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
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
|
/*-------------------------------------------------------------------------
*
* hio.c
* POSTGRES heap access method input/output code.
*
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Id: hio.c,v 1.39 2001/05/16 22:35:12 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/heapam.h"
#include "access/hio.h"
/*
* RelationPutHeapTuple - place tuple at specified page
*
* !!! ELOG(ERROR) IS DISALLOWED HERE !!!
*
* Note - we assume that caller hold BUFFER_LOCK_EXCLUSIVE on the buffer.
*
*/
void
RelationPutHeapTuple(Relation relation,
Buffer buffer,
HeapTuple tuple)
{
Page pageHeader;
OffsetNumber offnum;
Size len;
ItemId itemId;
Item item;
/*
* increment access statistics
*/
IncrHeapAccessStat(local_RelationPutHeapTuple);
IncrHeapAccessStat(global_RelationPutHeapTuple);
pageHeader = (Page) BufferGetPage(buffer);
len = MAXALIGN(tuple->t_len); /* be conservative */
Assert(len <= PageGetFreeSpace(pageHeader));
offnum = PageAddItem((Page) pageHeader, (Item) tuple->t_data,
tuple->t_len, InvalidOffsetNumber, LP_USED);
if (offnum == InvalidOffsetNumber)
elog(STOP, "RelationPutHeapTuple: failed to add tuple");
itemId = PageGetItemId((Page) pageHeader, offnum);
item = PageGetItem((Page) pageHeader, itemId);
ItemPointerSet(&((HeapTupleHeader) item)->t_ctid,
BufferGetBlockNumber(buffer), offnum);
/* return an accurate tuple */
ItemPointerSet(&tuple->t_self, BufferGetBlockNumber(buffer), offnum);
}
/*
* RelationGetBufferForTuple
*
* Returns exclusive-locked buffer with free space >= given len,
* being careful to select only a page at or beyond minblocknum
* in the relation.
*
* The minblocknum parameter is needed to prevent deadlock between
* concurrent heap_update operations; see heap_update for details.
* Pass zero if you don't particularly care which page you get.
*
* Note that we use LockPage to lock relation for extension. We can
* do this as long as in all other places we use page-level locking
* for indices only. Alternatively, we could define pseudo-table as
* we do for transactions with XactLockTable.
*
* ELOG(ERROR) is allowed here, so this routine *must* be called
* before any (unlogged) changes are made in buffer pool.
*/
Buffer
RelationGetBufferForTuple(Relation relation, Size len,
BlockNumber minblocknum)
{
Buffer buffer = InvalidBuffer;
Page pageHeader;
BlockNumber lastblock,
oldnblocks;
len = MAXALIGN(len); /* be conservative */
/*
* If we're gonna fail for oversize tuple, do it right away
*/
if (len > MaxTupleSize)
elog(ERROR, "Tuple is too big: size %lu, max size %ld",
(unsigned long) len, MaxTupleSize);
/*
* First, use relcache's record of table length to guess where the
* last page is, and try to put the tuple there. This cached value
* may be out of date, in which case we'll be inserting into a non-last
* page, but that should be OK. Note that in a newly created relcache
* entry, rd_nblocks may be zero; if so, we'll set it correctly below.
*/
if (relation->rd_nblocks > 0)
{
lastblock = relation->rd_nblocks - 1;
if (lastblock >= minblocknum)
{
buffer = ReadBuffer(relation, lastblock);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
pageHeader = (Page) BufferGetPage(buffer);
if (len <= PageGetFreeSpace(pageHeader))
return buffer;
/*
* Doesn't fit, so we'll have to try someplace else.
*/
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
/* buffer release will happen below... */
}
}
/*
* Before extending relation, make sure no one else has done
* so more recently than our last rd_nblocks update. (If we
* blindly extend the relation here, then probably most of the
* page the other guy added will end up going to waste.)
*
* We have to use a lock to ensure no one else is extending the
* rel at the same time, else we will both try to initialize the
* same new page.
*/
if (!relation->rd_myxactonly)
LockPage(relation, 0, ExclusiveLock);
oldnblocks = relation->rd_nblocks;
/*
* XXX This does an lseek - rather expensive - but at the moment it is
* the only way to accurately determine how many blocks are in a
* relation. Is it worth keeping an accurate file length in shared
* memory someplace, rather than relying on the kernel to do it for us?
*/
relation->rd_nblocks = RelationGetNumberOfBlocks(relation);
if ((BlockNumber) relation->rd_nblocks > oldnblocks)
{
/*
* Someone else has indeed extended the relation recently.
* Try to fit our tuple into the new last page.
*/
lastblock = relation->rd_nblocks - 1;
if (lastblock >= minblocknum)
{
buffer = ReleaseAndReadBuffer(buffer, relation, lastblock, false);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
pageHeader = (Page) BufferGetPage(buffer);
if (len <= PageGetFreeSpace(pageHeader))
{
/* OK, we don't need to extend again. */
if (!relation->rd_myxactonly)
UnlockPage(relation, 0, ExclusiveLock);
return buffer;
}
/*
* Doesn't fit, so we'll have to extend the relation (again).
*/
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
/* buffer release will happen below... */
}
}
/*
* Extend the relation by one page and update rd_nblocks for next time.
*
* Note: at this point minblocknum is ignored; we won't extend by more
* than one block...
*/
lastblock = relation->rd_nblocks;
buffer = ReleaseAndReadBuffer(buffer, relation, lastblock, true);
relation->rd_nblocks = lastblock + 1;
/*
* We need to initialize the empty new page.
*/
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
pageHeader = (Page) BufferGetPage(buffer);
Assert(PageIsNew((PageHeader) pageHeader));
PageInit(pageHeader, BufferGetPageSize(buffer), 0);
/*
* Release the file-extension lock; it's now OK for someone else
* to extend the relation some more.
*/
if (!relation->rd_myxactonly)
UnlockPage(relation, 0, ExclusiveLock);
if (len > PageGetFreeSpace(pageHeader))
{
/* We should not get here given the test at the top */
elog(STOP, "Tuple is too big: size %lu",
(unsigned long) len);
}
return buffer;
}
|
