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1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * xlogutils.c
4 : : *
5 : : * PostgreSQL write-ahead log manager utility routines
6 : : *
7 : : * This file contains support routines that are used by XLOG replay functions.
8 : : * None of this code is used during normal system operation.
9 : : *
10 : : *
11 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
12 : : * Portions Copyright (c) 1994, Regents of the University of California
13 : : *
14 : : * src/backend/access/transam/xlogutils.c
15 : : *
16 : : *-------------------------------------------------------------------------
17 : : */
18 : : #include "postgres.h"
19 : :
20 : : #include <unistd.h>
21 : :
22 : : #include "access/timeline.h"
23 : : #include "access/xlogrecovery.h"
24 : : #include "access/xlog_internal.h"
25 : : #include "access/xlogutils.h"
26 : : #include "miscadmin.h"
27 : : #include "storage/fd.h"
28 : : #include "storage/smgr.h"
29 : : #include "utils/hsearch.h"
30 : : #include "utils/rel.h"
31 : :
32 : :
33 : : /* GUC variable */
34 : : bool ignore_invalid_pages = false;
35 : :
36 : : /*
37 : : * Are we doing recovery from XLOG?
38 : : *
39 : : * This is only ever true in the startup process; it should be read as meaning
40 : : * "this process is replaying WAL records", rather than "the system is in
41 : : * recovery mode". It should be examined primarily by functions that need
42 : : * to act differently when called from a WAL redo function (e.g., to skip WAL
43 : : * logging). To check whether the system is in recovery regardless of which
44 : : * process you're running in, use RecoveryInProgress() but only after shared
45 : : * memory startup and lock initialization.
46 : : *
47 : : * This is updated from xlog.c and xlogrecovery.c, but lives here because
48 : : * it's mostly read by WAL redo functions.
49 : : */
50 : : bool InRecovery = false;
51 : :
52 : : /* Are we in Hot Standby mode? Only valid in startup process, see xlogutils.h */
53 : : HotStandbyState standbyState = STANDBY_DISABLED;
54 : :
55 : : /*
56 : : * During XLOG replay, we may see XLOG records for incremental updates of
57 : : * pages that no longer exist, because their relation was later dropped or
58 : : * truncated. (Note: this is only possible when full_page_writes = OFF,
59 : : * since when it's ON, the first reference we see to a page should always
60 : : * be a full-page rewrite not an incremental update.) Rather than simply
61 : : * ignoring such records, we make a note of the referenced page, and then
62 : : * complain if we don't actually see a drop or truncate covering the page
63 : : * later in replay.
64 : : */
65 : : typedef struct xl_invalid_page_key
66 : : {
67 : : RelFileLocator locator; /* the relation */
68 : : ForkNumber forkno; /* the fork number */
69 : : BlockNumber blkno; /* the page */
70 : : } xl_invalid_page_key;
71 : :
72 : : typedef struct xl_invalid_page
73 : : {
74 : : xl_invalid_page_key key; /* hash key ... must be first */
75 : : bool present; /* page existed but contained zeroes */
76 : : } xl_invalid_page;
77 : :
78 : : static HTAB *invalid_page_tab = NULL;
79 : :
80 : : static int read_local_xlog_page_guts(XLogReaderState *state, XLogRecPtr targetPagePtr,
81 : : int reqLen, XLogRecPtr targetRecPtr,
82 : : char *cur_page, bool wait_for_wal);
83 : :
84 : : /* Report a reference to an invalid page */
85 : : static void
86 : 0 : report_invalid_page(int elevel, RelFileLocator locator, ForkNumber forkno,
87 : : BlockNumber blkno, bool present)
88 : : {
89 : 0 : RelPathStr path = relpathperm(locator, forkno);
90 : :
91 [ # # ]: 0 : if (present)
92 [ # # # # : 0 : elog(elevel, "page %u of relation %s is uninitialized",
# # # # #
# ]
93 : : blkno, path.str);
94 : : else
95 [ # # # # : 0 : elog(elevel, "page %u of relation %s does not exist",
# # # # #
# ]
96 : : blkno, path.str);
97 : 0 : }
98 : :
99 : : /* Log a reference to an invalid page */
100 : : static void
101 : 0 : log_invalid_page(RelFileLocator locator, ForkNumber forkno, BlockNumber blkno,
102 : : bool present)
103 : : {
104 : 0 : xl_invalid_page_key key;
105 : 0 : xl_invalid_page *hentry;
106 : 0 : bool found;
107 : :
108 : : /*
109 : : * Once recovery has reached a consistent state, the invalid-page table
110 : : * should be empty and remain so. If a reference to an invalid page is
111 : : * found after consistency is reached, PANIC immediately. This might seem
112 : : * aggressive, but it's better than letting the invalid reference linger
113 : : * in the hash table until the end of recovery and PANIC there, which
114 : : * might come only much later if this is a standby server.
115 : : */
116 [ # # ]: 0 : if (reachedConsistency)
117 : : {
118 : 0 : report_invalid_page(WARNING, locator, forkno, blkno, present);
119 [ # # # # : 0 : elog(ignore_invalid_pages ? WARNING : PANIC,
# # # # #
# ]
120 : : "WAL contains references to invalid pages");
121 : 0 : }
122 : :
123 : : /*
124 : : * Log references to invalid pages at DEBUG1 level. This allows some
125 : : * tracing of the cause (note the elog context mechanism will tell us
126 : : * something about the XLOG record that generated the reference).
