On Tue, May 23, 2017 at 4:41 PM, Amit Kapila <amit.kapil...@gmail.com> wrote:
> Isn't this point contradictory? Basically, on one side you are > suggesting to calculate additional workers (work_remaining) based on > selectivity and on another side you are saying that it will fix > estimation errors. IIUC, then you are talking about some sort of > executor feedback to adjust a number of workers which might be a good > thing to do but I that is a different problem to solve. As of now, I > don't think we have that type of mechanism even for non-parallel > execution. > Yes, I am talking of a executor feedback mechanism sort of a thing. For non parallel execution it's a lot more challenging since the execution plan might need to be changed in the runtime, but in parallel query case only addition/subtraction of workers is to be dealt, which appears to be a less complex thing. Why I am thinking in this direction is because in my experience it seems very easy to regress with more workers when over-estimation is done and this runtime calculation of workers can mitigate it largely. However, I understand that this might require more proof than my experience alone. Let's see if anybody else shares my gut feeling. :) -- Regards, Rafia Sabih EnterpriseDB: http://www.enterprisedb.com/ -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers