25Mar 2014 by Grant Fritchey 12 Comments

Save Money On Your Training Server

Azure, T-SQL
You can spend less money. Some of us are lucky. We work for very large corporations who can easily set aside a spare desktop or even space on a rack for a server on which we can train. Others of us are not as lucky. We work for smaller organizations that have to be more careful with their money. Not only do we not get the extra machine to train on, but our laptops could be weak things that can't run two or more VMs. In this case, how can you go about learning stuff? Spend your own money? Sure, it's an option. There are some very cheap servers available out there that won't cost you even $1000 dollars to set up. And for pretty cheap you can buy some…
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19Mar 2014 by Grant Fritchey No Comments

Query Tuning Near You

SQL Server, T-SQL
It really is so much easier to just throw hardware at badly performing databases. Just buy a bigger, faster server with more and faster disks and you can put off doing tuning work for another 6-9 months, easily. But, for most of us, sooner or later, our performance problems get so big or, we just don't have any more money to spend, and we're stuck. We have to tune the queries. And frankly, query tuning is a pain in the nether regions. But, after you've tuned queries 20 or 30 times, you start to recognize the patterns and it gets easier (never easy, just not as hard). But, if you haven't done it 20 or 30 times, what do you do? My suggestion, talk to someone who has done it…
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18Mar 2014 by Grant Fritchey 2 Comments

Finding Mistakes

SQL Server, T-SQL
Ever had that moment where you start getting errors from code that you've tested a million times? I had that one recently. I had this little bit of code for pulling information directly from query plans in cache: WITH XMLNAMESPACES(DEFAULT N'http://schemas.microsoft.com/sqlserver/2004/07/showplan'), QueryPlans AS ( SELECT RelOp.pln.value(N'@PhysicalOp', N'varchar(50)') AS OperatorName, RelOp.pln.value(N'@NodeId',N'integer') AS NodeId, RelOp.pln.value(N'@EstimateCPU', N'decimal(10,9)') AS CPUCost, RelOp.pln.value(N'@EstimateIO', N'decimal(10,9)') AS IOCost, dest.text FROM sys.dm_exec_query_stats AS deqs CROSS APPLY sys.dm_exec_sql_text(deqs.sql_handle) AS dest CROSS APPLY sys.dm_exec_query_plan(deqs.plan_handle) AS deqp CROSS APPLY deqp.query_plan.nodes(N'//RelOp') RelOp (pln) ) SELECT qp.OperatorName, qp.NodeId, qp.CPUCost, qp.IOCost, qp.CPUCost + qp.IOCost AS EstimatedCost FROM QueryPlans AS qp WHERE qp.text = 'some query or other in cache' ORDER BY EstimatedCost DESC; I've probably run this... I don't know how many times. But... I'm suddenly getting an error: Msg 8114, Level 16, State 5,…
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11Mar 2014 by Grant Fritchey 4 Comments

sp_updatestats Is Not Smart

SQL Server, T-SQL
No, I don't mean the use of sp_updatestats is not smart. It's a fine, quick mechanism for getting statistics updated in your system. But the procedure itself is not smart. I keep seeing stuff like "sp_updatestats knows which statistics need to be updated" and similar statements. Nope. Not true. Wanna know how I know? It's tricky. Ready? I looked at the query. It's there, in full, at the bottom of the article (2014 CTP2 version, just in case yours is slightly different, like, for example, no Hekaton logic). Let's focus on just this bit: if ((@ind_rowmodctr <> 0) or ((@is_ver_current is not null) and (@is_ver_current = 0))) The most interesting part is right at the front, @ind_rowmodctr <> 0. That value is loaded with the cursor and comes from sys.sysindexes and the rowmodctr column…
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27Feb 2014 by Grant Fritchey 2 Comments

