07Feb 2012 by Grant Fritchey 6 Comments

Avoiding Bad Query Performance

T-SQL
There’s a very old saying, “When you find yourself in a hole, stop digging.” And my evidence today is: That’s certainly not the hairiest execution plan I’ve seen. In some ways, it’s not all that horrible. But it sure is evidence that someone was down in a hole and they were working that shovel hard. If you’re interested, most of the operators are scans against a table variable that’s 11 million rows deep. There are also table spools chugging away in there. And the select statement only returns 1500 rows. Please, stop digging.
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23May 2011 by Grant Fritchey 6 Comments

SQL Azure Query Tuning

Azure
SQL Azure is still SQL Server at the end of the day. This means it is entirely possible to write queries against SQL Azure that really… what’s a good word… stink. So what do you do? It’s all in the cloud. You couldn’t possibly tune the queries, right? Wrong. Many of the same tools that you have available to you, such as execution plans and dynamic management objects, are still available in SQL Azure. Let’s talk DMOs for a second. First off, don’t make the mistake I did of trying to run these outside the context of a specific database on SQL Azure. You’ll get extremely inconsistent results, trust me on this. Anyway, I did a quick run-down on some of the most used DMOs for performance tuning, the sys.dm_exec_*…
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17Feb 2011 by Grant Fritchey 1 Comment

SQL Rally

PASS
I believe I’ve been far too quiet about this event. In May, in Orlando Florida, there will be a two day SQL Server conference called SQL Rally put on by PASS. This is a somewhat unique event since the sessions have all been chosen by the community. That’s right, a series of votes was held online (and if you missed it, you weren’t paying attention) so that all of you were able to decide which sessions you’d most like to see. I’m bringing this up because, now, it’s up to you to register and go. Did I mention the pre-con? No? Well, there will be a one-day pre-conference seminar. There are multiple sessions of excellent material at the pre-con. These were also voted on by the community. One of them…
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06Dec 2010 by Grant Fritchey 12 Comments

Review: Idera SQL Doctor

SQL Server, T-SQL, Tools
Recently, a co-worker practically slammed me up against the wall, exclaiming “You have to check out this new tool, right now!” The piece of software he was so excited about was Idera’s SQL Doctor. Based on this assaultrecommendation, I decided to take a little time & look the software over. SQL Doctor, as the name implies, is a diagnostic tool. It runs a set of best practice rules against your server, your databases and your code. As the rules are executed, your system’s compliance with these best practices is evaluated and an interactive report is generated. With the report you can drill down on various aspects of your system to see where you may have gone wrong. All that sounds very clinical, just laid out like that. But the fact…
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28Oct 2010 by Grant Fritchey 1 Comment

SQL Rally: Performance Tuning Abstract

PASS
I get the call, you get the call, everyone gets the call. "Hey, my app/procedure/query/report is running slow." Now what do you do? You go to my full day session at SQL Rally, that's what. Assuming you vote for it. I didn't post the abstract I submitted for the SQL Rally before because I thought that it would be redudant. However, since it's not right off the voting page (unless they updated it since I voted), if you're interested, here's what I thought I would do for a day. If it sounds good to you, please go here and vote for it. One of the most common problems encountered in SQL Server is the slow running query. Once a query is identified as performing poorly, DBAs and developers frequently don’t understand how…
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05Apr 2010 by Grant Fritchey 25 Comments

nHibernate, First Look at TSQL

nHibernate
I've blogged in the past about the nHibernate project that has been going on at my company for the last eighteen months. Prior to today, I have only seen the database generated by nHibernate. But today I finally started seeing some TSQL code. My first impressions... oy! There are two levels of concern coming out of the gate. First, it appears that some of the programming decisions, completely independent of nHibernate, are going to cause problems. Second, it appears we're going to be hitting issues with nHibernate. First, the programming decision. I've been using Confio to monitor this server for a few days now (look for upcoming posts on my eval of Confio). Only one day has captured any real activity from the nHibernate team (and yes, I'm basically spying on…
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22Sep 2009 by Grant Fritchey No Comments

Gila Monster on Estimated vs. Actual Row Counts

SQL Server, T-SQL
I don't generally do lots of blog aggregation and cross post linking & stuff. It's just not something I'm that into. However, this time is an exception. Gail Shaw, Gila Monster to those who hang on out SQL Server Central, has posted an excellent explanation of times when Estimated and Actual row counts vary for a reason. I'm one of those who emphasises that differences between estimated & actual is an indication of... something. It could be out of date or missing statistics or it could be caused by query language like multi-statement table valued functions, but it's usually and indication of a problem. Except when it's not. Read Gail's explanation for more.
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11Sep 2009 by Grant Fritchey No Comments

LaRock on Monitoring

SQL Server, T-SQL
Since I just spent a bit more than half of my 24 Hours of PASS presentation on tuning queries talking about monitoring performance, you could probably tell that I think that the two are inextricably linked. I'm not alone. Tom LaRock has put a post on why it's important to understand the extent of your problem prior to attempting to fix it. It's absolutely spot-on and a must read. Remember, if someone says performance on a system you manage is slow, you have to ask, as compared to what? You need to understand what "normal" performance is on your system in order to arrive at the ability to identify a particular process as performing in an abnormal manner. That's not to say that you couldn't tune a query in complete…
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17Jul 2009 by Grant Fritchey 15 Comments

Execution Plan Compile Termination

SQL Server, T-SQL
Recently I've been seeing a lot of people with bad execution plans, desperately trying to tune them, but they were unable to explain why they had such bad plans. More often than no these were larger queries, with a number of derived tables, CTE's, CROSS APPLY, etc. In most cases the statistics appeared to be fine (this is usually checked by comparing estimated & actual rows within the operations in the execution plan) and the plans themselves didn't look crazy, but the execution plans were flat out, not good. If you're looking at a plan and it doesn't make much sense, one option that most people don't check... SQL Server didn't have enough time to complete optimization. The optimizer is a pretty amazing bit of code. The scary volume of…
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