The following review has been posted through the commitfest application:
make installcheck-world: not tested
Implements feature: not tested
Spec compliant: not tested
Documentation: not tested
For whatever it is worth, the patch looks good to me.
A minor nitpick would be to use a verb in the part:
`cost when the parameter in (0, 1)`
maybe:
`cost when the parameter's value is in (0, 1)` or similar.
Apart from that, I would suggest it that the patch could be moved to
Waiting for Author state.