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If a script has 'set nocount on' and doesn't revert it the sql to update the nschemer_version table with an updated version number returns false and the whole transition fails.

It might be worth programming defensively against this, by ensuring nocount is off.

To reproduce:

• Upgrade a database to Version 2
• Add an upgrade script for Version 1
• Try to run NSchemer

NSchemer tries to be clever (by ignoring the version 1 script since its lower than Version 2):

// From: SqlClientDatabase.Update()
foreach (ITransition v in Versions)
{
    if (!AllVersions.Contains(v.VersionNumber) && v.VersionNumber < DatabaseVersion)
        missingUpdates.Add(v);
}

However, the IsCurrent() check reports false since the Version 1 script hasn't been applied. So, the loop:

while (!IsCurrent() && appliedUpdate)

Never exits, since appliedUpdate never gets changed.

SqlScriptTransition provides a constructor that does not require an assembly to be passed. This constructor overloads the constructor that does require an assembly, by passing null as the sourceAssembly argument:

public SqlScriptTransition(double versionNumber, string name, string description, string embeddedResourceName) 
    : this(versionNumber, name, description, null, embeddedResourceName) { }

public SqlScriptTransition(double versionNumber, string name, string description, Assembly sourceAssembly,
    string embeddedResourceName)
{
    SourceAssembly = sourceAssembly ?? GetType().Assembly;
    EmbeddedResourceName = embeddedResourceName;
    Description = description;
    Name = name;
    VersionNumber = versionNumber;
}

The default assembly used in this case then resolves to the NSchemer assembly. This is a nonsensical scenario though - it would be difficult to embed a resource into the NSchemer assembly.

Perhaps a more sensible approach would be to:

• Throw an exception if sourceAssembly is passed as null; and
• Either remove the constructor which does not have the sourceAssembly parameter, or provide Assembly.GetCallingAssembly() as the default for sourceAssembly.

The default value is currently only used when a nullable column is changed to not-null (i.e. when adding a not-null column to an existing table - NSchemer first creates the nullable column, sets all rows to the provided value, and then changes the column to not-null).

What should the API look like here? Should a default constraint always be provided, or are there cases where the developer might want to populate existing rows with a default value without creating a default constraint to populate future rows?

If you script is something like:

-- do something
GO

-- do something else
GO[eof]

The script fails. The parser trying to split the script is searching for "\nGO\n" which obviously doesn't match when there is no newline at the end of the file.