问题
Can anyone provide the script for rebuilding and re-indexing the fragmented index when 'avg_fragmentation_in_percent' exceeds certain limits (better if cursor is not used)?
回答1:
To rebuild use:
ALTER INDEX __NAME_OF_INDEX__ ON __NAME_OF_TABLE__ REBUILD
or to reorganize use:
ALTER INDEX __NAME_OF_INDEX__ ON __NAME_OF_TABLE__ REORGANIZE
Reorganizing should be used at lower (<30%) fragmentations but only rebuilding (which is heavier to the database) cuts the fragmentation down to 0%.
For further information see https://msdn.microsoft.com/en-us/library/ms189858.aspx
回答2:
Two solutions: One simple and one more advanced.
Introduction
There are two solutions available to you depending on the severity of your issue
Replace with your own values, as follows:
- Replace
XXXMYINDEXXXXwith the name of an index. - Replace
XXXMYTABLEXXXwith the name of a table. - Replace
XXXDATABASENAMEXXXwith the name of a database.
Solution 1. Indexing
Rebuild all indexes for a table in offline mode
ALTER INDEX ALL ON XXXMYTABLEXXX REBUILD
Rebuild one specified index for a table in offline mode
ALTER INDEX XXXMYINDEXXXX ON XXXMYTABLEXXX REBUILD
Solution 2. Fragmentation
Fragmentation is an issue in tables that regularly have entries both added and removed.
Check fragmentation percentage
SELECT
ips.[index_id] ,
idx.[name] ,
ips.[avg_fragmentation_in_percent]
FROM
sys.dm_db_index_physical_stats(DB_ID(N'XXXMYDATABASEXXX'), OBJECT_ID(N'XXXMYTABLEXXX'), NULL, NULL, NULL) AS [ips]
INNER JOIN sys.indexes AS [idx] ON [ips].[object_id] = [idx].[object_id] AND [ips].[index_id] = [idx].[index_id]
Fragmentation 5..30%
If the fragmentation value is greater than 5%, but less than 30% then it is worth reorganising indexes.
Reorganise all indexes for a table
ALTER INDEX ALL ON XXXMYTABLEXXX REORGANIZE
Reorganise one specified index for a table
ALTER INDEX XXXMYINDEXXXX ON XXXMYTABLEXXX REORGANIZE
Fragmentation 30%+
If the fragmentation value is 30% or greater then it is worth rebuilding then indexes in online mode.
Rebuild all indexes in online mode for a table
ALTER INDEX ALL ON XXXMYTABLEXXX REBUILD WITH (ONLINE = ON)
Rebuild one specified index in online mode for a table
ALTER INDEX XXXMYINDEXXXX ON XXXMYTABLEXXX REBUILD WITH (ONLINE = ON)
回答3:
Here is the modified script which i took from http://www.foliotek.com/devblog/sql-server-optimization-with-index-rebuilding which i found useful to post here. Although it uses a cursor and i know what is the main problem with cursors it can be easily converted to a cursor-less version.
It is well-documented and you can easily read through it and modify to your needs.
IF OBJECT_ID('tempdb..#work_to_do') IS NOT NULL
DROP TABLE tempdb..#work_to_do
BEGIN TRY
--BEGIN TRAN
use yourdbname
-- Ensure a USE statement has been executed first.
SET NOCOUNT ON;
DECLARE @objectid INT;
DECLARE @indexid INT;
DECLARE @partitioncount BIGINT;
DECLARE @schemaname NVARCHAR(130);
DECLARE @objectname NVARCHAR(130);
DECLARE @indexname NVARCHAR(130);
DECLARE @partitionnum BIGINT;
DECLARE @partitions BIGINT;
DECLARE @frag FLOAT;
DECLARE @pagecount INT;
DECLARE @command NVARCHAR(4000);
DECLARE @page_count_minimum SMALLINT
SET @page_count_minimum = 50
DECLARE @fragmentation_minimum FLOAT
SET @fragmentation_minimum = 30.0
-- Conditionally select tables and indexes from the sys.dm_db_index_physical_stats function
-- and convert object and index IDs to names.
SELECT object_id AS objectid ,
index_id AS indexid ,
partition_number AS partitionnum ,
avg_fragmentation_in_percent AS frag ,
page_count AS page_count
INTO #work_to_do
FROM sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL, NULL,
'LIMITED')
WHERE avg_fragmentation_in_percent > @fragmentation_minimum
AND index_id > 0
AND page_count > @page_count_minimum;
IF CURSOR_STATUS('global', 'partitions') >= -1
BEGIN
PRINT 'partitions CURSOR DELETED' ;
CLOSE partitions
DEALLOCATE partitions
END
-- Declare the cursor for the list of partitions to be processed.
