mongo group by sum not working in same cases-CodePudding

I have 2 queries:

aggregate( [
  { 
      $match: {"user_id": 5918725, "shop_id": 1775207, "$text": {"$search" : "API"}}
  },
  { 
      $group: { 
          _id: "_id", 
          count: { 
              $sum: { 
                  $cond: [ { $eq: [ "$deleted_at", null ] }, 1, 0 ]  
              } 
          } 
      } 
  }
]);

and

aggregate( [
  { 
      $match: {"user_id": 5918725, "shop_id": 1775207, "$text": {"$search" : "APIU"}}
  },
  { 
      $group: { 
          _id: "_id", 
          count: { 
              $sum: { 
                  $cond: [ { $eq: [ "$deleted_at", null ] }, 1, 0 ]  
              } 
          } 
      } 
  }
]);

they are the same, only difference is a search keyword, but they behave differently, in case of the first query, result is :

{
    "_id" : null,
    "count" : 0.0
}

which is expected result, but in case of the second one, result is Fetched 0 record(s) (that is what my GUI shows). So for some reason in case of the second query it simply ignore group/sum and trying to get actual records. How can I solve it, thank you in advance!

CodePudding user response：

Query

the easy way to do it its on the driver, if no results you make this document with code
this is the way to do it on the database, with 2 extra stages, union and group, and one extra collection (in mongodb 5.3 we wouldnt need the extra collection)
put for example instead of 5 a negative number and even if no results you still get count : 0

Test code here

aggregate(
[{"$match":{"$expr":{"$lt":["$a", 5]}}},
 {"$group":{"_id":null, "count":{"$sum":1}}},
 {"$unionWith":{"coll":"2"}},
 {"$group":{"_id":null, "count":{"$sum":"$count"}}}])