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
|
/*-------------------------------------------------------------------------
*
* buf_table.c
* routines for finding buffers in the buffer pool.
*
* Portions Copyright (c) 1996-2003, 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 1.34 2003/12/14 00:34:47 neilc Exp $
*
*-------------------------------------------------------------------------
*/
/*
* OLD COMMENTS
*
* Data Structures:
*
* Buffers are identified by their BufferTag (buf.h). This
* file contains routines for allocating a shmem hash table to
* map buffer tags to buffer descriptors.
*
* Synchronization:
*
* All routines in this file assume BufMgrLock is held by their caller.
*/
#include "postgres.h"
#include "storage/buf_internals.h"
#include "storage/bufmgr.h"
static HTAB *SharedBufHash;
/*
* Initialize shmem hash table for mapping buffers
*/
void
InitBufTable(int size)
{
HASHCTL info;
/* assume lock is held */
/* 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
*/
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;
}
/*
* BufTableDelete
*/
bool
BufTableInsert(BufferTag *tagPtr, Buffer 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 else in the table? */
elog(ERROR, "shared buffer hash table corrupted");
result->id = buf_id;
return TRUE;
}
/*
* BufTableDelete
*/
bool
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");
return TRUE;
}
|
