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relmapper.c
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1 /*-------------------------------------------------------------------------
2  *
3  * relmapper.c
4  * Catalog-to-filenumber mapping
5  *
6  * For most tables, the physical file underlying the table is specified by
7  * pg_class.relfilenode. However, that obviously won't work for pg_class
8  * itself, nor for the other "nailed" catalogs for which we have to be able
9  * to set up working Relation entries without access to pg_class. It also
10  * does not work for shared catalogs, since there is no practical way to
11  * update other databases' pg_class entries when relocating a shared catalog.
12  * Therefore, for these special catalogs (henceforth referred to as "mapped
13  * catalogs") we rely on a separately maintained file that shows the mapping
14  * from catalog OIDs to filenumbers. Each database has a map file for
15  * its local mapped catalogs, and there is a separate map file for shared
16  * catalogs. Mapped catalogs have zero in their pg_class.relfilenode entries.
17  *
18  * Relocation of a normal table is committed (ie, the new physical file becomes
19  * authoritative) when the pg_class row update commits. For mapped catalogs,
20  * the act of updating the map file is effectively commit of the relocation.
21  * We postpone the file update till just before commit of the transaction
22  * doing the rewrite, but there is necessarily a window between. Therefore
23  * mapped catalogs can only be relocated by operations such as VACUUM FULL
24  * and CLUSTER, which make no transactionally-significant changes: it must be
25  * safe for the new file to replace the old, even if the transaction itself
26  * aborts. An important factor here is that the indexes and toast table of
27  * a mapped catalog must also be mapped, so that the rewrites/relocations of
28  * all these files commit in a single map file update rather than being tied
29  * to transaction commit.
30  *
31  * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
32  * Portions Copyright (c) 1994, Regents of the University of California
33  *
34  *
35  * IDENTIFICATION
36  * src/backend/utils/cache/relmapper.c
37  *
38  *-------------------------------------------------------------------------
39  */
40 #include "postgres.h"
41 
42 #include <fcntl.h>
43 #include <sys/stat.h>
44 #include <unistd.h>
45 
46 #include "access/xact.h"
47 #include "access/xlog.h"
48 #include "access/xloginsert.h"
49 #include "catalog/catalog.h"
50 #include "catalog/pg_tablespace.h"
51 #include "catalog/storage.h"
52 #include "miscadmin.h"
53 #include "pgstat.h"
54 #include "storage/fd.h"
55 #include "storage/lwlock.h"
56 #include "utils/inval.h"
57 #include "utils/relmapper.h"
58 
59 
60 /*
61  * The map file is critical data: we have no automatic method for recovering
62  * from loss or corruption of it. We use a CRC so that we can detect
63  * corruption. Since the file might be more than one standard-size disk
64  * sector in size, we cannot rely on overwrite-in-place. Instead, we generate
65  * a new file and rename it into place, atomically replacing the original file.
66  *
67  * Entries in the mappings[] array are in no particular order. We could
68  * speed searching by insisting on OID order, but it really shouldn't be
69  * worth the trouble given the intended size of the mapping sets.
70  */
71 #define RELMAPPER_FILENAME "pg_filenode.map"
72 #define RELMAPPER_TEMP_FILENAME "pg_filenode.map.tmp"
73 
74 #define RELMAPPER_FILEMAGIC 0x592717 /* version ID value */
75 
76 /*
77  * There's no need for this constant to have any particular value, and we
78  * can raise it as necessary if we end up with more mapped relations. For
79  * now, we just pick a round number that is modestly larger than the expected
80  * number of mappings.
81  */
82 #define MAX_MAPPINGS 64
83 
84 typedef struct RelMapping
85 {
86  Oid mapoid; /* OID of a catalog */
87  RelFileNumber mapfilenumber; /* its rel file number */
89 
90 typedef struct RelMapFile
91 {
92  int32 magic; /* always RELMAPPER_FILEMAGIC */
93  int32 num_mappings; /* number of valid RelMapping entries */
95  pg_crc32c crc; /* CRC of all above */
97 
98 /*
99  * State for serializing local and shared relmappings for parallel workers
100  * (active states only). See notes on active_* and pending_* updates state.
101  */
103 {
107 
108 /*
109  * The currently known contents of the shared map file and our database's
110  * local map file are stored here. These can be reloaded from disk
111  * immediately whenever we receive an update sinval message.
112  */
115 
116 /*
117  * We use the same RelMapFile data structure to track uncommitted local
118  * changes in the mappings (but note the magic and crc fields are not made
119  * valid in these variables). Currently, map updates are not allowed within
120  * subtransactions, so one set of transaction-level changes is sufficient.
