Recently I was looking at a query generating deadlocks as a result of a clustered index scan.  I saw that someone forced a LOOP JOIN on one of the offending queries.  At first glance it appeared as if the LOOP JOIN should have made an index seek more likely; however, after remembering a side effect […]

If you’ve ever wondered when a long running query was going to complete there is now a way to get some visibility into it.  Starting in SQL Server 2016 SP1 there is a lightweight query profiler that can be enabled with extended events or by enabling the 7412 trace flag.  When you enable this trace […]

This post is geared towards explaining why indexes are necessary in layman’s terms.  My goal is for this to be understandable to somebody that doesn’t necessarily have a database background. The Phonebook Example Finding a phonebook on my front doorstep is a nuiscance these days.  I’ve quit picking them up over the years to try […]

Have you ever had the joy of receiving this error message? The instance of the SQL Server Database Engine cannot obtain a LOCK resource at this time. Rerun your statement when there are fewer active users. Ask the database administrator to check the lock and memory configuration for this instance, or to check for long-running […]

In this post I will show you a simple way to see what parameters were used when an execution plan was compiled.  This can be valuable when trying to diagnose parameter sniffing problems. Our Example Plan The following is a screenshot of our example plan.  You can see the query is parameterized. How do I […]

Yes.  I’m always surprised when people perform index operations such as this as well as dropping and creating of indexes during the middle of the day.  These operations have an impact on performance.  In this post I’ll show you why index operations are blocking operations.  I will also discuss an option (only for Enterprise Edition […]

Earlier today I had a conversation with a colleague who thought statistics updates could cause blocking.  I have never seen this before, but since I consider this colleague to be pretty competent I second guessed myself.  I decided to put together a post as soon as I got home to verify this. To start with […]

On occasion you may have a query that starts picking up a bad plan as a result of an execution plan regression.  This can be for a variety of reasons (stats, parameter sniffing, etc).  If this occurs on a regular basis and you don’t have the luxury of query store, you can use sp_create_plan_guide_from_handle in […]

RESOURCE_SEMAPHORE waits occur when a query is unable to get enough memory to execute.  In this post I will describe how to see they are occurring.  I will also provide tips on ways to help reduce or eliminate them. How do I see them occurring? You can detect they are occurring by checking wait stats. […]

Have you ever seen a FETCH statement show up when monitoring via activity monitor, sysprocesses, dm_exec_requests, or name your monitoring tool of choice?  These surface when a process is programatically fetching through a cursor.  Most of the time the fetch statement isn’t of interest when performance tuning.  Instead it is of more use to see […]