Change prefetch logic in vacuum #620
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## Problem See https://neondb.slack.com/archives/C03QLRH7PPD/p1745003314183649 Vacuum doesn't use prefetch because this strange logic in `lazy_scan_heap`: ``` /* And only up to the next unskippable block */ if (next_prefetch_block + prefetch_budget > vacrel->next_unskippable_block) prefetch_budget = vacrel->next_unskippable_block - next_prefetch_block; ``` ## Summary of changes Disable prefetch only if vacuum jumps to next skippable block (there is SKIP_PAGES_THRESHOLD) which cancel seqscan and perform jump only if gap is large enough). Postgres PRs: neondatabase/postgres#620 neondatabase/postgres#621 neondatabase/postgres#622 neondatabase/postgres#623 --------- Co-authored-by: Konstantin Knizhnik <[email protected]>
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* Change prefetch logic in vacuum * Fix mistyping --------- Co-authored-by: Konstantin Knizhnik <[email protected]>
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See https://neondb.slack.com/archives/C03QLRH7PPD/p1745003314183649
Vacuum doesn't use prefetch because this strange logic in
lazy_scan_heap:Solution:
Disable prefetch only if vacuum jumps to next skippable block (there is SKIP_PAGES_THRESHOLD) which cancel seqscan and perform jump only if gap iOS larger enough).