121  *
122  * The active_xxx variables contain updates that are valid in our transaction
123  * and should be honored by RelationMapOidToFilenumber. The pending_xxx
124  * variables contain updates we have been told about that aren't active yet;
125  * they will become active at the next CommandCounterIncrement. This setup
126  * lets map updates act similarly to updates of pg_class rows, ie, they
127  * become visible only at the next CommandCounterIncrement boundary.
128  *
129  * Active shared and active local updates are serialized by the parallel
130  * infrastructure, and deserialized within parallel workers.
131  */
136 
137 
138 /* non-export function prototypes */
139 static void apply_map_update(RelMapFile *map, Oid relationId,
140  RelFileNumber fileNumber, bool add_okay);
141 static void merge_map_updates(RelMapFile *map, const RelMapFile *updates,
142  bool add_okay);
143 static void load_relmap_file(bool shared, bool lock_held);
144 static void read_relmap_file(RelMapFile *map, char *dbpath, bool lock_held,
145  int elevel);
146 static void write_relmap_file(RelMapFile *newmap, bool write_wal,
147  bool send_sinval, bool preserve_files,
148  Oid dbid, Oid tsid, const char *dbpath);
149 static void perform_relmap_update(bool shared, const RelMapFile *updates);
150 
151 
152 /*
153  * RelationMapOidToFilenumber
154  *
155  * The raison d' etre ... given a relation OID, look up its filenumber.
156  *
157  * Although shared and local relation OIDs should never overlap, the caller
158  * always knows which we need --- so pass that information to avoid useless
159  * searching.
160  *
161  * Returns InvalidRelFileNumber if the OID is not known (which should never
162  * happen, but the caller is in a better position to report a meaningful
163  * error).
164  */
166 RelationMapOidToFilenumber(Oid relationId, bool shared)
167 {
168  const RelMapFile *map;
169  int32 i;
170 
171  /* If there are active updates, believe those over the main maps */
172  if (shared)
173  {
174  map = &active_shared_updates;
175  for (i = 0; i < map->num_mappings; i++)
176  {
177  if (relationId == map->mappings[i].mapoid)
178  return map->mappings[i].mapfilenumber;
179  }
180  map = &shared_map;
181  for (i = 0; i < map->num_mappings; i++)
182  {
183  if (relationId == map->mappings[i].mapoid)
184  return map->mappings[i].mapfilenumber;
185  }
186  }
187  else
188  {
189  map = &active_local_updates;
190  for (i = 0; i < map->num_mappings; i++)
191  {
192  if (relationId == map->mappings[i].mapoid)
193  return map->mappings[i].mapfilenumber;
194  }
195  map = &local_map;
196  for (i = 0; i < map->num_mappings; i++)
197  {
198  if (relationId == map->mappings[i].mapoid)
199  return map->mappings[i].mapfilenumber;
200  }
201  }
202 
203  return InvalidRelFileNumber;
204 }
205 
206 /*
207  * RelationMapFilenumberToOid
208  *
209  * Do the reverse of the normal direction of mapping done in
210  * RelationMapOidToFilenumber.
211  *
212  * This is not supposed to be used during normal running but rather for
213  * information purposes when looking at the filesystem or xlog.
214  *
215  * Returns InvalidOid if the OID is not known; this can easily happen if the
216  * relfilenumber doesn't pertain to a mapped relation.
217  */
218 Oid
220 {
221  const RelMapFile *map;
222  int32 i;
223 
224  /* If there are active updates, believe those over the main maps */
225  if (shared)
226  {
227  map = &active_shared_updates;
228  for (i = 0; i < map->num_mappings; i++)
229  {
230  if (filenumber == map->mappings[i].mapfilenumber)
231  return map->mappings[i].mapoid;
232  }
233  map = &shared_map;
234  for (i = 0; i < map->num_mappings; i++)
235  {
236  if (filenumber == map->mappings[i].mapfilenumber)
237  return map->mappings[i].mapoid;
238  }
239  }
240  else
241  {
242  map = &active_local_updates;
243  for (i = 0; i < map->num_mappings; i++)
244  {
245  if (filenumber == map->mappings[i].mapfilenumber)
246  return map->mappings[i].mapoid;
247  }
248  map = &local_map;
249  for (i = 0; i < map->num_mappings; i++)
250  {
251  if (filenumber == map->mappings[i].mapfilenumber)
252  return map->mappings[i].mapoid;
253  }
254  }
255 
256  return InvalidOid;
257 }
258 
259 /*
260  * RelationMapOidToFilenumberForDatabase
261  *
262  * Like RelationMapOidToFilenumber, but reads the mapping from the indicated
263  * path instead of using the one for the current database.
