SQL 链接服务器查询非常非常慢
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SQL Linked server query very very slow
提问by arm
I am extracting large amount of data via linked server from VIEWS. I am using SQL Server 2012 and linked server is SQL Server 2008
我正在通过链接服务器从 VIEWS 中提取大量数据。我使用的是 SQL Server 2012，链接服务器是 SQL Server 2008
My select statement is
我的选择语句是
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. before it used to take couple of hours but now its take more than a 20 hr!!
我预计将近 700 个 ID 有 300K 行。以前需要几个小时，但现在需要 20 多个小时！！
Could you please suggest any alternative solution for this PAIN??
您能否为此 PAIN 提出任何替代解决方案？
Very many thanks in advance!
非常感谢提前！
回答by Dave Cullum
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 4 部分名称时[server].db.dbo.table，尤其是在 a 中时join，通常会通过网络将整个表复制到本地计算机，这显然是不理想的。
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.
使用这种方法，链接服务器将返回日期 > x 的所有行，然后本地服务器将通过本地表中的 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，索引仍然会在 do 中发挥作用SELECT * FROM DB.TABLE.VIEW WHERE DATE>'2012-01-01。
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 返回本地机器的远程查询（假设远程机器有本地作为链接）。
-- 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]
回答by Rahul
Others have already suggested about indexing. So I am not going there. suggest another option, if you could change that inner query
其他人已经提出了关于索引的建议。所以我不去那里。建议另一种选择，如果您可以更改该内部查询
SELECT * FROM LINKEDSERVER.DB.TABLE.VIEW
WHERE DATE>'2012-01-01' AND ID IN (SELECT ID FROM MY_LOCAL_VIEW)
To a joinedquery using inner joinsince you said having 700+ inlist elements. give it a try.
要在joined使用查询inner join，因为你说有700+ INLIST元素。试一试。
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'
