Thursday, 1 October 2009

RI Trigger Impact Analysis

The previous post discussed the need to regenerate programs that call changed RI triggers. The difficulty is in performing this impact analysis.

The Gen model does contain associations between action blocks and RI triggers (using IMPUSE associations if you are familiar with the Gen schema), but the important point to note is that these associations are maintained by the code generators. This means that if you change the data model, the IMPUSE association data in the model is not accurate until you have regenerated the affected code, which makes it useless in helping you understand what you need to regenerate!

We faced this issue when developing the impact analysis process that GuardIEn performs when it detects data model changes. To work out what RI triggers are directly affected by a data model change is straight forward, but the consequential impact on other triggers and action block / procedure steps involves a complex navigation though the data model, following cascade delete chains for example. It is also affected by the choice of generated or DBMS enforced RI rules.

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