127 : : */
128 [ # # ]: 0 : if (message_level_is_interesting(DEBUG1))
129 : 0 : report_invalid_page(DEBUG1, locator, forkno, blkno, present);
130 : :
131 [ # # ]: 0 : if (invalid_page_tab == NULL)
132 : : {
133 : : /* create hash table when first needed */
134 : 0 : HASHCTL ctl;
135 : :
136 : 0 : ctl.keysize = sizeof(xl_invalid_page_key);
137 : 0 : ctl.entrysize = sizeof(xl_invalid_page);
138 : :
139 : 0 : invalid_page_tab = hash_create("XLOG invalid-page table",
140 : : 100,
141 : : &ctl,
142 : : HASH_ELEM | HASH_BLOBS);
143 : 0 : }
144 : :
145 : : /* we currently assume xl_invalid_page_key contains no padding */
146 : 0 : key.locator = locator;
147 : 0 : key.forkno = forkno;
148 : 0 : key.blkno = blkno;
149 : 0 : hentry = (xl_invalid_page *)
150 : 0 : hash_search(invalid_page_tab, &key, HASH_ENTER, &found);
151 : :
152 [ # # ]: 0 : if (!found)
153 : : {
154 : : /* hash_search already filled in the key */
155 : 0 : hentry->present = present;
156 : 0 : }
157 : : else
158 : : {
159 : : /* repeat reference ... leave "present" as it was */
160 : : }
161 : 0 : }
162 : :
163 : : /* Forget any invalid pages >= minblkno, because they've been dropped */
164 : : static void
165 : 0 : forget_invalid_pages(RelFileLocator locator, ForkNumber forkno,
166 : : BlockNumber minblkno)
167 : : {
168 : 0 : HASH_SEQ_STATUS status;
169 : 0 : xl_invalid_page *hentry;
170 : :
171 [ # # ]: 0 : if (invalid_page_tab == NULL)
172 : 0 : return; /* nothing to do */
173 : :
174 : 0 : hash_seq_init(&status, invalid_page_tab);
175 : :
176 [ # # ]: 0 : while ((hentry = (xl_invalid_page *) hash_seq_search(&status)) != NULL)
177 : : {
178 [ # # # # : 0 : if (RelFileLocatorEquals(hentry->key.locator, locator) &&
# # ]
179 [ # # # # ]: 0 : hentry->key.forkno == forkno &&
180 : 0 : hentry->key.blkno >= minblkno)
181 : : {
182 [ # # # # ]: 0 : elog(DEBUG2, "page %u of relation %s has been dropped",
183 : : hentry->key.blkno,
184 : : relpathperm(hentry->key.locator, forkno).str);
185 : :
186 : 0 : if (hash_search(invalid_page_tab,
187 : 0 : &hentry->key,
188 [ # # ]: 0 : HASH_REMOVE, NULL) == NULL)
189 [ # # # # ]: 0 : elog(ERROR, "hash table corrupted");
190 : 0 : }
191 : : }
192 [ # # ]: 0 : }
193 : :
194 : : /* Forget any invalid pages in a whole database */
195 : : static void
196 : 0 : forget_invalid_pages_db(Oid dbid)
197 : : {
198 : 0 : HASH_SEQ_STATUS status;
199 : 0 : xl_invalid_page *hentry;
200 : :
201 [ # # ]: 0 : if (invalid_page_tab == NULL)
202 : 0 : return; /* nothing to do */
203 : :
204 : 0 : hash_seq_init(&status, invalid_page_tab);
205 : :
206 [ # # ]: 0 : while ((hentry = (xl_invalid_page *) hash_seq_search(&status)) != NULL)
207 : : {
208 [ # # ]: 0 : if (hentry->key.locator.dbOid == dbid)
209 : : {
210 [ # # # # ]: 0 : elog(DEBUG2, "page %u of relation %s has been dropped",
211 : : hentry->key.blkno,
212 : : relpathperm(hentry->key.locator, hentry->key.forkno).str);
213 : :
214 : 0 : if (hash_search(invalid_page_tab,
215 : 0 : &hentry->key,
216 [ # # ]: 0 : HASH_REMOVE, NULL) == NULL)
217 [ # # # # ]: 0 : elog(ERROR, "hash table corrupted");
218 : 0 : }
219 : : }
220 [ # # ]: 0 : }
221 : :
222 : : /* Are there any unresolved references to invalid pages? */
223 : : bool
224 : 0 : XLogHaveInvalidPages(void)
225 : : {
226 [ # # # # ]: 0 : if (invalid_page_tab != NULL &&
227 : 0 : hash_get_num_entries(invalid_page_tab) > 0)
228 : 0 : return true;
229 : 0 : return false;
230 : 0 : }
231 : :
232 : : /* Complain about any remaining invalid-page entries */
233 : : void
234 : 0 : XLogCheckInvalidPages(void)
235 : : {
236 : 0 : HASH_SEQ_STATUS status;
237 : 0 : xl_invalid_page *hentry;
238 : 0 : bool foundone = false;
239 : :
240 [ # # ]: 0 : if (invalid_page_tab == NULL)
241 : 0 : return; /* nothing to do */
242 : :
243 : 0 : hash_seq_init(&status, invalid_page_tab);
244 : :
245 : : /*
246 : : * Our strategy is to emit WARNING messages for all remaining entries and
247 : : * only PANIC after we've dumped all the available info.
248 : : */
249 [ # # ]: 0 : while ((hentry = (xl_invalid_page *) hash_seq_search(&status)) != NULL)
250 : : {
251 : 0 : report_invalid_page(WARNING, hentry->key.locator, hentry->key.forkno,
252 : 0 : hentry->key.blkno, hentry->present);
253 : 0 : foundone = true;
254 : : }
255 : :
256 [ # # ]: 0 : if (foundone)
257 [ # # # # : 0 : elog(ignore_invalid_pages ? WARNING : PANIC,
# # # # #
# ]
258 : : "WAL contains references to invalid pages");
259 : :
260 : 0 : hash_destroy(invalid_page_tab);
261 : 0 : invalid_page_tab = NULL;
262 [ # # ]: 0 : }
263 : :
264 : :
265 : : /*
266 : : * XLogReadBufferForRedo
267 : : * Read a page during XLOG replay
268 : : *
269 : : * Reads a block referenced by a WAL record into shared buffer cache, and
270 : : * determines what needs to be done to redo the changes to it. If the WAL
271 : : * record includes a full-page image of the page, it is restored.
