Runtime Metrics In Execution Plans

SQL Server 2016
Capturing query execution metrics is much easier now that you can see the runtime metrics in execution plans when you're using SQL Server 2016 SP1 or better in combination with SQL Server Management Studio 2017. When you capture an actual plan (using any method), you get the query execution time on the server as well as wait statistics and I/O for the query. Fundamentally, this changes how we can go about query tuning. Runtime Metrics To see these runtime metrics in action, let's start with a query: SELECT p.LastName, pp.PhoneNumber, pnt.Name FROM Person.Person AS p JOIN Person.PersonPhone AS pp ON pp.BusinessEntityID = p.BusinessEntityID JOIN Person.PhoneNumberType AS pnt ON pnt.PhoneNumberTypeID = pp.PhoneNumberTypeID WHERE pnt.PhoneNumberTypeID = 3; We'll run this query and capture the Actual Execution Plan using SSMS 2017. The changes…
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Bad Parameter Sniffing Decision Flow Chart

SQL Server 2005, SQL Server 2008, SQL Server 2012, SQL Server 2014, SQL Server 2016
Lots of people are confused by how to deal with bad parameter sniffing when it occurs. In an effort to help with this, I'm going to try to make a decision flow chart to walk you through the process. This is a rough, quite rough, first draft. I would love to hear any input. For this draft, I won't address the things I think I've left out. I want to see what you think of the decision flow and what you think might need to be included. Click on it to embiggen. Thanks to the attendees at my SQLSaturday Louisville pre-con for the great questions and the inspiration to get this done. Thank you in advance for any and all feedback.
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IT/Dev Connections 2017

Database Lifecycle Management, DevOps, SQL Server 2016
I'm very honored to be able to announce that I am going to be speaking at IT/Dev Connections in San Francisco. I'm not just speaking there, I'm presenting an all day seminar on the tools needed for query tuning. The title does say SQL Server 2016, but most of the tools I'll cover can be used be used from SQL Server 2012 to SQL Server 2017. I'll also throw in a few SQL Server 2017 tools just to spice things up. If you're looking for a lot of information about how to get your query tuning done, I'm here to help. I'm also going to be talking about two other favorite topics of mine, DevOps and Monitoring. Please check it out and join me at this event.
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I Love Entity Framework

DevOps
I love Entity Framework. I also like (not love) nHibernate. That's right, as a DBA and data professional, I'm telling you I love Object/Relational Mapping tools (ORM). I think this is a technology set that the DBA needs to more tightly embrace. Let me tell you why. Most of the Queries I know that the biggest pushback against Entity Framework (EF) and it's fellow ORM tools is that they generate crap code. I know this to be true. I've seen it. ORM tools can, and do, generate seriously poor T-SQL. That's not to mention the N+1 problem and a few others. However, as you see from the article in that link, these problems and how to avoid them are very well defined. You don't have to suffer from the issues.…
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Data About Execution Plans

SQL Server 2005, SQL Server 2008, SQL Server 2012, SQL Server 2014, SQL Server 2016
If you look at the Properties for the first operator of a graphical execution plan, you get all sorts of great information. I've talked about the data available there and how important it is in this older post. Checking out the properties of a plan you're working on is a fundamental part of tuning that plan. What happens when you don't know which plan you should be working on? What do you do, for example, if you want to see all the plans that are currently using ARITHABORT=FALSE or some other plan affecting setting? The "easy" answer to this question is to run an XQuery against the XML of the query plan itself. You can identify these properties and retrieve the appropriate values from within the plan. However, XQuery consumes quite a…
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Reinforcing the Importance of Statistics on Row Estimate

SQL Server 2005, SQL Server 2008, SQL Server 2012, SQL Server 2014, SQL Server 2016, TSQL
I recently wrote an introductory post about the importance of statistics. I just received a reinforcement on how important they are during my own work. Bad Estimate I hit a weird problem while I was setting up a query to illustrate a point (blog to be published next week). Let's take the basis of the problem and explain it. I wanted data with distribution skew, so I ran this query to find out if there was a wide disparity between the top and bottom of the range: SELECT i.BillToCustomerID, COUNT(i.BillToCustomerID) AS TestCount FROM Sales.Invoices AS i GROUP BY i.BillToCustomerID ORDER BY TestCount ASC; Sure enough, the bottom of the range returned three (3) rows and the top returned 21,551. If I then run a query to retrieve just a few rows…
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SELECT * Does Not Hurt Performance

SQL Server 2005, SQL Server 2008, SQL Server 2012, SQL Server 2014, SQL Server 2016, TSQL
I read all the time how SELECT * hurts performance. I even see where people have said that you just have to supply a column list instead of SELECT * to get a performance improvement. Let's test it, because I think this is bunkum. The Test I have here two queries: SELECT * FROM Warehouse.StockItemTransactions AS sit; --and SELECT sit.StockItemTransactionID, sit.StockItemID, sit.TransactionTypeID, sit.CustomerID, sit.InvoiceID, sit.SupplierID, sit.PurchaseOrderID, sit.TransactionOccurredWhen, sit.Quantity, sit.LastEditedBy, sit.LastEditedWhen FROM Warehouse.StockItemTransactions AS sit; I'm basically going to run this a few hundred times each from PowerShell. I'll capture the executions using Extended Events and we'll aggregate the results. The Results I ran the test multiple times because, funny enough, I kept seeing some disparity in the results. One test would show a clear bias for one method, another test would…
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Correlated Datetime Columns

SQL Server 2005, SQL Server 2008, SQL Server 2012, SQL Server 2014, SQL Server 2016, TSQL
SQL Server is a deep and complex product. There's always more to learn. For example, I had never heard of Correlated Datetime Columns. They were evidently introduced as a database option in SQL Server 2005 to help support data warehousing style queries (frequently using dates and times as join criteria or filter criteria). You can read up on the concept here from this older article from 2008 on MSDN. However, doing a search online I didn't find much else explaining how this  stuff worked (one article here, that didn't break this down in a way I could easily understand). Time for me to get my learn on. The concept is simple, turning this on for your database means that dates which have a relationship, the example from MSDN uses OrderDate and…
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Query Store and What Happened Earlier On Your Server

SQL Server 2016, TSQL
Here's a great question I received: We had a problem at 9:02 AM this morning, but we're not sure what happened. Can Query Store tell us? My first blush response is, no. Not really. Query Store keeps aggregate performance metrics about the queries on the database where Query Store is enabled. Aggregation means that we can't tell you what happened with an individual call at 9:02 AM... Well, not entirely true. The aggregations that Query Store keeps are actually broken up into intervals that you can control. The default interval is 60 minutes. This means that the information stored in the DMV covers sets of intervals. This means that if, at 9:02AM, you had a query, or queries, that ran considerably longer than normal, you may be able to take a look…
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Query Store and Plan Forcing: What Do You Use It For

SQL Server 2016, TSQL
If you're working with Azure SQL Database or you've moved into SQL Server 2016, one of the biggest new tools is the Query Store. It provides a mechanism of capturing query performance over time and persisting it with the database. You also get the execution plans for those queries. Finally, you can choose to have the Query Store override execution plan selection by use of Plan Forcing. I've written about Query Store a few times: Query Store, Force Plan and "Better" Plans Query Store, Force Plan and Dropped Objects Precedence Goes to Query Store or Plan Guide Query Store, Forced Plans and New Plans Query Store and Optimize For Ad Hoc Query Store and Recompile Finding Your Query in Query Store Removing All Query Store Data Monitor Query Performance OK,…
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