I wrote:
> That seems like a fairly bad idea: it will add extra contention
> on ProcArrayLock, and I see no real strong argument that the path
> can't get traversed often enough for that to matter. It would
> likely be better for KnownAssignedXidsCompress to obtain the lock
> for itself, only after it knows there is something worth doing.
Since we're running out of time in the current commitfest,
I went ahead and changed that, and made the cosmetic fixes
I wanted, and pushed.
regards, tom lane