Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * walsummary.c
4 : * Functions for accessing and managing WAL summary data.
5 : *
6 : * Portions Copyright (c) 2010-2026, PostgreSQL Global Development Group
7 : *
8 : * src/backend/backup/walsummary.c
9 : *
10 : *-------------------------------------------------------------------------
11 : */
12 :
13 : #include "postgres.h"
14 :
15 : #include <sys/stat.h>
16 : #include <unistd.h>
17 :
18 : #include "access/xlog_internal.h"
19 : #include "backup/walsummary.h"
20 : #include "common/int.h"
21 : #include "utils/wait_event.h"
22 :
23 : static bool IsWalSummaryFilename(char *filename);
24 : static int ListComparatorForWalSummaryFiles(const ListCell *a,
25 : const ListCell *b);
26 :
27 : /*
28 : * Get a list of WAL summaries.
29 : *
30 : * If tli != 0, only WAL summaries with the indicated TLI will be included.
31 : *
32 : * If start_lsn != InvalidXLogRecPtr, only summaries that end after the
33 : * indicated LSN will be included.
34 : *
35 : * If end_lsn != InvalidXLogRecPtr, only summaries that start before the
36 : * indicated LSN will be included.
37 : *
38 : * The intent is that you can call GetWalSummaries(tli, start_lsn, end_lsn)
39 : * to get all WAL summaries on the indicated timeline that overlap the
40 : * specified LSN range.
41 : */
42 : List *
43 23 : GetWalSummaries(TimeLineID tli, XLogRecPtr start_lsn, XLogRecPtr end_lsn)
44 : {
45 : DIR *sdir;
46 : struct dirent *dent;
47 23 : List *result = NIL;
48 :
49 23 : sdir = AllocateDir(XLOGDIR "/summaries");
50 204 : while ((dent = ReadDir(sdir, XLOGDIR "/summaries")) != NULL)
51 : {
52 : WalSummaryFile *ws;
53 : uint32 tmp[5];
54 : TimeLineID file_tli;
55 : XLogRecPtr file_start_lsn;
56 : XLogRecPtr file_end_lsn;
57 :
58 : /* Decode filename, or skip if it's not in the expected format. */
59 181 : if (!IsWalSummaryFilename(dent->d_name))
60 121 : continue;
61 135 : sscanf(dent->d_name, "%08X%08X%08X%08X%08X",
62 : &tmp[0], &tmp[1], &tmp[2], &tmp[3], &tmp[4]);
63 135 : file_tli = tmp[0];
64 135 : file_start_lsn = ((uint64) tmp[1]) << 32 | tmp[2];
65 135 : file_end_lsn = ((uint64) tmp[3]) << 32 | tmp[4];
66 :
67 : /* Skip if it doesn't match the filter criteria. */
68 135 : if (tli != 0 && tli != file_tli)
69 0 : continue;
70 135 : if (XLogRecPtrIsValid(start_lsn) && start_lsn >= file_end_lsn)
71 75 : continue;
72 60 : if (XLogRecPtrIsValid(end_lsn) && end_lsn <= file_start_lsn)
73 0 : continue;
74 :
75 : /* Add it to the list. */
76 60 : ws = palloc_object(WalSummaryFile);
77 60 : ws->tli = file_tli;
78 60 : ws->start_lsn = file_start_lsn;
79 60 : ws->end_lsn = file_end_lsn;
80 60 : result = lappend(result, ws);
81 : }
82 23 : FreeDir(sdir);
83 :
84 23 : return result;
85 : }
86 :
87 : /*
88 : * Build a new list of WAL summaries based on an existing list, but filtering
89 : * out summaries that don't match the search parameters.
90 : *
91 : * If tli != 0, only WAL summaries with the indicated TLI will be included.
92 : *
93 : * If start_lsn != InvalidXLogRecPtr, only summaries that end after the
94 : * indicated LSN will be included.
95 : *
96 : * If end_lsn != InvalidXLogRecPtr, only summaries that start before the
97 : * indicated LSN will be included.
