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Start with minimal prefetch distance to minimize prefetch overhead for exact or limited index scans #551

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Merged
knizhnik merged 1 commit into from
Jan 13, 2025
Merged

Start with minimal prefetch distance to minimize prefetch overhead for exact or limited index scans #551

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4 changes: 2 additions & 2 deletions src/backend/access/nbtree/nbtsearch.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1191,8 +1191,8 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
else if (!enable_indexscan_prefetch || !scan->heapRelation)
so->prefetch_maximum = 0; /* disable prefetch */

/* If key bounds are not specified, then we will scan the whole relation and it make sense to start with the largest possible prefetch distance */
so->current_prefetch_distance = (keysCount == 0) ? so->prefetch_maximum : 0;
/* Start with minimal prefetch distance to minimize prefetch overhead for exact or limited index scans */
so->current_prefetch_distance = 0;

/*
* If we found no usable boundary keys, we have to start from one end of
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