GPPLAN2DOT, a utility that can be used to convert the plan generated by Greenplum to dot. And the usage is very simple, just type:

go get -v github.com/hidva/gpplan2dot/gpplan2dot
psql -d tpch -t -A -c "EXPLAIN (format json) `cat q02.sql`" | gpplan2dot | dot -Tsvg > q02.svg

And open q02.svg will show: