August 17, 2023

tCouchDBOutput – Docs for ESB 5.x

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tCouchDBOutput

tcouchdboutput_icon32_white.png

Warning

This component will be available in the Palette of the studio on the condition that you have subscribed to
one of the Talend solutions with Big
Data.

tCouchDBOutput properties

Component family

Big Data / CouchDB

  

Function

tCouchDBOutput receives data from
the preceding component, and writes data into CouchDB.

Purpose

tCouchDBOutput allows you to load
JSON documents, write data into or remove data from them and then
save the documents back to the database on a CouchDB server.

Basic settings

Schema and Edit schema

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

Since version 5.6, both the Built-In mode and the Repository mode are
available in any of the Talend solutions.

Click Edit schema to make changes to the schema. If the
current schema is of the Repository type, three options are
available:

  • View schema: choose this option to view the
    schema only.

  • Change to built-in property: choose this option
    to change the schema to Built-in for local
    changes.

  • Update repository connection: choose this option to change
    the schema stored in the repository and decide whether to propagate the changes to
    all the Jobs upon completion. If you just want to propagate the changes to the
    current Job, you can select No upon completion and
    choose this schema metadata again in the [Repository
    Content]     window.

 

 

Built-In: You create and store the schema locally for this
component only. Related topic: see Talend Studio
User Guide.

 

 

Repository: You have already created the schema and
stored it in the Repository. You can reuse it in various projects and Job designs. Related
topic: see Talend Studio User Guide.

When the schema to be reused has default values that are integers or functions, ensure that
these default values are not enclosed within quotation marks. If they are, you must remove
the quotation marks manually.

For more details, see https://help.talend.com/display/KB/Verifying+default+values+in+a+retrieved+schema.
 

Sync columns

Click this button to retrieve schema from the previous component
connected in the Job.

Connection

Use existing connection

Select this check box and in the Component List click the
relevant connection component to reuse the connection details you already defined.
  DB Version

Select the CouchDB version that you are using.
 

Server

Hostname or IP address of the CouchDB server.
 

Port

Listening port number of the CouchDB server.
 

Database

Name of the database that you want to use.

Authentication

Required authentication

Select this check box to provide credentials for the CouchDB
authentication.

  • Username: Type in the
    user name for the CouchDB authentication.

  • Password: Type in the
    password for the CouchDB authentication.

To enter the password, click the […] button next to the
password field, and then in the pop-up dialog box enter the password between double quotes
and click OK to save the settings.

Replication

Use trigger replication

Select this check box to trigger replication between
databases.

Warning

This check box appears only if you do not select the Use an existing connection check
box.

Replicate target
database

Target DB name

Specify the target database to which the documents will be copied.
It can be a local database name or a remote database URL.
 

Continuous

Select this check box to continue a replication upon the server
restart.

 

Create target DB

Select this check box to create the target database if it does not
exist.
 

IS Canceled

Select this check box to cancel the existing replication between
the specified source database and target database at the end of the
Job.
 

Action on data

On the data of interest, you can perform:

  • Insert: Insert data into
    the database.

  • Update: Update data in
    the database.

  • Upsert: Insert the data
    if they do not exist or update the existing data.

  • Delete: Remove the data
    from the database.

JSON Configuration

Generate JSON Document

Select this check box to generate a JSON document and configure
the desired data structure for it.
 

Key

Select the key that you want to use from the list.
 

Configure JSON Tree

Click the […] button to open
the window for JSON tree configuration. For more information, see
Configuring a JSON Tree.
 

Group by

Customize the input columns based on which you want to group the
data.
 

Remove root node

Select this check box to remove the root node.
 

Die on error

This check box is cleared by default, meaning to skip the row on
error and to complete the process for error-free rows.

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

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_INSERTED: the number of rows inserted. This is an
After variable and it returns an integer.

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.

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 used as an output component and it always needs
an incoming link.

Log4j

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.

Limitation

n/a

Scenario: Replicating data from the source database to the target database

This scenario describes a Job that writes the information of books into a CouchDB
database, replicates the data to the target database, and then displays some replicated
information of interest on the console.

use_case_couchdboutput.png

Linking the components

  1. Drop the following components from the Palette onto the design workspace: tCouchDBConnection, tFileInputDelimited, tCouchDBOutput, tCouchDBInput, tLogRow and
    tCouchDBClose.

