The first time you see a new execution plan that you're examining to fix a performance problem, something broken, whatever, you should always start by looking at the first operator. First Operator The first operator is easily discerned (with an exception). It's the very first thing you see in a graphical execution plan, at the top, on the left. It says SELECT in this case: This is regardless of how you capture the execution plan (with an exception). Whether you're looking at an execution plan from the plan cache, Query Store, or through SSMS, the execution plan, regardless of complexity, has this first operator. In this case, it says UPDATE: If you get an execution plan plus runtime metrics (previously referred to as an "actual" execution plan), you'll still see…
A question that I've seen come up frequently just recently is, how to track CPU use over time. Further, like a disk filling up, people want to know how to predict their CPU usage, so that they can easily decide "now is when I upgrade the hardware". Well, the bad news is, that ain't easy. CPU Use Over Time There are a bunch of ways to look at processor usage. The simplest, and probably most common, is to use the Performance Monitor counters such as '% Processor Time'. Query this, you can get an average of the processor usage at a moment in time. Ta-da! Fixed it. I thought you said this was hard Grant. Well, hang on. Are you running on a single processor machine? If so, cool, maybe…
I consider myself to be the most responsible for making such a huge deal about the differences between what is labeled as an Estimated Plan and an Actual Plan. I walked it back in the second edition of the Execution Plans book. Hugo and I completely debunked the issue in the third edition of the Execution Plans book. That is the one you should all be referencing now. As I like to joke, the guy who wrote the first two editions of the book was an idiot (and lest anyone take offense, let's be clear, I'm the idiot). Now, I'm trying my best to make this whole issue more clear. Let's talk about the "different" plans you can capture in SQL Server. Estimated Plan This is where you have a…
Not really, but sort of. The beauty of containers, at least in a dev/test environment, is the ability to spin them up while you need them and then throw them away when you're done. Containers give you a bunch of functionality not otherwise available through a VM. However, once you've spun up a container, they're so dull. Why Are Containers Boring Grant? I'm so glad you asked. Last week I was presenting at SQLIntersection (great show, you should consider attending). I was talking about Query Store in SQL Server 2019. One person in the audience asked, "Can Query Store run inside a container?" I responded, "Great question, let's check." I then switched over to VS code to show this: docker run ` --name DemoSharedVol ` -p 1460:1433 ` -e "ACCEPT_EULA=Y"…
It's a somewhat late addition, but I have an all-day Training Day at SQLBits. It takes place on Thursday, February 28th. You can read all about it on the SQLBits web site. I want to take a moment here to expand on the information that we're going to cover. I think the abstract does a good job of conveying what we'll be doing all day, but I figured a little more detail won't hurt. Query Tuning is Hard This is the very first thing I talk about. Query tuning is hard. I've got a nearly 1,000 page book on the topic, which should give you an idea of just how much material there is to cover. With the training day I've decided to focus on the tools that Microsoft gives…
The question that came up during a recent class I was teaching was: What if you have a plan guide to get the plan you want, but then decide, instead of using the plan guide, you'll just force the plan? Ummmm…. No idea. Let's test it. First, Create a Plan Guide I have a couple of queries I use to teach about how statistics affects plan choice, so we'll use that here. I'm going to also define and create a plan guide that makes this plan use a small row count for all queries against it: CREATE OR ALTER PROC dbo.AddressByCity @City NVARCHAR(30) AS SELECT a.AddressID, a.AddressLine1, a.AddressLine2, a.City, sp.Name AS StateProvinceName, a.PostalCode FROM Person.Address AS a JOIN Person.StateProvince AS sp ON a.StateProvinceID = sp.StateProvinceID WHERE a.City = @City; GO…
Four years ago, after a bunch of dithering and some negotiations with Tony Davis, my editor, I started to update my book, SQL Server Execution Plans. We managed to convince Hugo Kornelis to be the tech editor. I started to do the real writing in early 2015. I was most of the way through a first draft and no one liked it. Tony was unhappy. Hugo was unhappy. I was unhappy. I was just trying to update the existing book, SQL Server Execution Plans. It wasn't working. We all came to the conclusion that the old book was wrong. Not simply in a technical sense, although there was a lot of that, but in a structural sense. So we started rearranging things. SQL Server 2014 came out, but I was…
I've posted a number of new videos to the Youtube channel that might be of interest if you're a data professional. First up, I've started migrating my Database Fundamentals posts over to Youtube as SQL Server Fundamentals. The first one is available: [embedyt] https://www.youtube.com/watch?v=NHkzj9ZRhbk[/embedyt] Speaking of DBAs, the job is not going away, but it is changing. Find out how to survive the change: [embedyt] https://www.youtube.com/watch?v=loUwmKQ_Eg4[/embedyt] Would you like to know how the Query Store works? Here's a getting started video: [embedyt] https://www.youtube.com/watch?v=XK8rBO9R43c[/embedyt] I also have a good video on how to combine capturing query metrics along with wait statistics using Extended Events: [embedyt]https://www.youtube.com/watch?v=nYyTSxry03A&t=97s[/embedyt] Wait until you see what Trace Flag 7412 can do for you. It's very cool. [embedyt]https://www.youtube.com/watch?v=ei2zJwZyRic&t=79s[/embedyt] Finally, if you are interested in attending one of my…
I place a lot of emphasis on capturing actual execution plans because of the runtime metrics, but with Trace Flag 7412, we don't need the plan. This is great news, because capturing execution plans, even using extended events, is an expensive proposition. However, using either the query_thread_profile event, or, Trace Flag 7412, we can get the runtime metrics without the plan. Trace Flag 7412 Here's how it works.You can either be running the extended event, query_thread_profile (a debug event, but one documented and supported by Microsoft) or, enable the Trace Flag 7412. I like to use the extended event in a targeted fashion to easily see behaviors on a query without having to capture the plan. You can even capture the information and then combine it with an estimated plan…
I'm desperately working to finish up a new version of my book on Execution Plans. We're close, so close. However, you do hit snags. Here's one. My editor decided to change one of my queries. I used a local variable so that I got one set of behaviors. He used a hard-coded value to get a different set. However, the really interesting thing was that his query, at least according to the execution plan, went to simple parameterization. Or did it? Simple Parameterization The core concept of simple parameterization is easy enough to understand. You have a trivial query using a hard-coded value like this: SELECT * FROM Person.Person AS p WHERE p.BusinessEntityID = 42; The resulting execution plan looks like this: The initial, graphical, pointer that we're seeing parameterization…