[英]SQL Linked server query very very slow
I am extracting large amount of data via linked server from VIEWS. 我通过链接服务器从VIEWS中提取大量数据。 I am using SQL Server 2012 and linked server is SQL Server 2008
我使用的是SQL Server 2012,链接的服务器是SQL Server 2008
My select statement is 我的选择陈述是
SELECT * INTO MY_LOCAL_TABLE
FROM
( SELECT * FROM LINKEDSERVER.DB.TABLE.VIEW
WHERE DATE>'2012-01-01' AND ID IN (SELECT ID FROM MY_LOCAL_VIEW)
) Q
I am expecting 300K rows for nearly 700+ IDs. 我期待近700多个ID的300K行。 before it used to take couple of hours but now its take more than a 20 hr!!
过去需要几个小时,但现在需要超过20小时!!
Could you please suggest any alternative solution for this PAIN?? 你能为这个PAIN建议任何替代解决方案吗?
Very many thanks in advance! 非常感谢提前!
When you use a 4-part name such as [server].db.dbo.table
, especially in a join
, often times the entire table is copied over the wire to the local machine, which is obviously not ideal. 当您使用
[server].db.dbo.table
这样的4部分名称时,尤其是在join
,通常会将整个表格通过线路复制到本地计算机,这显然不太理想。
A better approach is to use an OPENQUERY
-- which is handled at the source (linked server). 更好的方法是使用
OPENQUERY
- 在源(链接服务器)处理。
Try: 尝试:
SELECT *
FROM OPENQUERY([LINKEDSERVER], 'SELECT * FROM DB.TABLE.VIEW WHERE DATE>'2012-01-01')
AND ID IN (SELECT ID FROM MY_LOCAL_VIEW)
With this approach the linked server will return all rows for date > x, and then the local server will filter that by ID's in your local table. 使用此方法,链接服务器将返回date> x的所有行,然后本地服务器将按本地表中的ID过滤该行。
Of course, indexing will still play a factor for doing SELECT * FROM DB.TABLE.VIEW WHERE DATE>'2012-01-01
. 当然,索引仍将是执行
SELECT * FROM DB.TABLE.VIEW WHERE DATE>'2012-01-01
一个因素。
Another approach, which I use on large subsets, is to dump the local ID's to the remote server, THEN handle it all remotely, such as: 我在大型子集上使用的另一种方法是将本地ID转储到远程服务器,然后远程处理它,例如:
-- copy local table to linked server by executing remote query
DECLARE @SQL NVARCHAR(MAX)
SET @SQL = 'SELECT ID INTO db.dbo.tmpTable FROM [SERVER].DB.DBO.MY_LOCAL_VIEW'
EXEC(@SQL) AT [LINKEDSERVER]
-- index remote table?!?
DECLARE @SQL NVARCHAR(MAX)
SET @SQL = 'CREATE INDEX [IXTMP] ON db.dbo.tmpTable (ID)'
EXEC(@SQL) AT [LINKEDSERVER]
-- run query on local machine against both remote tables
SELECT *
-- INTO sometable
FROM OPENQUERY([LINKEDSERVER], 'SELECT *
FROM DB.TABLE.VIEW
WHERE DATE>''2012-01-01''
AND ID IN (SELECT ID FROM db.dbo.tmpTable)')
-- now drop remote temp table of id's
DECLARE @SQL NVARCHAR(MAX)
SET @SQL = 'DROP TABLE db.dbo.tmpTable'
EXEC(@SQL) AT [LINKEDSERVER]
If the local view is also large, then you may consider executing a remote query that uses an openquery back to the local machine (assuming the remote machine has the local as a link). 如果本地视图也很大,那么您可以考虑执行使用openquery返回本地计算机的远程查询(假设远程计算机将本地作为链接)。
-- copy local table to linked server by executing remote query
DECLARE @SQL NVARCHAR(MAX)
SET @SQL = 'SELECT ID INTO db.dbo.tmpTable FROM OPENQUERY([SERVER], ''SELECT ID FROM DB.DBO.MY_LOCAL_VIEW'')'
EXEC(@SQL) AT [LINKEDSERVER]
Others have already suggested about indexing. 其他人已经建议过索引。 So I am not going there.
所以我不会去那里。 suggest another option, if you could change that inner query
建议另一个选项,如果你可以改变那个内部查询
SELECT * FROM LINKEDSERVER.DB.TABLE.VIEW
WHERE DATE>'2012-01-01' AND ID IN (SELECT ID FROM MY_LOCAL_VIEW)
To a joined
query using inner join
since you said having 700+ inlist elements. 使用
inner join
joined
查询,因为您说有700多个inlist元素。 give it a try. 试试看。
SELECT lnv.* FROM LINKEDSERVER.DB.TABLE.VIEW lnv
inner join MY_LOCAL_VIEW mcv
on lnv.ID = mcv.ID
and lnv.DATE > '2012-01-01'
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