Merge Rows (diff) | Pentaho Data Integration

Let's say we're doing a delta load of new data at specific times ..

Based on keys for comparison, we can use this step to merge reference rows (previous data) with compare rows (new data) to create merged output rows.

A flag in the row indicates how the values were compared and merged. Flag values include:

i• dentical

The key was found in both rows, and the compared values are identical.

• changed

The key was found in both rows, but one or more compared values are different.

• new

The key was not found in the reference rows.

• deleted

The key was not found in the compare rows.

If the rows are flagged as deleted, the merged output rows are created based upon the original reference rows stream.

For identical, new, or changed rows, the merged output rows are created based upon the original compare rows stream.

This step can be used in conjunction with the Merge Rows (diff) transformation step. The Merge Rows (diff) transformation step appends a Flag column to each row, with a value of "identical", "changed", "new" or "deleted".

This flag column is then used by the Synchronize after merge transformation step to carry out updates/inserts/deletes on a connection table.

This step uses the flag value to perform the sync operations on the database table.

• Set the Key from both the Table and Stream.

• Get the Table / Stream Fields and ensure mapping is correct.

• Dont Update the Keys..!!

Option

Description

Default Value

Operation fieldname

This is a required field. This field is used by the step to obtain an operation flag for the current row.

flagfield

Insert when value equal

Specify the value of the Operation fieldname which signifies that anInsert should be carried out.

new

Update when value equal

Specify the value of the Operation fieldname which signifies that an Update should be carried out.

changed

Delete when value equal

Specify the value of the Operation fieldname which signifies that a Delete should be carried out.

deleted

Perform lookup

Performs a lookup when deleting or updating. If the lookup field is not found, then an exception is thrown. This option can be used as an extra check if you wish to check updates/deletes prior to their execution.

View the data in the Table.

Run the Transformation with the hop between the Merge Rows (diff) and Synchronize after merge .. disabled.

Run the Transformation with the hop enabled.
Examine and compare the records.