如何在ASP.NET MVC3中使用Nhibernate进行更有效的查询

Question

I have about 1 million records in my contact table in the DB, now I have to get only 30. How can I make the following query more efficient:

GetContacts Method

    private IQueryable<Contact> GetContacts()
    {

        return this.Query().Where(c => c.ActiveEmployer== true); // here ' this ' is the current service context 
    }

Gettin Contacts

 var contactlist = GetContacts(); // this will get all records from db 
 var finalcontacts = contactlist.Skip(0).Take(30).Fetch(c.Roles).Fetch(c.SalaryInfo).ThenFetch(c.Employer);

But this query takes almost 10 seconds or more some times, and in the future I can have 30 - 40 million contacts then what would I do?

Answer 1

There may be some people that could come up with a great fix for that query to help you without needing more information, but for that query and all others you can probably gain much more insight by taking a look at the query that is created by NHibernate. If you've not done that before you can enable Log4Net (and possibly NLog) to output the SQL statements NH produces, or you can profile the SQL connection inside SQL Server. You can then run that SQL yourself and select to show the query plan. This will tell you exactly what the query is doing and potentially you can solve the problem yourself. It might be missing index, the original WHERE or one or all of the subsequent FETCH statements. Another question would be, have you hand crafted a SQL statement to do something similar and how long does that take?