explanation of firebase docs about query(query, queryConstraints)?-CodePudding

I was looking about more details about the query function in firestore in docs reference of firestore and I found this pseudo syntax :

query(query, queryConstraints)

but in all firestore examples about this function they used in the first parameter a collection reference not query

form firestore examples :

// Create a reference to the cities collection
import { collection, query, where } from "firebase/firestore";
const citiesRef = collection(db, "cities");

// Create a query against the collection.
const q = query(citiesRef, where("state", "==", "CA"));

Is it the same function or this this another Signature for it ?

CodePudding user response：

A collection reference is a subclass of a query, so wherever the API expects a Query you can also pass a CollectionReference. So you can build a new query by passing a CollectionReference to the query function, or add conditions to an existing query by passing a Query to it.