[Bizgres-general] Question: Is 64-bit cache support valuable?

[Simon Riggs]

On Mon, 2005-07-18 at 16:45 -0700, Luke Lonergan wrote:
> I have a question for Data Warehousing / Business Intelligence users, is
> 64-bit support to allow large in-memory buffer cache within Postgres
> important?
> 
> There is a patch contributed by Koichi Suzuki of Nippon Telecom that shows
> very good results.  It extends the buffer cache of 8.0.3 to 64-bit, allowing
> for caches larger than 2GB.  See "[PATCHES] A couple of patches for
> PostgreSQL 64bit support" in the pgsql-patches list for details.
> 
> We could adopt this patch within Bizgres and test it, should this be a
> desirable feature.
> 
> Thoughts?

It's worth some thought, and testing on DBT-3.

8.0 uses a scan resistant buffer strategy. 8.1 does not, IIRC. I'm not
sure that having a large shared_buffers works well in either case. In
the former, scans won't put data in the cache, in the latter a scan of a
large table will flush much of the cache out. 

However, having a large work_mem would be very useful... I thought that
it would not be possible to do 64 bit support, but it seems I was wrong.
I'll look into how we could do that...

Best Regards, Simon Riggs