Re: [HACKERS] Re: pgsql: Add missing optimizer hooks for function cost and number of rows.

On Sat, Apr 24, 2010 at 3:31 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On Fri, 2010-04-23 at 18:55 -0400, Tom Lane wrote:
>> sriggs(at)postgresql(dot)org (Simon Riggs) writes:
>> > Log Message:
>> > -----------
>> > Add missing optimizer hooks for function cost and number of rows.
>> > Closely follow design of other optimizer hooks: if hook exists
>> > retrieve value from plugin; if still not set then get from cache.
>>
>> What exactly are we doing adding new features without discussion (or
>> documentation, or known use cases) at this stage of the release cycle?
>
> Existing hooks were not fully complete in their coverage. That has
> happened before, and we have discussed that before on hackers, so I took
> care not to deviate from that implementation. This is a very low impact
> change, isn't in a new area and similar optimizer related changes were
> made recently, so I saw little to object to in this particular change.
> No such hooks are documented, even ones with strong use cases.

The point isn't whether the existing hooks are complete or not. The
point is that we shouldn't be making undiscussed changes EVER, and
particularly not a week before beta. Hooks are frequently proposed
and rejected - every once in a while they are proposed and accepted.
So it is not as if there is any reason to believe that no one could
possibly object to this. And you carefully failed to answer Tom's
other point about lack of use case. I think the use case for these
hooks is pretty thin, but I don't really want to argue about it now.
I want you to revert the patch and resubmit it for 9.1 when there is
time to properly discuss it, and focus on the remaining open items so
that we can put out a beta.

...Robert