On 2016-08-15 12:02:18 -0400, Robert Haas wrote: > Thanks for taking a stab at this. I'd like to throw out a few concerns. > > One, I'm worried that adding an additional layer of pointer-jumping is > going to slow things down and make Andres' work to speed up the > executor more difficult. I don't know that there is a problem there, > and if there is a problem I don't know what to do about it, but I > think it's something we need to consider.
I'm quite concerned about that as well. > I am somewhat inclined to > believe that we need to restructure the executor in a bigger way so > that it passes around datums instead of tuples; I'm inclined to > believe that the current tuple-centric model is probably not optimal > even for the existing storage format. I actually prototyped that, and it's not an easy win so far. Column extraction cost, even after significant optimization, is still often a significant portion of the runtime. And e.g. projection only extracting all columns, after evaluating a restrictive qual referring to an "early" column, can be a significant win. We'd definitely have to give up on extracting columns 0..n when accessing later columns... Hm. Greetings, Andres Freund -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
