partitions, the log reader will fail. A relatively obscure bug, I know. Microsoft has recognized this as a confirmed bug, but I couldn't find it anywhere on the intertubes, thus the inspiration for this blog post. Microsoft's official solution for this issue is to upgrade to SQL Server 2008.
For various reasons, we were unable to execute an upgrade at the time. And since this was a 2 terabyte database, we wanted to come up with a solution that wouldn't involve reinitializing the entire publication. Our quick-fix while we were troubleshooting the issue was to create a linked server to the production box. Not ideal, I know, but it worked in a pinch and minimized exposure of the issue. Fortunately for us, we were able to solve the problem on the publication database pretty easily. All of the affected partition functions had empty partitions created several months in the future, so we simply merged any empty partition ranges for future dates. Our solution to our now-out-of-date subscribers was to apply static row filtering to any table with more than 100 million records. While this would introduce some overhead with the replication of these tables, it would allow us a much faster recovery time. We decided to use the start of the most recent hour as our filtering criteria, just to give us a "clean" filter, so we had to delete data from any table where we were going to apply the filter. After that, it was simply a matter of resuming replication.
All things considered, it took us a little over a day to recover from the issue. Most of that time was spent troubleshooting the problem and identifying a workable solution; actual execution of the changes was pretty quick. Moral of the story? Upgrade to SQL Server 2008.
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