Filter Service Records

This recipe combines common checks for a service record. Assume the schema has status as a string, owner as an optional object with a nullable string email, labels as a string-keyed map, and items as a list of objects with numeric price and quantity fields.

Match a useful record

status:in("open", "pending")
owner!.email~"@example\\.com$"
labels.has("tenant") labels.get("tenant")="north"
items:any(item=>item.price*item.quantity>=100)

The first predicate admits only active statuses. The postfix guard makes the optional owner path safe; when the owner is absent or has the wrong shape, that predicate is false. The two metadata checks distinguish a missing key from a stored null. The collection callback selects records with at least one qualifying line item.

Relax a condition safely

When a query accepts dynamic values, narrow the receiver before calling a family-specific method:

metadata.get("region"):[string]:lower="north"

The type guard preserves a matching string. A value of another type becomes internal no-value, which converts to a false predicate. If a missing value should also be accepted, express that policy explicitly with a separate predicate and ordinary short-circuit operators.

Keep collection and null behavior explicit

has() checks presence even when a value is null. get() returns null for both a missing key and a present null value, so combine them when presence matters. List callbacks short-circuit left-to-right, and cancellation or a resource-limit error remains an error rather than a non-match.

See the collection guide, callback guide, and evaluation specification for the complete rules.