从ASP.NET站点到LINQ to SQL存储过程的性能突然下降，包括超时

Question

The site is ASP.NET 2.0, using LINQ to SQL. Database is SQL Server 2008 R2.

Been working on an issue where performance suddenly took a huge drop one day and has remained that way since. Cannot figure out why. It has been just certain functionality of the site, not necessarily a site-wide problem. Have focused on a particular stored procedure in general that is taking a good 1000ms+ showing in profiler. When copying the TextData and running right in the query analyzer, it runs much quicker.

Have tried a sp_recompile on the stored procedure as well as the table used. The db server was restarted during a maintenance period and that also did not stabilize things. Is there any possible troubleshooting steps anyone could provide to help dig deeper on this? Absolutely stumped.

Answer 1

It could be a parameter sniffing problem. You can see the details here - http://blogs.msdn.com/b/turgays/archive/2013/09/10/parameter-sniffing-problem-and-workarounds . As suggested in the blog, you can try the following -

OPTION (OPTIMIZE FOR (@VARIABLE=VALUE))

OPTION (OPTIMIZE FOR (@VARIABLE UNKNOWN))

Use local variables - Basically declare local variables and assign the value of the parameter to local variable and use the local variable in the query.

OPTION (RECOMPILE) - Since you have already tried that you can ignore this

Could you post the query snippet which is causing this issue?