Re: Can we rely on the ordering of paths in pathlist? - Mailing list pgsql-hackers

From Álvaro Herrera
Subject Re: Can we rely on the ordering of paths in pathlist?
Date
Msg-id 202602040952.6vlirlski6od@alvherre.pgsql
Whole thread Raw
In response to Can we rely on the ordering of paths in pathlist?  (Richard Guo <guofenglinux@gmail.com>)
List pgsql-hackers
On 2023-Apr-11, Richard Guo wrote:

> As the comment above add_path() says, 'The pathlist is kept sorted by
> total_cost, with cheaper paths at the front.'  And it seems that
> get_cheapest_parallel_safe_total_inner() relies on this ordering
> (without being mentioned in the comments, which I think we should do).
> I'm wondering if this is the right thing to do, as in other places
> cheapest total cost is found by compare_path_costs(), which would
> consider startup cost if paths have the same total cost, and that seems
> more sensible.
> 
> Attach a trivial patch to make get_cheapest_parallel_safe_total_inner
> act this way.

Hello Richard, did you make you mind on whether you wanted to complete
this?
https://commitfest.postgresql.org/patch/4285/

Thanks

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/



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