release-25.4: opt: avoid more types of bad generic query plans #156904
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This commit extends #155163. Instead of tracking an auxiliary boolean value to indicate that a plan has one or more expressions with unbounded cardinality, the `memo.Cost` struct now tracks the number of read expressions (i.e., expressions that perform KV reads) that have unbounded cardinality. This helps to avoid picking generic query plans that will perform significantly worse than their related custom query plans. Fixes #156690 Release note: None
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michae2
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Nov 5, 2025
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@michae2 reviewed 5 of 5 files at r1, all commit messages.
Reviewable status:complete! 1 of 0 LGTMs obtained (waiting on @DrewKimball and @mgartner)
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Backport 1/1 commits from #156879 on behalf of @mgartner.
This commit extends #155163. Instead of tracking an auxiliary boolean
value to indicate that a plan has one or more expressions with unbounded
cardinality, the
memo.Coststruct now tracks the number of readexpressions (i.e., expressions that perform KV reads) that have
unbounded cardinality. This helps to avoid picking generic query plans
that will perform significantly worse than their related custom query
plans.
Fixes #156690
Release note: None
Release justification: Low-risk generic query plan improvement.