Reduce db roundtrips

Hi,

Is it possible to reduce db roundtrips by sending requests by batch ( Like NHibernate Future<T>() ) ?

For the paging example, it’s ok to have two requests, but could we send them togheter in one batch and parse the results one time ? :

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;
    }

    totalRecords = products.Count();

    return products.Skip((currentPage - 1) * pageSize).Take(pageSize).ToList();
  }
}

Thank you,

Yassine

[sdanyliv]

Hi, @loudadyassine, not yet. But we had thoughts about that. Not as it is done in NHibernate but in our way.

But, I’ve spent 20 minutes for writing for you simple class which should help in your situation if database supports Window functions.

public static class QueryPaginator
{
	private class Envelope<T>
	{
		public int TotalCount { get; set; }
		public T Data { get; set; }
	}

	public static List<T> Paginate<T>(IQueryable<T> query, int page, int pageSize, out int totalRecords)
	{
		var withCount = from q in query
			select new Envelope<T>
			{
				TotalCount = (int)Sql.Ext.Count().Over().ToValue(),
				Data = q
			};

		var items = withCount.Skip((page - 1) * pageSize).Take(pageSize).AsEnumerable();

		using (var enumerator = items.GetEnumerator())
		{
			List<T> result;
			if (!enumerator.MoveNext())
			{
				totalRecords = 0;
				result = new List<T>();
			}
			else
			{
				totalRecords = enumerator.Current.TotalCount;
				result = new List<T>(pageSize);
				do
				{
					result.Add(enumerator.Current.Data);
				} while (enumerator.MoveNext());
			}

			return result;
		}

	}
}

And usage:

var items = QueryPaginator.Paginate(products, currentPage, pageSize, out totalRecords);

[Powerz]

Hi, @loudadyassine, not yet. But we had thoughts about that. Not as it is done in NHibernate but in our way.

But, I’ve spent 20 minutes for writing for you simple class which should help in your situation if database supports Window functions.

This is awesome, thank you 👍