Re: unlogged tables vs. GIST

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Fri, Dec 17, 2010 at 3:03 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Yeah. I think that BM_UNLOGGED might be a poor choice for the flag name,
>> just because it overstates what the bufmgr needs to assume.

> I was actually thinking of adding BM_UNLOGGED even before this
> discussion, because that would allow unlogged buffers to be excluded
> from non-shutdown checkpoints. We could add two flags with different
> semantics that take on, under present rules, the same value, but I'd
> be disinclined to burn the extra bit without a concrete need.

bufmgr is currently using eight bits out of a 16-bit flag field, and
IIRC at least five of those have been there since the beginning. So our
accretion rate is something like one bit every four years. I think not
being willing to use two bits to describe two unrelated behaviors is
penny-wise and pound-foolish --- bufmgr is already complicated enough,
let's not add useless barriers to readability.

regards, tom lane