mongo 和 NodeJs 中的动态查询要求嵌入文档的字段？

Question

I am trying to make a dynamic query based on multiple selection of the user.

In my application I have the Publication schema that has the Pet schema embedded as follows:

var status = ["public", "private", "deleted"];

var publication_schema = new Schema({
  pet:{
    type: Schema.Types.ObjectId, 
    ref: "Pet"
  },
  status: {
    type: String,
    enum: status,
    default: status[0]
  }
});

module.exports = mongoose.model('Publication', publication_schema);

var pet_schema = new Schema({
  type: {
    type: String,
    require: true
  },
  createdDate: { 
    type: Date, 
    default: Date.now 
  }
});

module.exports = mongoose.model('Pet', pet_schema);

Insyde an async method I build the query, getting all the user input values from the object filter , also I have the query object where I push the different criteria and use it with an $and

  let query = {};
  let contentQuery = []

  if (filter.public && !filter.private) {
    contentQuery.push({ status: { $eq: "public" } });
  } else if (filter.privada && !filter.public) {
    contentQuery.push({ status: { $eq: "private" } });
  } 

 query = { $and: contentQuery }
 try {
    const publication = await Publication.find(query).populate('pet');

  } catch (e) {
    console.log(e)
  }

the problem is when I want to add more criteria such as follows:

if (filter.specie) { // for example filter.specie equals 'cat'
     contentQuery.push({ pet: { type: { $eq: filter.specie } } });
}

I get the error:

'Cast to ObjectId failed for value "{ type: { \'$eq\': \'cat\' } }" at path "pet" for model "Publication"',
  name: 'CastError',
  stringValue: '"{ type: { \'$eq\': \'cat\' } }"',
  kind: 'ObjectId',
  value: { type: { '$eq': 'cat' } },
  path: 'pet',
  reason: undefined,
  model: Model { Publication } }

So. How can I do to query the fields of publication and also the pet fields inside publication?

Answer 1

You can have a look on Populate Query Conditions

Instead of .populate('pet') you could do something like

Publication.find({})
  .populate({
    path: 'pet',
    match: { specie: 'cat'},
    // You can select the fields you want from pet, or remove the select attribute to select all
    select: 'name -_id',
    // Here you could add options (e.g. limit)
    options: { limit: 5 }
  }).exec();

The above query will get you all Publications with pet.specie equals to 'cat'