Optimization

Those of you who are familiar with db4o query processor may already suspect that LINQ queries as well as NQ and QueryByExample queries are converted to SODA Query under the hood. And that is true. The downside of this is that some of the queries cannot be converted to SODA and will run against all instances of matching class objects. Some of the cases when conversion is not possible:

there is no SODA alternative available
constraints on aggregates (avg(List) = constant)
constraints to values that are not available before query executions (Pilot.Points = Pilot.Name.Length

LinqExample.cs: SelectUnoptimized

01private static void SelectUnoptimized()
02        ...{
03            IObjectContainer container = Database();
04            if (container != null)
05            ...{
06                try
07                ...{
08                    IEnumerable<Pilot> result = from Pilot p in container
09                                                where p.Points == p.Name.Length
10                                  select p;
11
12                    ListResult(result);
13                }
14                catch (Exception ex)
15                ...{
16                    System.Console.WriteLine("System Exception: " + ex.Message);
17                }
18                finally
19                ...{
20                    CloseDatabase();
21                }
22            }
23        }

LinqExample.vb: SelectUnoptimized

01Private Shared Sub SelectUnoptimized()Sub SelectUnoptimized()
02            Dim container As IObjectContainer = Database()
03            If container IsNot Nothing Then
04                Try
05                    Dim pilots = From item In container _
06                                 Where item.GetType Is GetType(Pilot) Select CType(item, Pilot)
07                    Dim result As IEnumerable(Of Pilot) = From p _
08                        In pilots Where p.Points = p.Name.Length Select p
09                    ListResult(result)
10                Finally
11                    CloseDatabase()
12                End Try
13            End If
14        End Sub