Hi all,
I have a query, rather complex one to deal with more than 1 million rows, used to run 40 minutes in SQL Server 2000 in query analyzer. Now, it has been 10 hours in SQL Server 2005 in management studio. And still has not finished yet! Anything can go wrong here. Basically nothing changes, except for I have my server upgrade from SQL Server 2000 to SQL Server 2005. Seems something is wrong crazy in SQL Server 2005. Any suggestions?
Thanks,
Ning
Reminds me of some hotfix descriptions - Have you checked knowledgebase articles for "slow query"? Here's an example that relates to fast forward-only queries:
"FIX: The query performance is very slow when you use a fast forward-only cursor to run a query in SQL Server 2005": http://support.microsoft.com/default.aspx/kb/926024
|||I found the reason, but not sure why, either do I have a way to fix that.
In one of my select sentence, I have a field, nvarchar(2000), if I exclude that field in the select statement then everything is back to speed. Otherwise, we are cralwing like 1000 lines per minute, so 1 million lines will be 1000 minute ... (without that field we are at 100,000 per minute). I am not sure why a field can cause such a big deal 100 times in performance diff ...
Microsoft has to explain this ...
Thanks,
Ning
|||I am wondering if it is joining to the table containing this field early in the query and so having to carry the up to 2K a row of data round (for a million rows - that's up to 2G). This would probably show as an explosion in the size of tempdb (as this is where it is likely to be caching this data during the query).
Was it just the field or the table providing the field which you removed from the query. If it was the table you might try putting it at the bottom of the from clause and using the FORCE ORDER Query hint. However this will prevent the query planner rearranging any of the tables so you might want to put them in the order specified by the plan for the fast query without that field in.
