tHashInput Standard properties - 7.3

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 remotely stored in the Repository.

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: The schema is created and stored locally for this component only. Related topic: see the Talend Studio User Guide.

Repository: The schema already exists and is stored in the Repository, hence can be reused. Related topic: see the Talend Studio User Guide.

Link with a tHashOutput

Select this check box to connect to a tHashOutput component. It is always selected by default.

Component list

Drop-down list of available tHashOutput components.

Clear cache after reading

Select this check box to clear the cache after reading the data loaded by a certain tHashOutput component. This way, the following tHashInput components, if any, will not be able to read the cached data loaded by that tHashOutput component.

tStatCatcher Statistics

Select this check box to collect log data at the 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 processed. 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 rule

This component is used along with tHashOutput. It reads from the cache memory data loaded by tHashOutput. Together, these twin components offer high-speed data access to facilitate transactions involving a massive amount of data.