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Bill Gates might not have actually said the quote about 640k RAM being enough for anyone, but he did say the above statement. Too bad it didn’t prove true.

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Now the system has grown considerably and there have been many new processes added that retrieve data from the 3rd party stored procedures. The number of hits on the web application has also grown considerably. Today this little problem has become a nightmare. BUT I found the culprit.

I had occasion to review the sprocs in question while debugging some of these synch issues. One day while calling one of the sprocs manually, it started returning different data on each call – for the same product SKU! As quickly as it started, the weird behavior ceased. “Wow”, I thought. “They must be doing some updates on the database or something”. And the synch issues became worse yet.

The other day, I really took a hard look at one of the sprocs that is at the core of one of the calls we make to get product data. I had to look twice to be sure I was seeing the code correctly. Throughout many of the stored procedures, the vendor had used permanent tables as temporary tables. Now we all know that temp tables can be performance problems and using a real table could increase performance ( although there are still compilation and stats issues). I had a theory, so I created a little app to prove it.

I created a console app that called and recalled the sproc passing the same product SKU again and again. The app simply logs that data returned from the sproc. When I ran the app, I got what I expected – no errors and the correct data. Then I fired up 5 instances of the app at the same time, each with its own SKU. What do you think happened? It’s OK, I’ll wait while you think. That’s right! The data was shared between app instances! Product 1 got product 2, 3 and 4’s data as well as its own. In addition there were a host of errors related to the creation and dropping of the work table.

Ok, so what did I learn? If it smells bad it probably is bad. We had data anomalies for a long time, though they were very intermittent until recently. Since the data came through the sprocs, we should have reviewed them earlier. The good news is now we have hard evidence of where the problem really lies. I don’t envy the other vendor when the client calls…

BTW, if you use real tables as temp tables, you want to use what is called  a Process-Keyed table. This is simply a permanent table with one extra field which is the primary key. This key must be unique amongst all calling processes. The idea is that you add the key to the where clause when selecting from the table thereby guaranteeing you get the right data. Here’s a good article on the concept (and other concepts of sharing data in sprocs):

http://www.sommarskog.se/share_data.html

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I would think this would be a little more straight-forward in VS 2005 and 2008, but it isn’t. You can’t do a file name search in the GUI inside VS, but you can through the command line. to do the search:

• Open a Visual Studio Command Prompt
• In the following, replace [filename] and [TfsServer] with the appropriate values and paste into the command window.
  tf dir $/*[filename] /recursive /server:http://[TfsServer]:8080
• Supply any required credentials after running the command

You will be shown all locations of the file in the TFS server.

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1. Restore SQL Database
2. Find a String Between 2 Strings

// This search returns the substring between two strings, so 
// the first index is moved to the character just after the first string.
int first = str.IndexOf("$string1$") + "$string1$".Length;
int last = str.LastIndexOf("$string2$");
string str2 = str.Substring(first, last - first);

Technorati Tags: C#, Code, Code Sample, Visual Studio

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1. Restore SQL Database
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3. Title Case in C#

USE master — Must be connected to a different database

-- Get exclusive access
ALTER DATABASE XXXXXX_Stage  SET SINGLE_USER WITH ROLLBACK IMMEDIATE;

-- Restore from disk
-- Note WITH REPLACE http://msdn.microsoft.com/en-us/library/ms178615.aspx

RESTORE DATABASE XXXXXX_Stage  FROM DISK = 'F:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Backup\XXXXXX_Stage _20100505.bak' WITH REPLACE

-- Restore multi user access
ALTER DATABASE XXXXXX_Stage SET MULTI_USER WITH ROLLBACK IMMEDIATE;

Note the WITH ROLLBACK clauses. You should take a production database down and make sure all transactions have completed. Then do a restore through the IDE. If you use the code above, you may lose some transactions or logs. This usually doesn’t matter in a test environment.

Have fun!

Technorati Tags: SQL Server,SQL,Code Sample,Database,Server,backup

Technorati Tags: Code, Code Sample, Database, SQL, SQL Server

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1. Find a String Between 2 Strings
2. Create Singleton in C#
3. Title Case in C#

The Snippet Desginer IDE

I like this tool. I have had a few small issues with getting the tool to index alternate snippet folders, but that is a small thing compared to its usefulness. Try it. I think you might like it as much as I do.

Snippet Designer can be downloaded from http://snippetdesigner.codeplex.com/

Technorati Tags: Add-in, Code, Programming, Software Development, Tools, Visual Studio

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1. Create Singleton in C#
2. Restore SQL Database
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The classic approach to creating a Singleton looks like this:

public class SingletonGamma
 {
      private static SingletonGamma instance;
      private SingletonGamma()  { }

      public static SingletonGamma Instance
     {
         get 

         {
            if (instance == null) { instance = new SingletonGamma(); }
            return instance;
         }
     }
 } 

The basic approach is  to create a private constructor and an Instance method that returns the current instance if available, or returns a new instance if there is no current instance. We call that "lazy instantiation". The problem with this approach in C# is that it is not strictly thread-safe. That is, it is possible for 2 threads to create separate instances is some circumstances. This is not what we are looking to do. This approach does have an advantage in that there is a hook-point to do post-instantiation processing if required. In .Net though, this is not the approach usually recommended

The following example takes advantage of the better handling of variable ambiguity in .Net (vs. C++) to create a thread-safe Singleton:

public sealed class SingletonCSharp
    {
        private static readonly Singleton instance = new SingletonCSharp();

        private SingletonCSharp() { }

        public static SingletonCSharp Instance
        {
            get
            {
                return instance;
            }
        }
    }

This is the preferred approach in C# and is adequate for most programs. There are other approaches that allow for more flexibility and still maintain thread safety, but they introduce unnecessary complexity for most programs. Note the read only instance property that can only be set during instantiation and the sealed keyword that prevents inheritance of the class which could introduce unwanted side effects, such as secondary instances. This is a simple and straightforward approach to the design pattern. The only downside is the lack of flexibility to have non-standard constructors. For most applications, that will not be an issue.

Technorati Tags: Code, Design, Programming, Software Development, Tips, Visual Studio

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// Defines the string with mixed casing.
string myString = "this iS a StrIng with MIXED CaSe";

// Create a TextInfo based on the "en-US" culture.
TextInfo tInfo = new CultureInfo("en-US", false).TextInfo;

// Changes a string to titlecase.
// Note the ToLower(), needed to convert words in all caps like MIXED
Console.WriteLine("\"{0}\" to titlecase: {1}", myString, tInfo.ToTitleCase(myString.ToLower()));

//Result: This Is A String With Mixed Case
Console.ReadLine();

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1. Find a String Between 2 Strings

Be friendly to the planet when you dispose of old PCs!

http://www.staples.com/sbd/cre/marketing/ecoeasy/index2.html

Technorati Tags: Ecology, Help, Resources

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