98 : */
99 : List *
100 12 : FilterWalSummaries(List *wslist, TimeLineID tli,
101 : XLogRecPtr start_lsn, XLogRecPtr end_lsn)
102 : {
103 12 : List *result = NIL;
104 : ListCell *lc;
105 :
106 : /* Loop over input. */
107 35 : foreach(lc, wslist)
108 : {
109 23 : WalSummaryFile *ws = lfirst(lc);
110 :
111 : /* Skip if it doesn't match the filter criteria. */
112 23 : if (tli != 0 && tli != ws->tli)
113 4 : continue;
114 19 : if (XLogRecPtrIsValid(start_lsn) && start_lsn > ws->end_lsn)
115 0 : continue;
116 19 : if (XLogRecPtrIsValid(end_lsn) && end_lsn < ws->start_lsn)
117 0 : continue;
118 :
119 : /* Add it to the result list. */
120 19 : result = lappend(result, ws);
121 : }
122 :
123 12 : return result;
124 : }
125 :
126 : /*
127 : * Check whether the supplied list of WalSummaryFile objects covers the
128 : * whole range of LSNs from start_lsn to end_lsn. This function ignores
129 : * timelines, so the caller should probably filter using the appropriate
130 : * timeline before calling this.
131 : *
132 : * If the whole range of LSNs is covered, returns true, otherwise false.
133 : * If false is returned, *missing_lsn is set either to InvalidXLogRecPtr
134 : * if there are no WAL summary files in the input list, or to the first LSN
135 : * in the range that is not covered by a WAL summary file in the input list.
136 : */
137 : bool
138 12 : WalSummariesAreComplete(List *wslist, XLogRecPtr start_lsn,
139 : XLogRecPtr end_lsn, XLogRecPtr *missing_lsn)
140 : {
141 12 : XLogRecPtr current_lsn = start_lsn;
142 : ListCell *lc;
143 :
144 : /* Special case for empty list. */
145 12 : if (wslist == NIL)
146 : {
147 0 : *missing_lsn = InvalidXLogRecPtr;
148 0 : return false;
149 : }
150 :
151 : /* Make a private copy of the list and sort it by start LSN. */
152 12 : wslist = list_copy(wslist);
153 12 : list_sort(wslist, ListComparatorForWalSummaryFiles);
154 :
155 : /*
156 : * Consider summary files in order of increasing start_lsn, advancing the
157 : * known-summarized range from start_lsn toward end_lsn.
158 : *
159 : * Normally, the summary files should cover non-overlapping WAL ranges,
160 : * but this algorithm is intended to be correct even in case of overlap.
161 : */
162 19 : foreach(lc, wslist)
163 : {
164 19 : WalSummaryFile *ws = lfirst(lc);
165 :
166 19 : if (ws->start_lsn > current_lsn)
167 : {
168 : /* We found a gap. */
169 0 : break;
170 : }
171 19 : if (ws->end_lsn > current_lsn)
172 : {
173 : /*
174 : * Next summary extends beyond end of previous summary, so extend
175 : * the end of the range known to be summarized.
176 : */
177 19 : current_lsn = ws->end_lsn;
178 :
179 : /*
180 : * If the range we know to be summarized has reached the required
181 : * end LSN, we have proved completeness.
182 : */
183 19 : if (current_lsn >= end_lsn)
184 12 : return true;
185 : }
186 : }
187 :
188 : /*
189 : * We either ran out of summary files without reaching the end LSN, or we
190 : * hit a gap in the sequence that resulted in us bailing out of the loop
191 : * above.
192 : */
193 0 : *missing_lsn = current_lsn;
194 0 : return false;
195 : }
196 :
197 : /*
198 : * Open a WAL summary file.
199 : *
200 : * This will throw an error in case of trouble. As an exception, if
201 : * missing_ok = true and the trouble is specifically that the file does
202 : * not exist, it will not throw an error and will return a value less than 0.
203 : */
204 : File
205 19 : OpenWalSummaryFile(WalSummaryFile *ws, bool missing_ok)
206 : {
207 : char path[MAXPGPATH];
208 : File file;
209 :
210 19 : snprintf(path, MAXPGPATH,
211 : XLOGDIR "/summaries/%08X%08X%08X%08X%08X.summary",
212 : ws->tli,
213 19 : LSN_FORMAT_ARGS(ws->start_lsn),
214 19 : LSN_FORMAT_ARGS(ws->end_lsn));
215 :
216 19 : file = PathNameOpenFile(path, O_RDONLY);
217 19 : if (file < 0 && (errno != ENOENT || !missing_ok))
218 0 : ereport(ERROR,
219 : (errcode_for_file_access(),
220 : errmsg("could not open file \"%s\": %m", path)));
221 :
222 19 : return file;
223 : }
224 :
225 : /*
226 : * Remove a WAL summary file if the last modification time precedes the
227 : * cutoff time.
