asp.net - SQL Server query runs slower from ADO.NET than in SSMS

Question

I have a query from a web site that takes 15-30 seconds while the same query runs in .5 seconds from SQL Server Management studio. I cannot see any locking issues using SQL Profiler, nor can I reproduce the delay manually from SSMS. A week ago, I detached and reattached the database which seemed to miraculously fix the problem. Today when the problem reared its ugly head again, I tried merely rebuilding the indexes. This also fixed the problem. However, I don't think it's necessarily an index problem since the indexes wouldn't be automatically rebuilt on a simple detach/attach, to my knowledge.

Any idea what could be causing the delay? My first thought was that perhaps some parameter sniffing on the stored procedure being called (said stored proc runs a CTE, if that matters) was causing a bad query plan, which would explain the intermittent nature of the problem. Since both detaching / reattaching and an index rebuild should theoretically invalidate the cached query plan, this makes sense, but I'm unsure how to verify this. Additionally, why wouldn't the same query (copied directly from SQL Profiler with the exact same parameters) exhibit the same delay when run manually through SSMS?

Any thoughts?

Answer 1

I know I am weighing in on this topic very late, but I wanted to post a solution that I found when having a similar issue. In brief, adding the SET ARITHABORT ON command at the outset of my procedures brought website query performance in line with performance seen from SQL Server tools. This option is typically being set on the connection when you run a query from QA or SSMS (you can change that option, but it is the default).

In my case, I had about 15 different stored procs doing mathematical aggregates (SUMs, COUNTs, AVGs, STDEVs) across a fairly sizeable set of data (10s to 100s of thousands of rows) - adding the SET ARITHABORT ON option moved them all from running in 3-5 seconds each to 20-30ms.

So, hopefully that helps someone else out there.