264  */
267 {
268  RelMapFile map;
269  int i;
270 
271  /* Read the relmap file from the source database. */
272  read_relmap_file(&map, dbpath, false, ERROR);
273 
274  /* Iterate over the relmap entries to find the input relation OID. */
275  for (i = 0; i < map.num_mappings; i++)
276  {
277  if (relationId == map.mappings[i].mapoid)
278  return map.mappings[i].mapfilenumber;
279  }
280 
281  return InvalidRelFileNumber;
282 }
283 
284 /*
285  * RelationMapCopy
286  *
287  * Copy relmapfile from source db path to the destination db path and WAL log
288  * the operation. This is intended for use in creating a new relmap file
289  * for a database that doesn't have one yet, not for replacing an existing
290  * relmap file.
291  */
292 void
293 RelationMapCopy(Oid dbid, Oid tsid, char *srcdbpath, char *dstdbpath)
294 {
295  RelMapFile map;
296 
297  /*
298  * Read the relmap file from the source database.
299  */
300  read_relmap_file(&map, srcdbpath, false, ERROR);
301 
302  /*
303  * Write the same data into the destination database's relmap file.
304  *
305  * No sinval is needed because no one can be connected to the destination
306  * database yet. For the same reason, there is no need to acquire
307  * RelationMappingLock.
308  *
309  * There's no point in trying to preserve files here. The new database
310  * isn't usable yet anyway, and won't ever be if we can't install a relmap
311  * file.
312  */
313  write_relmap_file(&map, true, false, false, dbid, tsid, dstdbpath);
314 }
315 
316 /*
317  * RelationMapUpdateMap
318  *
319  * Install a new relfilenumber mapping for the specified relation.
320  *
321  * If immediate is true (or we're bootstrapping), the mapping is activated
322  * immediately. Otherwise it is made pending until CommandCounterIncrement.
323  */
324 void
325 RelationMapUpdateMap(Oid relationId, RelFileNumber fileNumber, bool shared,
326  bool immediate)
327 {
328  RelMapFile *map;
329 
331  {
332  /*
333  * In bootstrap mode, the mapping gets installed in permanent map.
334  */
335  if (shared)
336  map = &shared_map;
337  else
338  map = &local_map;
339  }
340  else
341  {
342  /*
343  * We don't currently support map changes within subtransactions, or
344  * when in parallel mode. This could be done with more bookkeeping
345  * infrastructure, but it doesn't presently seem worth it.
346  */
348  elog(ERROR, "cannot change relation mapping within subtransaction");
349 
350  if (IsInParallelMode())
351  elog(ERROR, "cannot change relation mapping in parallel mode");
352 
353  if (immediate)
354  {
355  /* Make it active, but only locally */
356  if (shared)
357  map = &active_shared_updates;
358  else
359  map = &active_local_updates;
360  }
361  else
362  {
363  /* Make it pending */
364  if (shared)
365  map = &pending_shared_updates;
366  else
367  map = &pending_local_updates;
368  }
369  }
370  apply_map_update(map, relationId, fileNumber, true);
371 }
372 
373 /*
374  * apply_map_update
375  *
376  * Insert a new mapping into the given map variable, replacing any existing
377  * mapping for the same relation.
378  *
379  * In some cases the caller knows there must be an existing mapping; pass
380  * add_okay = false to draw an error if not.
381  */
382 static void
383 apply_map_update(RelMapFile *map, Oid relationId, RelFileNumber fileNumber,
384  bool add_okay)
385 {
386  int32 i;
387 
388  /* Replace any existing mapping */
389  for (i = 0; i < map->num_mappings; i++)
390  {
391  if (relationId == map->mappings[i].mapoid)
392  {
393  map->mappings[i].mapfilenumber = fileNumber;
394  return;
395  }
396  }
397 
398  /* Nope, need to add a new mapping */
399  if (!add_okay)
400  elog(ERROR, "attempt to apply a mapping to unmapped relation %u",
401  relationId);
402  if (map->num_mappings >= MAX_MAPPINGS)
403  elog(ERROR, "ran out of space in relation map");
404  map->mappings[map->num_mappings].mapoid = relationId;
405  map->mappings[map->num_mappings].mapfilenumber = fileNumber;
406  map->num_mappings++;
407 }
408 
409 /*
410  * merge_map_updates
411  *
412  * Merge all the updates in the given pending-update map into the target map.
413  * This is just a bulk form of apply_map_update.
414  */
415 static void
416 merge_map_updates(RelMapFile *map, const RelMapFile *updates, bool add_okay)
417 {
418  int32 i;
419 
420  for (i = 0; i < updates->num_mappings; i++)
421  {
422  apply_map_update(map,
423  updates->mappings[i].mapoid,
424  updates->mappings[i].mapfilenumber,
425  add_okay);
426  }
427 }
428 
429 /*
430  * RelationMapRemoveMapping
431  *
432  * Remove a relation's entry in the map. This is only allowed for "active"
433  * (but not committed) local mappings. We need it so we can back out the
434  * entry for the transient target file when doing VACUUM FULL/CLUSTER on
435  * a mapped relation.
