Most "data lineage" you've seen answers a schema question: table B comes from table A, or column B.total comes from columns A.price and A.qty. That's genuinely useful, and tools like OpenLineage do it well. But notice what it doesn't tell you: it says which columns can influence an output. It never says which values actually did.
That gap is the whole subject of this post. I built a small, self-contained reference pipeline that captures provenance at the row and field level — "the value in this destination row, this field, was computed from these specific source (row, field) pairs" — and I want to walk through two things: why you'd ever want provenance at that granularity, and why it's genuinely hard once you commit to it.
Repo (dbt-core + DuckDB, no server, no cloud, runs on a clean checkout): https://github.com/stevenblough/row-level-prov
The one distinction everything follows from
Here's the sentence the entire project turns on:
