I was recently asked what I thought about ORMs (Entity Framework, NHibernate, Dapper, etc) while we were looking at implicit conversion warnings in execution plans. Before I answered the question, I let them know that my answer is based on being a production DBA and the numerous performance problems I have had to troubleshoot that…
Right now, Erik and I are presenting at the 24 Hours of PASS. We’re talking about Last Season’s Performance Tuning Techniques. You can register and join us now. Wanna play along with us as we show how your performance skills might be a little out of date? Here’s the demos and the slides: Last Season's…
Better than nothing Yesterday it was announced that global temp tables were available in public preview for Azure. That means that unmodified versions of sp_BlitzCache (which uses a global temp table to hold a whole bunch of information) will be compatible up there. This is a nice addition for Azure, and an even nicer addition…
SQL Server 2016 Service Pack 1 brought us performance tuners all kinds of shiny goodies – like the ability to see wait stats inside a query’s actual execution plan. I was really excited when this first came out, but I keep seeing some real oddities. Let’s keep this one really simple: I’m using the Stack…
I’ve been using the Stack Overflow public database for my performance tuning demos for a few years now, and I just keep finding more reasons to love it. It’s got a few simple tables with a lot of data. The main ones are Users, Posts (questions & answers), Comments, Votes, and Badges, ranging from 1GB…
Mindless Self Promotion I liked writing this blog post so much that I wrote an entire presentation on it. If you’d like to see it at GroupBy, click the link and vote. Much has been written about this It’s probably one of the lowest hanging items a performance tuner can deal with. Don’t need all…
Facemaking You know when you think you know something, and the obviousness of it makes you all the more confident that you know it? That’s usually the first sign that there’s a giant gotcha waiting for you. And that’s what happened to me over the weekend. The setup I answered a question. And after I…
Oh, so you’re the one While SQL Server 2016 adoption is still pretty low, and 2017 still quite isn’t out yet, that’s no reason to not invest a few days of dev time into a stored procedure that is only usable by the smallest portion of SQL Server users. Right? Look, someone around here has…
SQL Server has three ways to get execution plans from the plan cache: sys.dm_exec_query_plan – around since SQL Server 2005 sys.dm_exec_text_query_plan – added in 2005 SP2 sys.query_store_plan – new in SQL Server 2016 And there’s an important problem with the first one. To show it, let’s take one of my many bad ideas, building queries that take 12+…
Is that a nice way of saying typo? People will often tell you to clearly alias your tables, and they’re right. It will make them more readable and understandable to whomever has to read your code next, puzzling over the 52 self joins and WHERE clause that starts off with 1 = 2. It can…
I hate that you can do this Here’s the thing: I’m mostly writing this because I didn’t know you could do it. But it’s cool, because it’ll reinforce some other concepts, and I’ll show you why you shouldn’t do it. I’m talking, of course, about index hints. To be more specific, hinting multiple indexes on…
Short winded Quite often people will inherit and rely on views written back in the dark ages, before people were aware of the deleterious effects that scalar valued functions can have on performance. Of course, for some people, it’s still the dark ages. Sorry, you people. Questions and answers So what are the side effects…
I love Query Plans No seriously, I love digging into query plans. Even writing XQuery to dig into them in sp_BlitzCache. I was both honored and horrified to take over development of it from Jeremiah. It’s a beast, but it’s my kind of beast. At around 4500 lines of code, when you want to make…
I think I’ve mentioned that the most fun part of new features is testing them with old ideas to see how they react. It occurred to me that if Adaptive Joins didn’t work with APPLY, I might cry. So, here goes nothin’! Cross Simple Cross Apply…ies can use Adaptive Joins, though at first glance there’s…
I know, I know Here we are in 2017, which means we’re about two years away from the next Ska revival effort, if my watch is correct. I hope it isn’t, but since Brent sent it to me with a note that says “please stop blogging” and it starts shocking me every time I open…
But is it faster? Now, I know. There are very few “always” things out there in SQL Server. This is also true for functions. A lot of the time — I might even say most of the time, inline table valued functions are going to be faster that scalar and multi statement table valued functions….
What I don’t want you to take away from this Is that I want you to start using Multi Statement Table Valued Functions all over the place. There are still problems with them. Backed by table variables Lots of hidden I/O cost Number of executions may surprise you One important current limitation (May-ish of 2017)…
Hot Diggety! After reading an excellent tip by Dmitry Pilugin about the new hint for forcing a parallel plan in SQL Server 2017, I figured I’d test it out on SQL Server 2016’s latest CU to see if it had been back ported yet. Good news! It has. Obviously. That’s the title of the blog…
Warm fuzzies I think this is how my mom would have felt if I went to college. You see, once you stop cargo culting around index fragmentation, and disk queue length, you start to realize which things are actually important to query performance. Things like statistics, and cardinality estimation. And, sure, having the right indexes…
Recently, Julie Lerman contacted me about some strange SQL that Entity Framework Core (EF Core) was generating. Now, EF Core is fairly new and works with Microsoft’s newest framework .NET Core. I haven’t had a chance to get my hands on EF Core yet so I was excited to see what it was doing. And of course…
