Ident

Ident represents a single variable name, this typically refers to a table but not always. Invisible identities are a rare case where a user returns an embedded table from a map clause:

 case class Emb(id: Int, name: String) case class Parent(id: Int,
name: String, emb: Emb) case class GrandParent(id: Int, par: Parent)

query[GrandParent] .map(g => g.par).distinct .map(p => (p.name,
p.emb)).distinct .map(tup => (tup._1, tup._2)).distinct } 

In these situations, the identity whose properties need to be expanded in the ExpandNestedQueries phase, needs to be marked invisible.