272 : : *
273 : : * 'record.EndRecPtr' is compared to the page's LSN to determine if the record
274 : : * has already been replayed. 'block_id' is the ID number the block was
275 : : * registered with, when the WAL record was created.
276 : : *
277 : : * Returns one of the following:
278 : : *
279 : : * BLK_NEEDS_REDO - changes from the WAL record need to be applied
280 : : * BLK_DONE - block doesn't need replaying
281 : : * BLK_RESTORED - block was restored from a full-page image included in
282 : : * the record
283 : : * BLK_NOTFOUND - block was not found (because it was truncated away by
284 : : * an operation later in the WAL stream)
285 : : *
286 : : * On return, the buffer is locked in exclusive-mode, and returned in *buf.
287 : : * Note that the buffer is locked and returned even if it doesn't need
288 : : * replaying. (Getting the buffer lock is not really necessary during
289 : : * single-process crash recovery, but some subroutines such as MarkBufferDirty
290 : : * will complain if we don't have the lock. In hot standby mode it's
291 : : * definitely necessary.)
292 : : *
293 : : * Note: when a backup block is available in XLOG with the BKPIMAGE_APPLY flag
294 : : * set, we restore it, even if the page in the database appears newer. This
295 : : * is to protect ourselves against database pages that were partially or
296 : : * incorrectly written during a crash. We assume that the XLOG data must be
297 : : * good because it has passed a CRC check, while the database page might not
298 : : * be. This will force us to replay all subsequent modifications of the page
299 : : * that appear in XLOG, rather than possibly ignoring them as already
300 : : * applied, but that's not a huge drawback.
301 : : */
302 : : XLogRedoAction
303 : 0 : XLogReadBufferForRedo(XLogReaderState *record, uint8 block_id,
304 : : Buffer *buf)
305 : : {
306 : 0 : return XLogReadBufferForRedoExtended(record, block_id, RBM_NORMAL,
307 : 0 : false, buf);
308 : : }
309 : :
310 : : /*
311 : : * Pin and lock a buffer referenced by a WAL record, for the purpose of
312 : : * re-initializing it.
313 : : */
314 : : Buffer
315 : 0 : XLogInitBufferForRedo(XLogReaderState *record, uint8 block_id)
316 : : {
317 : 0 : Buffer buf;
318 : :
319 : 0 : XLogReadBufferForRedoExtended(record, block_id, RBM_ZERO_AND_LOCK, false,
320 : : &buf);
321 : 0 : return buf;
322 : 0 : }
323 : :
324 : : /*
325 : : * XLogReadBufferForRedoExtended
326 : : * Like XLogReadBufferForRedo, but with extra options.
327 : : *
328 : : * In RBM_ZERO_* modes, if the page doesn't exist, the relation is extended
329 : : * with all-zeroes pages up to the referenced block number. In
330 : : * RBM_ZERO_AND_LOCK and RBM_ZERO_AND_CLEANUP_LOCK modes, the return value
331 : : * is always BLK_NEEDS_REDO.
332 : : *
333 : : * (The RBM_ZERO_AND_CLEANUP_LOCK mode is redundant with the get_cleanup_lock
334 : : * parameter. Do not use an inconsistent combination!)
335 : : *
336 : : * If 'get_cleanup_lock' is true, a "cleanup lock" is acquired on the buffer
337 : : * using LockBufferForCleanup(), instead of a regular exclusive lock.
338 : : */
339 : : XLogRedoAction
340 : 0 : XLogReadBufferForRedoExtended(XLogReaderState *record,
341 : : uint8 block_id,
342 : : ReadBufferMode mode, bool get_cleanup_lock,
343 : : Buffer *buf)
344 : : {
345 : 0 : XLogRecPtr lsn = record->EndRecPtr;
346 : 0 : RelFileLocator rlocator;
347 : 0 : ForkNumber forknum;
348 : 0 : BlockNumber blkno;
349 : 0 : Buffer prefetch_buffer;
350 : 0 : Page page;
351 : 0 : bool zeromode;
352 : 0 : bool willinit;
353 : :
354 [ # # ]: 0 : if (!XLogRecGetBlockTagExtended(record, block_id, &rlocator, &forknum, &blkno,
355 : : &prefetch_buffer))
356 : : {
357 : : /* Caller specified a bogus block_id */
358 [ # # # # ]: 0 : elog(PANIC, "failed to locate backup block with ID %d in WAL record",
359 : : block_id);
360 : 0 : }
361 : :
362 : : /*
363 : : * Make sure that if the block is marked with WILL_INIT, the caller is
364 : : * going to initialize it. And vice versa.
365 : : */
366 [ # # ]: 0 : zeromode = (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK);
367 : 0 : willinit = (XLogRecGetBlock(record, block_id)->flags & BKPBLOCK_WILL_INIT) != 0;
368 [ # # # # ]: 0 : if (willinit && !zeromode)
369 [ # # # # ]: 0 : elog(PANIC, "block with WILL_INIT flag in WAL record must be zeroed by redo routine");
370 [ # # # # ]: 0 : if (!willinit && zeromode)
371 [ # # # # ]: 0 : elog(PANIC, "block to be initialized in redo routine must be marked with WILL_INIT flag in the WAL record");
372 : :
373 : : /* If it has a full-page image and it should be restored, do it. */
374 [ # # ]: 0 : if (XLogRecBlockImageApply(record, block_id))
375 : : {
376 [ # # ]: 0 : Assert(XLogRecHasBlockImage(record, block_id));
377 : 0 : *buf = XLogReadBufferExtended(rlocator, forknum, blkno,
378 : 0 : get_cleanup_lock ? RBM_ZERO_AND_CLEANUP_LOCK : RBM_ZERO_AND_LOCK,
379 : 0 : prefetch_buffer);
380 : 0 : page = BufferGetPage(*buf);
381 [ # # ]: 0 : if (!RestoreBlockImage(record, block_id, page))
382 [ # # # # ]: 0 : ereport(ERROR,
383 : : (errcode(ERRCODE_INTERNAL_ERROR),
384 : : errmsg_internal("%s", record->errormsg_buf)));
385 : :
386 : : /*
387 : : * The page may be uninitialized. If so, we can't set the LSN because
388 : : * that would corrupt the page.
