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Make binaryheap available to frontend code.

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There are a couple of places in frontend code that could make use
of this simple binary heap implementation.  This commit makes
binaryheap usable in frontend code, much like commit 26aaf97b68 did
for StringInfo.  Like StringInfo, the header file is left in lib/
to reduce the likelihood of unnecessary breakage.

The frontend version of binaryheap exposes a void *-based API since
frontend code does not have access to the Datum definitions.  This
seemed like a better approach than switching all existing uses to
void * or making the Datum definitions available to frontend code.

Reviewed-by: Tom Lane, Alvaro Herrera
Discussion: https://postgr.es/m/3612876.1689443232%40sss.pgh.pa.us
This commit is contained in:
Nathan Bossart
2023-09-18 12:18:33 -07:00
parent f73fa5a470
commit 5af0263afd
7 changed files with 52 additions and 20 deletions
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26
src/include/lib/binaryheap.h
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@@ -11,11 +11,23 @@
#ifndef BINARYHEAP_H
#define BINARYHEAP_H
/*
* We provide a Datum-based API for backend code and a void *-based API for
* frontend code (since the Datum definitions are not available to frontend
* code). You should typically avoid using bh_node_type directly and instead
* use Datum or void * as appropriate.
*/
#ifdef FRONTEND
typedef void *bh_node_type;
#else
typedef Datum bh_node_type;
#endif
/*
* For a max-heap, the comparator must return <0 iff a < b, 0 iff a == b,
* and >0 iff a > b. For a min-heap, the conditions are reversed.
*/
typedef int (*binaryheap_comparator) (Datum a, Datum b, void *arg);
typedef int (*binaryheap_comparator) (bh_node_type a, bh_node_type b, void *arg);
/*
* binaryheap
@@ -34,7 +46,7 @@ typedef struct binaryheap
bool bh_has_heap_property; /* debugging cross-check */
binaryheap_comparator bh_compare;
void *bh_arg;
Datum bh_nodes[FLEXIBLE_ARRAY_MEMBER];
bh_node_type bh_nodes[FLEXIBLE_ARRAY_MEMBER];
} binaryheap;
extern binaryheap *binaryheap_allocate(int capacity,
@@ -42,12 +54,12 @@ extern binaryheap *binaryheap_allocate(int capacity,
void *arg);
extern void binaryheap_reset(binaryheap *heap);
extern void binaryheap_free(binaryheap *heap);
extern void binaryheap_add_unordered(binaryheap *heap, Datum d);
extern void binaryheap_add_unordered(binaryheap *heap, bh_node_type d);
extern void binaryheap_build(binaryheap *heap);
extern void binaryheap_add(binaryheap *heap, Datum d);
extern Datum binaryheap_first(binaryheap *heap);
extern Datum binaryheap_remove_first(binaryheap *heap);
extern void binaryheap_replace_first(binaryheap *heap, Datum d);
extern void binaryheap_add(binaryheap *heap, bh_node_type d);
extern bh_node_type binaryheap_first(binaryheap *heap);
extern bh_node_type binaryheap_remove_first(binaryheap *heap);
extern void binaryheap_replace_first(binaryheap *heap, bh_node_type d);
#define binaryheap_empty(h) ((h)->bh_size == 0)