[james_cowling]

Yes the readsets aren't based on lists of objects but rather the data ranges that a query touches, i.e., they don't suffer from phantom read anomalies.

If you were to attempt to fetch all items from an empty shopping cart, that query will automatically be invalidated if any item is added to the cart, even though there were no documents returned from the original query. Query intersection always works.

The aggregate example isn't a great one in Convex since it doesn't currently support built-in aggregates - a full-table aggregate involves a table scan and therefore the readset would be the entire index. We may add built-in aggregates that are incrementally computed if there's enough demand.