DECLARE partitions CURSOR LOCAL
FOR
SELECT *
FROM #work_to_do;
-- Open the cursor.
OPEN partitions;
-- Loop through the partitions.
WHILE ( 1 = 1 )
BEGIN;
FETCH NEXT
FROM partitions
INTO @objectid, @indexid, @partitionnum, @frag, @pagecount;
IF @@FETCH_STATUS < 0
BREAK;
SELECT @objectname = QUOTENAME(o.name) ,
@schemaname = QUOTENAME(s.name)
FROM sys.objects AS o
JOIN sys.schemas AS s ON s.schema_id = o.schema_id
WHERE o.object_id = @objectid;
SELECT @indexname = QUOTENAME(name)
FROM sys.indexes
WHERE object_id = @objectid
AND index_id = @indexid;
SELECT @partitioncount = COUNT(*)
FROM sys.partitions
WHERE object_id = @objectid
AND index_id = @indexid;
SET @command = N'ALTER INDEX ' + @indexname + N' ON '
+ @schemaname + N'.' + @objectname + N' REBUILD';
IF @partitioncount > 1
SET @command = @command + N' PARTITION='
+ CAST(@partitionnum AS NVARCHAR(10));
EXEC (@command);
--print (@command); //uncomment for testing
PRINT N'Rebuilding index ' + @indexname + ' on table '
+ @objectname;
PRINT N' Fragmentation: ' + CAST(@frag AS VARCHAR(15));
PRINT N' Page Count: ' + CAST(@pagecount AS VARCHAR(15));
PRINT N' ';
END;
-- Close and deallocate the cursor.
CLOSE partitions;
DEALLOCATE partitions;
-- Drop the temporary table.
DROP TABLE #work_to_do;
--COMMIT TRAN
END TRY
BEGIN CATCH
--ROLLBACK TRAN
PRINT 'ERROR ENCOUNTERED:' + ERROR_MESSAGE()
END CATCH
回答4:
Query for REBUILD/REORGANIZE Indexes
- 30%<= Rebuild
- 5%<= Reorganize
- 5%> do nothing
Query:
SELECT OBJECT_NAME(ind.OBJECT_ID) AS TableName,
ind.name AS IndexName, indexstats.index_type_desc AS IndexType,
indexstats.avg_fragmentation_in_percent,
'ALTER INDEX ' + QUOTENAME(ind.name) + ' ON ' +QUOTENAME(object_name(ind.object_id)) +
CASE WHEN indexstats.avg_fragmentation_in_percent>30 THEN ' REBUILD '
WHEN indexstats.avg_fragmentation_in_percent>=5 THEN 'REORGANIZE'
ELSE NULL END as [SQLQuery] -- if <5 not required, so no query needed
FROM sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL, NULL, NULL) indexstats
INNER JOIN sys.indexes ind ON ind.object_id = indexstats.object_id
AND ind.index_id = indexstats.index_id
WHERE
--indexstats.avg_fragmentation_in_percent , e.g. >10, you can specify any number in percent
ind.Name is not null
ORDER BY indexstats.avg_fragmentation_in_percent DESC
Output
TableName IndexName IndexType avg_fragmentation_in_percent SQLQuery
--------------------------------------------------------------------------------------- ------------------------------------------------------
Table1 PK_Table1 CLUSTERED INDEX 75 ALTER INDEX [PK_Table1] ON [Table1] REBUILD
Table1 IX_Table1_col1_col2 NONCLUSTERED INDEX 66,6666666666667 ALTER INDEX [IX_Table1_col1_col2] ON [Table1] REBUILD
Table2 IX_Table2_ NONCLUSTERED INDEX 10 ALTER INDEX [IX_Table2_] ON [Table2] REORGANIZE
Table2 IX_Table2_ NONCLUSTERED INDEX 3 NULL
回答5:
I have found the following script is very good at maintaining indexes, you can have this scheduled to run nightly or whatever other timeframe you wish.
http://sqlfool.com/2011/06/index-defrag-script-v4-1/
回答6:
The real answer, in 2016 and 2017, is: Use Ola Hallengren's scripts:
https://ola.hallengren.com/sql-server-index-and-statistics-maintenance.html
That is all any of us need to know or bother with, at this point in our mutual evolution.
来源：https://stackoverflow.com/questions/1086812/script-for-rebuilding-and-reindexing-the-fragmented-index