DevShiba commented on issue #25011:
URL: https://github.com/apache/datafusion/issues/25011#issuecomment-5570609381

   Opened #25020 with a fix: skip the two tests under `force_hash_collisions` 
(same pattern already used for `count_distinct_spill` in 
`datafusion/core/tests/memory_limit/mod.rs`, added in #24918 for an analogous 
problem).
   
   On the question of intended coverage: the assertions in 
`assert_lazy_is_not_worse` compare allocator sizes between a lazily-built and a 
pre-allocated set at cardinalities chosen to span the warm-up threshold and the 
convergence point - none of that depends on hash distribution, so forcing every 
key into one bucket doesn't add or remove any coverage the tests were meant to 
provide, it just makes every insert O(n) instead of O(1), which is what drives 
the runtime to hours. Full reasoning and empirical timing data in the PR 
description.
   
   @adriangb tagging you too in case the intended coverage is broader than what 
I read from the test - happy to adjust the PR if so.
   


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