On Fri, 6 Sept 2024 at 19:19, Richard Guo <guofengli...@gmail.com> wrote: > * Currently, the costing code does not take run-time pruning into > consideration. How should we calculate the costs of the parameterized > paths on partitioned tables?
Couldn't we assume total_cost = total_cost / n_apppend_children for equality conditions and do something with DEFAULT_INEQ_SEL and DEFAULT_RANGE_INEQ_SEL for more complex cases. I understand we probably need to do something about this to have the planner have any chance of actually choose these Paths, so hacking something in there to test the idea is sound before going to the trouble of refining the cost model seems like a good idea. > * This approach generates additional paths at the scan level, which > may not be easily compared with regular scan paths. As a result, we > might need to retain these paths at every level of the join tree. I'm > afraid this could lead to a significant increase in planning time in > some cases. We need to find a way to avoid regressions in planning > time. How about just creating these Paths for partitioned tables (and partitions) when there's an EquivalenceClass containing multiple relids on the partition key? I think those are about the only cases that could benefit, so I think it makes sense to restrict making the additional Paths for that case. David
