buzz/migrations/0040_workflow_revision_binding.sql

-- Preserve exact signed workflow revisions without changing legacy execution.
-- Existing rows remain NULL until a new signed definition is ingested.
ALTER TABLE workflows
    ADD COLUMN definition_event_id BYTEA
        CHECK (definition_event_id IS NULL OR octet_length(definition_event_id) = 32);
ALTER TABLE workflow_runs
    ADD COLUMN definition_event_id BYTEA
        CHECK (definition_event_id IS NULL OR octet_length(definition_event_id) = 32);

-- A legacy writer does not mention definition_event_id. Column-targeted triggers
-- fire even for equal-value rewrites, where comparing OLD/NEW would invent
-- provenance. New writers rebind separately while still holding the row lock
-- in the signed-event transaction. Operational status/enabled updates keep it.
CREATE FUNCTION invalidate_workflow_revision() RETURNS TRIGGER AS $$
BEGIN
    NEW.definition_event_id := NULL;
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER workflows_invalidate_revision
BEFORE UPDATE OF id, community_id, owner_pubkey, channel_id, name, definition, definition_hash
ON workflows
FOR EACH ROW EXECUTE FUNCTION invalidate_workflow_revision();