> 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?
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 <t...@sss.pgh.pa.us> wrote: > Dane Foster <studdu...@gmail.com> 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 >
