MongoDB 有向无环图的设计模式

MongoDB 是一种流行的 NoSQL 数据库，它以其灵活的文档模型而闻名。除了基本的文档存储外，MongoDB 还支持许多高级特性，如有向无环图（Directed Acyclic Graph，DAG）。在这篇文章中，我们将探讨 MongoDB 中有向无环图的设计模式，并通过一个案例代码来说明。

javascript
db.tasks.insertMany([
  { _id: "task1", name: "任务1" },
  { _id: "task2", name: "任务2" },
  { _id: "task3", name: "任务3" },
  { _id: "task4", name: "任务4" }
]);

javascript
db.dependencies.insertMany([
  { source: "task1", target: "task2" },
  { source: "task2", target: "task3" },
  { source: "task1", target: "task4" }
]);

javascript
db.dependencies.find({ source: "task1" });

javascript
session.startTransaction();
try {
  db.tasks.deleteOne({ _id: "task1" });
  db.dependencies.deleteMany({ $or: [{ source: "task1" }, { target: "task1" }] });
  session.commitTransaction();
} catch (error) {
  session.abortTransaction();
  throw error;
} finally {
  session.endSession();
}