Thanks very much for the explanation Tom !! You are correct - there are dropped columns in the original.
Cheers, Steve On Mon, Nov 4, 2019 at 3:01 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > Steve Baldwin <steve.bald...@gmail.com> writes: > > I guess the difference doesn't have a huge bearing (as far as I can tell) > > on the result, but it just seems odd that the inner-most 'Output' step > > outputs the entire row in the case of the copy and only the required > field > > in the case of the original table. What triggers that behaviour? > > The plan with the full output row is actually slightly cheaper, or at > least so the planner thinks, because it saves a projection step. > I imagine the reason you're not getting that with the original table > is that there are some dropped column(s) in the original table, forcing > the projection to be done to get rid of them. > > regards, tom lane >
