On Thu, Dec 11, 2008 at 4:29 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Greg Stark <greg.stark@enterprisedb.com> writes:
>>> A variable prefetch_pages is defined as "unsigned" or "int"
>>> in some places. Why don't you define it only once in a header
>>> and include the header in source files?
>
>> Just... Which header?
>
> MHO: the header that goes with the source file that is most concerned with
> implementing the variable's behavior (which is also the file that should
> have the actual variable definition).
Well the trick here is that the variable actually affects how many
PrefetchBuffer() calls *callers* should make. The callers are various
places which are doing lots of ReadBuffer calls and know what buffer's
they'll need in the future. The main places are in
nodeBitmapHeapScan.c and nbtsearch.c. Neither of those are remotely
relevant.
I think i'm settling in that it should be in the same place as the
PrefetchBuffer() prototype since anyone who needs prefetch_buffers
will need that as well (except for guc.c). So I'll put it in bufmgr.h
for now.
--
greg