Separate Queries Instead Multiple Where Clause in Firestore

Question

I want to query firebase firestore data collection with two paramaters.

The collection: animals

"animals": {
   "1": {
      "animal1": "cat",
      "animal2": "dog",
      "animal3": "",
      "animal4": ""
   },
   "2": {
      "animal1": "dog",
      "animal2": "cat",
      "animal3": "",
      "animal4": ""
   },
   "3": {
      "animal1": "cat",
      "animal2": "bird",
      "animal3": "dog",
      "animal4": ""
   },
   "4": {
      "animal1": "wolf",
      "animal2": "dog",
      "animal3": "bird",
      "animal4": ""
   },
   "5": {
      "animal1": "turtle",
      "animal2": "dog",
      "animal3": "wolf",
      "animal4": "cat"
   },
   "6": {
      "animal1": "dog",
      "animal2": "wolf",
      "animal3": "turtle",
      "animal4": "bear"
   },
   "7": {
      "animal1": "spider",
      "animal2": "beatle",
      "animal3": "butterfly",
      "animal4": "Cat"
   }
}

I want getting list datas that include cat and dog . There is information In here Logical OR queries. In this case, you should create a separate query for each OR condition and merge the query results in your app.

I don't know how many separate query I need?

let param1 = 'cat';
let param2 = 'dog';

let query1 = db.collection('animals').where('animal1', '==', param1);
let query2 = db.collection('animals').where('animal2', '==', param1);
let query3 = db.collection('animals').where('animal3', '==', param2);
let query4 = db.collection('animals').where('animal4', '==', param3);

Answer 1

As you have noted "you should create a separate query for each OR condition and merge the query results in your app". Since, with your data model, you have 4 fields ( animal1 to animal4 ) you will need to create 4 queries for each param value you want to test for.

So in case of 2 params, as follows:

let param1 = 'cat';
let param2 = 'dog';

you will have to merge the results of 2*4 queries....

There is a possibility to decrease this number if you change your data model and use an array for storing the animal values. You could then take advantage of the array_contains operator.

Proposed data model:

"animals": {
   "1": {
      "animalArray": 
          [
             0: "cat",
             1: "dog"
          ] 
   },
   "2": {
      "animalArray": 
          [
             0: "turtle",
             1: "dog",
             2: "wolf",
             3: "bear",
          ]
   }
   .....
}

With our example of two params , you would need two queries only, as follows:

let query1 = db.collection('animals').where("animalArray", "array-contains", param1);
let query2 = db.collection('animals').where("animalArray", "array-contains", param2);