DB Design :: Rebuilding Clustered Indexes
Jul 23, 2015
Currently we are facing some performance issue while accessing the archive data from the archive tables. the archive table is hugh and it contains around 100,000,000 records and this archive table is being used in few reports and in our commission cycles too. since we are facing performance issues we are rebuilding index once in a week on all the indexes on this archive table.
We have 1 clustered index and 5 non clustered indexes, every time when we rebuild all these indexes on this table it is taking more time, more often rebuilding the clustered index itself is taking approx. 1hr which is consuming more time. wanted to know is there any useful to rebuild clustered indexes or not, if yes then what would be the better way. if not then do we need to rebuild only non clustered indexes.
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Sep 18, 2007
So I'm reading http://www.sql-server-performance.com/tips/clustered_indexes_p2.aspx and I come across this:
When selecting a column to base your clustered index on, try to avoid columns that are frequently updated. Every time that a column used for a clustered index is modified, all of the non-clustered indexes must also be updated, creating additional overhead. [6.5, 7.0, 2000, 2005] Updated 3-5-2004
Does this mean if I have say a table called Item with a clustered index on a column in it called itemaddeddate, and several non-clustered indexes associated with that table, that if a record gets modified and it's itemaddeddate value changes, that ALL my indexes on that table will get rebuilt? Or is it referring to the table structure changing?
If so does this "pseudocode" example also cause this to occur:
sqlstring="select * from item where itemid=12345"
rs.open sqlstring, etc, etc, etc
rs.Fields("ItemName")="My New Item Name"
rs.Fields("ItemPrice")=1.00
rs.Update
Note I didn't explicitly change the value of rs.fields("ItemAddedDate")...does rs.Fields("ItemAddedDate")=rs.Fields("ItemAddedDate") occur implicitly, which would force the rebuild of all the non-clustered indexes?
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Jun 25, 2015
I have a requirement to only rebuild the Clustered Indexes in the table ignoring the non clustered indexes as those are taken care of by the Clustered indexes.
In order to do that, I have taken the records based on the fragmentation %.
But unable to come up with a logic to only consider rebuilding the clustered indexes in the table.
create table #fragmentation
(
FragIndexId BigInt Identity(1,1),
--IDENTITY(int, 1, 1) AS FragIndexId,
DBNAME nvarchar(4000),
TableName nvarchar(4000),
[Code] ....
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Jun 17, 2007
I have a client that has a 800GB table. The current clustered index on this table is of low selectivity and is causing index scans on queries. I wish to drop the current index and create a new one that is of more use. What i really want to know is, what is the fastest method of rebuilding such a huge index? What would be the storage requirements to process this?
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Jan 14, 2002
Hi!
I was wondering what kind of locks (if any) SQL Server 2000 holds on tables while rebuilding clustered and non-clustered indexes.
Thanks!
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Sep 20, 2000
Do anyone know how to rebuild indexes on the maintenance plan??
I would like to automate rebuilding my indexes on the database about once every month.
I know you can manually do this by using DBCC DBREINDEX. This is to long and tedious.
Thanks in advance!
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Dec 2, 1999
All,
I have scheduled dbreindex command to run on an clustered indexed on a very large table over night, so far this as failed to complete successfully. I think it may have something to do with the amount of space available in the device; the table is approx 238mb in size and the available disk space left in the device is 200 mb.
Does anyone know how much space is required to reindex a table/index this size and if it is required on the same device as the table or in tempdb.
Or even better, if anyone can explain the inter-workings of how the dbreindex command reorgs the table.
Thanks Mathew
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Feb 23, 2004
Hello all,
I need to diagnose a problem, this Sunday a regular Database Maintenance plan which is supposed to rebuild indexes took exactly 6 hours and 32 minutes. Now that’s a hell lot of time and during all that process users were denied access to those tables. This is a production server. I want to know what caused that plan to run for so long and how can I avoid this to happen again plus if it ever happens again how can I make sure that atleast it doesn’t lock tables. I know DBCC INDEXDEFRAG doesn’t lock tables but how can I make Database Maintenance plan to run DBCC INDEXDEFRAG instead of DBCC DBREINDEX but more importantly why it took 6 hours.
Thanks all
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Jan 14, 2002
(Oops, sorry I posted this on the SQL 7 discussion earlier).
