Apollo query does not return cached data available using readFragment

Question

I have 2 queries: getGroups(): [Group] and getGroup($id: ID!): Group. One component first loads all groups using getGroups() and then later on a different component needs to access a specific Group data by ID.

I'd expect that Apollo's normalization would already have Group data in cache and would use it when getGroup($id: ID!) query is executed, but that's not the case.

When I set cache-only fetchPolicy nothing is returned. I can access the data using readFragment, but that's not as flexible as just using a query.

Is there an easy way to make Apollo return the cached data from a different query as I would expect?

Daniel Rearden Daniel Rearden · Accepted Answer · 2019-08-08T21:17:14

It's pretty common to have a query field that returns a list of nodes and another that takes an id argument and returns a single node. However, deciding what specific node or nodes are returned by a field is ultimately part of your server's domain logic.

As a silly example, imagine if you had a field like getFavoriteGroup(id: ID!) -- you may have the group with that id in your cache but that doesn't necessarily mean it should be returned by the field (it may not be favorited). There's any number of factors (other arguments execution context, etc.) that might affect what nodes(s) are returned by a field. As a client, it's not Apollo's place to make assumptions about your domain logic.

However, you can effectively duplicate that logic by implementing query redirects.

const cache = new InMemoryCache({
  cacheRedirects: {
    Query: {
      group: (_, args) => toIdValue(cache.config.dataIdFromObject({ __typename: 'Group', id: args.id })),
    },
  },
});

Apollo query does not return cached data available using readFragment

1 Answers