文章摘要
这篇文章描述了一个用于优化数据库索引的自动化过程。通过使用`CREATE TABLE`语句和`FETCH`语句，文章展示了如何将高碎片化的索引数据存储到临时表中，并根据索引的碎片程度（`FRAGMENTATION`）对索引进行重新组织（`REORGANIZE`）或重建（`REBUILD`）。文章还提到了如何遍历这些索引，并使用`ALTER INDEX`语句对目标索引进行优化操作。最后，通过`DROP TABLE`语句清理临时存储的索引数据。整个过程旨在提高索引性能，提升数据库运行效率。
USE [数据库名]
GO
DECLARE @NoOfPartitions BIGINT;
DECLARE @objectid INT;
DECLARE @indexid INT;
DECLARE @idxname NVARCHAR(255);
DECLARE @objname NVARCHAR(255);
DECLARE @partitionnum BIGINT;
DECLARE @schemaname NVARCHAR(255);
DECLARE @partitions BIGINT;
DECLARE @frag FLOAT;
DECLARE @statement VARCHAR(8000);
— checking existance of the table that we create for temporary purpose
IF OBJECT_ID(‘defrag_work’, ‘U’) IS NOT NULL
DROP TABLE defrag_work;
— Copy the fragmented indexes data into defrag_work table
— All the indexes that has fragmentation < 5 are getting stored into our work table
SELECT [object_id] AS objectid ,
index_id AS indexid ,
partition_number AS partition_no ,
avg_fragmentation_in_percent AS frag
INTO defrag_work
FROM sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL, NULL, ‘LIMITED’)
WHERE avg_fragmentation_in_percent >5.0 and index_id > 0;
— cursor to process the list of partitions
DECLARE partitions CURSOR
FOR
SELECT *
FROM defrag_work;
— Open the cursor.
OPEN partitions;
— Looping through the partitions
FETCH NEXT
FROM partitions
INTO @objectid, @indexid, @partitionnum, @frag;
WHILE @@FETCH_STATUS=0
BEGIN;
SELECT @objname=QUOTENAME(so.name) ,
@schemaname=QUOTENAME(ss.name)
FROM sys.objects AS so
JOIN sys.schemas AS ss ON ss.schema_id=so.schema_id
WHERE so.object_id=@objectid;
SELECT @idxname=QUOTENAME(name)
FROM sys.indexes
WHERE object_id=@objectid
AND index_id=@indexid;
SELECT @NoOfPartitions=COUNT(*)
FROM sys.partitions
WHERE object_id=@objectid
AND index_id=@indexid;
IF (@frag < 30.0) — @frag > 5 is already filtered in our first query, so we need that condition here
BEGIN;
SELECT @statement=’ALTER INDEX ‘ + @idxname + ‘ ON ‘
+ @schemaname + ‘.’ + @objname + ‘ REORGANIZE’;
IF @NoOfPartitions > 1
SELECT @statement=@statement + ‘ PARTITION=’
+ CONVERT (CHAR, @partitionnum);
EXEC (@statement);
END;
IF @frag >=30.0
BEGIN;
SELECT @statement=’ALTER INDEX ‘ + @idxname + ‘ ON ‘
+ @schemaname + ‘.’ + @objname + ‘ REBUILD’;
IF @NoOfPartitions > 1
SELECT @statement=@statement + ‘ PARTITION=’
+ CONVERT (CHAR, @partitionnum);
EXEC (@statement);
END;
PRINT ‘Executed ‘ + @statement;
FETCH NEXT FROM partitions INTO @objectid, @indexid, @partitionnum,
@frag;
END;
— Close and deallocate the cursor.
CLOSE partitions;
DEALLOCATE partitions;
— drop the table
IF OBJECT_ID(‘defrag_work’, ‘U’) IS NOT NULL
DROP TABLE defrag_work;