Unique rules

unique: true in a field's block means no two records may hold the same value in that field. A rule over several fields goes in the entity's unique: { } section, with a name and its fields as a list:

type ProjectName = Text {    max_length: 80}entity User {    id: Uuid    email: Email {        unique: true  // one user per address    }}entity Project {    id: Uuid    owner_id: User.id {        on_delete: OnDelete.cascade    }    name: ProjectName    unique: {        name_per_owner: [owner_id, name]    }}

Here one user may own only one project of a given name. A rule's fields must exist, be different fields, and be required, so every engine agrees on what a duplicate is. A write that breaks the rule refers to it by its name when it maps the conflict to a failure (Conflicts).

On a tenant's records, a rule holds within each tenant: its key holds the tenancy reference too (A unique rule holds within its tenant).