436  */
437 void
439 {
441  int32 i;
442 
443  for (i = 0; i < map->num_mappings; i++)
444  {
445  if (relationId == map->mappings[i].mapoid)
446  {
447  /* Found it, collapse it out */
448  map->mappings[i] = map->mappings[map->num_mappings - 1];
449  map->num_mappings--;
450  return;
451  }
452  }
453  elog(ERROR, "could not find temporary mapping for relation %u",
454  relationId);
455 }
456 
457 /*
458  * RelationMapInvalidate
459  *
460  * This routine is invoked for SI cache flush messages. We must re-read
461  * the indicated map file. However, we might receive a SI message in a
462  * process that hasn't yet, and might never, load the mapping files;
463  * for example the autovacuum launcher, which *must not* try to read
464  * a local map since it is attached to no particular database.
465  * So, re-read only if the map is valid now.
466  */
467 void
469 {
470  if (shared)
471  {
473  load_relmap_file(true, false);
474  }
475  else
476  {
478  load_relmap_file(false, false);
479  }
480 }
481 
482 /*
483  * RelationMapInvalidateAll
484  *
485  * Reload all map files. This is used to recover from SI message buffer
486  * overflow: we can't be sure if we missed an inval message.
487  * Again, reload only currently-valid maps.
488  */
489 void
491 {
493  load_relmap_file(true, false);
495  load_relmap_file(false, false);
496 }
497 
498 /*
499  * AtCCI_RelationMap
500  *
501  * Activate any "pending" relation map updates at CommandCounterIncrement time.
502  */
503 void
505 {
507  {
510  true);
512  }
514  {
517  true);
519  }
520 }
521 
522 /*
523  * AtEOXact_RelationMap
524  *
525  * Handle relation mapping at main-transaction commit or abort.
526  *
527  * During commit, this must be called as late as possible before the actual
528  * transaction commit, so as to minimize the window where the transaction
529  * could still roll back after committing map changes. Although nothing
530  * critically bad happens in such a case, we still would prefer that it
531  * not happen, since we'd possibly be losing useful updates to the relations'
532  * pg_class row(s).
533  *
534  * During abort, we just have to throw away any pending map changes.
535  * Normal post-abort cleanup will take care of fixing relcache entries.
536  * Parallel worker commit/abort is handled by resetting active mappings
537  * that may have been received from the leader process. (There should be
538  * no pending updates in parallel workers.)
539  */
540 void
541 AtEOXact_RelationMap(bool isCommit, bool isParallelWorker)
542 {
543  if (isCommit && !isParallelWorker)
544  {
545  /*
546  * We should not get here with any "pending" updates. (We could
547  * logically choose to treat such as committed, but in the current
548  * code this should never happen.)
549  */
552 
553  /*
554  * Write any active updates to the actual map files, then reset them.
555  */
557  {
560  }
562  {
565  }
566  }
567  else
568  {
569  /* Abort or parallel worker --- drop all local and pending updates */
570  Assert(!isParallelWorker || pending_shared_updates.num_mappings == 0);
571  Assert(!isParallelWorker || pending_local_updates.num_mappings == 0);
572 
577  }
578 }
579 
580 /*
581  * AtPrepare_RelationMap
582  *
583  * Handle relation mapping at PREPARE.
584  *
585  * Currently, we don't support preparing any transaction that changes the map.
586  */
587 void
589 {
594  ereport(ERROR,
595  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
596  errmsg("cannot PREPARE a transaction that modified relation mapping")));
597 }
598 
599 /*
600  * CheckPointRelationMap
601  *
602  * This is called during a checkpoint. It must ensure that any relation map
603  * updates that were WAL-logged before the start of the checkpoint are
604  * securely flushed to disk and will not need to be replayed later. This
605  * seems unlikely to be a performance-critical issue, so we use a simple
606  * method: we just take and release the RelationMappingLock. This ensures
607  * that any already-logged map update is complete, because write_relmap_file
608  * will fsync the map file before the lock is released.
609  */
610 void
612 {
613  LWLockAcquire(RelationMappingLock, LW_SHARED);
614  LWLockRelease(RelationMappingLock);
615 }
616 
617 /*
618  * RelationMapFinishBootstrap
619  *
620  * Write out the initial relation mapping files at the completion of
621  * bootstrap. All the mapped files should have been made known to us
622  * via RelationMapUpdateMap calls.
623  */
624 void
626 {
628 
629  /* Shouldn't be anything "pending" ... */
634 
635  /* Write the files; no WAL or sinval needed */
636  write_relmap_file(&shared_map, false, false, false,
637  InvalidOid, GLOBALTABLESPACE_OID, "global");
638  write_relmap_file(&local_map, false, false, false,
640 }
641 
642 /*
643  * RelationMapInitialize
644  *
645  * This initializes the mapper module at process startup. We can't access the
646  * database yet, so just make sure the maps are empty.
