ETL: Example of Sorting in Fore

This article describes an example of creating and executing an ETL task with source data sorting.

The repository must contain two tables T_Source, T_Destination, tables must be identical in structure and must contains the Value field. Sorting will be executed by the field values. 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, the Sorting 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.

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;
    Sort: IEtlPlainDataSort;
    Link, Link1: IEtlPlainLink;
    Shapes: IWxShapes;
    ProvFields, SortInFields, SortOutFields, ConsFields: IEtlPlainFields;
    Index: IEtlPlainIndex;
Begin

//Open the ETL task
    MB := MetabaseClass.Active;
    ETLTask := MB.ItemById("ETLTASKS").Edit As IEtlTask;
//Create 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 visual object the source
    CreateWX(ETLTask, EtlProvider, -60, 0);
//Create 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 Sort transformer
    Sort := ETLTask.Create(EtlObjectType.PlainDataSort) As IEtlPlainDataSort;
    Sort := Sort.Edit;
    Sort.Id := "Sort_Transform";
    Sort.Name := "Sorting";
     //Create a visual object of transformer
    CreateWX(ETLTask, Sort, 0, 0);
//Fill in lists of fields of all objects based on source fields list
     //Get fields list
    ProvFields := EtlProvider.PlainOutput.Fields;  //Source output
    SortInFields := Sort.PlainInput.Fields;  //Consumer input
    SortOutFields := Sort.PlainOutput.Fields;  //Transformer output
    ConsFields := EtlConsumer.PlainInput.Fields;  //Consumer input
     //Fill in fields lists
    FillFields(SortInFields, ProvFields);

    FillFields(SortOutFields, SortInFields);
    FillFields(ConsFields, SortOutFields);
     //Set up sorting index (determine fields used for sorting)
    Index := Sort.Index.Edit;
    Index.AddField;
    Index.PlainInputField(0, 0) := SortInFields.FindById("VALUE");
    Index.Save;
    Sort.IsFieldAscending(0) := False;
//Save all objects
    EtlProvider.Save;
    Sort.Save;
    EtlConsumer.Save;
//Link of transaformer with all objects
     //Create links
    Link := CreateLink(ETLTask, EtlProvider.PlainOutput, Sort.PlainInput);

    Link1 := CreateLink(ETLTask, Sort.PlainOutput, EtlConsumer.PlainInput);
     //Create visual links
    Shapes := ETLTask.Workspace.Shapes;
    CreateWXLink(ETLTask, Shapes.FindById(EtlProvider.Id), Shapes.FindById(Sort.Id), Link);
    CreateWXLink(ETLTask, Shapes.FindById(Sort.Id), Shapes.FindById(EtlConsumer.Id), Link1);
//Save a task
    (ETLTask As IMetabaseObject).Save;
//Execute a 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 in lists of fields of inputs/outputs
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;