Jeff Janes <jeff.ja...@gmail.com> writes: > count(*) and sum(1) do different things internally, and in my hands > sum(1) is ~10% slower. > I don't know how to dump the output of ExecBuildProjectionInfo into a > human readable form, so I don't know the basis of the difference. But > I wonder if using count(*) would lower the weight of the ExecProject > function.
Probably. count() doesn't actually have any arguments, so there's nothing for ExecProject to do. sum(1) invokes the generic case there (ExecTargetList). I suppose we could add another special-case path for constant tlist elements, but I suspect that would mostly be optimizing for benchmarks rather than helping real-world cases. regards, tom lane -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers