Tell apollo-client what gets returned from X query with Y argiments? - reactjs

Question

I have a list of Items of whatever type. I can query all of them with query items or one with query item(id).
I realize apollo can't know what will be returned. It knows the type, but it doesn't know the exact data. Maybe there is a way not to make additional request? Map one query onto another?
Pseudo-code:
// somewhere in Menu.tsx (renders first)
let items = useQuery(GET_ITEMS);
return items.map(item => <MenuItemRepresenation item={item} />);
// meanwhile in apollo cache (de-normalized for readability):
{ ROOT_QUERY: {
items: [ // query name per schema
{ id: 1, data: {...}, __typename: "Item" },
{ id: 2, data: {...}, __typename: "Item" },
{ id: 3, data: {...}, __typename: "Item" },
]
}
}
// somewhere in MainView.tsx (renders afterwards)
let neededId = getNeededId(); // 2
let item = useQuery(GET_ITEM, { variables: { id: neededId } } );
return <MainViewRepresentation item={item} />;
Code like this will do two fetches. Even though the data is already in the cache. But it seems apollo thinks on query level. I would like a way to explain to it: "If I make item query, you need to look over here at items query you did before. If it has no item with that id go ahead and make the request."
Something akin to this can be done by querying items in MainView.tsx and combing through the results. It might work for pseudo-code, but in a real app it's not that simple: cache might be empty in some cases. Or not sufficient to satisfy required fields. Which means we have to load all items when we need just one.
Upon further research Apollo Link looks promising. It might be possible to intercept outgoing queries. Will investigate tomorrow.

Answer 1

Never mind apollo link. What I was looking for is called cacheRedirects.
It's an option for ApolloClient or Cache constructor.
cacheRedirects: {
Query: {
node: (_, args, { getCacheKey }) => {
const cacheKey = getCacheKey({
__typename: "Item",
id: args.id,
});
return cacheKey;
},
},
},
I'd link to documentation but it's never stable. I've seen too many dead links from questions such as this.