digraph "gin" {
        layout=dot;
        node [label="", shape=box, style=filled, fillcolor=gray, width=1.4];

        m1 [label="meta page"];

        subgraph cluster01 {
                label="entry tree";
                subgraph egroup1 {
                        rank=same;
                        e1;
                }
                subgraph egroup2 {
                        rank=same;
                        e2 -> e3 -> e4;
                }
                subgraph egroup3 {
                        rank=same;
                        e5 -> e6 -> e7 -> e8 -> e9;
                }
                e1 -> e4;
                e1 -> e3;
                e1 -> e2;
                e2 -> e5;
                e2 -> e6;
                e3 -> e7;
                e4 -> e8;
                e4 -> e9;

                e6 [fillcolor=green, label="posting list"];
                e8 [fillcolor=green, label="posting list"];
                e9 [fillcolor=green, label="posting list"];
        }

        subgraph cluster02 {
                label="posting tree";
                subgraph pgroup1 {
                        rank=same;
                        p1;
                }
                subgraph pgroup2 {
                        rank=same;
                        p2 -> p3;
                }
                p1 -> p2;
                p1 -> p3;

                p2 [fillcolor=green, label="heap ptr"];
                p3 [fillcolor=green, label="heap ptr"];
        }

        subgraph cluster03 {
                label="posting tree";
                subgraph pgroup3 {
                        rank=same;
                        p4;
                }

                p4 [fillcolor=green, label="heap ptr"];
        }

        subgraph cluster04 {
                label="posting tree";
                subgraph pgroup4 {
                        rank=same;
                        p5;
                }
                subgraph pgroup5 {
                        rank=same;
                        p6 -> p7;
                }
                p5 -> p6;
                p5 -> p7;

                p6 [fillcolor=green, label="heap ptr"];
                p7 [fillcolor=green, label="heap ptr"];
        }

        subgraph cluster05 {
                label="pending list";
                node [style=filled, fillcolor=red];
                n1 -> n2 -> n3 -> n4;
        }

        m1 -> e1;
        e5 -> p1;
        e7 -> p4;
        e7 -> p5;
        m1 -> n1;

        e5 [style=filled, fillcolor=green4];
        e7 [style=filled, fillcolor=green4];
}