389 : : */
390 [ # # ]: 0 : if (!PageIsNew(page))
391 : : {
392 : 0 : PageSetLSN(page, lsn);
393 : 0 : }
394 : :
395 : 0 : MarkBufferDirty(*buf);
396 : :
397 : : /*
398 : : * At the end of crash recovery the init forks of unlogged relations
399 : : * are copied, without going through shared buffers. So we need to
400 : : * force the on-disk state of init forks to always be in sync with the
401 : : * state in shared buffers.
402 : : */
403 [ # # ]: 0 : if (forknum == INIT_FORKNUM)
404 : 0 : FlushOneBuffer(*buf);
405 : :
406 : 0 : return BLK_RESTORED;
407 : : }
408 : : else
409 : : {
410 : 0 : *buf = XLogReadBufferExtended(rlocator, forknum, blkno, mode, prefetch_buffer);
411 [ # # ]: 0 : if (BufferIsValid(*buf))
412 : : {
413 [ # # # # ]: 0 : if (mode != RBM_ZERO_AND_LOCK && mode != RBM_ZERO_AND_CLEANUP_LOCK)
414 : : {
415 [ # # ]: 0 : if (get_cleanup_lock)
416 : 0 : LockBufferForCleanup(*buf);
417 : : else
418 : 0 : LockBuffer(*buf, BUFFER_LOCK_EXCLUSIVE);
419 : 0 : }
420 [ # # ]: 0 : if (lsn <= PageGetLSN(BufferGetPage(*buf)))
421 : 0 : return BLK_DONE;
422 : : else
423 : 0 : return BLK_NEEDS_REDO;
424 : : }
425 : : else
426 : 0 : return BLK_NOTFOUND;
427 : : }
428 : 0 : }
429 : :
430 : : /*
431 : : * XLogReadBufferExtended
432 : : * Read a page during XLOG replay
433 : : *
434 : : * This is functionally comparable to ReadBufferExtended. There's some
435 : : * differences in the behavior wrt. the "mode" argument:
436 : : *
437 : : * In RBM_NORMAL mode, if the page doesn't exist, or contains all-zeroes, we
438 : : * return InvalidBuffer. In this case the caller should silently skip the
439 : : * update on this page. (In this situation, we expect that the page was later
440 : : * dropped or truncated. If we don't see evidence of that later in the WAL
441 : : * sequence, we'll complain at the end of WAL replay.)
442 : : *
443 : : * In RBM_ZERO_* modes, if the page doesn't exist, the relation is extended
444 : : * with all-zeroes pages up to the given block number.
445 : : *
446 : : * In RBM_NORMAL_NO_LOG mode, we return InvalidBuffer if the page doesn't
447 : : * exist, and we don't check for all-zeroes. Thus, no log entry is made
448 : : * to imply that the page should be dropped or truncated later.
449 : : *
450 : : * Optionally, recent_buffer can be used to provide a hint about the location
451 : : * of the page in the buffer pool; it does not have to be correct, but avoids
452 : : * a buffer mapping table probe if it is.
453 : : *
454 : : * NB: A redo function should normally not call this directly. To get a page
455 : : * to modify, use XLogReadBufferForRedoExtended instead. It is important that
456 : : * all pages modified by a WAL record are registered in the WAL records, or
457 : : * they will be invisible to tools that need to know which pages are modified.
458 : : */
459 : : Buffer
460 : 0 : XLogReadBufferExtended(RelFileLocator rlocator, ForkNumber forknum,
461 : : BlockNumber blkno, ReadBufferMode mode,
462 : : Buffer recent_buffer)
463 : : {
464 : 0 : BlockNumber lastblock;
465 : 0 : Buffer buffer;
466 : 0 : SMgrRelation smgr;
467 : :
468 [ # # ]: 0 : Assert(blkno != P_NEW);
469 : :
470 : : /* Do we have a clue where the buffer might be already? */
471 [ # # ]: 0 : if (BufferIsValid(recent_buffer) &&
472 [ # # # # ]: 0 : mode == RBM_NORMAL &&
473 : 0 : ReadRecentBuffer(rlocator, forknum, blkno, recent_buffer))
474 : : {
475 : 0 : buffer = recent_buffer;
476 : 0 : goto recent_buffer_fast_path;
477 : : }
478 : :
479 : : /* Open the relation at smgr level */
480 : 0 : smgr = smgropen(rlocator, INVALID_PROC_NUMBER);
481 : :
482 : : /*
483 : : * Create the target file if it doesn't already exist. This lets us cope
484 : : * if the replay sequence contains writes to a relation that is later
485 : : * deleted. (The original coding of this routine would instead suppress
486 : : * the writes, but that seems like it risks losing valuable data if the
487 : : * filesystem loses an inode during a crash. Better to write the data
488 : : * until we are actually told to delete the file.)
