Hi, > The check for parallel_safe should be even cheaper than cost comparison > so I think it's better to do that first. The attached patch does this > and also updates the comment to mention the requirement about being > parallel-safe.
The patch was marked as "Needs review" so I decided to take a look. I see the reasoning behind the proposed change, but I'm not convinced that there will be any measurable performance improvements. Firstly, compare_path_costs() is rather cheap. Secondly, require_parallel_safe is `false` in most of the cases. Last but not least, one should prove that this particular place is a bottleneck under given loads. I doubt it is. Most of the time it's a network, disk I/O or locks. So unless the author can provide benchmarks that show measurable benefits of the change I suggest rejecting it. -- Best regards, Aleksander Alekseev
