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The author:(作者)归海一刀
published in(发表于) 2014/2/3 6:44:02
如何将索引碎片数量降至最低_[SQL Server教程]

create table t3
(
i int primary key,
xx varchar(200) not null
)

declare @x int
set @x = 0
while @x <1000
begin
insert into t3 values (@x,'qweasdqweasdqweasdqweqweasdqwe')
set @x = @x+1
end

SELECT index_id,index_type_desc,avg_fragmentation_in_percent,page_count FROM sys.dm_db_index_physical_stats(db_id(), OBJECT_ID('t3'), NULL, NULL , 'LIMITED');

DBCC INDEXDEFRAG (test, 'dbo.t3', PK__t3__0EA330E9)

alter index PK__t3__0EA330E9 on t3
rebuild

dbcc dbreindex ('t3')

declare @x int
set @x = 1000
while @x <10000
begin
insert into t3 values (@x,'qweasdqweasdqweasdqweqweasdqwe')
set @x = @x+1
end

SELECT index_id,index_type_desc,avg_fragmentation_in_percent,page_count FROM sys.dm_db_index_physical_stats(db_id(), OBJECT_ID('t3'), NULL, NULL , 'LIMITED');

alter index t3index on t3
rebuild

-- ensure a USE statement has been executed first.
SET NOCOUNT ON;
DECLARE @objectid int;
DECLARE @indexid int;
DECLARE @partitioncount bigint;
DECLARE @schemaname sysname;
DECLARE @objectname sysname;
DECLARE @indexname sysname;
DECLARE @partitionnum bigint;
DECLARE @partitions bigint;
DECLARE @frag float;
DECLARE @command varchar(8000);
-- ensure the temporary table does not exist
IF EXISTS (SELECT name FROM sys.objects WHERE name = 'work_to_do')
DROP TABLE work_to_do;
-- conditionally select from the function, converting 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
INTO work_to_do
FROM sys.dm_db_index_physical_stats (DB_ID(), NULL, NULL , NULL, 'LIMITED')
WHERE avg_fragmentation_in_percent > 10.0 AND index_id > 0;
-- Declare the cursor for the list of partitions to be processed.
DECLARE partitions CURSOR FOR SELECT * FROM work_to_do;

-- Open the cursor.
OPEN partitions;

-- Loop through the partitions.
FETCH NEXT
FROM partitions
INTO @objectid, @indexid, @partitionnum, @frag;

WHILE @@FETCH_STATUS = 0
BEGIN;
SELECT @objectname = o.name, @schemaname = 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 = 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;

-- 30 is an arbitrary decision point at which to switch between reorganizing and rebuilding
IF @frag < 30.0
BEGIN;
SELECT @command = 'ALTER INDEX ' + @indexname + ' ON ' + @schemaname + '.' + @objectname + ' REORGANIZE';
IF @partitioncount > 1
SELECT @command = @command + ' PARTITION=' + CONVERT (CHAR, @partitionnum);
EXEC (@command);
END;

IF @frag >= 30.0
BEGIN;
SELECT @command = 'ALTER INDEX ' + @indexname +' ON ' + @schemaname + '.' + @objectname + ' REBUILD';
IF @partitioncount > 1
SELECT @command = @command + ' PARTITION=' + CONVERT (CHAR, @partitionnum);
EXEC (@command);
END;
PRINT 'Executed ' + @command;

FETCH NEXT FROM partitions INTO @objectid, @indexid, @partitionnum, @frag;
END;
-- Close and deallocate the cursor.
CLOSE partitions;
DEALLOCATE partitions;

-- drop the temporary table
IF EXISTS (SELECT name FROM sys.objects WHERE name = 'work_to_do')
DROP TABLE work_to_do;
GO

> 5% 且 < = 30%

ALTER INDEX REORGANIZE

> 30%

ALTER INDEX REBUILD WITH (ONLINE = ON)*

小于5没必要重建，所以上面的SQL语句还是有得商量的地方。

来源:http://www.cnblogs.com/perfectdesign

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