Re: Extensible Rmgr for Table AMs

Hi,

On Tue, Feb 01, 2022 at 03:38:32PM -0800, Jeff Davis wrote:
> On Tue, 2022-02-01 at 20:45 +0800, Julien Rouhaud wrote:
> >
> > One last thing, did you do some benchmark with a couple custom rmgr
> > to see how
> > much the O(n) access is showing up in profiles?
>
> What kind of a test case would be reasonable there? You mean having a
> lot of custom rmgrs?
>
> I was expecting that few people would have more than one custom rmgr
> loaded anyway, so a sparse array or hashtable seemed wasteful. If
> custom rmgrs become popular we probably need to have a larger ID space
> anyway, but it seems like overengineering to do so now.

I agree that having dozen of custom rmgrs doesn't seem likely, but I also have
no idea of how much overhead you get by not doing a direct array access. I
think it would be informative to benchmark something like simple OLTP write
workload on a fast storage (or a ramdisk, or with fsync off...), with the used
rmgr being the 1st and the 2nd custom rmgr. Both scenario still seems
plausible and shouldn't degenerate on good hardware.