----------------------
I was wondering what kind of locks (if any) SQL Server 2000 holds on tables while rebuilding clustered and non-clustered indexes.
Thanks!
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Feb 23, 2004
Hello all,
I need to diagnose a problem, this Sunday a regular Database Maintenance plan which is supposed to rebuild indexes took exactly 6 hours and 32 minutes. Now that’s a hell lot of time and during all that process users were denied access to those tables. This is a production server. I want to know what caused that plan to run for so long and how can I avoid this to happen again plus if it ever happens again how can I make sure that atleast it doesn’t lock tables. I know DBCC INDEXDEFRAG doesn’t lock tables but how can I make Database Maintenance plan to run DBCC INDEXDEFRAG instead of DBCC DBREINDEX but more importantly why it took 6 hours.
Thanks all
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Jun 13, 2008
Hello,
I'm new to rebuilding and reorg indexes. I used the standard report feature in 2005 to look up Index Physical Statistics on one db. I found recommendation to rebuild a few indexes that contain a number of fragments. I created a maint. task, I know maint. tasks are not a cure-all but so far I am just testing the waters. I created two tasks, one to rebuild and another to reorg. After I ran the job, I looked at the report and it still showed recommendation to rebuild the indexes. What is a better solution for my case?
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Feb 25, 2007
Hi,
I have recenlty had to rebuild the indexes for the entire database as they were running a little slow. It prompted me to further investigate the health of the indexes on the database. I have been using the sys.dm_db_index_physical_stats view to do this. I had a query with regards to the avg_fragmentation_in_percent column that the view displays. I have rebuilt all the indexes and for some of the indexes the fragmentation value remains the same. The following is an example of what is returned by the sys.dm_db_index_physical_stats for a single index:
Table, IndexName, avg_fragmentation_in_percent, avg_page_space_used_in_percent
Links, PK_Links, 77.7777777777778, 97.1501606127996
Links, PK_Links, 0, 1.42080553496417
I do not understand why this index the fragmentation is so high even though I have rebuilt it. It is not just this index it occurs for other indexes as well. What could be some of the factors that are causing this to occur?
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Jul 20, 2005
HiI got the advice to rebuild the indexes on the databases once a year.Espesially if the database have grown much. The question is: How do Ido that?If I try to run the indexscript wich was run when the databases werecreated, I only get the message that the indexes already exists.Are there a command to automatically rebuild the indexesautomatically?Roger
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Nov 24, 2014
What is the easiest way to remember the definitions of clustered and non clustered indexes.
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Sep 14, 2006
Aight, so I added a full text catalog and a full text index for one specific column and table in my database.Now the issue is, whenever I rebuild it, it locks the full text index forever, making it unsuable. Now, there are only 30,000 records i need to search, so it isn't like there is this massive amount of data. What am I doing wrong to where it is locking the index and disallowing me to use the stored procedure that does the searching?
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Mar 19, 2015
Is it possible to reclaim space after rebuilding indexes(shrinking is not an option).
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Sep 26, 2007
Hi all,
When I am rebuilding the indexes on the tables, I am getting lot of free space( unallocated) on the database.
Before rebuilding the indexes , the size of the database = 385 Gb
After rebuilding the indexes, the size jumps to = 572 Gb (i.e.) This means 187 Gb of unallocated space .
The Command use to rebuild indexes is:
USE [databasename]
GO
ALTER INDEX [PK_index] ON [dbo].[tablename] REBUILD WITH
( PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, SORT_IN_TEMPDB = ON, ONLINE = OFF )
GO
So, every time we rebuild indexes, we have to shrink the database
(or)
Is there anything else ,I should be doing.
Thanks.
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Jun 3, 2014
I was under impression that rebuilding index online largely means that the index will remain available for use during rebuild and my procs and query will be able to use it during rebuild. Also my understanding was that table will be locked very briefly while the schema change will be completing.But when I was rebuilding the clustered index online on a large table with some 3 million records, the table got locked and I was not able even to read the data from it for some 5 minutes. Then I cancelled the operation as it was production server and it was one of our main transaction table.