647  */
648 void
650 {
651  /* The static variables should initialize to zeroes, but let's be sure */
652  shared_map.magic = 0; /* mark it not loaded */
653  local_map.magic = 0;
660 }
661 
662 /*
663  * RelationMapInitializePhase2
664  *
665  * This is called to prepare for access to pg_database during startup.
666  * We should be able to read the shared map file now.
667  */
668 void
670 {
671  /*
672  * In bootstrap mode, the map file isn't there yet, so do nothing.
673  */
675  return;
676 
677  /*
678  * Load the shared map file, die on error.
679  */
680  load_relmap_file(true, false);
681 }
682 
683 /*
684  * RelationMapInitializePhase3
685  *
686  * This is called as soon as we have determined MyDatabaseId and set up
687  * DatabasePath. At this point we should be able to read the local map file.
688  */
689 void
691 {
692  /*
693  * In bootstrap mode, the map file isn't there yet, so do nothing.
694  */
696  return;
697 
698  /*
699  * Load the local map file, die on error.
700  */
701  load_relmap_file(false, false);
702 }
703 
704 /*
705  * EstimateRelationMapSpace
706  *
707  * Estimate space needed to pass active shared and local relmaps to parallel
708  * workers.
709  */
710 Size
712 {
713  return sizeof(SerializedActiveRelMaps);
714 }
715 
716 /*
717  * SerializeRelationMap
718  *
719  * Serialize active shared and local relmap state for parallel workers.
720  */
721 void
722 SerializeRelationMap(Size maxSize, char *startAddress)
723 {
724  SerializedActiveRelMaps *relmaps;
725 
726  Assert(maxSize >= EstimateRelationMapSpace());
727 
728  relmaps = (SerializedActiveRelMaps *) startAddress;
731 }
732 
733 /*
734  * RestoreRelationMap
735  *
736  * Restore active shared and local relmap state within a parallel worker.
737  */
738 void
739 RestoreRelationMap(char *startAddress)
740 {
741  SerializedActiveRelMaps *relmaps;
742 
747  elog(ERROR, "parallel worker has existing mappings");
748 
749  relmaps = (SerializedActiveRelMaps *) startAddress;
752 }
753 
754 /*
755  * load_relmap_file -- load the shared or local map file
756  *
757  * Because these files are essential for access to core system catalogs,
758  * failure to load either of them is a fatal error.
759  *
760  * Note that the local case requires DatabasePath to be set up.
761  */
762 static void
763 load_relmap_file(bool shared, bool lock_held)
764 {
765  if (shared)
766  read_relmap_file(&shared_map, "global", lock_held, FATAL);
767  else
769 }
770 
771 /*
772  * read_relmap_file -- load data from any relation mapper file
773  *
774  * dbpath must be the relevant database path, or "global" for shared relations.
775  *
776  * RelationMappingLock will be acquired released unless lock_held = true.
777  *
778  * Errors will be reported at the indicated elevel, which should be at least
779  * ERROR.
780  */
781 static void
782 read_relmap_file(RelMapFile *map, char *dbpath, bool lock_held, int elevel)
783 {
784  char mapfilename[MAXPGPATH];
785  pg_crc32c crc;
786  int fd;
787  int r;
788 
789  Assert(elevel >= ERROR);
790 
791  /*
792  * Grab the lock to prevent the file from being updated while we read it,
793  * unless the caller is already holding the lock. If the file is updated
794  * shortly after we look, the sinval signaling mechanism will make us
795  * re-read it before we are able to access any relation that's affected by
796  * the change.
797  */
798  if (!lock_held)
799  LWLockAcquire(RelationMappingLock, LW_SHARED);
800 
801  /*
802  * Open the target file.
803  *
804  * Because Windows isn't happy about the idea of renaming over a file
805  * that someone has open, we only open this file after acquiring the lock,
806  * and for the same reason, we close it before releasing the lock. That
807  * way, by the time write_relmap_file() acquires an exclusive lock, no
808  * one else will have it open.
