Re: [GSoC2014] Patch ALTER TABLE ... SET LOGGED

Robert Haas <robertmhaas@gmail.com> writes:
> 2. The patch seems to think that it can sometimes be safe to change
> the relpersistence of an existing relation.  Unless you can be sure
> that no buffers can possibly be present in shared_buffers and nobody
> will use an existing relcache entry to read a new one in, it's not,
> because the buffers won't have the right BM_PERSISTENT marking.  I'm
> very nervous about the fact that this patch seems not to have touched
> bufmgr.c, but maybe I'm missing something.

Maybe I misunderstood something, but I had the impression that this was
handled by assigning a new relfilenode (and hence copying all the data).
So the buffers with one marking would be disjoint from the ones with the
other marking.
        regards, tom lane