489 : : */
490 : 0 : smgrcreate(smgr, forknum, true);
491 : :
492 : 0 : lastblock = smgrnblocks(smgr, forknum);
493 : :
494 [ # # ]: 0 : if (blkno < lastblock)
495 : : {
496 : : /* page exists in file */
497 : 0 : buffer = ReadBufferWithoutRelcache(rlocator, forknum, blkno,
498 : 0 : mode, NULL, true);
499 : 0 : }
500 : : else
501 : : {
502 : : /* hm, page doesn't exist in file */
503 [ # # ]: 0 : if (mode == RBM_NORMAL)
504 : : {
505 : 0 : log_invalid_page(rlocator, forknum, blkno, false);
506 : 0 : return InvalidBuffer;
507 : : }
508 [ # # ]: 0 : if (mode == RBM_NORMAL_NO_LOG)
509 : 0 : return InvalidBuffer;
510 : : /* OK to extend the file */
511 : : /* we do this in recovery only - no rel-extension lock needed */
512 [ # # ]: 0 : Assert(InRecovery);
513 : 0 : buffer = ExtendBufferedRelTo(BMR_SMGR(smgr, RELPERSISTENCE_PERMANENT),
514 : 0 : forknum,
515 : : NULL,
516 : : EB_PERFORMING_RECOVERY |
517 : : EB_SKIP_EXTENSION_LOCK,
518 : 0 : blkno + 1,
519 : 0 : mode);
520 : : }
521 : :
522 : : recent_buffer_fast_path:
523 [ # # ]: 0 : if (mode == RBM_NORMAL)
524 : : {
525 : : /* check that page has been initialized */
526 : 0 : Page page = BufferGetPage(buffer);
527 : :
528 : : /*
529 : : * We assume that PageIsNew is safe without a lock. During recovery,
530 : : * there should be no other backends that could modify the buffer at
531 : : * the same time.
532 : : */
533 [ # # ]: 0 : if (PageIsNew(page))
534 : : {
535 : 0 : ReleaseBuffer(buffer);
536 : 0 : log_invalid_page(rlocator, forknum, blkno, true);
537 : 0 : return InvalidBuffer;
538 : : }
539 [ # # ]: 0 : }
540 : :
541 : 0 : return buffer;
542 : 0 : }
543 : :
544 : : /*
545 : : * Struct actually returned by CreateFakeRelcacheEntry, though the declared
546 : : * return type is Relation.
547 : : */
548 : : typedef struct
549 : : {
550 : : RelationData reldata; /* Note: this must be first */
551 : : FormData_pg_class pgc;
552 : : } FakeRelCacheEntryData;
553 : :
554 : : typedef FakeRelCacheEntryData *FakeRelCacheEntry;
555 : :
556 : : /*
557 : : * Create a fake relation cache entry for a physical relation
558 : : *
559 : : * It's often convenient to use the same functions in XLOG replay as in the
560 : : * main codepath, but those functions typically work with a relcache entry.
561 : : * We don't have a working relation cache during XLOG replay, but this
562 : : * function can be used to create a fake relcache entry instead. Only the
563 : : * fields related to physical storage, like rd_rel, are initialized, so the
564 : : * fake entry is only usable in low-level operations like ReadBuffer().
565 : : *
566 : : * This is also used for syncing WAL-skipped files.
567 : : *
568 : : * Caller must free the returned entry with FreeFakeRelcacheEntry().
569 : : */
570 : : Relation
571 : 9261 : CreateFakeRelcacheEntry(RelFileLocator rlocator)
572 : : {
573 : 9261 : FakeRelCacheEntry fakeentry;
574 : 9261 : Relation rel;
575 : :
576 : : /* Allocate the Relation struct and all related space in one block. */
577 : 9261 : fakeentry = palloc0_object(FakeRelCacheEntryData);
578 : 9261 : rel = (Relation) fakeentry;
579 : :
580 : 9261 : rel->rd_rel = &fakeentry->pgc;
581 : 9261 : rel->rd_locator = rlocator;
582 : :
583 : : /*
584 : : * We will never be working with temp rels during recovery or while
585 : : * syncing WAL-skipped files.
586 : : */
587 : 9261 : rel->rd_backend = INVALID_PROC_NUMBER;
588 : :
589 : : /* It must be a permanent table here */
590 : 9261 : rel->rd_rel->relpersistence = RELPERSISTENCE_PERMANENT;
591 : :
592 : : /* We don't know the name of the relation; use relfilenumber instead */
593 : 9261 : sprintf(RelationGetRelationName(rel), "%u", rlocator.relNumber);
594 : :
595 : : /*
596 : : * We set up the lockRelId in case anything tries to lock the dummy
597 : : * relation. Note that this is fairly bogus since relNumber may be
598 : : * different from the relation's OID. It shouldn't really matter though.
599 : : * In recovery, we are running by ourselves and can't have any lock
600 : : * conflicts. While syncing, we already hold AccessExclusiveLock.
601 : : */
602 : 9261 : rel->rd_lockInfo.lockRelId.dbId = rlocator.dbOid;
603 : 9261 : rel->rd_lockInfo.lockRelId.relId = rlocator.relNumber;
604 : :
605 : : /*
606 : : * Set up a non-pinned SMgrRelation reference, so that we don't need to
607 : : * worry about unpinning it on error.
608 : : */
609 : 9261 : rel->rd_smgr = smgropen(rlocator, INVALID_PROC_NUMBER);
610 : :
611 : 18522 : return rel;
612 : 9261 : }
613 : :
614 : : /*
615 : : * Free a fake relation cache entry.
616 : : */
617 : : void
618 : 9261 : FreeFakeRelcacheEntry(Relation fakerel)
619 : : {
620 : 9261 : pfree(fakerel);
621 : 9261 : }
622 : :
623 : : /*
624 : : * Drop a relation during XLOG replay
625 : : *
626 : : * This is called when the relation is about to be deleted; we need to remove
627 : : * any open "invalid-page" records for the relation.
628 : : */
629 : : void
630 : 0 : XLogDropRelation(RelFileLocator rlocator, ForkNumber forknum)
631 : : {
632 : 0 : forget_invalid_pages(rlocator, forknum, 0);
633 : 0 : }
634 : :
635 : : /*
636 : : * Drop a whole database during XLOG replay
637 : : *
638 : : * As above, but for DROP DATABASE instead of dropping a single rel
639 : : */
640 : : void
641 : 0 : XLogDropDatabase(Oid dbid)
642 : : {
643 : : /*
644 : : * This is unnecessarily heavy-handed, as it will close SMgrRelation
645 : : * objects for other databases as well. DROP DATABASE occurs seldom enough
646 : : * that it's not worth introducing a variant of smgrdestroy for just this
647 : : * purpose.
