Relationship between QueryObserver and queryCache.clear

[bulksup]

Hello,

I have a question regarding the relationship between QueryObserver and queryCache.clear() in React Query.
I created a new QueryObserver and subscribed to it using the subscribe method.

I then called queryCache.clear() to remove all cache.
After that, I updated the query data using setQueryData, but I noticed that the existing observer did not emit the new data.

So I created another new QueryObserver and subscribed again, which worked as expected.

However, I later found that the original observer (which had already been "removed") emitted the old cached data once the staleTime of 10 minutes passed.

Questions:

• Is it an expected behavior that an observer continues to emit data based on staleTime, even after queryCache.clear() is called?
• If this is intentional, does it mean we must manually unsubscribe existing observers before calling queryCache.clear() to avoid this?
• Am I missing something in my understanding of how queryCache.clear() interacts with observers?

Thanks in advance for the clarification!

[TkDodo]

not sure what the use-case is for working with observers directly? when you clear the cache, active observers are not informed about those changes. I usually don’t recommend clearing the cache while there are active queries. However, when an observer receives an update e.g. because useQuery re-renders, it would just re-create the cache entry an re-fetch data.

After that, I updated the query data using setQueryData, but I noticed that the existing observer did not emit the new data.

yeah that can’t work because the new query doesn’t know anything about the old observer. I don’t think this is supported.

However, I later found that the original observer (which had already been "removed") emitted the old cached data once the staleTime of 10 minutes passed.

the observer hasn’t been “removed”, you removed the query it was observing, it sounds like the observer is still there? Really curious what you are trying to achieve with all that because it sounds way too low level for an application. If you just useQuery things should work.