Re: Pathify RHS unique-ification for semijoin planning

On 3/9/2025 11:12, Richard Guo wrote:
> On Tue, Sep 2, 2025 at 7:56 PM Andrei Lepikhov <lepihov@gmail.com> wrote:
>> No questions, it is good enough optimisation. I'm worried only about
>> implementation: It creates one more RelOptInfo that may look like a
>> baserel, but we can't find it by find_base_rel or even find_join_rel. It
>> seems a little inconsistent to me.
>> Don't think it is critical - just complicates life for extension
>> developers in some cases.
> 
> The RelOptInfo representing the unique-ified rel is intended to be
> used only internally during path generation for semi-joins, and should
> be opaque outside of that.  I don't think extensions should know about
> it.
I just stated the fact - it is not for debate ;).
To understand how deeply developers utilise the core, take a look at the 
pg_hint_plan. The extensibility of the Postgres planner isn't flexible 
enough (and will never be) for the developers' purposes. So, they 
exploit every exported function, variable and type.
Every feature intended to be hidden from extensions should be wrapped 
into an internal type, not exposed in .h files.
It leads us to a discussion about the voice of extension developers in 
the core decisions. I think it is worth debating at one of the 
conferences in the near future.

-- 
regards, Andrei Lepikhov