Join coverage

The share of rows that found a match when a table was joined to a reference. It is published as a number with a configured threshold. An unpublished coverage figure is how a join that dropped a third of the rows still reports a confident average of whatever happened to survive it.

Principle 8 · Thresholds are configuration, not code

Where does Join coverage come from?

Principle 8 of the Kymira doctrine, Thresholds are configuration, not code. Join coverage is the name the doctrine gives to what that principle requires in practice.

What failure is Join coverage named after?

The join that quietly covers 62%. A reference join drops a third of rows and the report says nothing, because nothing asked.

What does it look like on a real file?

A reference join covering 62% of rows is published as 62% and rejected by the threshold, not averaged over the survivors.

Not for

Not a quality score for the match itself. Coverage counts rows that found a partner; it says nothing about whether the partner was right.

Nearest terms

Refuse, don't guessThe rule that ambiguity is an error to raise, not a heuristic to apply Relabel, never revalueThe line between cleaning data and authoring it Flag stakesWhat a flag must carry to count as one: the flagged row's share of every headline it feeds, at...

Last updated 2026-09-02 · Dylan, founder · one of 40 terms in the Kymira glossary, each one named after something we watched go wrong in a real build or in our own audits.

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