Trouble with Multi-Tenant Schema Generator Example - codefluent

Question

We are attempting to use CFE to generate one schema for each tenant as outlined in the CodeFluent blog post (http://blog.codefluententities.com/2014/12/04/multi-tenant-using-multiple-schema/). In this scenario, we are expecting that each schema generated should be identical and we are using the ICodeFluentPersistence Hook system to identify the company for a user and then properly set the schema to be used. All of that works fine, but when we run the code to generate the multiple schemas (https://github.com/SoftFluent/CodeFluent-Entities/tree/master/Extensions/SoftFluent.MultiTenantGenerator), it is removing the constraints. I then tried to see if there was an issue with my configuration, but running the sample program from GitHub produces the same results. After running the sample program, the Primary key was not present in the contoso schema, even though is was properly defined in the dbo schema (and in the model).
Has anyone used the CFE Multi-Schema generator or have any insight into what the issue may be?

Answer 1

Thanks for your response, but I am not sure that I agree. The whole reason (at least of me) to use the Multi-Tenant generator is to create as many database schemas as needed (one per client) from a single CFE model. The idea that you would lose the constraints in all but one of them didn't feel right so I did a bit more investigation and found the following in "Microsoft SQL Server 2012 Internals" by Kalen Delaney and Craig Freeman (through Google Books):
And in fact was able to do a quick test to prove this out by creating two identical tables with identical PK names:
So it would appear to me that CFE should be able to create the two identical databases from the same model and seems to point to a deficiency in the SQLServer diff engine.

Answer 2

The multi-schema generator loads the model and change it dynamically to modify the schema of the entities. Then it call the standard code production process with only the database producers (SQL Server, Oracle, etc.).
So if you want to generate 2 differents schema (dbo and contoso) against an empty database, the process is the following:
Generate the database for the dbo schema from a blank database
Generate the database for the contoso schema from the previously generated database
Before creating a constraint, the SQL Server diff engine drops the constraint with the same name. In fact SQL Server does not allow 2 constraints to have the same name (I can't find a page on MSDN with more details about that). So in your case the existing PK is dropped when you generate the contoso schema because the name of the PK is the same as the one that exists in the dbo schema. Maybe this can be improved, but the diffs engine tries to generate a code that works for SQL Server 2000 to SQL Server 2016.
Workarounds
You can generate each schema in a different database, so the diffs engine will generate the code you expect. Then you can run the generated scripts on the production database. Not the easiest way but it should work.
You can use the patch producer to replace the name of the schema in the file. For SQL files you should use the SqlServerPatchProducer as explain in the KnowledgeBase:
namespace Sample
{
public class SqlServerPatchProducer : SqlServerProducer
{
public SqlServerPatchProducer()
{
}
protected override void RunProceduresScript()
{
string path = GetPath(Project.DefaultNamespace + "_procedures.sql");
ProduceFrom(path, "before");
SearchAndReplaceProducer.ProducePatches(Project, null, this, null, ProductionFlags, Element);
Utilities.RunFileScript(path, Database, OutputEncoding);
ProduceFrom(path, "after");
}
}
}