This patch has been "Needs Review" and bouncing from CF to CF. It actually looks like it got quite a bit of design discussion and while James Coleman seems convinced of its safety it doesn't sound like Tom Lane and Robert Haas are yet and it doesn't look like that's going to happen in this CF.
I think I'm going to mark this Returned With Feedback on the basis that it did actually get a significant amount of discussion and no further review seems to be forthcoming. Perhaps a more rigorous approach of proving the correctness or perhaps an easier-to-reason-about set of constraints would make it easier to reach a consensus? Once you think the patchset is ready for review again, you (or any interested party) can resurrect the patch entry by visiting https://commitfest.postgresql.org/42/2851/ and changing the status to "Needs Review", and then changing the status again to "Move to next CF". (Don't forget the second step; hopefully we will have streamlined this in the near future!) -- Gregory Stark As Commitfest Manager