ETL: Example of Data Filtering in Fore

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

The repository must contain two tables T_Source, T_Destination», the tables must be identical in structure and must contain the ID field. Values of this field are used to set up filtering condition. 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 Filter converter and repository consumer. The required properties are defined for all objects, links are set and filtering condition is defined:

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;
    Filter: IEtlPlainDataFilter;
    Link, Link1: IEtlPlainLink;
    Shapes: IWxShapes;
    ProvFields, FilterInFields, FilterOutFields, ConsFields: IEtlPlainFields;
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 Filter converter
    Filter := ETLTask.Create(EtlObjectType.PlainDataFilter) As IEtlPlainDataFilter;
    Filter := Filter.Edit;
    Filter.Id := "Filter_Transform";
    Filter.Name := "Filter";

     //Create a visual object of transformer
    CreateWX(ETLTask, Filter, 0, 0);
//Fill in lists of fields of all objects based on source fields list
     //Get fields list
    ProvFields := EtlProvider.PlainOutput.Fields;  //Source output
    FilterInFields := Filter.PlainInput.Fields;  //Transformer input
    FilterOutFields := Filter.PlainOutput.Fields;  //Transformer output
    ConsFields := EtlConsumer.PlainInput.Fields;  //Consumer input
     //Fill in fields lists
    FillFields(FilterInFields, ProvFields);
    FillFields(FilterOutFields, FilterInFields);
    FillFields(ConsFields, FilterOutFields);

     //Set up filtering parameters: skip all records, for which ID<30
    Filter.FilterIf.AsString := Filter.PlainInput.Id + ".ID<30";
    Filter.KeepIfFulfillCondition := False;
//Save all objects
    EtlProvider.Save;
    Filter.Save;
    EtlConsumer.Save;
//Link of transformer with all objects
     //Create links
    Link := CreateLink(ETLTask, EtlProvider.PlainOutput, Filter.PlainInput);
    Link1 := CreateLink(ETLTask, Filter.PlainOutput, EtlConsumer.PlainInput);

//Create visual links Shapes:=ETLTask.Workspace.Shapes; CreateWXLink(ETLTask,Shapes.FindById(EtlProvider.Id),Shapes.FindById(Filter.Id),Link); CreateWXLink(ETLTask,Shapes.FindById(Filter.Id),Shapes.FindById(EtlConsumer.Id),Link1); //Save task (ETLTaskAsIMetabaseObject).Save; //Perform task ETLTask.Execute(Null); EndSubUserProc; //Create visual objects SubCreateWX(ETLTask:IEtlTask;ETLObject:IEtlObject;XPosition:Integer;YPosition:Integer); Var WxRect:IWxRectangle;

WxETLObj:IWxEtlObject; Begin WxRect:=ETLTask.Workspace.CreateRectangle; WxRect.Id:=ETLObject.Id; WxETLObj:=NewWxEtlObject.Create; WxETLObj.EtlObject:=ETLObject; WxRect.Style.TextPosition:=WxTextPosition.Bottom; WxRect.Style.PictureMarginTop:=-10; WxRect.PinPosition:=NewGxPointF.Create(XPosition,YPosition); WxRect.Extension:=WxETLObjAsIWxShapeExtension; EndSubCreateWX; //Fill lists of input/output lists SubFillFields(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;

EndFunctionCreateLink; //Create visual links SubCreateWXLink(ETLTask:IEtlTask;Shape1:IWxShape;Shape2:IWxShape;Link:IEtlPlainLink); Var WLink:IWxLink; WxETLLink:IWxEtlObject; Begin //Create visual objects of the link WLink:=ETLTask.Workspace.AutoLinkShapes(Shape1,Shape2); WLink.Style.LinePenBeginWxCap:=WxLineCap.Flat; WLink.Style.LinePenEndWxCap:=WxLineCap.Arrow30DegreeFilled; WxETLLink:=NewWxEtlObject.Create; WxETLLink.EtlObject:=Link; WLink.Extension:=WxETLLinkAsIWxShapeExtension; EndSubCreateWXLink;