Validates that root where predicates do not rely on empty in lists.

This catches filters whose candidate list is already known to contain no non-nil values.

Examples

Bad:

ids = []

from(Thing, as: :thing)
|> where([thing: t], t.id in ^ids)

Why this is bad:

The query can never match a row because the candidate list has no non-nil values. Running it still spends database work on a known-empty result.

Better:

if Enum.empty?(ids) do
  []
else
  from(Thing, as: :thing)
  |> where([thing: t], t.id in ^ids)
  |> Repo.all()
end

Why this is better:

The caller uses a cheap application fast path and only queries the database when there are candidates to match.

Notes

This check only trusts supported root in predicates. It intentionally leaves broader contradictory business logic to ConflictingWherePredicates.

Such queries usually have a cheaper fast path: return [] before calling the repo. This check is separate from Bylaw.Ecto.Query.Checks.ConflictingWherePredicates because an empty list is usually a missing fast path rather than contradictory business logic.

The check is intentionally narrow. It evaluates root schema fields and only trusts direct in predicates in AND where expressions. Ecto.Enum fields are normalized through the schema enum mapping. or_where and or expressions are handled as separate branches and only rejected when every branch contains an empty in predicate. Fragments, subqueries, and non-root bindings are ignored.

Options

• :validate - explicit false disables the check. Defaults to true.

Usage

Add this module to the explicit check list passed through Bylaw.Ecto.Query. See Bylaw.Ecto.Query for the full Ecto.Repo.prepare_query/3 setup.