I am writing a function to query a Firestore database collection for documents that have only certain properties. The filters is defined as an array of "key, value" pairs. eg:
[
["Colour", "green"],
["Colour", "blue"],
["Greeting", "hello"]
]
This array can be of any length, and I am trying to get every document in the database that does not have values listed in the filter array.
I can do this by using:
await db.collection("database")
.where("Colour", "!=", "blue")
.where("Colour", "!=", "green")
.where("Greeting", "!=", "hello")
.get()
My issue is that the filter can be any length, so I cannot write the query to have a set number of .where()
methods. Is there any way in JavaScript that I can dynamically add methods to a query like shown above (not knowing how many methods I need to add)?
My workaround right now is just to query the entire database, then sort it using Javascript filter functions, but I would like to only have to query the database for the values needed.
Alternatively, are there any other Firestore queries that could complete this filter? I was looking at the docs, but the way my filter is set up with key/value pairs that could be repeated or undefined, it did not seem that any of the complex query methods would work.
CodePudding user response:
Assuming that you are building an array full of only excluded key-value pairs and the values you are excluding are properly indexed, we can start off defining some constants:
const collectionRef = db.collection("database");
const excludedKeyValuePairs = [
["Colour", "green"],
["Colour", "blue"],
["Greeting", "hello"],
]
Now we have those, we can build the query using Array#reduce.
const query = excludedKeyValuePairs
.reduce(
(query, [key, value]) => query.where(key, "!=", value), // appends the new constraint, returning the new query object
collectionRef
);
const querySnapshot = await query.get();
However, if you can use the newer modular Firestore SDK, you can also achieve the same result using:
import { getFirestore, getDocs, collection, query, where } from "firebase/firestore";
const db = getFirestore();
const collectionRef = collection(db, "database");
const constraints = [
where("Colour", "!=", "green"),
where("Colour", "!=", "blue"),
where("Greeting", "!=", "Hello")
// elements can also be added or removed using standard array methods as needed.
]
// OR const constraints = excludedKeyValuePairs.map(([key, value]) => where(key, "!=", value))
const querySnapshot = await getDocs(query(collectionRef, ...constraints));
CodePudding user response:
You can map from your array of conditions to where clauses with:
const exclusions = [
["Colour", "green"],
["Colour", "blue"],
["Greeting", "hello"],
]
let collectionRef = db.collection("database");
const conditions = exclusions.map((e) => where(e[0], "!=", e[1]));
let query = query(collectRef, conditions);
const querySnapshot = await getDocs(query);