Re: Custom/Foreign-Join-APIs (Re: [v9.5] Custom Plan API)

> On 2015-05-10 21:26:26 -0400, Robert Haas wrote:
> > On Sun, May 10, 2015 at 8:41 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > > > This commit reverts create_plan_recurse() as static function.
> > > Yes.  I am not convinced that external callers should be calling that,
> > > and would prefer not to enlarge createplan.c's API footprint without a
> > > demonstration that this is right and useful.  (This is one of many
> > > ways in which this patch is suffering from having gotten committed
> > > without submitted use-cases.)
>
> Wasn't there a submitted use case? IIRC Kaigai had referenced some
> pg-strom (?) code using it?
>
> I'm failing to see how create_plan_recurse() being exposed externally is
> related to "having gotten committed without submitted use-cases".  Even
> if submitted, presumably as simple as possible code, doesn't use it,
> that's not a proof that less simple code does not need it.
>
Yes, PG-Strom code uses create_plan_recurse() to construct child plan
node of the GPU accelerated custom-join logic, once it got chosen.
Here is nothing special. It calls create_plan_recurse() as built-in
join path doing on the underlying inner/outer paths.
It is not difficult to submit as a working example, however, its total
code size (excludes GPU code) is 25KL at this moment.

I'm not certain whether it is a simple example.

> > Your unwillingness to make functions global or to stick PGDLLIMPORT
> > markings on variables that people want access to is hugely
> > handicapping extension authors.  Many people have complained about
> > that on multiple occasions.  Frankly, I find it obstructionist and
> > petty.
>
> While I don't find the tone of the characterization super helpful, I do
> tend to agree that we're *far* too conservative on that end.  I've now
> seen a significant number of extension that copied large swathes of code
> just to cope with individual functions not being available.  And even
> cases where that lead to minor forks with such details changed.
>
I may have to join the members?

> I know that I'm "fearful" of asking for functions being made
> public. Because it'll invariably get into a discussion of merits that's
> completely out of proportion with the size of the change.  And if I, who
> has been on the list for a while now, am "afraid" in that way, you can
> be sure that others won't even dare to ask, lest argue their way
> through.
>
> I think the problem is that during development the default often is to
> create function as static if they're used only in one file. Which is
> fine. But it really doesn't work if it's a larger battle to change
> single incidences.  Besides the pain of having to wait for the next
> major release...
>
Thanks,
--
NEC Business Creation Division / PG-Strom Project
KaiGai Kohei <kaigai@ak.jp.nec.com>