Package-level declarations

A query backend over one index. Before the aggregate's first write its index does not exist yet; every read of a missing index answers nothing (no rows, a count of 0, no groups), as the snapshot store's load does, rather than failing.

Compiles admitted filters to Elasticsearch queries. Every field, system fields included, compiles at the physical path its admission resolved; a root exact match on _id becomes an ids query.

The mapping of an index, cached per index until refresh.