User Algorithm: Example of Creating

This article describes an example of creating and executing an ETL task with the use of user algorithm of data transformation.

The repository must contain two tables T_Source, T_Destination and a unit with the USER_PLAIN_MODULE identifier containing the UserSubChangeValues macro. Structure of tables must satisfy the implemented data transformation algorithm. The repository must also contain an ETL task with the ETLTASKS identifier. On executing the example presented below three objects are created in the ETL task: repository source, theUser Algorithm transformer and repository consumer. The required properties and links are set for all objects:

After objects are created and saved, the ETL task is executed. The similar code applied to different objects is placed into separate procedures or functions.

The macro that implements the required class is given in the example for IEtlCustomUser.Transform.

Add links to the Andy, Db, Drawing, Dt, Etl, Metabase system assemblies.

Sub UserProc;
Var
    MB: IMetabase;
    ETLTask: IEtlTask;
    EtlProvider: IEtlPlainDataProvider;
    MetabaseProvider: IDtMetabaseProvider;
    EtlConsumer: IEtlPlainDataConsumer;
    MetabaseConsumer: IDtMetabaseConsumer;
    UserAlg: IEtlPlainDataUser;
    UserInput: IEtlPlainInput;
    UserOutput: IEtlPlainOutput;

    Link, Link1: IEtlPlainLink;
    Shapes: IWxShapes;
    ProvFields, UserInFields, UserOutFields, ConsFields: IEtlPlainFields;
Begin
//Open ETL task
    MB := MetabaseClass.Active;
    ETLTask := MB.ItemById("ETLTASKS").Edit As IEtlTask;
//Create a provider
    EtlProvider := ETLTask.Create(EtlObjectType.PlainDataMetabaseProvider) As IEtlPlainDataProvider;
    EtlProvider := EtlProvider.Edit;

    EtlProvider.Id := "Metabase_Provider";
    EtlProvider.Name := "Import from table";
    MetabaseProvider := EtlProvider.Provider As IDtMetabaseProvider;
    MetabaseProvider.Dataset := MB.ItemById("T_Source").Bind As IDatasetModel;
    EtlProvider.FillDefault;
     //Create a visual object of provider
    CreateWX(ETLTask, EtlProvider, -60, 0);
//Create a consumer
    EtlConsumer := ETLTask.Create(EtlObjectType.PlainDataMetabaseConsumer) As IEtlPlainDataConsumer;
    EtlConsumer := EtlConsumer.Edit;

    EtlConsumer.Id := "Metabase_Consumer";
    EtlConsumer.Name := "Export to table";
    MetabaseConsumer := EtlConsumer.Consumer As IDtMetabaseConsumer;
    MetabaseConsumer.Dataset := MB.ItemById("T_Destination").Bind As IDatasetModel;
     //Create a visual object of consumer
    CreateWX(ETLTask, EtlConsumer, 60, 0);
//Create the "User Algorithm" transformer
    UserAlg := ETLTask.Create(EtlObjectType.PlainDataUser) As IEtlPlainDataUser;
    UserAlg := UserAlg.Edit;
    UserAlg.Id := "UserAlg_Transform";
    UserAlg.Name := "User Algorithm";
    UserAlg.Module := MB.ItemById("USER_PLAIN_MODULE");
    UserAlg.ForeSub := "UserSubChangeValues";
    UserAlg.PlainInputs.Add;

    UserAlg.PlainOutputs.Add;
    UserInput := UserAlg.PlainInputs.Item(0);
    UserOutput := UserAlg.PlainOutputs.Item(0);
     //Create a visual object of transformer
    CreateWX(ETLTask, UserAlg, 0, 0);
//Fill lists of fields of all objects based on the list of provider fields
     //Get list of fields
    ProvFields := EtlProvider.PlainOutput.Fields;  //Provider output
    UserInFields := UserInput.Fields;  //Transformer input
    UserOutFields := UserOutput.Fields;  //Transformer output
    ConsFields := EtlConsumer.PlainInput.Fields;  //Consumer input
     //Fill lists of fields
    FillFields(UserInFields, ProvFields);
    FillFields(UserOutFields, UserInFields);

    FillFields(ConsFields, UserOutFields);
//Save all objects
    EtlProvider.Save;
    UserAlg.Save;
    EtlConsumer.Save;
//Link of transformer with all objects
     //Create links
    Link := CreateLink(ETLTask, EtlProvider.PlainOutput, UserInput);
    Link1 := CreateLink(ETLTask, UserOutput, EtlConsumer.PlainInput);
     //Create visual links
    Shapes := ETLTask.Workspace.Shapes;
    CreateWXLink(ETLTask, Shapes.FindById(EtlProvider.Id), Shapes.FindById(UserAlg.Id), Link);

    CreateWXLink(ETLTask, Shapes.FindById(UserAlg.Id), Shapes.FindById(EtlConsumer.Id), Link1);
//Save task
    (ETLTask As IMetabaseObject).Save;
//Execute task
    ETLTask.Execute(Null);
End Sub UserProc;
//Create visual objects
Sub CreateWX(ETLTask: IEtlTask; ETLObject: IEtlObject; XPosition: Integer; YPosition: Integer);
Var
    WxRect: IWxRectangle;
    WxETLObj: IWxEtlObject;

Begin
    WxRect := ETLTask.Workspace.CreateRectangle;
    WxRect.Id := ETLObject.Id;
    WxETLObj := New WxEtlObject.Create;
    WxETLObj.EtlObject := ETLObject;
    WxRect.Style.TextPosition := WxTextPosition.Bottom;
    WxRect.Style.PictureMarginTop := -10;
    WxRect.PinPosition := New GxPointF.Create(XPosition, YPosition);
    WxRect.Extension := WxETLObj As IWxShapeExtension;
End Sub CreateWX;
//Fill lists of input/output fields
Sub FillFields(Fields, FieldsSource: IEtlPlainFields);
Begin
    Fields := Fields.Edit;
    Fields.Fill(FieldsSource);

    Fields.Save;
End Sub FillFields;
//Create a link between objects
Function CreateLink(ETLTask: IEtlTask; Output: IEtlPlainOutput; Input: IEtlPlainInput): IEtlPlainLink;
Var
    Link: IEtlPlainLink;
Begin
    Link := ETLTask.CreatePlainLink;
    Link.SourceObjectOutput := Output;
    Link.DestinationObjectInput := Input;
    Link.FillDefault;

    Return Link;
End Function CreateLink;
//Create visual links
Sub CreateWXLink(ETLTask: IEtlTask; Shape1: IWxShape; Shape2: IWxShape; Link: IEtlPlainLink);
Var
    WLink: IWxLink;
    WxETLLink: IWxEtlObject;
Begin
     //Create visual link objects
    WLink := ETLTask.Workspace.AutoLinkShapes(Shape1, Shape2);

    WLink.Style.LinePenBeginWxCap := WxLineCap.Flat;
    WLink.Style.LinePenEndWxCap := WxLineCap.Arrow30DegreeFilled;
    WxETLLink := New WxEtlObject.Create;
    WxETLLink.EtlObject := Link;
    WLink.Extension := WxETLLink As IWxShapeExtension;
End Sub CreateWXLink;