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Basic binary heap implementation.

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There are probably other places where this can be used, but for now,
this just makes MergeAppend use it, so that this code will have test
coverage.  There is other work in the queue that will use this, as
well.

Abhijit Menon-Sen, reviewed by Andres Freund, Robert Haas, Álvaro
Herrera, Tom Lane, and others.
This commit is contained in:
Robert Haas
2012-11-29 11:13:08 -05:00
parent 086cf1458c
commit 7a2fe9bd03
5 changed files with 383 additions and 93 deletions
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53
src/include/lib/binaryheap.h Normal file
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@@ -0,0 +1,53 @@
/*
* binaryheap.h
*
* A simple binary heap implementation
*
* Portions Copyright (c) 2012, PostgreSQL Global Development Group
*
* src/include/lib/binaryheap.h
*/
#ifndef BINARYHEAP_H
#define BINARYHEAP_H
/*
* 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);
/*
* binaryheap
*
* bh_size how many nodes are currently in "nodes"
* bh_space how many nodes can be stored in "nodes"
* bh_has_heap_property no unordered operations since last heap build
* bh_compare comparison function to define the heap property
* bh_arg user data for comparison function
* bh_nodes variable-length array of "space" nodes
*/
typedef struct binaryheap
{
int bh_size;
int bh_space;
bool bh_has_heap_property; /* debugging cross-check */
binaryheap_comparator bh_compare;
void *bh_arg;
Datum bh_nodes[FLEXIBLE_ARRAY_MEMBER];
} binaryheap;
extern binaryheap *binaryheap_allocate(int capacity,
binaryheap_comparator compare,
void *arg);
extern void binaryheap_free(binaryheap *heap);
extern void binaryheap_add_unordered(binaryheap *heap, Datum 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);
#define binaryheap_empty(h) ((h)->bh_size == 0)
#endif /* BINARYHEAP_H */

8
src/include/nodes/execnodes.h
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@@ -1100,10 +1100,8 @@ typedef struct AppendState
* nkeys number of sort key columns
* sortkeys sort keys in SortSupport representation
* slots current output tuple of each subplan
* heap heap of active tuples (represented as array indexes)
* heap_size number of active heap entries
* heap heap of active tuples
* initialized true if we have fetched first tuple from each subplan
* last_slot last subplan fetched from (which must be re-called)
* ----------------
*/
typedef struct MergeAppendState
@@ -1114,10 +1112,8 @@ typedef struct MergeAppendState
int ms_nkeys;
SortSupport ms_sortkeys; /* array of length ms_nkeys */
TupleTableSlot **ms_slots; /* array of length ms_nplans */
int *ms_heap; /* array of length ms_nplans */
int ms_heap_size; /* current active length of ms_heap[] */
struct binaryheap *ms_heap; /* binary heap of slot indices */
bool ms_initialized; /* are subplans started? */
int ms_last_slot; /* last subplan slot we returned from */
} MergeAppendState;
/* ----------------