$in not comparing all values in golang using mongodb

Question

I am using golang as a backend with mongodb

My Collections are

**department**
    {
     dept_id:1,
     dept_name:'CSE',
     dept_overview:'overview'
    }
   ................

**employee**
    {
    emp_id:1,
    emp_name:'abc',
    qualification:'PHD',
    emp_dept:'CSE',
    city:'xyz'
    }
    {
    emp_id:2,
    emp_name:'xyz',
    qualification:'PHD',
    emp_dept:['CSE','ME'],
    city:'xyz',
    status:1
    }
    ..........

Below is my Go code using pipeline

 var conditionParam []bson.M
        if city == "" {
            conditionParam = []bson.M{
                bson.M{"$eq": []string{"$$element.qualification", "PHD"}},
                bson.M{"$in": []interface{}{"$$element.emp_dept", ["CSE"]}},
                bson.M{"$or": []interface{}{"$$element.emp_dept", "CSE"}},
                bson.M{"$eq": []string{"$$element.city", "xyz"}},
                bson.M{"$or": []interface{}{"$exists", []interface{}{"$$element.status", false}}},
                bson.M{"$or": []interface{}{"$$element.status", 1}}, 
            }
    } else if(){
    --------------------
}

matchStage:=bson.M{"$match":bson.M{'dept_id':1}}
lookupStage:=bson.M{"$lookup": bson.M{
    "from":         "employee",
    "localField":   "dept_name",
    "foreignField": "emp_dept",
    "as":           "result_list",
}}
    pipeline := getCollection.Pipe([]bson.M{
            matchStage,
            lookupStage,
            {"$addFields": bson.M{
                "result_list": bson.M{
                    "$filter": bson.M{
                        "input": "$result_list",
                        "as":    "element",
                        "cond": bson.M{
                            "$and": conditionParam,
                        },
                    },
                },
            }},
        })

In my collection some of data stored in string for emp_dept and some of the data stored in string slice. So I am using $in for comparing slice values and $or for string values for emp_dept.$in operator working for database string values but is not working for comparing emp_dept database values in slice. How we can return both values for slice and string for this particular key of mongodb collection.

varman · Accepted Answer · 2020-08-29 07:34:47Z

1

The problem I understood is, you need to filter the array by $result_list.emp_dept which is in two different type that are string and array. You can use $type to check whether it's an array or string. If the scenario is correct, the following query works fine. Since you have written the pipeline in Go, I hope you can convert the following query to Go. Bcs I'm not a Go developer.

[
  {
    "$lookup": {
      "from": "employee",
      "localField": "dept_name",
      "foreignField": "emp_dept",
      "as": "result_list"
    }
  },
  {
    $addFields: {
      "result_list": {
        $filter: {
          input: "$result_list",
          cond: {
            $cond: [
              {
                $eq: [ { $type: "$$this.emp_dept" }, "string" ]
              },
              { // if the type is string
                $and: [
                  {
                    $eq: [ "CSE", "$$this.emp_dept" ]
                  },
                  {
                    $eq: [ "$$this.qualification", "PHD" ]
                  },
                  {
                    $eq: [ "$$this.city", "xyz" ]
                  }
                  // Other comparison
                ]
              },
              {  // if the type is NOT string
                $and: [
                  {
                    $in: [ "CSE", "$$this.emp_dept" ]
                  },
                  {
                    $eq: [ "$$this.qualification", "PHD" ]
                  },
                  {
                    $eq: [ "$$this.city", "xyz" ]
                  }
                  // Other comparison
                ]
              }
            ]
          }
        }
      }
    }
  }
]

Working Mongo playground

edited Aug 29, 2020 at 7:34

answered Aug 29, 2020 at 7:22

varman

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6 Comments

Rajandeep Kaur Over a year ago

can we check type inside $and then use $eq and $in accordingly for emp_dept only because I have no of parameters for comparison. like if type=='string' then $eq else $in

varman Over a year ago

Of course yes, You can check $eq and $in another stage

Rajandeep Kaur Over a year ago

I want to use only one $and and compare type for dept inside it without effecting other elements but I did not understand how to do it?

varman Over a year ago

You expect mongoplayground.net/p/whiMB9HbZSs ???

Rajandeep Kaur Over a year ago

$varman where to compare the other element as $cond takes only 3 arguments?

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