How to specify that at least one field is required out of three in total?

Question

In my MongoDB model, there are 3 fields in total. Any document added to this collection must contain at least 1 of those 3 fields.

How can this be specified in the validation staged?

Answer 1

You can enum validation constraint which collection creation as below:

db.createCollection("jobs", {
   validator: {
      $jsonSchema: {
         bsonType: "object",
         required: [ "status" ],
         properties: {
            status: {
               enum: [ "Done", "Failed", "Initial" ],
               description: "can only be one of the enum values and is required"
            },
         }
      }
   }
})

From the docs

Mongoose has several inbuilt validators. Strings have enum as one of the validators. So enum creates a validator and checks if the value is given in an array. E.g:

var userSchema = new mongooseSchema({
   status: {
        type: String,
        enum : ['Done','Failed', 'Initial'],
        default: 'Initial'
    },
})

---

You can use custom validator to check if we have one of 3 keys in the object

const testSchema = mongoose.Schema({
  field1: {
    type: String,
    validate: {
      validator: function(v) {
        if (this.field2 == undefined && this.field3 == undefined) {
          return true;
        }
        return false;
      },
    },
  },
  field2: {
    type: String,
    validate: {
      validator: function(v) {
        if (this.field1 == undefined && this.field3 == undefined) {
          return true;
        }
        return false;
      },
    },
  },
  field3: {
    type: String,
    validate: {
      validator: function(v) {
        if (this.field2 == undefined && this.field1 == undefined) {
          return true;
        }
        return false;
      },
    },
  },
});