On Tue, Mar 5, 2019 at 3:00 AM Etsuro Fujita
<fujita.etsuro@lab.ntt.co.jp> wrote:
> apply_projection_to_path() not only jams the given tlist into the
> existing path but updates its tlist eval costs appropriately except for
> the cases of Gather and GatherMerge:
I had forgotten that detail, but I don't think it changes the basic
picture. Once you've added a bunch of Paths to a RelOptInfo, it's too
late to change their *relative* cost, because add_path() puts the list
in a certain order, and adjusting the path costs won't change that
ordering. You've got to have the costs already correct at the time
add_path() is first called for any given Path.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