Let’s Talk Query Tuning

Professional Development, SQL Server, T-SQL
I spend quite a bit of time writing about query tuning on this blog. I've written (re-written and am actively re-writing) books on query tuning. But what I like most is talking about query tuning. I love giving sessions at various events on different aspects of query tuning, but, what I like the most is spending a whole day, trying to do a complete brain dump to get as much information out there as possible. Sound attractive? Then I've got a great deal for you. Come to Louisville on June 20th, 2014. We will talk query tuning at length. You have a specific question? Let's get it answered. Then, the next day, we can all go to SQL Saturday 286 there in Louisville to get more learning and some serious…
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18Feb 2014 by Grant Fritchey 14 Comments

The CASE Statement and Performance

SQL Server, T-SQL
In case you don't know, this query: UPDATE dbo.Test1 SET C2 = 2 WHERE C1 LIKE '%33%'; Will run quite a bit slower than this query: UPDATE dbo.Test1 SET C2 = 1 WHERE C1 LIKE '333%'; Or this one: UPDATE dbo.Test1 SET C2 = 1 WHERE C1 = '333'; That's because the second two queries have arguments in the filter criteria that allow SQL Server to use the statistics in an index to look for specific matching values and then use the balanced tree, B-Tree, of the index to retrieve specific rows. The argument in the first query requires a full scan against the index because there is no way to know what values might match or any path through the index to simply retrieve them. But, what if we…
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11Dec 2013 by Grant Fritchey 4 Comments

SQL Server 2014 Backup to URL

Azure, T-SQL
I'm absolutely in love with the concept of being able to create a backup directly to a protected, off-site location. Yeah, you can spend all sorts of money on terribly wonderful technology to enable that within your enterprise. And if you have that kind of money, great. But, what if you're like most everyone else and you just want a little more protection without mortgaging the house? Let's take a look at one possibility, backup to URL. There have been ways to backup to hosted storage, whether it was DropBox, AWS or Azure blob storage, for quite a while. But, every method I tried out involved setting up some type of drive on your system. As soon as you had your K:\ drive mapped out to AWS or whatever, you…
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29Oct 2013 by Grant Fritchey 1 Comment

Query Tuning in Dallas

SQL Server, T-SQL
Let's have some fun. This Friday, November 1, 2013, I'm putting on an all day seminar on query tuning. It's set up as a pre-conference event for SQL Saturday 255 in Dallas. It's a 200 level course on understanding how the query optimizer works, the importance of statistics, constraints and indexes, how to read execution plans, and how to take all that knowledge and go to work on tuning your queries. Here's the fun. Sign up for the seminar, and bring a nasty query you've been trying to tune or a query you don't understand or an execution plan that's making you crazy. Depending on the time available near the end of the day, we'll walk through a few of them. I've slightly restructured the seminar so I have some…
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18Sep 2013 by Grant Fritchey 17 Comments

Finding Ad Hoc Queries with Query Hash

SQL Server, T-SQL
I was presenting a session on how to read execution plans when I received a question: Do you have a specific example of how you can use the query hash to identify similar query plans. I do, but I couldn't show it right then, so the person asking requested this blog post. If you're dealing with lots of application generated, dynamic or ad hoc T-SQL queries, then attempting to determine tuning opportunities, missing indexes, incorrect structures, etc., becomes much more difficult because you don't have a single place to go to see what's happening. Each ad hoc query looks different... or do they. Introduced in SQL Server 2008 and available in the standard Dynamic Management Objects (DMO), we have a mechanism to identify ad hoc queries that are similar in…
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16Sep 2013 by Grant Fritchey 1 Comment

Why the Lazy Spool Is Bad

SQL Server, T-SQL
First thing, there are no bad operators, just bad parents, uh, I mean query writers, or database designers, or ORM tools. Why do I say this? Because all the operators within a query execution plan serve a purpose. They are there to fulfill a task. Depending on where and when you see them, they're doing exactly what you ask of them. The issues come up because you're asking them to do a task that they may not be well suited for. This comes from inappropriate structures and inappropriate code. Lazy spools are not really bad (that was just link bait). In fact, depending on the query, what's being done, how you're retrieving data, what data is being retrieved, the lazy spool is actually awesome. But, it's good to know what…
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