809  */
810  snprintf(mapfilename, sizeof(mapfilename), "%s/%s", dbpath,
812  fd = OpenTransientFile(mapfilename, O_RDONLY | PG_BINARY);
813  if (fd < 0)
814  ereport(elevel,
816  errmsg("could not open file \"%s\": %m",
817  mapfilename)));
818 
819  /* Now read the data. */
821  r = read(fd, map, sizeof(RelMapFile));
822  if (r != sizeof(RelMapFile))
823  {
824  if (r < 0)
825  ereport(elevel,
827  errmsg("could not read file \"%s\": %m", mapfilename)));
828  else
829  ereport(elevel,
831  errmsg("could not read file \"%s\": read %d of %zu",
832  mapfilename, r, sizeof(RelMapFile))));
833  }
835 
836  if (CloseTransientFile(fd) != 0)
837  ereport(elevel,
839  errmsg("could not close file \"%s\": %m",
840  mapfilename)));
841 
842  if (!lock_held)
843  LWLockRelease(RelationMappingLock);
844 
845  /* check for correct magic number, etc */
846  if (map->magic != RELMAPPER_FILEMAGIC ||
847  map->num_mappings < 0 ||
848  map->num_mappings > MAX_MAPPINGS)
849  ereport(elevel,
850  (errmsg("relation mapping file \"%s\" contains invalid data",
851  mapfilename)));
852 
853  /* verify the CRC */
854  INIT_CRC32C(crc);
855  COMP_CRC32C(crc, (char *) map, offsetof(RelMapFile, crc));
856  FIN_CRC32C(crc);
857 
858  if (!EQ_CRC32C(crc, map->crc))
859  ereport(elevel,
860  (errmsg("relation mapping file \"%s\" contains incorrect checksum",
861  mapfilename)));
862 }
863 
864 /*
865  * Write out a new shared or local map file with the given contents.
866  *
867  * The magic number and CRC are automatically updated in *newmap. On
868  * success, we copy the data to the appropriate permanent static variable.
869  *
870  * If write_wal is true then an appropriate WAL message is emitted.
871  * (It will be false for bootstrap and WAL replay cases.)
872  *
873  * If send_sinval is true then a SI invalidation message is sent.
874  * (This should be true except in bootstrap case.)
875  *
876  * If preserve_files is true then the storage manager is warned not to
877  * delete the files listed in the map.
878  *
879  * Because this may be called during WAL replay when MyDatabaseId,
880  * DatabasePath, etc aren't valid, we require the caller to pass in suitable
881  * values. Pass dbpath as "global" for the shared map.
882  *
883  * The caller is also responsible for being sure no concurrent map update
884  * could be happening.
885  */
886 static void
887 write_relmap_file(RelMapFile *newmap, bool write_wal, bool send_sinval,
888  bool preserve_files, Oid dbid, Oid tsid, const char *dbpath)
889 {
890  int fd;
891  char mapfilename[MAXPGPATH];
892  char maptempfilename[MAXPGPATH];
893 
894  /*
895  * Fill in the overhead fields and update CRC.
896  */
897  newmap->magic = RELMAPPER_FILEMAGIC;
898  if (newmap->num_mappings < 0 || newmap->num_mappings > MAX_MAPPINGS)
899  elog(ERROR, "attempt to write bogus relation mapping");
900 
901  INIT_CRC32C(newmap->crc);
902  COMP_CRC32C(newmap->crc, (char *) newmap, offsetof(RelMapFile, crc));
903  FIN_CRC32C(newmap->crc);
904 
905  /*
906  * Construct filenames -- a temporary file that we'll create to write the
907  * data initially, and then the permanent name to which we will rename it.
908  */
909  snprintf(mapfilename, sizeof(mapfilename), "%s/%s",
910  dbpath, RELMAPPER_FILENAME);
911  snprintf(maptempfilename, sizeof(maptempfilename), "%s/%s",
912  dbpath, RELMAPPER_TEMP_FILENAME);
913 
914  /*
915  * Open a temporary file. If a file already exists with this name, it must
916  * be left over from a previous crash, so we can overwrite it. Concurrent
917  * calls to this function are not allowed.
918  */
919  fd = OpenTransientFile(maptempfilename,
920  O_WRONLY | O_CREAT | O_TRUNC | PG_BINARY);
921  if (fd < 0)
922  ereport(ERROR,
924  errmsg("could not open file \"%s\": %m",
925  maptempfilename)));
926 
927  /* Write new data to the file. */
929  if (write(fd, newmap, sizeof(RelMapFile)) != sizeof(RelMapFile))
930  {
931  /* if write didn't set errno, assume problem is no disk space */
932  if (errno == 0)
933  errno = ENOSPC;
934  ereport(ERROR,
936  errmsg("could not write file \"%s\": %m",
937  maptempfilename)));
938  }
940 
941  /* And close the file. */
942  if (CloseTransientFile(fd) != 0)
943  ereport(ERROR,
945  errmsg("could not close file \"%s\": %m",
946  maptempfilename)));
947 
948  if (write_wal)
949  {
950  xl_relmap_update xlrec;
951  XLogRecPtr lsn;
952 
953  /* now errors are fatal ... */
955 
956  xlrec.dbid = dbid;
957  xlrec.tsid = tsid;
958  xlrec.nbytes = sizeof(RelMapFile);
959 
960  XLogBeginInsert();
961  XLogRegisterData((char *) (&xlrec), MinSizeOfRelmapUpdate);
962  XLogRegisterData((char *) newmap, sizeof(RelMapFile));
963 
964  lsn = XLogInsert(RM_RELMAP_ID, XLOG_RELMAP_UPDATE);
965 
966  /* As always, WAL must hit the disk before the data update does */
967  XLogFlush(lsn);
968  }
969 
970  /*
971  * durable_rename() does all the hard work of making sure that we rename
972  * the temporary file into place in a crash-safe manner.
