Data engineering·Files, formats and table layers
the vendor added three columns and renamed one over the weekend, and nobody told anybody.
Schema drift
Also calledstructural drift, unannounced schema change
The source's structure changing without coordination — added, removed, renamed or retyped fields. It is distinct from planned schema evolution in exactly the way that matters: nobody agreed to it, so no compatibility rule was applied. Handling it means deciding in advance whether unknown fields are absorbed, ignored or fatal, and a pipeline that has never made that decision has made it implicitly by whichever the library defaults to.