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In Firebase Cloud Firestore, I have "user_goals" in collections and goals may be a predefined goal (master_id: "XXXX") or a custom goal (no "master_id" key)
In JavaScript, I need to write two functions, one to get all predefined goals and other to get all custom goals.
I have got some workaround to get custom goals by setting "master_id" as "" empty string and able to get as below:
db.collection('user_goals') .where('challenge_id', '==', '') // workaround works .get() Still this is not the correct way, I continued to use this for predefined goals where it has a "master_id" as below
db.collection('user_goals') .where('challenge_id', '<', '') // this workaround .where('challenge_id', '>', '') // is not working .get() Since Firestore has no "!=" operator, I need to use "<" and ">" operator but still no success.
Question: Ignoring these workarounds, what is the preferred way to get docs by checking whether a specific field exists or does not exists?
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There are three ways to retrieve data stored in Cloud Firestore. Any of these methods can be used with documents, collections of documents, or the results of queries: Call a method to get the data once. Set a listener to receive data-change events.
Collections and documents are created implicitly in Cloud Firestore. Simply assign data to a document within a collection. If either the collection or document does not exist, Cloud Firestore creates it.
A DocumentReference refers to a document location in a Firestore database and can be used to write, read, or listen to the location. The document at the referenced location may or may not exist. A DocumentReference can also be used to create a CollectionReference to a subcollection.
Is there any way to get the last created document in Firebase Firestore collection? Yes, there is! The simplest way to achieve this is to add a date property to each object in your collection, then simply query it according to this new property descending and call limit(1) function. That's it!
As @Emile Moureau solution. I prefer
.orderBy(`field`) To query documents with the field exists. Since it will work with any type of data with any value even for null.
But as @Doug Stevenson said:
You can't query for something that doesn't exist in Firestore. A field needs to exist in order for a Firestore index to be aware of it.
You can't query for documents without the field. At least for now.
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The preferred way to get docs where a specified field exists is to use the:
.orderBy(fieldPath) As specified in the Firebase documentation:
Thus the answer provided by @hisoft is valid. I just decided to provide the official source, as the question was for the preferred way.
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