只对现有字段进行排序

Question

我有这样的收藏品。只有少数用户有sortOrder字段

[{
    "_id": "59ccf78bde3d14019169c105",
    "name": "Best FX broker ",
},
{
    "_id": "59ccf78bde3d14019169c102",
    "name": "Best automated Performance tool ",
    "sortOrder": 1,
},
{
    "_id": "59ccf78bde3d14019169c104",
    "name": "Best Regtech/ reporting solution ",
},
{
    "_id": "59ccf78bde3d14019169c106",
    "name": "NEW: BEST CRYPTO SERVICE PROVIDER",
    "sortOrder": 2,
}]

当我按sort({"sortOrder": 1})排序时，我得到了这个

[{
    "_id": "59ccf78bde3d14019169c105",
    "name": "Best FX broker ",
},
{
    "_id": "59ccf78bde3d14019169c104",
    "name": "Best Regtech/ reporting solution ",
},
{
   "_id": "59ccf78bde3d14019169c102",
    "name": "Best automated Performance tool ",
    "sortOrder": 1,
},
{
    "_id": "59ccf78bde3d14019169c106",
    "name": "NEW: BEST CRYPTO SERVICE PROVIDER",
    "sortOrder": 2,
}]

但是我需要像这样对集合进行排序(值的顶部是sortOrder字段)

[ {
   "_id": "59ccf78bde3d14019169c102",
    "name": "Best automated Performance tool ",
    "sortOrder": 1,
},
{
    "_id": "59ccf78bde3d14019169c106",
    "name": "NEW: BEST CRYPTO SERVICE PROVIDER",
    "sortOrder": 2,
},
{
    "_id": "59ccf78bde3d14019169c105",
    "name": "Best FX broker ",
},
{
    "_id": "59ccf78bde3d14019169c104",
    "name": "Best Regtech/ reporting solution ",
}]

我应该写什么查询才能得到这个？

Answer 1

db.collection.aggregate([
{$project : {"_id" : 1, "sortOrder" : 1,"name":1, "sortOrder": { "$ifNull": [ "$sortOrder", ""] }}},
{$sort : {sortOrder : 1}}   
])

Answer 2

您可以使用回调以几乎任何方式处理该类型。

虽然我的解决方案效率低得令人讨厌(对不起)，但它有效：

array.sort(function (a, b) {
  if (a.sortOrder == undefined && b.sortOrder == undefined) {
    return 0;
  }
  if (a.sortOrder == undefined) {
    return 1;
  }
  if (b.sortOrder == undefined) {
    return -1;
  }
  if (a.sortOrder > b.sortOrder) {
    return 1;
  }
  if (a.sortOrder < b.sortOrder) {
    return -1;
  }

  return 0;
});

这里的a和b变量是数组中的元素，这里返回-1将其移动到数组的前面，0不变，1将其移回数组的后面，如果这是合理的话。