[GENERAL] join_collapse_limit = 14

Hi all.

 

I have a query which takes forever and the only way I've been able to make it perform reasonably well is increasing join_collapse_limit to 14 (12 still produced lots of nest-loops).

This way lots of nest-loops (which I think caused the slowness) was made into hash-joins and performance was acceptable again.

 

I wonder; In general, is there any downside of having join_collapse_limit = 14 on modern hardware (32 cores, 64GB RAM), and geqo_threshold=16 ?

I'm aware of it increasing planning-time, but is this really an issue in practice?

 

Thanks.