Re: inefficient/wrong plan cache mode selection for queries with partitioned tables (postgresql 17)

On Mon, 12 May 2025, 05:08 Andrei Lepikhov, <lepihov@gmail.com> wrote:

> Thanks for this puzzle!
> I suppose, in case generic planning is much faster than custom one,
> there are two candidates exist:
> 1. Touching the index during planning causes too much overhead - see
> get_actual_variable_range
> 2. You have a massive default_statistics_target for a table involved.
>

This is just an artifact of the fact that runtime pruning is not factored
into the costs. Note the cost of the generic plan. The plan_cache_mode GUC
is about the only way to overrule the choice to use the custom plan.

David

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