Knobit of Data modelling · K-826 · Skill

Recognises undetected drift between database and model

What it means

Nothing that compares the deployed catalogue with the current generated DDL. Hotfix indexes, emergency nullability changes and a column someone added under incident pressure accumulate in production, and the model stops describing the thing people actually query — while continuing to look right, which is what makes it dangerous.

How it is assessed

Flags the deficient case and passes the acceptable one. Deficient: `ix_fact_payment_status_code` added in production during an incident eighteen months ago. It exists in no environment's DDL and in no model, and the next rebuild of the mart is slow for reasons nobody can reconstruct Acceptable: A scheduled comparison of the deployed catalogue (`information_schema`, or the engine's own schema-compare tooling) with the generated DDL, each difference closed deliberately — into the model, or out of the database — and the comparison's result part of the stage-8 evidence

Builds on

Explains testing DDL by execution and detecting driftK-859 · Knowledge
Explains forward and reverse engineering of data modelsK-914 · Knowledge

Needed by

None