648 : : */
649 : 0 : smgrdestroyall();
650 : :
651 : 0 : forget_invalid_pages_db(dbid);
652 : 0 : }
653 : :
654 : : /*
655 : : * Truncate a relation during XLOG replay
656 : : *
657 : : * We need to clean up any open "invalid-page" records for the dropped pages.
658 : : */
659 : : void
660 : 0 : XLogTruncateRelation(RelFileLocator rlocator, ForkNumber forkNum,
661 : : BlockNumber nblocks)
662 : : {
663 : 0 : forget_invalid_pages(rlocator, forkNum, nblocks);
664 : 0 : }
665 : :
666 : : /*
667 : : * Determine which timeline to read an xlog page from and set the
668 : : * XLogReaderState's currTLI to that timeline ID.
669 : : *
670 : : * We care about timelines in xlogreader when we might be reading xlog
671 : : * generated prior to a promotion, either if we're currently a standby in
672 : : * recovery or if we're a promoted primary reading xlogs generated by the old
673 : : * primary before our promotion.
674 : : *
675 : : * wantPage must be set to the start address of the page to read and
676 : : * wantLength to the amount of the page that will be read, up to
677 : : * XLOG_BLCKSZ. If the amount to be read isn't known, pass XLOG_BLCKSZ.
678 : : *
679 : : * The currTLI argument should be the system-wide current timeline.
680 : : * Note that this may be different from state->currTLI, which is the timeline
681 : : * from which the caller is currently reading previous xlog records.
682 : : *
683 : : * We switch to an xlog segment from the new timeline eagerly when on a
684 : : * historical timeline, as soon as we reach the start of the xlog segment
685 : : * containing the timeline switch. The server copied the segment to the new
686 : : * timeline so all the data up to the switch point is the same, but there's no
687 : : * guarantee the old segment will still exist. It may have been deleted or
688 : : * renamed with a .partial suffix so we can't necessarily keep reading from
689 : : * the old TLI even though tliSwitchPoint says it's OK.
690 : : *
691 : : * We can't just check the timeline when we read a page on a different segment
692 : : * to the last page. We could've received a timeline switch from a cascading
693 : : * upstream, so the current segment ends abruptly (possibly getting renamed to
694 : : * .partial) and we have to switch to a new one. Even in the middle of reading
695 : : * a page we could have to dump the cached page and switch to a new TLI.
696 : : *
697 : : * Because of this, callers MAY NOT assume that currTLI is the timeline that
698 : : * will be in a page's xlp_tli; the page may begin on an older timeline or we
699 : : * might be reading from historical timeline data on a segment that's been
700 : : * copied to a new timeline.
701 : : *
702 : : * The caller must also make sure it doesn't read past the current replay
703 : : * position (using GetXLogReplayRecPtr) if executing in recovery, so it
704 : : * doesn't fail to notice that the current timeline became historical.
705 : : */
706 : : void
707 : 0 : XLogReadDetermineTimeline(XLogReaderState *state, XLogRecPtr wantPage,
708 : : uint32 wantLength, TimeLineID currTLI)
709 : : {
710 : 0 : const XLogRecPtr lastReadPage = (state->seg.ws_segno *
711 : 0 : state->segcxt.ws_segsize + state->segoff);
712 : :
713 [ # # ]: 0 : Assert(XLogRecPtrIsValid(wantPage) && wantPage % XLOG_BLCKSZ == 0);
714 [ # # ]: 0 : Assert(wantLength <= XLOG_BLCKSZ);
715 [ # # # # ]: 0 : Assert(state->readLen == 0 || state->readLen <= XLOG_BLCKSZ);
716 [ # # ]: 0 : Assert(currTLI != 0);
717 : :
718 : : /*
719 : : * If the desired page is currently read in and valid, we have nothing to
720 : : * do.
721 : : *
722 : : * The caller should've ensured that it didn't previously advance readOff
723 : : * past the valid limit of this timeline, so it doesn't matter if the
724 : : * current TLI has since become historical.
725 : : */
726 [ # # ]: 0 : if (lastReadPage == wantPage &&
727 [ # # # # ]: 0 : state->readLen != 0 &&
728 [ # # ]: 0 : lastReadPage + state->readLen >= wantPage + Min(wantLength, XLOG_BLCKSZ - 1))
729 : 0 : return;
730 : :
731 : : /*
732 : : * If we're reading from the current timeline, it hasn't become historical
733 : : * and the page we're reading is after the last page read, we can again
734 : : * just carry on. (Seeking backwards requires a check to make sure the
735 : : * older page isn't on a prior timeline).
736 : : *
737 : : * currTLI might've become historical since the caller obtained the value,
738 : : * but the caller is required not to read past the flush limit it saw at
739 : : * the time it looked up the timeline. There's nothing we can do about it
740 : : * if StartupXLOG() renames it to .partial concurrently.
741 : : */
742 [ # # # # ]: 0 : if (state->currTLI == currTLI && wantPage >= lastReadPage)
743 : : {
744 [ # # ]: 0 : Assert(!XLogRecPtrIsValid(state->currTLIValidUntil));
745 : 0 : return;
746 : : }
747 : :
748 : : /*
749 : : * If we're just reading pages from a previously validated historical
750 : : * timeline and the timeline we're reading from is valid until the end of
751 : : * the current segment we can just keep reading.
752 : : */
753 [ # # ]: 0 : if (XLogRecPtrIsValid(state->currTLIValidUntil) &&
754 [ # # ]: 0 : state->currTLI != currTLI &&
755 [ # # # # ]: 0 : state->currTLI != 0 &&
756 : 0 : ((wantPage + wantLength) / state->segcxt.ws_segsize) <
757 : 0 : (state->currTLIValidUntil / state->segcxt.ws_segsize))
758 : 0 : return;
759 : :
760 : : /*
761 : : * If we reach this point we're either looking up a page for random
762 : : * access, the current timeline just became historical, or we're reading
763 : : * from a new segment containing a timeline switch. In all cases we need
764 : : * to determine the newest timeline on the segment.
