Re: About "Our CLUSTER implementation is pessimal" patch

Takahiro Itagaki <itagaki.takahiro@oss.ntt.co.jp> writes:
>  * I'd prefer to separate cost calculation routines from create_index_path()
>    and cost_sort(), rather than using a dummy planner.

Don't go that way.  The cost functions have enough dependencies on
low-level planner functionality that making them be standalone would be
a serious mess, both immediately and in terms of future maintenance.
(As an example, someday we'll probably get around to having cost_sort
actually look at the specific columns being sorted by, and that's
going to involve a lot of interaction with pathkeys.)

What I do think is that the quoted code snippet has no business being
outside the planner proper.  It'd be better to put it in planner.c
or someplace like that.
        regards, tom lane