title: SSRS report VERY SLOW in prod but SQL query runs FAST
body: <p>I've spent hours troubleshooting this and I need some fresh perspective . . .</p>
  
  <p>We have a relatively simple report setup in SSRS, simple matrix with columns across the top and data points going down.  The SQL query behind the report is "medium" complexity -- has some subqueries and several joins, but nothing real crazy.</p>
  
  <p>Report has worked fine for months and recently has become REALLY slow.  Like, 15-20 minutes to generate the report.  I can clip-and-paste the SQL query from the Report Designer into SQL Mgmt Studio, replace the  necessary variables, and it ruturns results in less than 2 seconds.  I even went so far as to use SQL profiler to get the <em>exact</em> query that SSRS is executing, and clipped-and-pasted this into Mgmt Studio, still the same thing, sub-second results.  The parameters and date ranges specified don't make any difference, I can set parameters to return a small dataset (&lt; 100 rows) or a humongous one (> 10,000 rows) and still the same results; super-fast in Mgmt Studio but 20 minutes to generate the SSRS report.</p>
  
  <p>Troubleshooting I've attempted so far:
  Deleted and re-deployed the report in SSRS.
  Tested in Visual Studio IDE on multiple machines and on the SSRS server, same speed (~20 minutes) both places
  Used SQL Profiler to monitor the SPID executing the report, captured all SQL statements being executed, and tried them individualy (and together) in Mgmt Studio -- runs fast in Mgmt Studio (&lt; 2 seconds)
  Monitored server performance during report execution.  Processor is pretty darn hammered during the 20 minute report generation, disk I/O is slightly above baseline</p>