1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
|
/*-------------------------------------------------------------------------
*
* buf_table.c
* routines for mapping BufferTags to buffer indexes.
*
* NOTE: this module is called only by freelist.c, and the "buffer IDs"
* it deals with are whatever freelist.c needs them to be; they may not be
* directly equivalent to Buffer numbers.
*
* Note: all routines in this file assume that the BufMgrLock is held
* by the caller, so no synchronization is needed.
*
*
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/buffer/buf_table.c,v 1.38.4.1 2005/02/03 23:30:04 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "storage/buf_internals.h"
#include "storage/bufmgr.h"
/* entry for buffer lookup hashtable */
typedef struct
{
BufferTag key; /* Tag of a disk page */
int id; /* Associated buffer ID */
} BufferLookupEnt;
static HTAB *SharedBufHash;
/*
* Estimate space needed for mapping hashtable
* size is the desired hash table size (possibly more than NBuffers)
*/
int
BufTableShmemSize(int size)
{
return hash_estimate_size(size, sizeof(BufferLookupEnt));
}
/*
* Initialize shmem hash table for mapping buffers
* size is the desired hash table size (possibly more than NBuffers)
*/
void
InitBufTable(int size)
{
HASHCTL info;
/* assume no locking is needed yet */
/* BufferTag maps to Buffer */
info.keysize = sizeof(BufferTag);
info.entrysize = sizeof(BufferLookupEnt);
info.hash = tag_hash;
SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table",
size, size,
&info,
HASH_ELEM | HASH_FUNCTION);
if (!SharedBufHash)
elog(FATAL, "could not initialize shared buffer hash table");
}
/*
* BufTableLookup
* Lookup the given BufferTag; return buffer ID, or -1 if not found
*/
int
BufTableLookup(BufferTag *tagPtr)
{
BufferLookupEnt *result;
if (tagPtr->blockNum == P_NEW)
return -1;
result = (BufferLookupEnt *)
hash_search(SharedBufHash, (void *) tagPtr, HASH_FIND, NULL);
if (!result)
return -1;
return result->id;
}
/*
* BufTableInsert
* Insert a hashtable entry for given tag and buffer ID
*/
void
BufTableInsert(BufferTag *tagPtr, int buf_id)
{
BufferLookupEnt *result;
bool found;
result = (BufferLookupEnt *)
hash_search(SharedBufHash, (void *) tagPtr, HASH_ENTER, &found);
if (!result)
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of shared memory")));
if (found) /* found something already in the table? */
elog(ERROR, "shared buffer hash table corrupted");
result->id = buf_id;
}
/*
* BufTableDelete
* Delete the hashtable entry for given tag (which must exist)
*/
void
BufTableDelete(BufferTag *tagPtr)
{
BufferLookupEnt *result;
result = (BufferLookupEnt *)
hash_search(SharedBufHash, (void *) tagPtr, HASH_REMOVE, NULL);
if (!result) /* shouldn't happen */
elog(ERROR, "shared buffer hash table corrupted");
}
|
