04Jun 2008 by Grant Fritchey No Comments

Top Vs Max

SQL Server, T-SQL
I finished a set of research and tests. I put it all together and gave it to Chuck Heintzleman at SQL Server Standard (that web site can use some help). Hopefully he likes it and publishes it. I understand that the upcoming issue will be on performance tuning. If he doesn't like it, I'll get it over to Peter Ward at SQL Server Performance or to Steve Jones at SQL Server Central. I'm posting this because I see so many web searches looking for information comparing TOP to MAX. Here are some short answers for those interested. Data to support these suggestions is included with the article. ROW_NUMBER works best with smaller data sets. TOP has more consistent operation over a range a data. MAX frequently resolves as a TOP operation, but sometimes…
Read More
29May 2008 by Grant Fritchey 1 Comment

Break Down Complex Execution Plans

T-SQL
I've seen this question posted in a lot places and I've seen the search come in to the blog: "How do you break down a complex execution plan?" The short answer; just like eating an elephant, one bite at a time. The longer answer... First you have to define what you mean by a complex execution plan. For example, I've seen 16 page stored procedures that consist of about 50 or more different statements executed in series (and I 've heard of worse). No single statement was very big, but trying to dig through all the statements to identify which may be causing slow execution was a problem. This is the easiest type of complex execution plan to solve. In SQL Server 2005 and 2008, when you turn on a graphical…
Read More
29Apr 2008 by Grant Fritchey 9 Comments

nHibernate Recompiles and Execution Plans

nHibernate
One little potential for performance problems that we've seen comes out of how nHibernate generates it's parameratized queries. It limits the length of any parameter to the length of the column, but if the length of that parameter is less than the column, it uses tha smaller length when declaring the variable. This results in a query that looks like this: exec sp_executesql N'INSERT INTO dbo.users (Name, Password, EmailAddress, LastLogon, LogonId) VALUES (@p0, @p1, @p2, @p3, @p4)',N'@p0 nvarchar(8),@p1 nvarchar(6),@p2 nvarchar(12),@p3 datetime,@p4 nvarchar(8)',@p0=N'Ted Cool',@p1=N'abc123',@p2=N'ted@cool.com',@p3='2008-04-29 14:10:44:000',@p4=N'ted_cool' Note the parameter @p4 which is the parameter mapping to the primary key for the little sample table. In this query it's declared as nvarchar( 8 ) because 'ted_cool' is composed of eight characters. But if we changed it to 'ted_coolish': exec sp_executesql N'INSERT INTO dbo.users…
Read More
25Apr 2008 by Grant Fritchey No Comments

Easy Fix To Problem #1

nHibernate, Object Relational Mapping, Tools
I did a little bit, and I mean a little bit, of looking through the documentation on nHibernate and located a spot for the schema, actually  a couple of spots. It can be added to the Hibernate Mapping definition, which will make it a default for all classes within the definition, and by extension all the tables in the database you connect to. You can also add it to the class definition, specifying a particular schema for a given table. So now the query looks like this: exec sp_executesql N'INSERT INTO dbo.users (Name, Password, EmailAddress, LastLogon, LogonId) VALUES (@p0, @p1, @p2, @p3, @p4)',N'@p0 nvarchar(9),@p1 nvarchar(6),@p2 nvarchar(13),@p3 datetime,@p4 nvarchar(9)',@p0=N'Jane Cool',@p1=N'abc123',@p2=N'jane@cool.com',@p3='2008-04-25 11:11:48:000',@p4=N'jane_cool' On to the data length problem.
Read More
25Apr 2008 by Grant Fritchey 1 Comment

nHibernate First Impressions

Object Relational Mapping, Tools
If I'm going to have to support it, I want to understand it. So, I got going yesterday, installing nHibernate 2.0 and walking through the Quick Start Guide. My C# is a bit rusty, to say the least, but I managed to sqeak by. The Guide is meant for an older version of nHibernate and there have been a few changes made that affect the code displayed. What that means is, I had to do more than simply type up what was presented to me. Which, was actually good because it forced me to do a bit more learning in order to get everything to work. What I found was interesting. I can see why developers like this. It really does let you treat the database as just another object…
Read More
21Mar 2008 by Grant Fritchey No Comments

Top vs. Max

T-SQL
The company I work for has a very well defined need for versioned data. In a lot of instances, we don't do updates, we do inserts. That means that you have to have mechanisms for storing the data that enables you to pull out the latest version of all the data or a particular version of all the data, or the data at a particular moment in time, regardless of version.  That means maintaining a version table and a series of inserts into various tables. Some tables will have pretty much a new row for each version, some tables may only have one or two versions out of a chain. With the help of a very smart Microsoft consultant, Bill Sulcius, we have a mechanism that works very well. However,…
Read More
18Mar 2008 by Grant Fritchey No Comments

SQL Inspect

Tools
I was asked if I would look at a new tool from a company I hadn't heard of. It's SQL Inspect from Yohz Software. Nominally this is a SQL query editor. However, strictly as a query editor, especially when compared to what's available in SQL 2008 or what tools like Red Gate's SQLPrompt or SQLRefactor can do for you, it's not so hot. Luckily, that's not where its strengths lie. Instead, it's all about performance tuning your queries and it does this very well indeed. It takes a query and returns a tree structured execution plan, looking a bit like the old text plans, but much more sophisticated with roll-ups, etc. It shows you all the details of the operations, just like an execution plan, but immediately accessible on the screen,…
Read More
17Mar 2008 by Grant Fritchey No Comments

Presentation Last Week

Misc, SQL Server, T-SQL
Last week I presented at the Southern New England SQL Server User Group (SNESSUG) where I'm the Program Director. I presented from the book, Dissecting Execution Plans, that is supposed to be published any day now. I kept it basic and it flowed very well. The audience seemed receptive and there were a few questions. Mostly around figuring out what to do when you saw certain problems within the execution plans. Since that was the goal of the presentation, I was ready for most of the questions. I got stumped once on a Constant Scan operation. I finally looked it up this morning and feel silly. Here's the query: INSERT INTO [AdventureWorks].[Person].[Address]      ([AddressLine1]      ,[AddressLine2]      ,[City]      ,[StateProvinceId]      ,[PostalCode]      ,[rowguid]      ,[ModifiedDate] VALUES ('1313 Mockingbird Lane'…
Read More