Re: SLRU optimization - configurable buffer pool and partitioning the SLRU lock

I wrote:
> It looks like SLRU_PAGE_EMPTY has (by chance, or deliberately)
> the numeric value of zero, so I guess the majority of our BF
> animals are understanding this as "address != NULL".  But that
> doesn't look like a useful test to be making.

In hopes of noticing whether there are other similar thinkos,
I permuted the order of the SlruPageStatus enum values, and
now I get the expected warnings from gcc:

In file included from ../../../../src/include/postgres.h:45,
                 from slru.c:59:
slru.c: In function ‘SimpleLruWaitIO’:
slru.c:436:38: warning: comparison between pointer and integer
  Assert(&shared->page_status[slotno] != SLRU_PAGE_EMPTY);
                                      ^~
../../../../src/include/c.h:862:9: note: in definition of macro ‘Assert’
   if (!(condition)) \
         ^~~~~~~~~
slru.c: In function ‘SimpleLruWritePage’:
slru.c:717:43: warning: comparison between pointer and integer
  Assert(&ctl->shared->page_status[slotno] != SLRU_PAGE_EMPTY);
                                           ^~
../../../../src/include/c.h:862:9: note: in definition of macro ‘Assert’
   if (!(condition)) \
         ^~~~~~~~~

So it looks like it's just these two places.

            regards, tom lane