Re: Make relfile tombstone files conditional on WAL level

On Fri, Mar 5, 2021 at 11:02 AM Thomas Munro <thomas(dot)munro(at)gmail(dot)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.