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Backport: Add inline murmurhash32(uint32) function.

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The function already existed in tidbitmap.c but more users requiring
fast hashing of 32bit ints are coming up.

Author: Andres Freund
Discussion:
    https://postgr.es/m/20170914061207.zxotvyopetm7lrrp@alap3.anarazel.de
    https://postgr.es/m/15ae5ae2-bc74-ebef-f9d6-34b16423cc04@blackducksoftware.com
Original-Commit: 791961f59b792fbd4f0a992d3ccab47298e79103
This commit is contained in:
Andres Freund 2017-09-22 13:38:42 -07:00
parent 1b2a3860d3
commit c0fda304df
2 changed files with 29 additions and 18 deletions
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20
src/backend/nodes/tidbitmap.c
View File

@ -45,6 +45,7 @@
#include "nodes/tidbitmap.h"
#include "storage/lwlock.h"
#include "utils/dsa.h"
#include "utils/hashutils.h"
/*
* The maximum number of tuples per page is not large (typically 256 with
@ -237,30 +238,13 @@ static int tbm_comparator(const void *left, const void *right);
static int tbm_shared_comparator(const void *left, const void *right,
void *arg);
/*
* Simple inline murmur hash implementation for the exact width required, for
* performance.
*/
static inline uint32
hash_blockno(BlockNumber b)
{
uint32 h = b;
h ^= h >> 16;
h *= 0x85ebca6b;
h ^= h >> 13;
h *= 0xc2b2ae35;
h ^= h >> 16;
return h;
}
/* define hashtable mapping block numbers to PagetableEntry's */
#define SH_USE_NONDEFAULT_ALLOCATOR
#define SH_PREFIX pagetable
#define SH_ELEMENT_TYPE PagetableEntry
#define SH_KEY_TYPE BlockNumber
#define SH_KEY blockno
#define SH_HASH_KEY(tb, key) hash_blockno(key)
#define SH_HASH_KEY(tb, key) murmurhash32(key)
#define SH_EQUAL(tb, a, b) a == b
#define SH_SCOPE static inline
#define SH_DEFINE

27
src/include/utils/hashutils.h Normal file
View File

@ -0,0 +1,27 @@
/*
* Utilities for working with hash values.
*
* Portions Copyright (c) 2017, PostgreSQL Global Development Group
*/
#ifndef HASHUTILS_H
#define HASHUTILS_H
/*
* Simple inline murmur hash implementation hashing a 32 bit ingeger, for
* performance.
*/
static inline uint32
murmurhash32(uint32 data)
{
uint32 h = data;
h ^= h >> 16;
h *= 0x85ebca6b;
h ^= h >> 13;
h *= 0xc2b2ae35;
h ^= h >> 16;
return h;
}
#endif /* HASHUTILS_H */