带存储过程的多租户EF实施

Question

When using SProcs in EF4, I understand the concept of mapping views to entities, then using function imports to map my set/update/deletes to sprocs. The question I have is how this applies to multi tenant architecture. Consider the following scenario:

We have several hundred customers utilizing our multi-tenant database/application. Each customer has somewhere between 50-200 Accounts in the Accounts table. If I expose a view to EF, I cannot parameterize that view. So the following line:

query = (from e in context.Accounts select e).where(e => e.companyID = 1)
[forgive me if I'm syntactically incorrect. still learning EF!]

,by definition, would have to return all of the Accounts first, then filter using my wear clause. is this correct? I can't imagine how else the process would work.

Am I missing something here?

Answer 1

That is the difference between Linq-To-Objects and Linq-To-Entities. Linq-To-Objects operates on IEnumerable<T> and you pass delegates to its methods to define the query which will be executed in the memory. Linq-To-Entities operates on IQueryable<T> and you pass expressions to its methods do define expression tree which is transformed by Linq-to-entities provider into another syntax - to SQL!

So your query will be executed in the database and filtering will be done in the database as well. Be aware that after executing commands like AsEnumerable , ToArray , ToDictionary or ToList you transform the rest of the query to Linq-to-objects.

If you write the query on the result of stored procedure execution you are always doing Linq-to-objects only querying ObjectSets directly forms Linq-to-entities queries.

Answer 2

EF shouldn't be bringing all the accounts back first and then filtering. Rather, it should be be emitting a query with a WHERE clause.

You can check using SQL Profiler, just to be 100% sure.