973  *
974  * NB: Although we instruct durable_rename() to use ERROR, we will often
975  * be in a critical section at this point; if so, ERROR will become PANIC.
976  */
978  durable_rename(maptempfilename, mapfilename, ERROR);
980 
981  /*
982  * Now that the file is safely on disk, send sinval message to let other
983  * backends know to re-read it. We must do this inside the critical
984  * section: if for some reason we fail to send the message, we have to
985  * force a database-wide PANIC. Otherwise other backends might continue
986  * execution with stale mapping information, which would be catastrophic
987  * as soon as others began to use the now-committed data.
988  */
989  if (send_sinval)
990  CacheInvalidateRelmap(dbid);
991 
992  /*
993  * Make sure that the files listed in the map are not deleted if the outer
994  * transaction aborts. This had better be within the critical section
995  * too: it's not likely to fail, but if it did, we'd arrive at transaction
996  * abort with the files still vulnerable. PANICing will leave things in a
997  * good state on-disk.
998  *
999  * Note: we're cheating a little bit here by assuming that mapped files
1000  * are either in pg_global or the database's default tablespace.
1001  */
1002  if (preserve_files)
1003  {
1004  int32 i;
1005 
1006  for (i = 0; i < newmap->num_mappings; i++)
1007  {
1008  RelFileLocator rlocator;
1009 
1010  rlocator.spcOid = tsid;
1011  rlocator.dbOid = dbid;
1012  rlocator.relNumber = newmap->mappings[i].mapfilenumber;
1013  RelationPreserveStorage(rlocator, false);
1014  }
1015  }
1016 
1017  /* Critical section done */
1018  if (write_wal)
1019  END_CRIT_SECTION();
1020 }
1021 
1022 /*
1023  * Merge the specified updates into the appropriate "real" map,
1024  * and write out the changes. This function must be used for committing
1025  * updates during normal multiuser operation.
1026  */
1027 static void
1028 perform_relmap_update(bool shared, const RelMapFile *updates)
1029 {
1030  RelMapFile newmap;
1031 
1032  /*
1033  * Anyone updating a relation's mapping info should take exclusive lock on
1034  * that rel and hold it until commit. This ensures that there will not be
1035  * concurrent updates on the same mapping value; but there could easily be
1036  * concurrent updates on different values in the same file. We cover that
1037  * by acquiring the RelationMappingLock, re-reading the target file to
1038  * ensure it's up to date, applying the updates, and writing the data
1039  * before releasing RelationMappingLock.
1040  *
1041  * There is only one RelationMappingLock. In principle we could try to
1042  * have one per mapping file, but it seems unlikely to be worth the
1043  * trouble.
1044  */
1045  LWLockAcquire(RelationMappingLock, LW_EXCLUSIVE);
1046 
1047  /* Be certain we see any other updates just made */
1048  load_relmap_file(shared, true);
1049 
1050  /* Prepare updated data in a local variable */
1051  if (shared)
1052  memcpy(&newmap, &shared_map, sizeof(RelMapFile));
1053  else
1054  memcpy(&newmap, &local_map, sizeof(RelMapFile));
1055 
1056  /*
1057  * Apply the updates to newmap. No new mappings should appear, unless
1058  * somebody is adding indexes to system catalogs.
1059  */
1060  merge_map_updates(&newmap, updates, allowSystemTableMods);
1061 
1062  /* Write out the updated map and do other necessary tasks */
1063  write_relmap_file(&newmap, true, true, true,
1064  (shared ? InvalidOid : MyDatabaseId),
1065  (shared ? GLOBALTABLESPACE_OID : MyDatabaseTableSpace),
1066  (shared ? "global" : DatabasePath));
1067 
1068  /*
1069  * We successfully wrote the updated file, so it's now safe to rely on the
1070  * new values in this process, too.
