tFilterRow - 6.3

Talend Open Studio for Big Data Components Reference Guide

EnrichVersion
6.3
EnrichProdName
Talend Open Studio for Big Data
task
Data Governance
Data Quality and Preparation
Design and Development
EnrichPlatform
Talend Studio

Function

tFilterRow filters input rows by setting one or more conditions on the selected columns.

Purpose

tFilterRow helps parametrizing filters on the source data.

tFilterRow Properties

Component family

Processing

 

Basic settings

Schema and Edit Schema

A schema is a row description. It defines the number of fields (columns) to be processed and passed on to the next component. The schema is either Built-In or stored remotely in the Repository.

The schema of this component is built-in only.

 

Logical operator used to combine conditions

Select a logical operator to combine simple conditions and to combine the filter results of both modes if any advanced conditions are defined.

And: returns the boolean value of true if all conditions are true; otherwise false. For each two conditions combined using a logical AND, the second condition is evaluated only if the first condition is evaluated to be true.

Or: returns the boolean value of true if any condition is true; otherwise false. For each two conditions combined using a logical OR, the second condition is evaluated only if the first condition is evaluated to be false.

 

Conditions

Click the plus button to add as many simple conditions as needed. Based on the logical operator selected, the conditions are evaluated one after the other in sequential order for each row. When evaluated, each condition returns the boolean value of true or false.

Input column: Select the column of the schema the function is to be operated on

Function: Select the function on the list

Operator: Select the operator to bind the input column with the value

Value: Type in the filtered value, between quotes if needed.

 

Use advanced mode

Select this check box when the operations you want to perform cannot be carried out through the standard functions offered, for example, different logical operations in the same component. In the text field, type in the regular expression as required.

If multiple advanced conditions are defined, use a logical operator between two conditions:

&& (logical AND): returns the boolean value of true if both conditions are true; otherwise false. The second condition is evaluated only if the first condition is evaluated to be true.

|| (logical OR): returns the boolean value of true if either condition is true; otherwise false. The second condition is evaluated only if the first condition is evaluated to be false.

Advanced settings

tStatCatcher Statistics

Select this check box to gather the Job processing metadata at the Job level as well as at each component level.

Global Variables

ERROR_MESSAGE: the error message generated by the component when an error occurs. This is an After variable and it returns a string. This variable functions only if the Die on error check box is cleared, if the component has this check box.

NB_LINE: the number of rows read by an input component or transferred to an output component. This is an After variable and it returns an integer.

NB_LINE_OK: the number of rows matching the filter. This is an After variable and it returns an integer.

NB_LINE_REJECTED: the number of rows rejected. This is an After variable and it returns an integer.

A Flow variable functions during the execution of a component while an After variable functions after the execution of the component.

To fill up a field or expression with a variable, press Ctrl + Space to access the variable list and choose the variable to use from it.

For further information about variables, see Talend Studio User Guide.

Usage

This component is not startable (green background) and it requires an output component.

Log4j

If you are using a subscription-based version of the Studio, the activity of this component can be logged using the log4j feature. For more information on this feature, see Talend Studio User Guide.

For more information on the log4j logging levels, see the Apache documentation at http://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/Level.html.

Scenario 1: Filtering a list of names using simple conditions

The following scenario shows a Job that uses simple conditions to filter a list of records. This scenario will output two tables: the first will list all male persons with a last name shorter than nine characters and aged between 10 and 80 years; the second will list all rejected records. An error message for each rejected record will display in the same table to explain why such a record has been rejected.

Dropping and linking components

  1. Drop tFixedFlowInput, tFilterRow and tLogRow from the Palette onto the design workspace.

  2. Connect the tFixedFlowInput to the tFilterRow, using a Row > Main link. Then, connect the tFilterRow to the tLogRow, using a Row > Filter link.

  3. Drop tLogRow from the Palette onto the design workspace and rename it as reject. Then, connect the tFilterRow to the reject, using a Row > Reject link.

  4. Label the components to better identify their roles in the Job.

Configuring the components

  1. Double-click tFixedFlowInput to display its Basic settings view and define its properties.

  2. Click the [...] button next to Edit schema to define the schema for the input data. In this example, the schema is made of the following four columns: LastName (type String), Gender (type String), Age (type Integer) and City (type String).

    When done, click OK to validate the schema setting and close the dialog box. A new dialog box opens and asks you if you want to propagate the schema. Click Yes.

  3. Set the row and field separators in the corresponding fields if needed. In this example, use the default settings for both, namely the row separator is a carriage return and the field separator is a semi-colon.

  4. Select the Use Inline Content(delimited file) option in the Mode area and type in the input data in the Content field.

    The input data used in this example is shown below:

    Van Buren;M;73;Chicago
    Adams;M;40;Albany
    Jefferson;F;66;New York
    Adams;M;9;Albany
    Jefferson;M;30;Chicago
    Carter;F;26;Chicago
    Harrison;M;40;New York
    Roosevelt;F;15;Chicago
    Monroe;M;8;Boston
    Arthur;M;20;Albany
    Pierce;M;18;New York
    Quincy;F;83;Albany
    McKinley;M;70;Boston
    Coolidge;M;4;Chicago
    Monroe;M;60;Chicago
  5. Double-click tFilterRow to display its Basic settings view and define its properties.

  6. In the Conditions table, add four conditions and fill in the filtering parameters.

    • From the InputColumn list field of the first row, select LastName, from the Function list field, select Length, from the Operator list field, select Lower than, and in the Value column, type in 9 to limit the length of last names to nine characters.

    • From the InputColumn list field of the second row, select Gender, from the Operator list field, select Equals, and in the Value column, type in M in double quotes to filter records of male persons.

      Warning

      In the Value field, you must type in your values between double quotes for all types of values, except for integer values, which do not need quotes.

    • From the InputColumn list field of the third row, select Age, from the Operator list field, select Greater than, and in the Value column, type in 10 to set the lower limit to 10 years.

    • From the InputColumn list field of the four row, select Age, from the Operator list field, select Lower than, and in the Value column, type in 80 to set the upper limit to 80 years.

  7. To combine the conditions, select And as that only those records that meet all the defined conditions are accepted.

  8. In the Basic settings of tLogRow components, select Table (print values in cells of a table) in the Mode area.

Executing the Job

  • Save your Job and press F6 to execute it.

    As shown above, the first table lists the records of male persons aged between 10 and 80 years, whose last names are made up of less than nine characters, and the second table lists all the records that do not match the filter conditions. Each rejected record has a corresponding error message that explains the reason of rejection.

Scenario 2: Filtering a list of names through different logical operations

Based on the previous scenario, this scenario further filters the input data so that only those records of people from New York and Chicago are accepted. Without changing the filter settings defined in the previous scenario, advanced conditions are added in this scenario to enable both logical AND and logical OR operations in the same tFilterRow component.

  1. Double-click the tFilterRow component to show its Basic settings view.

  2. Select the Use advanced mode check box, and type in the following expression in the text field:

    input_row.City.equals("Chicago") || input_row.City.equals("New York")

    This defines two conditions on the City column of the input data to filter records that contain the cities of Chicago and New York, and uses a logical OR to combine the two conditions so that records satisfying either condition will be accepted.

  3. Press Ctrl+S to save the Job and press F6 to execute it.

    As shown above, the result list of the previous scenario has been further filtered, and only the records containing the cities of New York and Chicago are accepted.