- These are like the previous queries, (e.g. orders of a customer on a given date).
- But slow because we can't do a lookup by customer id which is fast. That's not
how the record storage is organized.
Could add an index: e.g. invoice key → (customer key, order key)
- Fixes the performance problem.
- But why is lookup by invoice key so unlike lookup by customer key?
- Because the hierarchical model doesn't abstract storage very much.