Re: parallel mode and parallel contexts

On Mon, Apr 20, 2015 at 6:49 PM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> I see that you're using git format-patch to generate this. But the
> patch is only patch 1/4. Is that intentional? Where are the other
> pieces?
>
> I think that the parallel seqscan patch, and the assessing parallel
> safety patch are intended to fit together with this patch, but I can't
> find a place where there is a high level overview explaining just how
> they fit together (I notice Amit's patch has an "#include
> "access/parallel.h", which is here, but that wasn't trivial to figure
> out). I haven't been paying too much attention to this patch series.

The intended order of application is:

- parallel mode/contexts
- assess parallel safety
- parallel heap scan
- parallel seq scan

The parallel heap scan patch should probably be merged into the
parallel seq scan patch, which should probably then be split into
several patches, one or more with general parallel query
infrastructure and then another with stuff specific to parallel
sequential scan. But we're not quite there yet. Until we can get
agreement on how to finalize the parallel mode/contexts patch, I
haven't been too worried about getting the other stuff sorted out
exactly right.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company