Is rebuilding index online supposed to work this way? The table has no other index.The parameteres I used are:
REBUILD WITH (PAD_INDEX = ON, SORT_IN_TEMPDB = ON, ONLINE = ON, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 95)
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Jul 7, 2015
I have come across a database system which isn't designed to work optimally. It is fairly large (~400GB) and performance of loading and querying is degrading (improper data types, fragmented indexes, non unique clustering key and other problems). So, I have quite a task in front of me, but I am up for the challenge. I figure this is not a unique situation, many of us would have come across this before. I have done this before too, but only for smaller databases, some of the operations here I expect to take a couple of hours or more to complete (depending on load/infrastructure speed etc, I know).
My plan is thus:
+ Take a full backup of the database
+ Set the recovery model of the DB to simple
+ Drop non clustered indexes
+ Drop clustered indexes
+ Remove PKs (wrong data types, too large!)
+ Narrow data types (add new column, update column in batches to old value, rename new column to old column)
+ Add PKs, which will create clustered indexes automatically based on PK ID
+ Create non clustered indexes
+ Run a SHRINKDB (normal operations I would never do this, but this is a special case, ensure log file is truncated to a logical size especially after all those table modifications...)
+ Set the recovery model of the DB to Full
+ Ensure everything works OK or better
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Feb 25, 2008
I am trying to automate my index rebuild and reorg based off of the percentage of fragmentation level. The first time you run it you have to change the alter proce Sp_NCRNRecreate then change it to Alter proc. It seems to run okay no errors but it doesn't seem to actually rebuild them. Please take a look and let me know if you see a program error somewhere. I would like create this sp to run automatically
use master
GO
Alter PROC sp_NCR_RecreateIndexes @AutoRun bit=0 AS
BEGIN
DECLARE @DatabaseName varchar(128), @SchemaName varchar(128), @objectName varchar(128), @IndexName varchar(128), @PercentFragmented float, @command varchar(max)
SELECT db_name(s.database_id) as DatabaseName, schema_name(o.schema_id) as SchemaName, o.name as TableName, i.name as IndexName, s.avg_fragmentation_in_percent AS PercentFragmented
INTO #IndexesToRebuild
FROM sys.dm_db_index_physical_stats (db_id(), Null, NULL, NULL, NULL) s
INNER JOIN sys.objects o ON s.object_id=o.object_id
INNER JOIN sys.indexes i ON s.object_id=i.object_id AND s.index_id=i.index_id
WHERE s.avg_fragmentation_in_percent > 10.0 AND s.index_id > 0
SELECT * FROM #IndexesToRebuild
DECLARE IndexCursor CURSOR FOR SELECT DatabaseName, SchemaName, TableName, IndexName, PercentFragmented FROM #IndexesToRebuild
OPEN IndexCursor
FETCH IndexCursor INTO @DatabaseName, @SchemaName, @objectName, @IndexName, @PercentFragmented
WHILE @@FETCH_STATUS=0
BEGIN
SELECT @command = 'ALTER INDEX ' + @indexname +' ON ' + @databaseName + '.' + @schemaname + '.' + @objectName + CASE WHEN @PercentFragmented<30 THEN ' REORGANIZE' ELSE ' REBUILD' END;
print @command
IF @AutoRun=1
EXEC(@command)
FETCH IndexCursor INTO @DatabaseName, @SchemaName, @objectName, @IndexName, @PercentFragmented
END
--SELECT * FROM #IndexStats
END
GO
EXEC sys.sp_MS_marksystemobject sp_NCR_RecreateIndexes
GO
EXEC otis..sp_NCR_RecreateIndexes
EXEC ncrCommon..sp_NCR_RecreateIndexes
GO
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Aug 31, 2015
If I'm doing data compression(page level) does it rebuild indexes too? and how about stats, does it update stats too?
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Apr 24, 2006
I'm using SQL Server 2005 SP1 Standard.
On the Rebuild Index Task there is a checkbox at the bottom that says 'Keep index online while reindexing'.
Great I thought, I'll check that.
Later, when I tested the job, I got this error:
'Online index operations can only be performed in Enterprise edition of SQL Server.'
Why have that checkbox available to check, if I'm running a version that doesn't allow it? Where's the bug?
Thanks
Ed
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Jan 17, 2007
Hi,
We have a client that has a large (5Gb) database replicated to 13 subscribers, the publisher is Sql 2005, the subscribers are Sql Express. The publication has as few filtered articles too. I have found that after several months of continuous running Replication Monitor is taking a long time to report history on each subscriber.
Do people tend to rebuild the indexes on the system merge replication tables on production servers, or should the standard replication jobs take care of this?
