Thursday, September 11, 2008

SQL Server script to rebuild all indexes for all tables and all databases

Problem
One of the main functions of a DBA is to maintain database indexes. There have been several tips written about different commands to use for both index rebuilds and index defrags as well as the differences between index maintenance with SQL Server 2000 and SQL Server 2005. In addition, other tips have been written about using maintenance plans to maintain indexes on all databases. One of the issues with maintenance plans is that they don't always seem to be as reliable as you would hope and you also sometimes get false feedback on whether the task actually was successful or not. What other options are there to rebuild indexes on all databases besides using a maintenance plan?

Solution
The one nice thing about maintenance plans is that it works across multiple databases and therefore you can push out one task to handle the same activity across all of your databases. The problem that I have seen with maintenance plans though is that sometimes they do not work as expected, therefore here is another approach.

The script below allows you to rebuild indexes for all databases and all tables within a database. This could be further tweaked to handle only indexes that need maintenance as well as doing either index defrags or index rebuilds.

The script uses two cursors one for the databases and another cursor for the tables within the database. In addition, it uses the INFORMATION_SCHEMA.TABLES view to list all of the tables within a database.

Because we need to change from database to database we also need to create dynamic SQL code for the queries. For the DBCC DBREINDEX option we can just pass in the parameters, but for the ALTER INDEX statement we need to again build the query dynamically.

DECLARE @Database VARCHAR(255)
DECLARE @Table VARCHAR(255)
DECLARE @cmd NVARCHAR(500)
DECLARE @fillfactor INT

SET @fillfactor = 90

DECLARE DatabaseCursor CURSOR FOR
SELECT name FROM master.dbo.sysdatabases
WHERE name NOT IN ('master','model','msdb','tempdb','distrbution')
ORDER BY 1

OPEN DatabaseCursor

FETCH NEXT FROM DatabaseCursor INTO @Database
WHILE @@FETCH_STATUS = 0
BEGIN

SET @cmd = 'DECLARE TableCursor CURSOR FOR SELECT table_catalog + ''.'' + table_schema + ''.'' + table_name as tableName
FROM ' + @Database + '.INFORMATION_SCHEMA.TABLES WHERE table_type = ''BASE TABLE'''

-- create table cursor
EXEC (@cmd)
OPEN TableCursor

FETCH NEXT FROM TableCursor INTO @Table
WHILE @@FETCH_STATUS = 0
BEGIN

-- SQL 2000 command
--DBCC DBREINDEX(@Table,' ',@fillfactor)

-- SQL 2005 command
SET @cmd = 'ALTER INDEX ALL ON ' + @Table + ' REBUILD WITH (FILLFACTOR = ' + CONVERT(VARCHAR(3),@fillfactor) + ')'
EXEC (@cmd)

FETCH NEXT FROM TableCursor INTO @Table
END

CLOSE TableCursor
DEALLOCATE TableCursor

FETCH NEXT FROM DatabaseCursor INTO @Database
END
CLOSE DatabaseCursor
DEALLOCATE DatabaseCursor

The DBCC DBREINDEX command will work for both SQL 2000 and SQL 2005, but the new syntax that you should use for SQL Server 2005 is the ALTER INDEX command, so based on this you could do the following:

SQL 2000
uncomment this line
DBCC DBREINDEX(@Table,' ',@fillfactor)
comment these lines
SET @cmd = 'ALTER INDEX ALL ON ' + @Table + ' REBUILD WITH (FILLFACTOR = ' + CONVERT(VARCHAR(3),@fillfactor) + ')'
EXEC (@cmd)
SQL 2005
comment this line
DBCC DBREINDEX(@Table,' ',@fillfactor)
uncomment these lines
SET @cmd = 'ALTER INDEX ALL ON ' + @Table + ' REBUILD WITH (FILLFACTOR = ' + CONVERT(VARCHAR(3),@fillfactor) + ')'
EXEC (@cmd)
Also, I have excluded the system databases, so you can include these or also add other databases to exclude from you index maintenance routines.

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