Add support of Futures

Hi,

It would be a great value for the library to have Future support. What I mean by Future is the possibility to batch multiple Sql queries in a single request to the server and parse the result one time.

You can see a practical case in Ayend’s blog, But nowadays it’s more important to have such a feature.

As many applications, we have a Saas application deployed on the Cloud, a Single Page Application :

• When the application first loads, it fetchs a lot of data from the server, just a bunch of Selects to get the current user name, the notifications, some elements on the dashboard, and other business elements etc… The Sql server is hosted in the cloud too, sometimes not the same Network than the server so there is a lot of firewall between the two. Without Future, we would need to send each request, wait for the result, parse the result, and then send the second request, during all this time Sql Server is in Idle mode ( Because of Session pooling, we won’t face TCP Warm up problem ).
• In our application, we follow UnitOfWork Pattern, at the beginning of the request we open a transaction, at the end of the request we flush all the Updates/Inserts/Deletes, that make a big request of many queries, a fire&forget query because we don’t read anything from this point, without Future, we would need to wait for each Update/Insert/Delete to finish to run the next one, and during this time Sql Server is in Idle mode.
• We have a SPA, so the reactivity of our application is directly related to the performance of each small webservice, and because we precalculate everything, the webservices will have just to fetch data from sql server. Think of it like a Dashbord showing a lot of data, User experience depends directly on the speed of fetching the data from the Sql Server and serving it to the App.

If we can do something like this that would be great :

public static List<Product> Search(string searchFor, int currentPage, int pageSize, out int totalRecords)
{
  using (var db = new DbNorthwind())
  {
    var products = from p in db.Product 
                   select p;

    if (searchFor != null)
    {
      products = from p in products 
                 where p.Name.Contains(searchFor) 
                 select p;
    }

    var lTotalRecords = products.Future().Count();  // That would return a Lazy<int>

    var ret = products.Skip((currentPage - 1) * pageSize).Take(pageSize).Future().ToList();  // That would return a Lazy<List<Product>>

    totalRecords = lTotalRecords.Value; // At this moment the ret.Value will have also the value set.

    return ret.Value;      
  }
}

[sdanyliv]

I have API prototype which is more sophisticated and has to cover more functionality. But I don’t have time this year.

var count   = db.GetTable<Person>().DeferValue(q => q.Count());
var persons = db.GetTable<Person>().DeferValue(q => q.ToList());

db.CompleteDefer();

persons.Value - will contain list and count.Value will have Count

And how to insert graph of records:

var newId  = db.GetTable<Person>()
   .Value(p => UserName, "some")
   .DeferValue(i => i.InsertWithInt32Identity());

db.GetTable<Child>()
   .Value(c => c.Name,     () => "Child1")
   .Value(c => c.PersonId, () => newId.Value)
   .Defer(i => i.Insert())

db.GetTable<Child>()
   .Value(c => c.Name,     () => "Child2")
   .Value(c => c.PersonId, () => newId.Value)
   .Defer(i => i.Insert())

db.CompleteDefer();

db.CompleteDefer() is not required if last call is not deferred.

Library should understand that database provider support multiple record-sets and combine queries accordingly.

For Firebird it will be two separated database requests:

1. Insert into Person
2. Insert two items into Child table

For SQL Server it will be one round trip to database, because we can store result of first insert into SQL variable.

[frankiDotNet]

@sdanyliv : Are there any news for a future support? The ef core extension has also a nice implementation. What I missed for all implementations is a kind of group, something like:

using(var db = new DbContext()){
    string idPersonQuery = 'Query1';
    string idCardsQuery = 'Query2';

    var persons =     db.GetTable<Person>().ToFuture(){Id = idPersonQuery  };
    var pCount =     db.GetTable<Person>().ToFutureCount( ){Id = idPersonQuery  };

    var cards=     db.GetTable<Cards>().ToFuture(){Id = idPersonQuery  };
    var cCount =     db.GetTable<Cards>().ToFutureCount(){Id = idPersonQuery  };

    // only persons and count of persons is executed
    var pList = persons .ToList();

    // only cards and count of cards is executed
    var cList = cards.ToList();
}