Age Owner TLA Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * datapagemap.c
4 : * A data structure for keeping track of data pages that have changed.
5 : *
6 : * This is a fairly simple bitmap.
7 : *
8 : * Copyright (c) 2013-2023, PostgreSQL Global Development Group
9 : *
10 : *-------------------------------------------------------------------------
11 : */
12 :
13 : #include "postgres_fe.h"
14 :
15 : #include "common/logging.h"
16 : #include "datapagemap.h"
17 :
18 : struct datapagemap_iterator
19 : {
20 : datapagemap_t *map;
21 : BlockNumber nextblkno;
22 : };
23 :
24 : /*****
25 : * Public functions
26 : */
27 :
28 : /*
29 : * Add a block to the bitmap.
30 : */
31 : void
2939 heikki.linnakangas 32 CBC 2800 : datapagemap_add(datapagemap_t *map, BlockNumber blkno)
33 : {
34 : int offset;
35 : int bitno;
36 :
37 2800 : offset = blkno / 8;
38 2800 : bitno = blkno % 8;
39 :
40 : /* enlarge or create bitmap if needed */
41 2800 : if (map->bitmapsize <= offset)
42 : {
43 393 : int oldsize = map->bitmapsize;
44 : int newsize;
45 :
46 : /*
47 : * The minimum to hold the new bit is offset + 1. But add some
48 : * headroom, so that we don't need to repeatedly enlarge the bitmap in
49 : * the common case that blocks are modified in order, from beginning
50 : * of a relation to the end.
51 : */
52 393 : newsize = offset + 1;
53 393 : newsize += 10;
54 :
55 393 : map->bitmap = pg_realloc(map->bitmap, newsize);
56 :
57 : /* zero out the newly allocated region */
58 393 : memset(&map->bitmap[oldsize], 0, newsize - oldsize);
59 :
60 393 : map->bitmapsize = newsize;
61 : }
62 :
63 : /* Set the bit */
64 2800 : map->bitmap[offset] |= (1 << bitno);
65 2800 : }
66 :
67 : /*
68 : * Start iterating through all entries in the page map.
69 : *
70 : * After datapagemap_iterate, call datapagemap_next to return the entries,
71 : * until it returns false. After you're done, use pg_free() to destroy the
72 : * iterator.
73 : */
74 : datapagemap_iterator_t *
75 781 : datapagemap_iterate(datapagemap_t *map)
76 : {
77 : datapagemap_iterator_t *iter;
78 :
79 781 : iter = pg_malloc(sizeof(datapagemap_iterator_t));
80 781 : iter->map = map;
81 781 : iter->nextblkno = 0;
82 :
83 781 : return iter;
84 : }
85 :
86 : bool
87 4056 : datapagemap_next(datapagemap_iterator_t *iter, BlockNumber *blkno)
88 : {
89 4056 : datapagemap_t *map = iter->map;
90 :
91 : for (;;)
92 66445 : {
93 70501 : BlockNumber blk = iter->nextblkno;
94 70501 : int nextoff = blk / 8;
95 70501 : int bitno = blk % 8;
96 :
97 70501 : if (nextoff >= map->bitmapsize)
98 781 : break;
99 :
100 69720 : iter->nextblkno++;
101 :
102 69720 : if (map->bitmap[nextoff] & (1 << bitno))
103 : {
104 3275 : *blkno = blk;
105 3275 : return true;
106 : }
107 : }
108 :
109 : /* no more set bits in this bitmap. */
110 781 : return false;
111 : }
112 :
113 : /*
114 : * A debugging aid. Prints out the contents of the page map.
115 : */
116 : void
117 391 : datapagemap_print(datapagemap_t *map)
118 : {
119 : datapagemap_iterator_t *iter;
120 : BlockNumber blocknum;
121 :
122 391 : iter = datapagemap_iterate(map);
123 2420 : while (datapagemap_next(iter, &blocknum))
1469 peter 124 1638 : pg_log_debug("block %u", blocknum);
125 :
2859 fujii 126 391 : pg_free(iter);
2939 heikki.linnakangas 127 391 : }
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