765 : : *
766 : : * If it's the current timeline we can just keep reading from here unless
767 : : * we detect a timeline switch that makes the current timeline historical.
768 : : * If it's a historical timeline we can read all the segment on the newest
769 : : * timeline because it contains all the old timelines' data too. So only
770 : : * one switch check is required.
771 : : */
772 : : {
773 : : /*
774 : : * We need to re-read the timeline history in case it's been changed
775 : : * by a promotion or replay from a cascaded replica.
776 : : */
777 : 0 : List *timelineHistory = readTimeLineHistory(currTLI);
778 : 0 : XLogRecPtr endOfSegment;
779 : :
780 : 0 : endOfSegment = ((wantPage / state->segcxt.ws_segsize) + 1) *
781 : 0 : state->segcxt.ws_segsize - 1;
782 [ # # ]: 0 : Assert(wantPage / state->segcxt.ws_segsize ==
783 : : endOfSegment / state->segcxt.ws_segsize);
784 : :
785 : : /*
786 : : * Find the timeline of the last LSN on the segment containing
787 : : * wantPage.
788 : : */
789 : 0 : state->currTLI = tliOfPointInHistory(endOfSegment, timelineHistory);
790 : 0 : state->currTLIValidUntil = tliSwitchPoint(state->currTLI, timelineHistory,
791 : 0 : &state->nextTLI);
792 : :
793 [ # # # # ]: 0 : Assert(!XLogRecPtrIsValid(state->currTLIValidUntil) ||
794 : : wantPage + wantLength < state->currTLIValidUntil);
795 : :
796 : 0 : list_free_deep(timelineHistory);
797 : :
798 [ # # # # ]: 0 : elog(DEBUG3, "switched to timeline %u valid until %X/%08X",
799 : : state->currTLI,
800 : : LSN_FORMAT_ARGS(state->currTLIValidUntil));
801 : 0 : }
802 [ # # ]: 0 : }
803 : :
804 : : /* XLogReaderRoutine->segment_open callback for local pg_wal files */
805 : : void
806 : 0 : wal_segment_open(XLogReaderState *state, XLogSegNo nextSegNo,
807 : : TimeLineID *tli_p)
808 : : {
809 : 0 : TimeLineID tli = *tli_p;
810 : 0 : char path[MAXPGPATH];
811 : :
812 : 0 : XLogFilePath(path, tli, nextSegNo, state->segcxt.ws_segsize);
813 : 0 : state->seg.ws_file = BasicOpenFile(path, O_RDONLY | PG_BINARY);
814 [ # # ]: 0 : if (state->seg.ws_file >= 0)
815 : 0 : return;
816 : :
817 [ # # ]: 0 : if (errno == ENOENT)
818 [ # # # # ]: 0 : ereport(ERROR,
819 : : (errcode_for_file_access(),
820 : : errmsg("requested WAL segment %s has already been removed",
821 : : path)));
822 : : else
823 [ # # # # ]: 0 : ereport(ERROR,
824 : : (errcode_for_file_access(),
825 : : errmsg("could not open file \"%s\": %m",
826 : : path)));
827 [ # # ]: 0 : }
828 : :
829 : : /* stock XLogReaderRoutine->segment_close callback */
830 : : void
831 : 0 : wal_segment_close(XLogReaderState *state)
832 : : {
833 : 0 : close(state->seg.ws_file);
834 : : /* need to check errno? */
835 : 0 : state->seg.ws_file = -1;
836 : 0 : }
837 : :
838 : : /*
839 : : * XLogReaderRoutine->page_read callback for reading local xlog files
840 : : *
841 : : * Public because it would likely be very helpful for someone writing another
842 : : * output method outside walsender, e.g. in a bgworker.
843 : : */
844 : : int
845 : 0 : read_local_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr,
846 : : int reqLen, XLogRecPtr targetRecPtr, char *cur_page)
847 : : {
848 : 0 : return read_local_xlog_page_guts(state, targetPagePtr, reqLen,
849 : 0 : targetRecPtr, cur_page, true);
850 : : }
851 : :
852 : : /*
853 : : * Same as read_local_xlog_page except that it doesn't wait for future WAL
854 : : * to be available.
855 : : */
856 : : int
857 : 0 : read_local_xlog_page_no_wait(XLogReaderState *state, XLogRecPtr targetPagePtr,
858 : : int reqLen, XLogRecPtr targetRecPtr,
859 : : char *cur_page)
860 : : {
861 : 0 : return read_local_xlog_page_guts(state, targetPagePtr, reqLen,
862 : 0 : targetRecPtr, cur_page, false);
863 : : }
864 : :
865 : : /*
866 : : * Implementation of read_local_xlog_page and its no wait version.
867 : : */
868 : : static int
869 : 0 : read_local_xlog_page_guts(XLogReaderState *state, XLogRecPtr targetPagePtr,
870 : : int reqLen, XLogRecPtr targetRecPtr,
871 : : char *cur_page, bool wait_for_wal)
872 : : {
873 : 0 : XLogRecPtr read_upto,
874 : : loc;
875 : 0 : TimeLineID tli;
876 : 0 : int count;
877 : 0 : WALReadError errinfo;
878 : 0 : TimeLineID currTLI;
879 : :
880 : 0 : loc = targetPagePtr + reqLen;
881 : :
882 : : /*
883 : : * Loop waiting for xlog to be available if necessary
884 : : *
885 : : * TODO: The walsender has its own version of this function, which uses a
886 : : * condition variable to wake up whenever WAL is flushed. We could use the
887 : : * same infrastructure here, instead of the check/sleep/repeat style of
888 : : * loop.
889 : : */
890 : 0 : while (1)
891 : : {
892 : : /*
893 : : * Determine the limit of xlog we can currently read to, and what the
894 : : * most recent timeline is.
