我最近也遇到过几次完全相同的问题(使用MS-SQL2008)。特定的存储过程运行起来会非常慢(几分钟),但粘贴到SSMS中的同一个SQL只需几秒钟。
比较执行计划
Ctrl-M
是此的键盘快捷键)。
然后将存储过程的内容粘贴到窗口中,然后调用实际的存储过程。
从ID=10的用户中选择FirstName和LastName
同时运行两个查询,然后比较两个查询的执行计划。我不得不说,在我的例子中,对每个查询的“查询成本”估计根本没有帮助,并且把我指向了错误的方向。相反,请仔细查看正在使用的索引、是否正在执行扫描而不是查找以及正在处理的行数。
计划应该有所不同,这有助于确定需要进一步调查的表和索引。
在另一个实例中,我发现更新并重建查询中使用的特定表的索引会产生很大的不同。
我已使用此SQL查找并重新生成适当的索引:
/* Originally created by Microsoft */
/* Error corrected by Pinal Dave (http://www.SQLAuthority.com) */
/* http://blog.sqlauthority.com/2008/03/04/sql-server-2005-a-simple-way-to-defragment-all-indexes-in-a-database-that-is-fragmented-above-a-declared-threshold/ */
/* Catch22: Added parameters to filter by table & view proposed changes */
-- Specify your Database Name
USE AdventureWorks
/* Parameters */
Declare @MatchingTableName nvarchar(100) = 'MyTablePrefix' -- Specify Table name (can be prefix of table name) or blank for all tables
DECLARE @ViewOnly bit = 1 -- Set to 1 to view proposed actions, set to 0 to Execute proposed actions:
-- Declare variables
SET NOCOUNT ON
DECLARE @tablename VARCHAR(128)
DECLARE @execstr VARCHAR(255)
DECLARE @objectid INT
DECLARE @indexid INT
DECLARE @frag decimal
DECLARE @maxreorg decimal
DECLARE @maxrebuild decimal
DECLARE @IdxName varchar(128)
DECLARE @ReorgOptions varchar(255)
DECLARE @RebuildOptions varchar(255)
-- Decide on the maximum fragmentation to allow for a reorganize.
-- AVAILABLE OPTIONS: http://technet.microsoft.com/en-us/library/ms188388(SQL.90).aspx
SET @maxreorg = 20.0
SET @ReorgOptions = 'LOB_COMPACTION=ON'
-- Decide on the maximum fragmentation to allow for a rebuild.
SET @maxrebuild = 30.0
-- NOTE: only specifiy FILLFACTOR=x if x is something other than zero:
SET @RebuildOptions = 'PAD_INDEX=OFF, SORT_IN_TEMPDB=ON, STATISTICS_NORECOMPUTE=OFF, ALLOW_ROW_LOCKS=ON, ALLOW_PAGE_LOCKS=ON'
-- Declare a cursor.
DECLARE tables CURSOR FOR
SELECT CAST(TABLE_SCHEMA AS VARCHAR(100))
+'.'+CAST(TABLE_NAME AS VARCHAR(100))
AS Table_Name
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_TYPE = 'BASE TABLE'
AND TABLE_NAME like @MatchingTableName + '%'
-- Create the temporary table.
if exists (select name from tempdb.dbo.sysobjects where name like '#fraglist%')
drop table #fraglist
CREATE TABLE #fraglist (
ObjectName CHAR(255),
ObjectId INT,
IndexName CHAR(255),
IndexId INT,
Lvl INT,
CountPages INT,
CountRows INT,
MinRecSize INT,
MaxRecSize INT,
AvgRecSize INT,
ForRecCount INT,
Extents INT,
ExtentSwitches INT,
AvgFreeBytes INT,
AvgPageDensity INT,
ScanDensity decimal,
BestCount INT,
ActualCount INT,
LogicalFrag decimal,
ExtentFrag decimal)
-- Open the cursor.
OPEN tables
-- Loop through all the tables in the database.
FETCH NEXT
FROM tables
INTO @tablename
WHILE @@FETCH_STATUS = 0
BEGIN
-- Do the showcontig of all indexes of the table
INSERT INTO #fraglist
EXEC ('DBCC SHOWCONTIG (''' + @tablename + ''')
WITH FAST, TABLERESULTS, ALL_INDEXES, NO_INFOMSGS')
FETCH NEXT
FROM tables
INTO @tablename
END
-- Close and deallocate the cursor.
CLOSE tables
DEALLOCATE tables
-- Declare the cursor for the list of indexes to be defragged.
DECLARE indexes CURSOR FOR
SELECT ObjectName, ObjectId, IndexId, LogicalFrag, IndexName
FROM #fraglist
WHERE ((LogicalFrag >= @maxreorg) OR (LogicalFrag >= @maxrebuild))
AND INDEXPROPERTY (ObjectId, IndexName, 'IndexDepth') > 0
-- Open the cursor.
OPEN indexes
-- Loop through the indexes.
FETCH NEXT
FROM indexes
INTO @tablename, @objectid, @indexid, @frag, @IdxName
WHILE @@FETCH_STATUS = 0
BEGIN
IF (@frag >= @maxrebuild)
BEGIN
IF (@ViewOnly=1)
BEGIN
PRINT 'WOULD be executing ALTER INDEX ' + RTRIM(@IdxName) + ' ON ' + RTRIM(@tablename) + ' REBUILD WITH ( ' + @RebuildOptions + ' ) -- Fragmentation currently ' + RTRIM(CONVERT(VARCHAR(15),@frag)) + '%'
END
ELSE
BEGIN
PRINT 'Now executing ALTER INDEX ' + RTRIM(@IdxName) + ' ON ' + RTRIM(@tablename) + ' REBUILD WITH ( ' + @RebuildOptions + ' ) -- Fragmentation currently ' + RTRIM(CONVERT(VARCHAR(15),@frag)) + '%'
SELECT @execstr = 'ALTER INDEX ' + RTRIM(@IdxName) + ' ON ' + RTRIM(@tablename) + ' REBUILD WITH ( ' + @RebuildOptions + ' )'
EXEC (@execstr)
END
END
ELSE IF (@frag >= @maxreorg)
BEGIN
IF (@ViewOnly=1)
BEGIN
PRINT 'WOULD be executing ALTER INDEX ' + RTRIM(@IdxName) + ' ON ' + RTRIM(@tablename) + ' REORGANIZE WITH ( ' + @ReorgOptions + ' ) -- Fragmentation currently ' + RTRIM(CONVERT(VARCHAR(15),@frag)) + '%'
END
ELSE
BEGIN
PRINT 'Now executing ALTER INDEX ' + RTRIM(@IdxName) + ' ON ' + RTRIM(@tablename) + ' REORGANIZE WITH ( ' + @ReorgOptions + ' ) -- Fragmentation currently ' + RTRIM(CONVERT(VARCHAR(15),@frag)) + '%'
SELECT @execstr = 'ALTER INDEX ' + RTRIM(@IdxName) + ' ON ' + RTRIM(@tablename) + ' REORGANIZE WITH ( ' + @ReorgOptions + ' )'
EXEC (@execstr)
END
END
FETCH NEXT
FROM indexes
INTO @tablename, @objectid, @indexid, @frag, @IdxName
END
-- Close and deallocate the cursor.
CLOSE indexes
DEALLOCATE indexes
-- Delete the temporary table.
DROP TABLE #fraglist
