Re: Make relfile tombstone files conditional on WAL level

On Fri, Mar 5, 2021 at 11:02 AM Thomas Munro <thomas.munro@gmail.com> wrote:
> This is a WIP with an open question to research: what could actually
> break if we did this?

I thought this part of bgwriter.c might be a candidate:

       if (FirstCallSinceLastCheckpoint())
       {
           /*
            * After any checkpoint, close all smgr files.  This is so we
            * won't hang onto smgr references to deleted files indefinitely.
            */
            smgrcloseall();
       }

Hmm, on closer inspection, isn't the lack of real interlocking with
checkpoints a bit suspect already?  What stops bgwriter from writing
to the previous relfilenode generation's fd, if a relfilenode is
recycled while BgBufferSync() is running?  Not sinval, and not the
above code that only runs between BgBufferSync() invocations.