Click the Select button next to the Record Map field and then, in the Select a Map dialog box that opens, select the map you want to use and then click OK.
This map must have been previously created in Talend Data Mapper .
Note that the input and output representations are those defined in the map, and cannot be changed in the component.
Click Next.
Tell the component where each new record begins. In order for you to be able to do so, you need to fully understand the structure of your data.
Exactly how you do this varies depending on the input representation being used, and you will be presented with one of the following options.
Separator lets you specify a separator indicator, such as \n, to identify a new line.
Supported indicators are \n for a Unix-type new line, \r\n for Windows and \r for Mac, and \t for tab characters.
Start/End with lets you specify the initial characters that indicate a new record, such as <root, or the characters that indicate where a record ends. This can also be a regular expression.
Start with also supports new lines, \n for a Unix-type new line, \r\n for Windows and \r for Mac, and \t for tab characters.
Testing the signature lets you check that the total number of records and their minimum and maximum length corresponds to what you expect based on your knowledge of the data. This step assumes you have a local subset of your data to use as a sample.
Click Finish.
Minimum Record Size corresponds to the size in bytes of the smallest record. If you set this value too low, you may encounter performance issues, since the component will perform more checks than necessary when looking for a new record.
Maximum Record Size corresponds to the size in bytes of the largest record, and is used to determine how much memory is allocated to read the input.
Testing the signature lets you check that the total number of records and their minimum and maximum length corresponds to what you expect based on your knowledge of the data. This step assumes you have a local subset of your data to use as a sample.
Footer Size corresponds to the size in bytes of the footer, if any. At runtime, the footer will be ignored rather than being mistakenly included in the last record. Leave this field empty if there is no footer.
Click the Next button to open the Signature Parameters window, select the fields that define the signature of your record input structure (that is, to identify where a new record begins), update the Operation and Value columns as appropriate, and then click Next.
In the Record Signature Test window that opens, check that your Records are correctly delineated by scrolling through them with the Back and Next buttons and performing a visual check, and then click Finish.
Create if you want the mapping process to create a new file.
Overwrite if you want the mapping process to overwrite an existing file.
If the check box is unselected, you can retrieve the rejected records in a file. One of these mechanisms triggers this feature: (1) a context variable (Connect the tHMapFile component to an output component, for example tAvroOutput, using a talend_transform_reject_file_path) and (2) a system variable set in the Advanced Job parameters (spark.hadoop.talend.transform.reject.file.path).
When you set the file path on the Hadoop Distributed File System (HDFS), no further configurations are needed. When you set the file on Amazon S3 or any other Hadoop-compatible file systems, add the associated Spark advanced configuration parameter.
In case of errors at runtime, tHMapFile checks if one of the mechanisms exists and, if so, appends the rejected record to the designated file. The reject file content includes the concatenation of the rejected records without any additional metadata.
If the file system you use does not support appending to a file, a separate file is created for each rejection. The file uses the provided file path as the prefix and adds a suffix that is the offset of the input file and the size of the rejected record.