How would you fetch a single element using its key with TanStack DB?

[MalekIhdene]

Hello, I went through the documentation and I haven't found a way to fetch a single element without calling the list endpoint of my query collection. Essentially, I would like to have people and people/:id where :id would be my collection item key. Is there a pattern for that anywhere? Should I simply create a fetch function and then do a direct write to the cache?

Thank you for your time and consideration.

[joshuadutton]

To get a single item from a collection:

1. Live query builder using findOne: https://tanstack.com/db/latest/docs/guides/live-queries#findone
2. get directly on the collection: https://tanstack.com/db/latest/docs/reference/interfaces/Collection#get

But I think you are asking how to fetch only one item from your API using a queryCollection. To do that, you can use an on-demand query collection and use the loadSubsetOptions to get the filter/where expression to show which item is being requested. I have a list endpoint that uses filters, so I convert this expression to the filters that my API understands to just fetch one item. If your list endpoint doesn't support that, you could parse the filter from Tanstack DB to determine if only one item is being requested and then request that instead of using the list endpoint. See https://tanstack.com/db/latest/docs/collections/query-collection#queryfn-and-predicate-push-down