Re: [v9.5] Custom Plan API

On Wed, Sep 17, 2014 at 7:40 PM, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com> wrote:
> At this moment, I revised the above portion of the patches.
> create_custom_plan() was modified to call "PlanCustomPath" callback
> next to the initialization of tlist and clauses.
>
> It's probably same as what you suggested.

create_custom_plan() is mis-named. It's actually only applicable to
the custom-scan case, because it's triggered by create_plan_recurse()
getting a path node with a T_CustomScan pathtype. Now, we could
change that; although in general create_plan_recurse() dispatches on
pathtype, we could make CustomPath an exception; the top of that
function could say if (IsA(best_path, CustomPath)) { /* do custom
stuff */ }. But the problem with that idea is that, when the custom
path is specifically a custom scan, rather than a join or some other
thing, you want to do all of the same processing that's in
create_scan_plan().

So I think what should happen is that create_plan_recurse() should
handle T_CustomScan the same way it handles T_SeqScan, T_IndexScan, et
al: by calling create_scan_plan(). The switch inside that function
can then call a function create_customscan_plan() if it sees
T_CustomScan. And that function will be simpler than the
create_custom_plan() that you have now, and it will be named
correctly, too.

In ExplainNode(), I think sname should be set to "Custom Scan", not
"Custom". And further down, the custom_name should be printed as
"Custom Plan Provider" not just "Custom".

setrefs.c has remaining handling for the scanrelid = 0 case; please remove that.

--
Robert Haas
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