Detecting Cardinality Estimate Issues with sys.dm_exec_query_stats

SQL Server 2008 R2 SP1 and SQL Server 2012 RTM+ includes actual row count statistics in the sys.dm_exec_query_stats dynamic management view.  This includes the total_rows, last_rows, min_rows and max_rows columns, which are intuitively named. One potential use of the row statistics data is to detect cardinality estimate issues where the actual count of rows is […]

Thinking about the inaccurate_cardinality_estimate Event

SQL Server 2012 introduces the new inaccurate_cardinality_estimate extended event, and I had a few miscellaneous thoughts about it that I wanted to discuss on this post. Background reading If you’re unfamiliar with this event, there isn’t anything as of today in Books Online, but there are two blog references / discussions: How the query execution […]

SQLPerformance.com “TRANSACTION_MUTEX and Multi-Session Transaction Access”

My third guest blog post was published today on SQLPerformance.com: TRANSACTION_MUTEX and Multi-Session Transaction Access This is related to a recent SQL Server instance I was working with that had high TRANSACTION_MUTEX accumulated wait time.  Based on this observation, I explored a three different functionality areas that could be associated with this wait type.

Exploring Column Correlation and Cardinality Estimates

Last Thursday I presented a session at the PASS Winter 2012 Performance Palooza.  It was a great experience and I appreciated the opportunity.  The topic was “Troubleshooting Query Plan Quality Issues” and I received a few email questions after the presentation, so I thought I would walk through the full scenario, weaving in a few […]