runAggregate sometimes produces more than one plan executor. Each PlanExecutor needs to be associated to one and only one ShardRole::TransactionResources. Since only the "main" executor has associated ShardRole acquisitions, that executor will be bound to the TransactionResources that back these acquisitions. The rest of the executors, which can be related to exchange or to mongot metadata pipelines, will be bound to an empty set of TransactionResources, since they never reference ShardRole acquisitions.