Projected Entities do not fetch subprops

BIZ TMS Aurelius
1

As you describe here we could

Limiting the selected properties

I gave this a try by doing this:

    hChildren := hManager.Find<TChild>
      .Select(TProjections.ProjectionList
        .Add(Linq['Caption'])
        .Add(Linq['Parent.Caption'])
      )
      .List;

Using your OnSqlExecuting and logging SQL I got this:

SELECT A.ID AS A_ID, A.CAPTION AS A_CAPTION
FROM CHILD A
  LEFT JOIN PARENT B ON (B.ID = A.PARENT_ID)

That's my model:

type
  TEntityId = Integer;

  [AbstractEntity, Automapping]
  TBaseEntity = class(TObject)
  private
    FId: TEntityId;
    FCaption: string;
  public
    property Id: Integer read FId write FId;
    property Caption: string read FCaption write FCaption;
  end;

  [Entity, Automapping]
  TParent = class(TBaseEntity)
  end;

  [Entity, Automapping]
  TChild = class(TBaseEntity)
  private
    FParent: Proxy<TParent>;

    function GetParent: TParent; // => Result := FParent.Value
    procedure SetParent(const Value: TParent); // => FParent.Value := Value...
  public
    property Parent: TParent read GetParent write SetParent;
  end;

Afterwards I saw, that you are using FetchEager in your docs, so I did this:

    hChildren := hManager.Find<TChild>
      .Select(TProjections.ProjectionList
        .Add(Linq['Caption'])
        .Add(Linq['Parent.Caption'])
      )
      .FetchEager('Parent')
      .List;

but I got the same SQL...

SELECT A.ID AS A_ID, A.CAPTION AS A_CAPTION
FROM CHILD A
  LEFT JOIN PARENT B ON (B.ID = A.PARENT_ID)

In both cases hChild.Parent is nil, so that I could not access my fetched subproperty...

2

Did you try a CreateAlias for Parent before adding to the ProjectionList ?

3

I did not, but now I did and it also does not work...

    Result := aManager.Find<TChild>
      .CreateAlias('Parent', 'prnt')
      .Select(TProjections.ProjectionList
        .Add(Linq['Caption'])
        .Add(Linq['prnt.Caption'])
      )
      .List;

I also put result into an AureliusDataset with following Fields:

- Caption
- prntCaption

while using Aliased Linq:

    Result := aManager.Find<TChild>
      .CreateAlias('Parent', 'prnt')
      .Select(TProjections.ProjectionList
        .Add(Linq['Caption'])
        .Add(Linq['prnt.Caption'].As_('prntCaption'))
      )

prntCaption stays empty...

4

ohhh .. now I see...
Use .ListValues instead of .List

5

Yeah, this would work, BUT I need TList<TChild>, not a criteria-Result list.

and as described in documents, .List should also work...

6

With the projection you'd get only child Caption and parent Caption at the same "row level". It does not work on a TCHild structure returned from .List.

If you want a TList, FetchEager on Parent should work. Maybe there's another mapping issue to solve.

7

Try declaring FParent without Proxy. This will force eager loading.
Or you could try the complete association attributes.

8

You have to explicitly tell Aurelius that you want the association to be included in select. Do this:

    hChildren := hManager.Find<TChild>
      .Select(TProjections.ProjectionList
        .Add(Linq['Caption'])
        .Add(Linq['Parent'])
        .Add(Linq['Parent.Caption'])
      )
      .List;
9

Ok, but why does your example not work?

  Estimates := Manager.Find<TEstimate>
    .Select(TProjections.ProjectionList
      .Add(Linq['EstimateNo'])
      .Add(Linq['Customer'])
      .Add(Linq['Customer.Name'])
      .Add(Linq['Customer.Sex'])
      .Add(Linq['Customer.Country'])
      .Add(Linq['Customer.Country.Id'])
    )
    .FetchEager('Customer')
    .FetchEager('Customer.Country')
    .List

should FetchEager not do the same?

10

ok, finally I saw this in your example...
It's a little bit confusing combined with FetchEager

1 Like
11

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