Fix assertion in MergeTreePrefetchedReadPool::startPrefetches#96123
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alexey-milovidov merged 3 commits intomasterfrom Feb 7, 2026
Merged
Fix assertion in MergeTreePrefetchedReadPool::startPrefetches#96123alexey-milovidov merged 3 commits intomasterfrom
MergeTreePrefetchedReadPool::startPrefetches#96123alexey-milovidov merged 3 commits intomasterfrom
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The assertion checked that the top of `prefetch_queue` had a priority equal to `highest_priority`, but not all tasks are prefetched — some are skipped due to `filesystem_prefetch_max_memory_usage` or prefetch count limits. When the first tasks of all threads are skipped, the top of the queue has a higher priority value, violating the `==` assertion. Closes #78287 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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nickitat
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Feb 6, 2026
…assertion.sql Co-authored-by: Nikita Taranov <nikita.taranov@clickhouse.com>
Co-authored-by: Nikita Taranov <nikita.taranov@clickhouse.com>
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Feb 6, 2026
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The assertion checked that the top of
prefetch_queuehad a priority equal tohighest_priority, but not all tasks are prefetched — some are skipped due tofilesystem_prefetch_max_memory_usageor prefetch count limits. When the first tasks of all threads are skipped, the top of the queue has a higher priority value, violating the==assertion.Closes #78287
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