Table of Contents


  1. Preface
  2. Using the Designer
  3. Working with Sources
  4. Working with Flat Files
  5. Working with Targets
  6. Mappings
  7. Mapplets
  8. Mapping Parameters and Variables
  9. Working with User-Defined Functions
  10. Using the Debugger
  11. Viewing Data Lineage
  12. Comparing Objects
  13. Managing Business Components
  14. Creating Cubes and Dimensions
  15. Using the Mapping Wizards
  16. Datatype Reference
  17. Configure the Web Browser

Understanding the Mapping

Understanding the Mapping

The slowly growing target mapping performs the following tasks:
  • Selects all rows
  • Caches the existing target as a lookup table
  • Compares logical key columns in the source against corresponding columns in the target lookup table
  • Filters out existing rows
  • Generates a primary key for new rows
  • Inserts new rows to the target
The following figure shows a mapping that the Getting Started Wizard creates when you create a slowly growing target mapping:
The Source Qualifier transformation connects to a Filter transformation that passes data through an Update Strategy transformation to a target. The source qualifier also connects to a Lookup transformation, which passes data through an Expression transformation to the Filter transformation. The mapping also contains a Sequence Generator transformation that passes data directly to the target.
The slowly growing target mapping uses a Lookup and an Expression transformation to compare source data against existing target data. When you step through the Getting Started Wizard you enter the logical key columns in the source to compare against the existing target. When the Expression transformation detects source rows without matching key columns in the target, it flags the row new.
A Filter transformation passes only new rows to the Update Strategy transformation. The Update Strategy transformation marks new rows for insert and a Sequence Generator creates a new primary key value for each row written to the target.

Updated July 02, 2020