tUniqRow Standard properties

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. When you create a Spark Job, avoid the reserved word line when naming the fields.

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.

This component offers the advantage of the dynamic schema feature. This allows you to retrieve unknown columns from source files or to copy batches of columns from a source without mapping each column individually. For further information about dynamic schemas, see Talend Studio User Guide.

This dynamic schema feature is designed for the purpose of retrieving unknown columns of a table and is recommended to be used for this purpose only; it is not recommended for the use of creating tables.

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.

Unique key

In this area, select one or more columns to carry out deduplication on the particular column(s)

- Select the Key attribute check box to carry out deduplication on all the columns

- Select the Case sensitive check box to differentiate upper case and lower case

Only once each duplicated key

Select this check box if you want to have only the first duplicated entry in the column(s) defined as key(s) sent to the output flow for duplicates.

Use of disk (suitable for processing large row set)

Select this check box to enable generating temporary files on the hard disk when processing a large amount of data. This helps to prevent Job execution failure caused by memory overflow. With this check box selected, you need also to define:

- Buffer size in memory: Select the number of rows that can be buffered in the memory before a temporary file is to be generated on the hard disk.

- Directory for temp files: Set the location where the temporary files should be stored.

Ignore trailing zeros for BigDecimal

Select this check box to ignore trailing zeros for BigDecimal data.

tStatCatcher Statistics

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

Global Variables

NB_UNIQUES: the number of unique rows. This is an After variable and it returns an integer.

NB_DUPLICATES: the number of duplicate rows. 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 rule

This component handles flow of data therefore it requires input and output, hence is defined as an intermediary step.