[realtime database] concurrent queries on the same path don't work

[monodop]

Whenever I have multiple react components that reference the same path (.e.g /users), the library seems to get the results mixed up. In my project, I had a navbar element that displayed an "Admin" button if the user is an admin, and a table that shows all of the users, with some cursor-based pagination. Between those components, only the last query would yield any results. Switching to the second page and back to the first yields zero results, even though the queries passed in are the same (I verified this in the debugger).

As part of my troubleshooting, I tried using get() directly from firebase/database instead of using reactfire, and I had the same issue. This lead me to believe that the root cause comes from firebase-js-sdk instead of reactfire. I found the following issue logged there, but it's been open since February with no fix yet. firebase/firebase-js-sdk#6038

I'm not sure if this should be logged in this project, but it pretty much means this library is completely broken for any real-life applications when using realtime database.

Version info

React: 17.0.2

Firebase: 9.8.1

ReactFire: 4.2.0

Other (e.g. Node, browser, operating system) (if applicable): Chrome 101.0.4951.54

Test case

https://codesandbox.io/s/reactfire-repro-4p16yo

Steps to reproduce

The test case shows that the three queries do not work at the same time. The last loaded table seems to take precedence. If you comment out any of the tables and reload the page, you should be able to see that each query works independently.

I've also seen an issue where sometimes the data doesn't come back at all, but I don't have a repro for that yet.

Expected behavior

Multiple queries on the same page should be able to produce different outputs

Actual behavior

Multiple queries on the same page all produce the same output, or no output at all.

[jhuleatt]

Thanks for the detailed report and repro @monodop! Seems like something is up with the code that differentiates Realtime DB queries:

reactfire/src/database.tsx

Lines 13 to 19 in 823eaa2

	function getUniqueIdForDatabaseQuery(query: DatabaseQuery) {
	const index = cachedQueries.findIndex((cachedQuery) => cachedQuery.isEqual(query));
	if (index > -1) {
	return index;
	}
	return cachedQueries.push(query) - 1;
	}

[felixhayashi]

Hi, maybe this is issue is now solved via firebase/firebase-js-sdk#6038 (comment)