node.js - 查询获取mongodb数组中的所有_id？

Question

我有以下收藏

{
    "_id" : ObjectId("5acdb95d5ea63a27c1facf92"),
    "venue" : ObjectId("5acdb95d5ea63a27c1facf8c"),
    "author" : ObjectId("5ac8ba3582c2345af70d4658"),
}
{
    "_id" : ObjectId("5acdb95d5ea63a27c1facf93"),
    "venue" : ObjectId("5acdb95d5ea63a27c1facf8c"),
    "author" : ObjectId("5ac8ba3582c2345af70d4658"),
}
{
    "_id" : ObjectId("5acdb95d5ea63a27c1facf91"),
    "venue" : ObjectId("5acdb95d5ea63a27c1facf8c"),
    "author" : ObjectId("5ac8ba3582c2345af70d4658"),
}

如何获取具有相同地点的数组中的所有_id

我的输出应该是这样的

{array: ['5acdb95d5ea63a27c1facf91', '5acdb95d5ea63a27c1facf91', '5acdb95d5ea63a27c1facf93']}

Answer 1

尝试这个查询:

db.colelction.aggregate([
  {$match:{"venue" : ObjectId("5acdb95d5ea63a27c1facf8c")}},
  {$group:{_id:null, array:{$push:"$_id"}}},
  {$project:{_id:0}}
])

输出是:

/* 1 */
{
   "array" : [ 
       ObjectId("5acdb95d5ea63a27c1facf92"), 
       ObjectId("5acdb95d5ea63a27c1facf93"), 
       ObjectId("5acdb95d5ea63a27c1facf91")
   ]
}