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c103d07381
This commit introduces binaryheap_remove_node(), which can be used to remove any node from a binary heap. The implementation is straightforward. The target node is replaced with the last node in the heap, and then we sift as needed to preserve the heap property. This new function is intended for use in a follow-up commit that will improve the performance of pg_restore. Reviewed-by: Tom Lane Discussion: https://postgr.es/m/3612876.1689443232%40sss.pgh.pa.us
70 lines
2.2 KiB
C
70 lines
2.2 KiB
C
/*
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* binaryheap.h
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*
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* A simple binary heap implementation
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*
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* Portions Copyright (c) 2012-2023, PostgreSQL Global Development Group
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*
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* src/include/lib/binaryheap.h
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*/
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#ifndef BINARYHEAP_H
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#define BINARYHEAP_H
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/*
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* We provide a Datum-based API for backend code and a void *-based API for
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* frontend code (since the Datum definitions are not available to frontend
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* code). You should typically avoid using bh_node_type directly and instead
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* use Datum or void * as appropriate.
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*/
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#ifdef FRONTEND
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typedef void *bh_node_type;
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#else
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typedef Datum bh_node_type;
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#endif
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/*
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* For a max-heap, the comparator must return <0 iff a < b, 0 iff a == b,
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* and >0 iff a > b. For a min-heap, the conditions are reversed.
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*/
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typedef int (*binaryheap_comparator) (bh_node_type a, bh_node_type b, void *arg);
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/*
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* binaryheap
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*
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* bh_size how many nodes are currently in "nodes"
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* bh_space how many nodes can be stored in "nodes"
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* bh_has_heap_property no unordered operations since last heap build
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* bh_compare comparison function to define the heap property
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* bh_arg user data for comparison function
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* bh_nodes variable-length array of "space" nodes
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*/
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typedef struct binaryheap
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{
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int bh_size;
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int bh_space;
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bool bh_has_heap_property; /* debugging cross-check */
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binaryheap_comparator bh_compare;
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void *bh_arg;
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bh_node_type bh_nodes[FLEXIBLE_ARRAY_MEMBER];
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} binaryheap;
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extern binaryheap *binaryheap_allocate(int capacity,
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binaryheap_comparator compare,
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void *arg);
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extern void binaryheap_reset(binaryheap *heap);
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extern void binaryheap_free(binaryheap *heap);
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extern void binaryheap_add_unordered(binaryheap *heap, bh_node_type d);
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extern void binaryheap_build(binaryheap *heap);
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extern void binaryheap_add(binaryheap *heap, bh_node_type d);
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extern bh_node_type binaryheap_first(binaryheap *heap);
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extern bh_node_type binaryheap_remove_first(binaryheap *heap);
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extern void binaryheap_remove_node(binaryheap *heap, int n);
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extern void binaryheap_replace_first(binaryheap *heap, bh_node_type d);
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#define binaryheap_empty(h) ((h)->bh_size == 0)
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#define binaryheap_size(h) ((h)->bh_size)
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#define binaryheap_get_node(h, n) ((h)->bh_nodes[n])
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#endif /* BINARYHEAP_H */
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