Tuesday, 29 September 2009

RI Triggers

In my experience, one of the more misunderstood aspects of Gen development is RI triggers, and the impact of making a change in the data model.

In many cases, users think that they only need to regenerate the RI triggers once they have made their data model changes. Unfortunately it is more complex than that.

The correct process is:

1) Implement any changes to table or column names in the data structure
2) Run the Ref. Integrity Process (accessed from the toolset Design menu) to synchronise the technical design RI constraints with the data model
3) Generate the affected RI triggers
4) Re-generate all action blocks that call the re-generated RI triggers
5) Install re-generated code

Steps (1) and (2) can either be performed separately or accomplished using the Retransformation tool.

The reason why you need to regenerate the action blocks that call the RI triggers is that the code generated for a DELETE, DISASSOCIATE, TRANSFER, etc. depends on the RI rules in the model. If these rules change (for example changing a relationship from cascade delete to pendent delete), then the action blocks require regeneration as well as the RI triggers.

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