ICYMI – Adding Filtered Indexes, Wait Statistics, Comparing Windows Azure Performance

A digest of great articles originally appearing at SQLPerformance.com. Dirty Secrets of the CASE Expression Aaron Bertrand ( b | t ) of SQL Sentry takes a look at some unexpected behavior with the CASE expression and some of its derivatives. Did you know that Aaron is both an uber-genius and a curling fanatic? Improbable, I know. An Unexpected Side-Effect of Adding a Filtered Index Paul White’s ( b | t ) deep dive post explains some of the limitations in the special use and usefully special kind of index, the filtered index. When applied in the appropriate scenarios, filtered indexes … [Read more...]

ICYMI – Read Committed Snapshot Isolation, How Automatic Updates to Statistics Can Affect Query Performance, #temp table

A digest of great articles originally appearing at SQLPerformance.com. Read Committed Snapshot Isolation Paul White ( b | t ) has been doing a phenomenal series on SQL Server behavior under each of the major isolation levels. This particular post details the inner workings of READ COMMITTED SNAPSHOT, but there are more articles on this specific isolation level as well. I recommend Paul’s content generally, but this is an especially good series of articles, if you’re not up to speed on isolation levels and how they can alter SQL Server’s default performance. How Automatic Updates to … [Read more...]

ICYMI – Avoiding Performance Tuning, Wait Statistics, Incremental Statistics

A digest of great articles originally appearing at SQLPerformance.com. Avoiding Knee-Jerk Performance Tuning Paul Randal of SQLskills.com starts a new series on knee-jerk troubleshooting, discussing many areas where SQL Server folks jump to conclusions when trying to fix a performance issue. Knee-Jerk Wait Statistics: SOS_SCHEDULER_YIELD Paul Randal continues his series on knee-jerk performance troubleshooting. In this post, he talks about SOS_SCHEDULER_YIELD, and how to determine whether it is a wait to worry about in your scenario. SQL Server 2014 Incremental Statistics Benjamin … [Read more...]

ICYMI – Troubleshooting SQL Performance Issues, Missing Indexes, and DROP and TRUNCATE TABLE

A digest of great articles originally appearing at SQLPerformance.com. Troubleshooting SQL Server CPU Performance Issues This outstanding article from Joe Sack ( b | t ) of SQLskills.com steps you through a methodical and insightful series of DMVs and queries that can pinpoint CPU issues on your SQL Server instances. Don’t just blindly create those "missing" indexes! Our own Aaron Bertrand ( b | t ) discusses ways to get better and more balanced information used in decisions about creating new indexes than offered as suggestions by native SQL Server tools. The Myth that DROP and … [Read more...]

ICYMI: Parameter Sniffing, Friends with Partition Benefits, and SELECT INTO Parallelism – SQL Server Performance

Great topics for further reading about tuning SQL Server performance: Exploring SQL Server 2014 SELECT INTO Parallelism Joe Sack (b | t) provides us with a peak into the performance improvements and new behaviors of SQL Server 2014 in the way it can now parallelize large SELECT INTO operations. Parameter Sniffing, Embedding, and the RECOMPILE Options Parameter sniffing is a term used to describe the processes by which SQL Server attempts to reuse execution plans where certain parameters might frequently change. If you’re only familiar in passing with the term, it probably has … [Read more...]

ICYMI: Partitioning Advice, Purging Data Bloat, and an example of TVF Misbehavior – SQL Server Performance

Here are some oldies, but goodies that I recommend you read: Two Partitioning Peculiarities and Aggregates and Partitioning Most of us know that partitions are one of the best ways to scale very large databases or very large IO workloads.  However, there are risks, two of which are explored in detail by internals master Paul White (b | t). The Price of Not Purging Holding on to data long after its useful lifespan contributes to bloat and added preventative maintenance headaches. Read this informative post from Erin Stellato (b | t), of SQLSkills.com, where you’ll find a lot of useful … [Read more...]

ICYMI: Troubleshooting CPU, Logging Myths, Missing Indexes, and Query Tuning Examples

Great Articles at SQLPerformance.com There are so many good articles from SQLPerformance.com this ICYMI article that it’s hard to know which are best to highlight in the limited space. So, I’ll be arbitrary and simply choose a few of my favorite entries as well look back: Troubleshooting SQL Server CPU Performance Issues This outstanding article from Joe Sack (b | t) of SQLSkills steps you through a methodical and insightful series of DMVs and queries that can pinpoint CPU issues on your SQL Server instances. Don’t just blindly create those “missing” indexes! Aaron Bertrand (b | … [Read more...]

ICYMI: the Halloween Problem and DBCC CheckConstraints – SQL Server Performance

Don't miss these great articles on SQLPerformance.com from the industry’s top experts: A Look At DBCC CHECKCONSTRAINTS and I/O Erin Stellato (b | t) of SQLskills takes a deep look into the SQL Server performance impact, especially I/O, of running DBCC CHECKCONSTRAINTS, including explaining why some check methods may consume a lot more I/O than others. The Halloween Problem, Part 1 of a 4-Part Series Paul White (b| t) provides unique insight into a long-standing data modification issue, the infamous Halloween Problem.  Much has been written over the years about understanding and … [Read more...]

ICYMI: Ten Query Techniques Every SQL Programmer Should Know (Video)

Update 09-Mar-2015: The original PASS links I provided were behind a firewall. Thanks reader MMcDonald, we have a working link on YouTube. One of the benefits of joining PASS is that you get access to their expansive library of conference videos. (Membership is free. So join now. What'dya want, a hand-written invitation?!?) I want to take a moment to point out a good one that I think anybody who writes SQL code on SQL Server should watch. If you know anything about the staff here at SQL Sentry, then you’re probably expecting me and my colleague Microsoft MVP Aaron Bertrand (b | t) to be … [Read more...]

The SQL Sentry forum for SQL Statement Tuning

The SQL Sentry forum for SQL Statement Tuning Have you ever looked at our community site specifically dedicated to helping users tune their SQL queries, http://answers.SQLPerformance.com? You can easily upload an execution plan directly from our free Plan Explorer tool or from good ol' SQL Server Management Studio to the discussion forum.  Once uploaded, our internal team and forum members will provide plenty of tips and input on how to improve the plan and/or explain what the plan is actually doing.  The renown SQL execution plan expert, Paul White (b|t), is the moderator of the site. But … [Read more...]