Query Optimizer and Data Definition Language Queries

Data Definition Language queries don’t go through the optimizer, right? While normally, my short answer to this question in the past would have been, yes. However, with testing comes knowledge and I want to be sure about the statement. I’m working with a team of people to completely rewrite the SQL Server Execution Plans book. We’...

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Query Store, Force Plan and “Better” Plans

I am endlessly fascinated by how the Query Store works. I love teaching it at every opportunity too. Plus, almost every time I teach it, I get a new question about the behavior that makes me delve into the Query Store just a little bit more, enabling me to better understand how it works. I […]

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Azure SQL Data Warehouse Execution Plans

Azure SQL Data Warehouse can sometimes feel like it’s completely different from SQL Server, but under the covers, it is still (mostly) SQL Server and it does have execution plans. Let’s take a look at one. I’ve created a new SQL Data Warehouse using the sample database available on the portal, AdventureWorksDW. Here’s a quer...

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Query Store, Force Plan and Dropped Objects

I love the Query Store. Seriously. It’s a huge leap forward in the capabilities of Azure SQL Database and SQL Server in support of performance monitoring and query optimization. One of my favorite aspects of the Query Store is the ability to force plans. Frankly though, it’s also the scariest part of the Query Store. […]

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Common Table Expression, Just a Name

The Common Table Expression (CTE) is a great tool in T-SQL. The CTE provides a mechanism to define a query that can be easily reused over and over within another query. The CTE also provides a mechanism for recursion which, though a little dangerous and overused, is extremely handy for certain types of queries. However, the […]

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Query Store and Recompile

One of the many advantages of SQL Cruise is the ability to have enough time during a presentation to be able to answer questions from the people there in great detail. One question came up while I was showing the new functionality of Query Store (available soon in SQL Server 2016, available right now in […]

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Generating Estimated Plan and the Plan Cache

Does generating an Estimated Plan cause that plan to be loaded into the plan cache? No.   What? Still here? You want more? Proof? Fine. Let’s first run this bit of code (but please, not on your production server): DBCC FREEPROCCACHE(); That will remove all plans from cache. Now, let’s take this query and generate […]

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Differences Between Actual & Estimated Plans

I have, in the past, made way too much of the need for Actual Plans when doing performance troubleshooting. The primary reason for this is to get the Actual Plan in order to see the differences between the Actual and Estimated Row Counts as a means of understanding how the optimizer saw the data. But, is […]

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“Pretty Plans vs. Performance” or “Grant Gets Pwned”

If you get an execution plan that looks like this: I wouldn’t blame you for immediately thinking about query tuning. Especially if the code that generated it looks like this: SELECT soh.OrderDate, sod.OrderQty, sod.LineTotal FROM Sales.SalesOrderHeader AS soh INNER JOIN Sales.SalesOrderDetail AS sod ON sod.SalesOrderID = soh.SalesOrderID WHER...

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The Utility of Execution Plans in Natively Compiled Procedures

I’m actually having problems identifying the utility of execution plans when working with natively compiled procedures. Or, put another way, why bother? I’ve posted a couple of times on natively compiled procedures and SQL Server execution plans. I’ve found the differences interesting and enlightening, but I’m seriously ques...

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