如何用MongoDB聚合实现优先取likes、无则取dislikes并过滤无值文档？

你可以通过MongoDB聚合的$match阶段实现需求，核心逻辑是过滤掉同时不存在likes和dislikes字段的文档，保留至少存在其中一个字段的文档：

db.collection.aggregate([
  {
    $match: {
      $or: [
        { likes: { $exists: true } },
        { dislikes: { $exists: true } }
      ]
    }
  }
])

逻辑说明 #

• $match阶段用于筛选符合条件的文档：
  • $or表达式指定两个可选条件，满足任意一个即可保留文档：
    • { likes: { $exists: true } }：匹配存在likes字段的文档（无论是否包含dislikes）
    • { dislikes: { $exists: true } }：匹配仅存在dislikes字段的文档

该逻辑会自动过滤掉既无likes也无dislikes的文档，最终结果与你给出的期望输出完全一致。

验证示例 #

输入数据 #

const data = [
  { _id: 0, name: "jane", joined: ISODate("2011-03-02"), dislikes: 9 },
  { _id: 1, name: "joe", joined: ISODate("2012-07-02") },
  { _id: 2, name: "Ant", joined: ISODate("2012-07-02"), likes: 60, dislikes: 2 },
  { _id: 2, name: "Ant", joined: ISODate("2012-07-02"), dislikes: 12 },
  { _id: 2, name: "Ant", joined: ISODate("2012-07-02"), dislikes: 12 },
  { _id: 2, name: "Ant", joined: ISODate("2012-07-02") }
]

输出结果 #

[
  { _id: 0, name: "jane", joined: ISODate("2011-03-02"), dislikes: 9 },
  { _id: 2, name: "Ant", joined: ISODate("2012-07-02"), likes: 60, dislikes: 2 },
  { _id: 2, name: "Ant", joined: ISODate("2012-07-02"), dislikes: 12 },
  { _id: 2, name: "Ant", joined: ISODate("2012-07-02"), dislikes: 12 }
]

内容的提问来源于stack exchange，提问作者Zillur Rahman