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Commit57b83a4

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nathan-bossartpull[bot]
authored andcommitted
Add function for removing arbitrary nodes in binaryheap.
This commit introduces binaryheap_remove_node(), which can be usedto remove any node from a binary heap. The implementation isstraightforward. The target node is replaced with the last node inthe heap, and then we sift as needed to preserve the heap property.This new function is intended for use in a follow-up commit thatwill improve the performance of pg_restore.Reviewed-by: Tom LaneDiscussion:https://postgr.es/m/3612876.1689443232%40sss.pgh.pa.us
1 parentebdbe27 commit57b83a4

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‎src/common/binaryheap.c

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@@ -215,6 +215,35 @@ binaryheap_remove_first(binaryheap *heap)
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returnresult;
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}
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/*
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* binaryheap_remove_node
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*
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* Removes the nth (zero based) node from the heap. The caller must ensure
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* that there are at least (n + 1) nodes in the heap. O(log n) worst case.
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*/
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void
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binaryheap_remove_node(binaryheap*heap,intn)
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{
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intcmp;
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Assert(!binaryheap_empty(heap)&&heap->bh_has_heap_property);
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Assert(n >=0&&n<heap->bh_size);
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/* compare last node to the one that is being removed */
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cmp=heap->bh_compare(heap->bh_nodes[--heap->bh_size],
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heap->bh_nodes[n],
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heap->bh_arg);
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/* remove the last node, placing it in the vacated entry */
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heap->bh_nodes[n]=heap->bh_nodes[heap->bh_size];
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/* sift as needed to preserve the heap property */
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if (cmp>0)
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sift_up(heap,n);
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elseif (cmp<0)
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sift_down(heap,n);
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}
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/*
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* binaryheap_replace_first
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*

‎src/include/lib/binaryheap.h

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@@ -59,8 +59,11 @@ extern void binaryheap_build(binaryheap *heap);
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externvoidbinaryheap_add(binaryheap*heap,bh_node_typed);
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externbh_node_typebinaryheap_first(binaryheap*heap);
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externbh_node_typebinaryheap_remove_first(binaryheap*heap);
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externvoidbinaryheap_remove_node(binaryheap*heap,intn);
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externvoidbinaryheap_replace_first(binaryheap*heap,bh_node_typed);
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#definebinaryheap_empty(h)((h)->bh_size == 0)
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#definebinaryheap_size(h)((h)->bh_size)
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#definebinaryheap_get_node(h,n)((h)->bh_nodes[n])
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#endif/* BINARYHEAP_H */

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