Josh Berkus <josh@agliodbs.com> writes:
> Here's a case which it seems like we ought to be able to optimize for:
> [ offset skips all the output of a sort node ]
> Is there some non-obvious reason which would make this kind of
> optimization difficult? Doesn't the executor know at that point how
> many rows it has?
In principle, yeah, we could make it do that, but it seems like a likely
source of maintenance headaches. This example is not exactly compelling
enough to make me want to do it. Large OFFSETs are always going to be
problematic from a performance standpoint, and the fact that we could
short-circuit this one corner case isn't really going to make them much
more usable.
regards, tom lane