tMapROjaiInput Standard properties

A schema is a row description. It defines the number of fields (columns) to be processed and passed on to the next component. When you create a Spark Job, avoid the reserved word line when naming the fields.

• Built-In: You create and store the schema locally for this component only.

• Repository: You have already created the schema and stored it in the Repository. You can reuse it in various projects and Job designs.

Click Edit schema to make changes to the schema. If you make changes, the schema automatically becomes built-in.

• 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.

This component supports the Document type. If a field is for entire documents, select Document in the Type column for this field in the schema editor.

Click Sync columns to retrieve the schema from the previous component connected in the Job.

Use kerberos authentication

If you are accessing a MapR-DB as-OJAI database running with Kerberos security, select this check box, then, enter the Kerberos principal name and password in the displayed fields.

Every time when you launch your Job, the component submits this authentication information to Kerberos for a new kinit ticket.

Select the Use a keytab to authenticate check box to log into a Kerberos-enabled system using a given keytab file. A keytab file contains pairs of Kerberos principals and encrypted keys. You need to enter the principal to be used in the Principal field and the access path to the keytab file itself in the Keytab field. This keytab file must be stored in the machine in which your Job actually runs, for example, on a Talend JobServer.

Note that the user that executes a keytab-enabled Job is not necessarily the one a principal designates but must have the right to read the keytab file being used. For example, the username you are using to execute a Job is user1 and the principal to be used is guest; in this situation, ensure that user1 has the right to read the keytab file to be used.

Restrict partial sorts with Secondary Indexes

Select this check box to force the query to explicitly sort on the actual data. This way, you avoid in your query the partial sorts that could otherwise occur due to the asynchronous secondary indexes.

For further information about this partial sorts issue of MapR OJAI, see Asynchronous Secondary Index Updates from the MapR documentation.

Do not select this check box if you do not expect to encounter the lags in the asynchronous indexes or you know that the impact of the lags is trivial. By keeping this check box clear, your query benefits from the ordering advantages provided by the secondary indexes of MapR-DB JSON tables.

Table name

Enter the name of the table to be processed.

Query

Specify the where clause of the query to be performed by tMapROjaiInput.

For example, type in "{id:{$eq: 4}}" or "{id:4}}"to retrieve the record in which id is 4.

As OJAI uses MongoDB query format for queries, see Query Operators from the MongoDB documentation for available operators.

Mapping

Each column of the schema defined for this component represents a field of the documents to be read. In this table, you need to specify the parent nodes of these fields, if any.

{
               _id: ObjectId("5099803df3f4948bd2f98391"),
               person: { first: "Joe", last: "Walker" }
            }

Column     Parent node path
_id
first       "person"
last        "person"

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.

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 more information about variables, see Using contexts and variables.

Usage rule

tMapROjaiInput executes queries to read data from a given MapR-DB database. It is a starting component of a Job and requires an outgoing link to send data to its following component.