On Mon, 24 Jun 2019 at 18:01, James Coleman <jtc...@gmail.com> wrote:
> On Mon, Jun 24, 2019 at 12:56 PM Simon Riggs <si...@2ndquadrant.com> > wrote: > > > What is the specific use case for this? This sounds quite general case. > > They are both general cases in some sense, but the concerns lie mostly > with what happens when they're unexpectedly encountered. For example, > if the expected row count or group size is off by a good bit and we > effectively have to perform a sort of all (or most) possible rows. > > If we can get the performance to a point where that misestimated row > count or group size doesn't much matter, then ISTM including the patch > becomes a much more obvious total win. > I was trying to think of ways of using external information/circumstance to knowingly avoid negative use cases. i.e. don't treat sort as a black box, use its context. -- Simon Riggs http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Solutions for the Enterprise
