Re: [HACKERS] Parallel Append implementation

On Fri, Sep 29, 2017 at 7:48 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> I think in general the non-partial paths should be cheaper as compared
> to partial paths as that is the reason planner choose not to make a
> partial plan at first place. I think the idea patch is using will help
> because the leader will choose to execute partial path in most cases
> (when there is a mix of partial and non-partial paths) and for that
> case, the leader is not bound to complete the execution of that path.
> However, if all the paths are non-partial, then I am not sure much
> difference it would be to choose one path over other.

The case where all plans are non-partial is the case where it matters
most!  If the leader is going to take a share of the work, we want it
to take the smallest share possible.

It's a lot fuzzier what is best when there are only partial plans.

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


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