895 : : */
896 [ # # ]: 0 : if (!RecoveryInProgress())
897 : 0 : read_upto = GetFlushRecPtr(&currTLI);
898 : : else
899 : 0 : read_upto = GetXLogReplayRecPtr(&currTLI);
900 : 0 : tli = currTLI;
901 : :
902 : : /*
903 : : * Check which timeline to get the record from.
904 : : *
905 : : * We have to do it each time through the loop because if we're in
906 : : * recovery as a cascading standby, the current timeline might've
907 : : * become historical. We can't rely on RecoveryInProgress() because in
908 : : * a standby configuration like
909 : : *
910 : : * A => B => C
911 : : *
912 : : * if we're a logical decoding session on C, and B gets promoted, our
913 : : * timeline will change while we remain in recovery.
914 : : *
915 : : * We can't just keep reading from the old timeline as the last WAL
916 : : * archive in the timeline will get renamed to .partial by
917 : : * StartupXLOG().
918 : : *
919 : : * If that happens after our caller determined the TLI but before we
920 : : * actually read the xlog page, we might still try to read from the
921 : : * old (now renamed) segment and fail. There's not much we can do
922 : : * about this, but it can only happen when we're a leaf of a cascading
923 : : * standby whose primary gets promoted while we're decoding, so a
924 : : * one-off ERROR isn't too bad.
925 : : */
926 : 0 : XLogReadDetermineTimeline(state, targetPagePtr, reqLen, tli);
927 : :
928 [ # # ]: 0 : if (state->currTLI == currTLI)
929 : : {
930 : :
931 [ # # ]: 0 : if (loc <= read_upto)
932 : 0 : break;
933 : :
934 : : /* If asked, let's not wait for future WAL. */
935 [ # # ]: 0 : if (!wait_for_wal)
936 : : {
937 : 0 : ReadLocalXLogPageNoWaitPrivate *private_data;
938 : :
939 : : /*
940 : : * Inform the caller of read_local_xlog_page_no_wait that the
941 : : * end of WAL has been reached.
942 : : */
943 : 0 : private_data = (ReadLocalXLogPageNoWaitPrivate *)
944 : 0 : state->private_data;
945 : 0 : private_data->end_of_wal = true;
946 : : break;
947 : 0 : }
948 : :
949 [ # # ]: 0 : CHECK_FOR_INTERRUPTS();
950 : 0 : pg_usleep(1000L);
951 : 0 : }
952 : : else
953 : : {
954 : : /*
955 : : * We're on a historical timeline, so limit reading to the switch
956 : : * point where we moved to the next timeline.
957 : : *
958 : : * We don't need to GetFlushRecPtr or GetXLogReplayRecPtr. We know
959 : : * about the new timeline, so we must've received past the end of
960 : : * it.
961 : : */
962 : 0 : read_upto = state->currTLIValidUntil;
963 : :
964 : : /*
965 : : * Setting tli to our wanted record's TLI is slightly wrong; the
966 : : * page might begin on an older timeline if it contains a timeline
967 : : * switch, since its xlog segment will have been copied from the
968 : : * prior timeline. This is pretty harmless though, as nothing
969 : : * cares so long as the timeline doesn't go backwards. We should
970 : : * read the page header instead; FIXME someday.
971 : : */
972 : 0 : tli = state->currTLI;
973 : :
974 : : /* No need to wait on a historical timeline */
975 : 0 : break;
976 : : }
977 : : }
978 : :
979 [ # # ]: 0 : if (targetPagePtr + XLOG_BLCKSZ <= read_upto)
980 : : {
981 : : /*
982 : : * more than one block available; read only that block, have caller
983 : : * come back if they need more.
984 : : */
985 : 0 : count = XLOG_BLCKSZ;
986 : 0 : }
987 [ # # ]: 0 : else if (targetPagePtr + reqLen > read_upto)
988 : : {
989 : : /* not enough data there */
990 : 0 : return -1;
991 : : }
992 : : else
993 : : {
994 : : /* enough bytes available to satisfy the request */
995 : 0 : count = read_upto - targetPagePtr;
996 : : }
997 : :
998 [ # # ]: 0 : if (!WALRead(state, cur_page, targetPagePtr, count, tli,
999 : : &errinfo))
1000 : 0 : WALReadRaiseError(&errinfo);
1001 : :
1002 : : /* number of valid bytes in the buffer */
1003 : 0 : return count;
1004 : 0 : }
1005 : :
1006 : : /*
1007 : : * Backend-specific convenience code to handle read errors encountered by
1008 : : * WALRead().
1009 : : */
1010 : : void
1011 : 0 : WALReadRaiseError(WALReadError *errinfo)
1012 : : {
1013 : 0 : WALOpenSegment *seg = &errinfo->wre_seg;
1014 : 0 : char fname[MAXFNAMELEN];
1015 : :
1016 : 0 : XLogFileName(fname, seg->ws_tli, seg->ws_segno, wal_segment_size);
1017 : :
1018 [ # # ]: 0 : if (errinfo->wre_read < 0)
1019 : : {
1020 : 0 : errno = errinfo->wre_errno;
1021 [ # # # # ]: 0 : ereport(ERROR,
1022 : : (errcode_for_file_access(),
1023 : : errmsg("could not read from WAL segment %s, offset %d: %m",
1024 : : fname, errinfo->wre_off)));
1025 : 0 : }
1026 [ # # ]: 0 : else if (errinfo->wre_read == 0)
1027 : : {
1028 [ # # # # ]: 0 : ereport(ERROR,
1029 : : (errcode(ERRCODE_DATA_CORRUPTED),
1030 : : errmsg("could not read from WAL segment %s, offset %d: read %d of %d",
1031 : : fname, errinfo->wre_off, errinfo->wre_read,
1032 : : errinfo->wre_req)));
1033 : 0 : }
1034 : 0 : }
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