Thanks for your help
Graham
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Apr 30, 2008
We are using SQL 1005 Standard Edt, so online Rebuild index is not available. Any way to figure out how much time will it take to rebuild index on given size of database so i can make sure i set schedule for rebuilding index when it is okay not to answer DB traffice during that time.
Thanks,
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Aug 28, 2015
I desire to have a clustered index on a column other than the Primary Key. I have a few junction tables that I may want to alter, create table, or ...
I have practiced with an example table that is not really a junction table. It is just a table I decided to use for practice. When I execute the script, it seems to do everything I expect. For instance, there are not any constraints but there are indexes. The PK is the correct column.
CREATE TABLE [dbo].[tblNotificationMgr](
[NotificationMgrKey] [int] IDENTITY(1,1) NOT NULL,
[ContactKey] [int] NOT NULL,
[EventTypeEnum] [tinyint] NOT NULL,
[code]....
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Jan 31, 2005
I would like to find information on Clustered and Non-clustered indexes and how B-trees are used. I know a clustered index is placed into a b-tree which makes sense for fast ordered searching. What data structure does a non-clustered index use and how? I tried to find info. on the web but couldn't get much detail...
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Jun 26, 2015
With some performance issues faced as I checked on Google came across Paul Randal's article on Logging & Recovery: URL...In this regard, and with some schema changes required, ended up with a decision to drop and re-create a database. What are the proper way to do the same and following queries:
A) What would be the recommended way to shift data from some tables of former database to that of the newer one (The latter ones created with the Script Table transaction)?
B) Would a simple Drop Database completely delete the former database completely and clean up the memory (database pages etc.) or I need to take some additional steps for clearing up the space?
C) Most of the data tables have been updated via loading the Bulk Insert commands time to time from CSV/flat files. Could that be somehow the cause of enlarging the the size of Database and Log?
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Feb 2, 2015
I've been trying to get a definitive answer to this question but alas I have conflicting and patchy answers so far from other sources. I have an index that, lets say, requires 10GB of data space to rebuild..This index resides on a filegroup that spans 2 files on two seperate drives (i.e. a mdf and ndf)
When I rebuild this index how will each of these datafiles grow as the rebuild proceeds to completion? Lets for the time being remove the caveats of any other activity hitting the example index/database in question.My tests seem to show that only the mdf will grows (or the file with the lowest id in the that filegroup) provided there is enough space available in that particular file to complete the operation. The secondary ndf dat file doesnt grow at all if the mdf has enough space.
Is expected behavior? i.e. the index will be rebuilt in a contiguous manner relative to the files contained with the filegroup i.e. fileid 1 will grow till limit reached then next fileid grows etc?
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Feb 18, 2006
hi,
how clustered indexes and non-clustered indexes been saved in memory?
non-clustered is a table of a references to the actual table?
and what about clustered indexes?
thanks.
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Mar 19, 1999
Can anyone help ?
If you have a clustered index on an identity field are appends then forced onto the last page anyway because of the identity field order. So is there any advanbtage of having a clustered identity field ?
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Mar 4, 1999
I need to convert several tables that currently have nonclustered indexes (primary keys) to clustered. Could anyone suggest what the easiest way of doing this would be.
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Sep 10, 2007
hi
can someone tell me why there are only 249 non-clustered indexes,
is there any significance to that number
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Jul 20, 2005
Hi,The more I read, the more confused I'm getting ! (no wonder they sayignorance is bliss)I just got back from the bookstore and was flipping through some SQL ServerAdministration books.One says, that to get the best query performance, youi do two things:1. Cover all the columns used in each SELECT (including the WHERE, ORDERBY , etc.) with an index2. Make sure it's a NON-CLUSTERED index.In this way, the author says, you avoid ever going directly to the basetables for data to resolve the query - i.e. it's resolved in the index.So, for example, he argues if you have:SELECT Lname,Fname, CompanyNamefrom Contactsinner join Customerson (contacts.custid = customers.custid)that you use two non-clustered indexes:1. Lname,Fname and custid from the Contacts table2. CompanyName and custid from Customers(as opposed to the standard approach of a clustered index on the PK's ofeach table)He says that clustered indexes don't speed up performance because they'rethe same as a full table scan. Should I drop clustered indexes from mylarge tables, given that there are multiple non-clustered indexes on them?Is it better to just use multiple non-clustered indexes on a heap table?Steve
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