25May 2011 by Grant Fritchey 26 Comments

Oh ****!

SQL Server
Did you ever accidentally close SQL Server Management Studio? And, in closing SSMS, did you get the prompt that says “Save changes to the following items?” And did you, completely unthinkingly, with a query you had just been working on, hit Cancel? Yeah, me neither. What kind of idiot does that…. OK. I confess. I just did that. Silly thing it was, but I had just spent at least 1/2 an hour working on a query and now it was gone…. or was it? I had just run the query and had been looking at the results when I closed SSMS. Initially, I panicked and started thinking about how I could get the data back (somewhere there’s a file I’ve heard). Then it occurred to me, I had just been…
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02May 2011 by Grant Fritchey 3 Comments

I’ve got 99 Problems, but a disk ain’t one

nHibernate, Object Relational Mapping, SQL Server, T-SQL, Tools
Tom LaRock has a new meme for Meme Monday. It’s all about the problems caused in your system other than disks. Thankfully, despite the title, I don’t have to list 99 separate things, only 9, but you know what, 99 is possible. I’m going to present the problems. You find the solutions on your own today. Let’s go. Recompiles I’ve seen queries so big that they take more than three minutes to compile. That’s the edge case, but as an edge case it is educational. The most important thing to remember about recompiles is that they are driven by data changes. Once a threshold is reached on any given set of statistics, all queries referencing that set of statistics gets marked for recompile. The key words and tricky phrase here…
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06Apr 2011 by Grant Fritchey 4 Comments

SQL University: Index Usage

SQL Server, T-SQL
Greetings. Welcome once more to the Miskatonic University branch of SQL University. Does anyone know where to buy some camping equipment, cheap? I’ve been tagged to go an expedition to Antarctica and I need some cold weather gear a bit more substantial than my LL Bean boots. Evidently the last expedition found some caves in some mountains down there. Sounds like the perfect place to get away from all the crazy stuff that goes on here at Miskatonic. I mean, what could happen? Anyway, our last several talks have all been about indexes and indexing. One of the things that we haven’t talked about is how to tell if, how or when your indexes are being used. Starting with SQL Server 2005, and continuing to 2008 and R2, there has…
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04Apr 2011 by Grant Fritchey 6 Comments

SQL University–Recommendations for a Clustered Index

SQL Server, T-SQL
Welcome, SQL University Students to another extension class here at Miskatonic University, home to the Fighting Cephalopods (GO PODS!). Never mind the stains on the floor, or the walls…or those really nasty ones on the ceiling. There was a… oh what did the dean call it… an incident last week when one of the students had a little accident after reading Die Vermiss Mysteriis one too many times. But we’re not here to talk about arcane tomes and unspeakable horrors today. No, today we’re here to talk about clustered indexes. SQL Server storage is really predicated around the idea of clustered indexes. Don’t believe me? Let’s list a few places that require a clustered index: Partitioning. A table in SQL Azure In order to create XML indexes What about the…
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21Mar 2011 by Grant Fritchey 10 Comments

Communication

Object Relational Mapping, SQL Server, T-SQL, Tools, Visual Studio
It sure seems like there’s a lot of miscommunication between developers and database specialists. In fact, the communication can become so poor that outright hostility between the groups is common. At the end of the day we are all working towards a common goal, to add value to whatever organization we are working for. It's a shame that we all lose sight of this commonality and create such a false dichotomy between the groups. I think there are some ways that we, as database specialists, can use to attempt to cross that gap. Prior to being suborned to the dark side, I was a developer. I had a little over 10 years experience working in VB, Java & C#. I remember, distinctly, cursing our database team for being so problematic…
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17Mar 2011 by Grant Fritchey 4 Comments

Where does slow performance come from?

SQL Server, T-SQL, Visual Studio
I have my opinions and experience, and I’ve no doubt you have yours. Paul Randal (blog|twitter) has put up another one of his interesting surveys to try to collect our opinions and our experience. You should run right over to here and vote immediately. Now that you’ve completed that, I’ll tell you what I think. Based on my experience (neither particularly broad, nor particularly deep, but there has been quite a bit of it), I’ve mostly seen problems in code. When talking about databases, the T-SQL code. When talking about apps, the application code. This is followed not too far back by really poor database structures and poor indexing strategies. I’m sure other people have seen other things, but these really are the areas where I’ve seen the most problems. The one…
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14Mar 2011 by Grant Fritchey 1 Comment

ANSI Connection Settings

SQL Server, T-SQL
It’s reasonably well known that you can get different execution plans if you change the ANSI connection settings. But the question comes up, fairly often, how do you know what the settings are. It’s actually surprisingly simple. They’re stored right inside the execution plan, but they’re in one of the operators that most people ignore. Heck, I used to ignore this operator. Which operator is it you ask? Let’s find out. Let’s use AdventureWorks2008R2 (because I’m lazy). We’ll call one of the stored procedures there like so: EXEC dbo.uspGetBillOfMaterials @StartProductID = 0, -- int     @CheckDate = '2011-03-10 02:31:39' – datetime If you execute this with “Include Actual Execution Plan” enabled you’re likely to end up with the following execution plan: Don’t worry about the fact that you can’t really…
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07Mar 2011 by Grant Fritchey 1 Comment

Execution Plan Stability

SQL Server
I’ve talked before about one of the primary things that the Query Optimizer team at Microsoft tries to avoid, regressions. Basically, they want a plan that worked well in SQL Server 2005 to work well in SQL Server 2008 R2. What’s more, they want everything to work well between service packs, updates and cumulative updates. Ever wonder how they do it? Well, they cheat. OK, that’s mean and not entirely accurate, but it gets the idea across. No, what they do is, identify when they have a breaking change, when they’ve got a special cumulative update or service pack that fixes some bad behavior, but that can cause plans to “break,” they wall it off. Note, in most cases, this “breakage” is actually a question of plans working correctly, but…
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14Feb 2011 by Grant Fritchey 6 Comments

DBA 101: Why Don’t People Run Backups

SQL Server, T-SQL
It happened multiple times this week. It happens multiple times every week. Some poor soul is posting on a message board, usually with the heading “URGENT” (why that one word so frequently, I just don’t know), that they deleted production data/dropped a production table/updated production data/dropped a database/received a data corruption error/whatever. Now, they need to get the data back. “URGENT, What do I do now?” And so you ask, as you should, what kind of backups do you have? Over and over the answer is: “Backups? What’s a backup” or “Oh, the system guys backup of the MDF files every night” or “We don’t really need those” or “We don’t have room to back up our databases” or some other excuse that simple comes down to, we didn’t set…
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08Feb 2011 by Grant Fritchey 8 Comments

TSQL Tuesday #15–Automation in SQL Server

SQL Server, T-SQL
Automation is the separation point for the professional DBA from the amateur. That makes this a very important topic. Thanks to Pat Wright (blog|twitter) for coming up with something great to write about and hosting the event. I recently wrote an article for the SQL Spackle series over on SQL Server Central on how to “Set Up and Schedule a Server Side Trace.” That covers well what to do to set up a trace on your system so that you can automate it. But I think I left out a few details that I think are worth pointing out here. The basics on creating the Server Side Trace using Profiler and scheduling it using SQL Agent are well covered in the article. The extra areas I want to address are…
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