On Friday I had to help a client out with an error that kept appearing in their event logs:
Login failed for user ‘domain\user’. Reason: Failed to open the explicitly specified database. [CLIENT: 192.168.0.25]
It took me a while to troubleshoot the error. The client’s internal system administrator (who was quite sharp) only had to call me in in the first place because the error was a little misleading. See the first thing I did when I saw that was audit login failures. In the trace, the database was listed as master. The user had full access to master. However, I later learned that the user was switching from master to a non-existent database, which was triggering this error. I figured this out thanks to Sadequl Hussain‘s article, SQL Server Error 18456: Finding the Missing Databases.
Sadequl explains in detail the how and the why. However, the take home is you need to trace for User Error Message to get the message that tells you what database you are connecting to.
This took me about an hour to solve. Honestly, it was a bit humbling of an experience. It took me an hour to figure out something a full time senior DBA would probably be able to solve in 15 minutes. However, I’ll probably be able to solve this error in 15 minutes myself go forward. Finally, the fact that it took me a while to find this one blog article that explained what the issue actually was proves how dependent I’ve become upon google.
I first became aware of the open source Atlantis Interactive Schema Engine on Febuary 24th 2011 thanks to a retweet by Paul Randal. Its a .NET assembly which contains most of the “heavy lifting” code related to the schema operations in their various products. Matt Whitfield, the sole proprietor of Atlantis Interactive, is going to setup an account on codeplex or one of the other forges so people can post bugs, feature requests, and of course patches. Personally, I have several ideas for feature requests. However, I have no channel at the moment for these requests besides emailing Matt. While Matt has been very responsive, I wanted the conversation to be more public, I talked to Matt and he agreed it was a good idea to create put them on this blog post. Please use the comments to add your own bugs, feature requests, or patches, or comment on my feature requests.
Now, here are the feature requests.
Integration with ILSpy
ILSpy is a free and open source .NET decompiler. Development was accelerated by the fact that Redgate Reflector ceased to be free. It would be great if the library could decompile CLR assemblies to C# with this tool. It would be great to produce a diff of the decompiled source of two CLR assemblies.
Powershell related improvements
I’ve written about using the schema engine with powershell previously. Its a relatively pleasant experience, but it could be improved with powershell cmdlets. I’m pretty new to powershell, so I don’t have a clear direction on where I’d like these to go. However, I might consider taking the initiative on this one.
Shortened namespaces for the Enums
Basically, in powershell you have no using statements, and the Enums that are used as parameters are several namespaces deep. It might not make sense to change them. However, I am just throwing this out there.
More flexibility for creating SchemaReaders
I’m looking to be able to do a few things:
- Pass an existing connection object
- Create a pooled connection string. While that doesn’t make sense for desktop apps, it might make sense if I was using the library from a web app. Being able to sync databases from a web app would be really cool.
Get the existing connection string from SchemaCollection
Its self explanatory.
Be able to script a schema to a Microsoft Sql Server Project
I’d like to be able to point the library at a database and have a function in SchemaCollection that will script everything to a visual studio database project. Initially it would be easiest to hard code this functionality. However, it would probably be best if it was template (t4?) based so that you could easily support other database versions.
Naturally a long term possibility would be to be able to do a schema sync between databases and sql server projects.
Support for Mono
I actually started a port of this. Its very easy to get it to compile (comment out like 3 lines), but you do lose Geospatial support. For this reason, it might make sense to have separate mono and .NET builds. In my limited time testing it I could not get my linux vm to connect to SQL server, so I don’t know if it would actually work. I want to pursue this path a bit myself, even if it just leads to me filing upstream bugs in mono.
Support for other databases
It seems like the object model is pretty well organized. That being said I realize this exercise would be far from mechanical. I don’t think cross database compares will ever be practical on a whole database level. Below are the specific databases I’d like to see supported.
I don’t actually see much of a case for this other than “it can be done” and all windows machines have support for the JetSQL engine.
Support for SQLite in .net is very good via System.Data.SQLite.
Its been a while since I used NPgsql, but its pretty stable and robust. That being said, there will always be edge cases here since postgres is so customizable and extensible.
