# when extension only is kept
- alf: |-
    project(extend(suppliers, a: "A", b: "B"), [:a, :b])
  optimized: |-
    project(extend(suppliers, a: "A", b: "B"), [:a, :b])
# when extension is not at all touched
- alf: |-
    project(extend(suppliers, a: "A", b: "B"), [:sid, :a, :b])
  optimized: |-
    project(extend(suppliers, a: "A", b: "B"), [:sid, :a, :b])
# when extension is entirely removed
- alf: |-
    project(extend(suppliers, a: "A", b: "B"), [:sid])
  optimized: |-
    project(suppliers, [:sid])
# when extension is partially removed
- alf: |-
    project(extend(suppliers, a: "A", b: "B"), [:sid, :a])
  optimized: |-
    project(extend(suppliers, a: "A"), [:sid, :a])