Does SQL Server Reporting Services execute queries sequentially or in parallel?

May 20th, 2008 Russell Posted in SQL Reporting Services |

I saw an interesting thread today I thought I would pass along. In essence, one of my colleagues wanted to know if the twenty-ish queries behind his SSRS report would all fire at the same time, or sequentially.

The answer is (of course, we’re Microsoft) “it depends”. Robert Bruckner from the SSRS product team pointed to the “Use Single Transaction” option on the data source properties dialog in Report Designer. If  this option is enabled (it’s disabled by default), then we run queries sequentially. If the option is disabled, we run in parallel assuming we have available threads in the SSRS thread pool.

Interesting stuff!