r0 := UnboundTable: t
  a int64

r1 := Filter[r0]
  r0.a < 42
  r0.a >= 42

r2 := Project[r1]
  a: r1.a
  x: r1.a + 42

r3 := Aggregate[r2]
  groups:
    x: r2.x
  metrics:
    y: Sum(r2.a)

Limit[r3, n=10]