228 : */
229 : void
230 0 : RemoveWalSummaryIfOlderThan(WalSummaryFile *ws, time_t cutoff_time)
231 : {
232 : char path[MAXPGPATH];
233 : struct stat statbuf;
234 :
235 0 : snprintf(path, MAXPGPATH,
236 : XLOGDIR "/summaries/%08X%08X%08X%08X%08X.summary",
237 : ws->tli,
238 0 : LSN_FORMAT_ARGS(ws->start_lsn),
239 0 : LSN_FORMAT_ARGS(ws->end_lsn));
240 :
241 0 : if (lstat(path, &statbuf) != 0)
242 : {
243 0 : if (errno == ENOENT)
244 0 : return;
245 0 : ereport(ERROR,
246 : (errcode_for_file_access(),
247 : errmsg("could not stat file \"%s\": %m", path)));
248 : }
249 0 : if (statbuf.st_mtime >= cutoff_time)
250 0 : return;
251 0 : if (unlink(path) != 0)
252 0 : ereport(ERROR,
253 : (errcode_for_file_access(),
254 : errmsg("could not remove file \"%s\": %m", path)));
255 0 : ereport(DEBUG2,
256 : (errmsg_internal("removing file \"%s\"", path)));
257 : }
258 :
259 : /*
260 : * Test whether a filename looks like a WAL summary file.
261 : */
262 : static bool
263 181 : IsWalSummaryFilename(char *filename)
264 : {
265 316 : return strspn(filename, "0123456789ABCDEF") == 40 &&
266 135 : strcmp(filename + 40, ".summary") == 0;
267 : }
268 :
269 : /*
270 : * Data read callback for use with CreateBlockRefTableReader.
271 : */
272 : int
273 19 : ReadWalSummary(void *wal_summary_io, void *data, int length)
274 : {
275 19 : WalSummaryIO *io = wal_summary_io;
276 : int nbytes;
277 :
278 19 : nbytes = FileRead(io->file, data, length, io->filepos,
279 : WAIT_EVENT_WAL_SUMMARY_READ);
280 19 : if (nbytes < 0)
281 0 : ereport(ERROR,
282 : (errcode_for_file_access(),
283 : errmsg("could not read file \"%s\": %m",
284 : FilePathName(io->file))));
285 :
286 19 : io->filepos += nbytes;
287 19 : return nbytes;
288 : }
289 :
290 : /*
291 : * Data write callback for use with WriteBlockRefTable.
292 : */
293 : int
294 18 : WriteWalSummary(void *wal_summary_io, void *data, int length)
295 : {
296 18 : WalSummaryIO *io = wal_summary_io;
297 : int nbytes;
298 :
299 18 : nbytes = FileWrite(io->file, data, length, io->filepos,
300 : WAIT_EVENT_WAL_SUMMARY_WRITE);
301 18 : if (nbytes < 0)
302 0 : ereport(ERROR,
303 : (errcode_for_file_access(),
304 : errmsg("could not write file \"%s\": %m",
305 : FilePathName(io->file))));
306 18 : if (nbytes != length)
307 0 : ereport(ERROR,
308 : (errcode_for_file_access(),
309 : errmsg("could not write file \"%s\": wrote only %d of %d bytes at offset %u",
310 : FilePathName(io->file), nbytes,
311 : length, (unsigned) io->filepos),
312 : errhint("Check free disk space.")));
313 :
314 18 : io->filepos += nbytes;
315 18 : return nbytes;
316 : }
317 :
318 : /*
319 : * Error-reporting callback for use with CreateBlockRefTableReader.
320 : */
321 : void
322 0 : ReportWalSummaryError(void *callback_arg, char *fmt,...)
323 : {
324 : StringInfoData buf;
325 : va_list ap;
326 : int needed;
327 :
328 0 : initStringInfo(&buf);
329 : for (;;)
330 : {
331 0 : va_start(ap, fmt);
332 0 : needed = appendStringInfoVA(&buf, fmt, ap);
333 0 : va_end(ap);
334 0 : if (needed == 0)
335 0 : break;
336 0 : enlargeStringInfo(&buf, needed);
337 : }
338 0 : ereport(ERROR,
339 : errcode(ERRCODE_DATA_CORRUPTED),
340 : errmsg_internal("%s", buf.data));
341 : }
342 :
343 : /*
344 : * Comparator to sort a List of WalSummaryFile objects by start_lsn.
345 : */
346 : static int
347 8 : ListComparatorForWalSummaryFiles(const ListCell *a, const ListCell *b)
348 : {
349 8 : WalSummaryFile *ws1 = lfirst(a);
350 8 : WalSummaryFile *ws2 = lfirst(b);
351 :
352 8 : return pg_cmp_u64(ws1->start_lsn, ws2->start_lsn);
353 : }
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