Queries and mappers

const findAdmins = JIT.query(Users)
  .params({ minimumScore: JIT.number() })
  .filter((q, params) =>
    q.and(q.eq("role", "admin"), q.gte("score", params.minimumScore)),
  )
  .select("id", "name")
  .compile();

The generated query does not allocate a filter result before mapping. It preallocates one output array, writes by cursor and trims once. count, sum, avg, min and max avoid result arrays entirely.

Mappers whitelist the destination shape and compile renames, nested mapping and bulk many() loops. Callback overrides remain external bindings and are reported when they cannot be emitted safely by AOT.

Aggregation

const revenue = JIT.query(Orders)
  .filter((q) => q.eq("status", "paid"))
  .sum("total")
  .compile();

count and sum return zero for empty input. avg, min and max return undefined. Aggregates do not allocate an output array.

Params versus constants

Use .params(shape) for values supplied per call. Use JIT.const(value) for a primitive compiler literal. Ordinary closure values become safe external bindings. No untrusted value is interpolated into generated source.

Collection outputs

unique retains first occurrences, keyed returns a Map, groupBy returns arrays per key and orderBy performs a global sort. Mutation operators rebuild collections immutably and require a filter to prevent accidental full-table updates/deletes.

Mapper strategy

Prefer declarative renames and target schemas for portable AOT. Callback fields are useful at runtime but may prevent build-time emission unless represented by an explicit importable external.

For all incremental operators and output backends, see Query operators.