// build initial plan
            this.plan = buildInitialPlan(taskSegments);
        }

        BuildContext() {
            this.session = null;
            this.reactorContext = null;
            this.threads = 1;
            this.executor = null;
            this.plan = null;
        }

        public BuildPlan buildInitialPlan(List<TaskSegment> taskSegments) {
            int nThreads = Math.min(