graphviz semijoin task loop without operator loop

semijoin-cycle.dot

# dot -Tsvg -o semijoin-cycle.svg semijoin-cycle.dot
digraph {
	rankdir=TB;
	subgraph cluster_map2 {
		label="Map 2";
		TS_2 -> JOIN_1 -> JOIN_2 -> FS_1;
		JOIN_1 -> RS_4;
		FS_1 -> RS_4 [label="artificial", style="dashed", color="red", constraint=false]; 
	}
	subgraph cluster_map1 {
		label="Map 1";
		TS_0 -> RS_1 -> JOIN_1;
	}
	subgraph cluster_map3 {
		label="Map 3";
		TS_4 -> RS_3;
		RS_4 -> TS_4 [label="semijoin", style="dashed", constraint=false];
		RS_3 -> JOIN_2;
	}
}