> If the sort is the inner input to a merge join, this could reflect
> mark-and-restore rescanning of the sort's output. Are there a
> whole lot of duplicate keys on the merge's other side?
> mark-and-restore rescanning of the sort's output. Are there a
> whole lot of duplicate keys on the merge's other side?
Yes. The course_id column's values repeat a LOT on the merge side.
Dane
On Fri, Aug 4, 2023 at 11:10 AM Tom Lane <tgl@xxxxxxxxxxxxx> wrote:
Dane Foster <studdugie@xxxxxxxxx> writes:
> I'm trying to understand a bit of weirdness in a plan output. There is a
> sort node above a sequential scan node where the scan node produces 26,026
> rows yet the sort node above it produces 42,995,408. How is it possible to
> sort more data than you received?
If the sort is the inner input to a merge join, this could reflect
mark-and-restore rescanning of the sort's output. Are there a
whole lot of duplicate keys on the merge's other side?
regards, tom lane
