Drop a standalone/pipe query clause — the composable cousin of Mutare.Ecto.Query's whole-from clause drop, and the query-side twin of Mutare.Ecto.Changeset's validator drop. Where Query removes a where:/limit: clause from a from(…) keyword list, this removes the same kinds of clause written as a standalone call or pipe stage:

q |> where([u], u.active)   →  q          "is this filter tested?"
q |> limit(10)              →  q          "is the page size pinned?"
q |> group_by([u], u.role)  →  q          "is this grouping tested?"

A surviving mutant means no test exercises what that clause contributes — the primary motivating mutation for a query builder (NOTES "ClauseDrop: the pipe form was the common one").

Delivery is the shared pipe-aware stage drop (Mutare.Ecto.StageDrop): piped, the stage becomes Function.identity/1; written directly, the call collapses to its query argument. The call is resolved through Mutare.Calls, so it matches the direct, aliased, and (common) import Ecto.Query forms alike, and never a same-named user function.

Families

The recorded family mirrors Mutare.Ecto.Query, so the same semantic mutation carries the same family regardless of which syntax wrote it:

• where/or_where/having/or_having → :filter_drop;
• limit/offset → :bound (the bound family also covers the n→n±1 bumps);
• every other clause builder (group_by, distinct, select/select_merge, join, preload, lock, with_cte, windows, the set-operation macros) → :clause_drop.

order_by/prepend_order_by are deliberately not droppable (an unordered query's row order is SQL-unspecified); the implicit-direction flip in Mutare.Ecto.Ordering is the reliable ordering mutant instead.

A dropped stage can leave a later stage referencing a binding/CTE/window the query no longer has — but these macros build the query at runtime, so that surfaces as a runtime error when the mutant is exercised (killing it), never a compile error of the single metamutant build.