Relational
Marker interface with unique key, which allows all RelationalOperatorFactory implementations to exist in a Map<OperatorFactoryKey, OperatorFactory>.
Implementations of this interface also define a create function, each with a different signature, but always returning an instance of RelationExpression, which is ready to be evaluated as part of query evaluation. Within the create function, the factory factory may access any values placed in its org.partiql.lang.domains.PartiqlPhysical.Impl.staticArgs, which may be relevant to the operator's implementation and perform any compile-time initialization of the RelationExpression.