Re: Add a greedy join search algorithm to handle large join problems

On 12/2/25 14:04, Chengpeng Yan wrote:
> Hi,
> 
> 
> 
>> On Dec 2, 2025, at 18:56, Tomas Vondra <tomas@vondra.me> wrote:
>>
>> I think a much broader evaluation will be needed, comparing not just the
>> planning time, but also the quality of the final plan. Which for the
>> starjoin tests does not really matter, as the plans are all equal in
>> this regard.
> 
> 
> Many thanks for your feedback. 
> 
> You are absolutely right — plan quality is also very important. In my
> initial email I only showed the improvements in planning time, but did
> not provide results regarding plan quality. I will run tests on more
> complex join scenarios, evaluating both planning time and plan quality.
> 

I was trying to do some simple experiments by comparing plans for TPC-DS
queries, but unfortunately I get a lot of crashes with the patch. All
the backtraces look very similar - see the attached example. The root
cause seems to be that sort_inner_and_outer() sees

    inner_path = NULL

I haven't investigated this very much, but I suppose the GOO code should
be calling set_cheapest() from somewhere.

regards

-- 
Tomas Vondra