  2. Connect tFileInputDelimited to tCouchDBOutput using a Row > Main link.

  3. Do the same to connect tCouchDBInput to
    tLogRow.

  4. Connect tCouchDBConnection to tFileInputDelimited using a Trigger > OnSubjobOk
    link.

  5. Do the same to connect tFileInputDelimited to tCouchDBInput and tCouchDBInput to tCouchDBClose.

  6. Label the components to better identify their functions.

Configuring the components

Opening a CouchDB connection and triggering replication

  1. Double-click the tCouchDBConnection
    component to open its Basic settings view
    in theComponent tab.

    use_case_couchdboutput1.png

  2. In the Server and Port fields, type in the connection details.

  3. In the Database field, type in the name
    of the database you want to use: bookstore_old in this example.

  4. Select the CouchDB version that you are using from the DB Version list.

  5. Select the Use trigger replication check
    box.

  6. In the Replicate target database area,
    click [+] to add one line for database
    replication settings.

  7. Enter the name of the target database name: bookstore_new in this example.

  8. Select the Continuous check box to
    continue the replication upon the server restart.

  9. In this example, the target database does not exist. Select the Create target DB check box to create the target
    database.

  10. Select the Is Canceled check box to
    cancel the replication between bookstore_old and bookstore_new at the end of the Job.

Reading the input data

  1. Double-click the tFileInputDelimited
    component to open its Component
    view.

    use_case_couchdboutput2.png

  2. Click the […] button next to the
    File name/Stream field to browse to the
    file that you want to read data from. In this scenario, it is D:/Input/bookstore.txt. The file contains six
    columns: _id, title, author, category, ISBN, and abstract.

  3. In the Header field, type in 1 so that the header of the file will be
    skipped.

  4. Click Edit schema to define the data to
    pass on to the tCouchDBOutput component.

    use_case_couchdboutput3.png

Writing data into one database and replicating the data

  1. Double-click the tCouchDBOutput component
    to open its Basic settings view in the
    Component tab.

    use_case_couchdboutput4.png

  2. Click Sync columns to retrieve the schema
    from the preceding component.

  3. Select the Use an existing connection
    check box. In this example, the replication is triggered when opening the
    CouchDB connection.

  4. Select Upsert from the Action on data drop-down list.

Extracting the replicated data of interest

  1. Double-click the tCouchDBInput component
    to open its Component view.

    use_case_couchdboutput5.png

  2. Click Edit schema to define the data
    structure to be read from the CouchDB database.

    By default, the Include docs check box is
    selected, so the id, key, value and jsonDoc columns are available in the
    schema.

    In this example, we define four columns to be extracted: id, title,
    author and category.

    use_case_couchdboutput6.png

  3. Enter the Server and Port information.

  4. In the Database field, enter the name of
    the database from which the replicated data will be read. In this example,
    it is bookstore_new.

  5. In the Querying options area, type in the
    start key and end key to set the range of the data to be read: “001” and “006” in this example.

  6. Select the Extract JSON field check box
    to extract the desired data.

  7. Select jsonDoc from the JSON field list.

  8. In the Mapping area, click [+] to add items. Select the schema output column
    from the list and then type in the proper XPath query.

Displaying the extracted data

  1. Double-click the tLogRow component to
    open its Component view.

  2. Click Edit schema to define the data
    structure to be displayed on the console. In this example, we need to remove
    the jsonDoc column.

  3. In the Mode area, select Table (print values in cells of a table).

Closing the CouchDB connection

  1. Double-click the tCouchDBClose component
    to open its Component view.

    use_case_couchdboutput7.png

  2. Select the connection to be closed from the Component List.

Saving and executing the Job

  1. Press Ctrl+S to save your Job.

  2. Execute the Job by pressing F6 or
    clicking Run on the Run tab.

    use_case_couchdboutput8.png

    The book information read from the replicated database is shown on the
    console.

Document get from Talend https://help.talend.com
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Docs 5.x
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