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
|
/*-------------------------------------------------------------------------
*
* itemptr.c
* POSTGRES disk item pointer code.
*
* Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/storage/page/itemptr.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "storage/itemptr.h"
/*
* ItemPointerEquals
* Returns true if both item pointers point to the same item,
* otherwise returns false.
*
* Note:
* Asserts that the disk item pointers are both valid!
*/
bool
ItemPointerEquals(ItemPointer pointer1, ItemPointer pointer2)
{
/*
* We really want ItemPointerData to be exactly 6 bytes. This is rather a
* random place to check, but there is no better place.
*/
StaticAssertStmt(sizeof(ItemPointerData) == 3 * sizeof(uint16),
"ItemPointerData struct is improperly padded");
if (ItemPointerGetBlockNumber(pointer1) ==
ItemPointerGetBlockNumber(pointer2) &&
ItemPointerGetOffsetNumber(pointer1) ==
ItemPointerGetOffsetNumber(pointer2))
return true;
else
return false;
}
/*
* ItemPointerCompare
* Generic btree-style comparison for item pointers.
*/
int32
ItemPointerCompare(ItemPointer arg1, ItemPointer arg2)
{
/*
* Use ItemPointerGet{Offset,Block}NumberNoCheck to avoid asserting
* ip_posid != 0, which may not be true for a user-supplied TID.
*/
BlockNumber b1 = ItemPointerGetBlockNumberNoCheck(arg1);
BlockNumber b2 = ItemPointerGetBlockNumberNoCheck(arg2);
if (b1 < b2)
return -1;
else if (b1 > b2)
return 1;
else if (ItemPointerGetOffsetNumberNoCheck(arg1) <
ItemPointerGetOffsetNumberNoCheck(arg2))
return -1;
else if (ItemPointerGetOffsetNumberNoCheck(arg1) >
ItemPointerGetOffsetNumberNoCheck(arg2))
return 1;
else
return 0;
}
/*
* ItemPointerInc
* Increment 'pointer' by 1 only paying attention to the ItemPointer's
* type's range limits and not MaxOffsetNumber and FirstOffsetNumber.
* This may result in 'pointer' becoming !OffsetNumberIsValid.
*
* If the pointer is already the maximum possible values permitted by the
* range of the ItemPointer's types, then do nothing.
*/
void
ItemPointerInc(ItemPointer pointer)
{
BlockNumber blk = ItemPointerGetBlockNumberNoCheck(pointer);
OffsetNumber off = ItemPointerGetOffsetNumberNoCheck(pointer);
if (off == PG_UINT16_MAX)
{
if (blk != InvalidBlockNumber)
{
off = 0;
blk++;
}
}
else
off++;
ItemPointerSet(pointer, blk, off);
}
/*
* ItemPointerDec
* Decrement 'pointer' by 1 only paying attention to the ItemPointer's
* type's range limits and not MaxOffsetNumber and FirstOffsetNumber.
* This may result in 'pointer' becoming !OffsetNumberIsValid.
*
* If the pointer is already the minimum possible values permitted by the
* range of the ItemPointer's types, then do nothing. This does rely on
* FirstOffsetNumber being 1 rather than 0.
*/
void
ItemPointerDec(ItemPointer pointer)
{
BlockNumber blk = ItemPointerGetBlockNumberNoCheck(pointer);
OffsetNumber off = ItemPointerGetOffsetNumberNoCheck(pointer);
if (off == 0)
{
if (blk != 0)
{
off = PG_UINT16_MAX;
blk--;
}
}
else
off--;
ItemPointerSet(pointer, blk, off);
}
|