So thats a tall list of requests. When we have an issue tracker I will be transferring them all there. Until then, use the comments.
Update: Added link to the scripts on github.
If you’ve worked with SQL Server for any length of time, you’ve probably written some stored procedures and user defined functions. If you’re like me, you’ve written many. Usually, when you edit a stored proc or UDF. you do it from Visual Studio or Sql Server Management Studio (SSMS). However, what if you want to script the sproc or udf from the command line? Well, there are quite a few ways to skin this cat, and I’ll go through a few.
The simplest way to do this is the command line client that ships with SQL server 2005 and up, sqlcmd, and a system stored proc called sp_helptext. For our example lets have sp_helptext script itself.
sqlcmd -S .sqlexpress2k8r2 -d master -h-1 -s"" -W -w 1024 -Q "EXEC sp_helptext 'sp_help'" -o sp_helptext.sql
Lets breakdown the arguments:
- -S .sqlexpress2k8 this is the named instance of sql server I am connecting to. If you want to connect to the local default instance, you can omit this
- -d master This is the database we want to connect to. This can be omitted if you want to script an object from the users default catalog.
- -h-1 -s”” -W -w 1024 These format the output of sqlcmd in a way that makes sense for this task. If you want to understand these options, look at the sqlcmd msdn page, or this stackoverflow question.
- -Q “EXEC sp_helptext ‘sp_helptext’” -Q means “execute this T-SQL and exit.
- -o sp_helptext.sql This writes the command output to the text file sp_helptext.sql
Using a batch file
Now we could easily wrap this in a batch file as I demonstrate here:
C:UserszippyDocumentsdeleteme>type scriptProcOrUdf.cmd @echo off sqlcmd -S %1 -d %2 -h-1 -s"" -W -w 1024 -Q "EXEC sp_helptext '%3'" -o "%3.sql"<span style="font-family: Georgia, 'Times New Roman', 'Bitstream Charter', Times, serif; font-size: 13px; line-height: 19px; white-space: normal;"> </span>
So we saved ourselves a few keystrokes with a 2 line batch file.
Batch files work, but they’re so 2002. Powershell is the CLI of choice these days on windows. So lets see how we would do this in powershell:
So apparently it took me 26 lines of Powershell (if you remove the BSD License) to accomplish what I could have done in a 2 line batch file. Whats the point you might be asking? Well, honestly if you just want the quickest way to script stored procedures to a file from the command line, I’d use the batch file. However, if you wanted to make changes to this script, for example, make it script all stored procedures and udfs in the database. You’d have an easier job with Powershell. You could turn the body of the script into a Poweshell function that takes a SqlConnection object and object name as a parameter. You could then get a list of all the stored procedures and functions with the T-SQL statement SELECT [ROUTINE_NAME], [ROUTINE_TYPE], [ROUTINE_DEFINITION] FROM [INFORMATION_SCHEMA].[ROUTINES]. I’ll leave writing that script as an exercise to the reader.
Using Powershell and “Original Thinking” to do it in less than 26 LOC
In the fictional Star Trek universe,
Denny Crane, James T. Kirk cheated on the Kobayashi Maru by reprogramming the no-win scenario to allow him to win. He was awarded for his original thinking. Our scenario is less dire. However, like Kirk, we can change the rules. I chose to use a the open source .NET assemble Atlantis.SchemaEngine.dll. This dll is used for synchronizing schema between two SQL server databases. We don’t want to synchronize or compare anything. However, the library synchronizes database schema’s by generating SQL scripts. Therefore, it can generate DDL for any script-able object in a database. So lets take a look at our leaner, meaner script.
So we went from 26 to 15 lines. That’s a savings of 42%. Some of those are pretty long lines since we have to fully qualify our namespaces in Powershell. However, its a net simplification compared to making the ADO.NET calls directly.
I showed you 4 ways to script a stored proc. I also left plenty of room for you the reader to explore on your own. The code for ScriptProc.ps1 and Script-Object.ps1 lives in the justaprogrammer powershell github repo. If you have any improvements, feel free to leave a comment or pingback below. Also, pull requests are always welcome. Happy Scripting!