1071  */
1072  if (shared)
1073  memcpy(&shared_map, &newmap, sizeof(RelMapFile));
1074  else
1075  memcpy(&local_map, &newmap, sizeof(RelMapFile));
1076 
1077  /* Now we can release the lock */
1078  LWLockRelease(RelationMappingLock);
1079 }
1080 
1081 /*
1082  * RELMAP resource manager's routines
1083  */
1084 void
1086 {
1087  uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
1088 
1089  /* Backup blocks are not used in relmap records */
1090  Assert(!XLogRecHasAnyBlockRefs(record));
1091 
1092  if (info == XLOG_RELMAP_UPDATE)
1093  {
1094  xl_relmap_update *xlrec = (xl_relmap_update *) XLogRecGetData(record);
1095  RelMapFile newmap;
1096  char *dbpath;
1097 
1098  if (xlrec->nbytes != sizeof(RelMapFile))
1099  elog(PANIC, "relmap_redo: wrong size %u in relmap update record",
1100  xlrec->nbytes);
1101  memcpy(&newmap, xlrec->data, sizeof(newmap));
1102 
1103  /* We need to construct the pathname for this database */
1104  dbpath = GetDatabasePath(xlrec->dbid, xlrec->tsid);
1105 
1106  /*
1107  * Write out the new map and send sinval, but of course don't write a
1108  * new WAL entry. There's no surrounding transaction to tell to
1109  * preserve files, either.
1110  *
1111  * There shouldn't be anyone else updating relmaps during WAL replay,
1112  * but grab the lock to interlock against load_relmap_file().
1113  *
1114  * Note that we use the same WAL record for updating the relmap of an
1115  * existing database as we do for creating a new database. In the
1116  * latter case, taking the relmap log and sending sinval messages is
1117  * unnecessary, but harmless. If we wanted to avoid it, we could add a
1118  * flag to the WAL record to indicate which operation is being
1119  * performed.
1120  */
1121  LWLockAcquire(RelationMappingLock, LW_EXCLUSIVE);
1122  write_relmap_file(&newmap, false, true, false,
1123  xlrec->dbid, xlrec->tsid, dbpath);
1124  LWLockRelease(RelationMappingLock);
1125 
1126  pfree(dbpath);
1127  }
1128  else
1129  elog(PANIC, "relmap_redo: unknown op code %u", info);
1130 }
signed int int32
Definition: c.h:430
#define PG_BINARY
Definition: c.h:1209
unsigned char uint8
Definition: c.h:440
size_t Size
Definition: c.h:541
int errcode_for_file_access(void)
Definition: elog.c:718
int errcode(int sqlerrcode)
Definition: elog.c:695
int errmsg(const char *fmt,...)
Definition: elog.c:906
#define FATAL
Definition: elog.h:37
#define PANIC
Definition: elog.h:38
#define ERROR
Definition: elog.h:35
#define ereport(elevel,...)
Definition: elog.h:145
int durable_rename(const char *oldfile, const char *newfile, int elevel)
Definition: fd.c:688
int CloseTransientFile(int fd)
Definition: fd.c:2609
int OpenTransientFile(const char *fileName, int fileFlags)
Definition: fd.c:2433
bool allowSystemTableMods
Definition: globals.c:124
Oid MyDatabaseTableSpace
Definition: globals.c:91
char * DatabasePath
Definition: globals.c:97
Oid MyDatabaseId
Definition: globals.c:89
#define write(a, b, c)
Definition: win32.h:14
#define read(a, b, c)
Definition: win32.h:13
void CacheInvalidateRelmap(Oid databaseId)
Definition: inval.c:1492
int i
Definition: isn.c:73
Assert(fmt[strlen(fmt) - 1] !='\n')
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1194
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1802
@ LW_SHARED
Definition: lwlock.h:113
@ LW_EXCLUSIVE
Definition: lwlock.h:112
void pfree(void *pointer)
Definition: mcxt.c:1306
#define IsBootstrapProcessingMode()
Definition: miscadmin.h:402
#define START_CRIT_SECTION()
Definition: miscadmin.h:148
#define END_CRIT_SECTION()
Definition: miscadmin.h:150
#define ERRCODE_DATA_CORRUPTED
Definition: pg_basebackup.c:41
#define MAXPGPATH
uint32 pg_crc32c
Definition: pg_crc32c.h:38
#define COMP_CRC32C(crc, data, len)
Definition: pg_crc32c.h:89
#define EQ_CRC32C(c1, c2)
Definition: pg_crc32c.h:42
#define INIT_CRC32C(crc)
Definition: pg_crc32c.h:41
#define FIN_CRC32C(crc)
Definition: pg_crc32c.h:94
return crc
#define snprintf
Definition: port.h:238
#define InvalidOid
Definition: postgres_ext.h:36
unsigned int Oid
Definition: postgres_ext.h:31
static int fd(const char *x, int i)
Definition: preproc-init.c:105
RelFileNumber RelationMapOidToFilenumberForDatabase(char *dbpath, Oid relationId)
Definition: relmapper.c:266
static RelMapFile pending_local_updates
Definition: relmapper.c:135
Size EstimateRelationMapSpace(void)
Definition: relmapper.c:711
void RelationMapRemoveMapping(Oid relationId)
Definition: relmapper.c:438
struct RelMapping RelMapping
void SerializeRelationMap(Size maxSize, char *startAddress)
Definition: relmapper.c:722
#define RELMAPPER_FILEMAGIC
Definition: relmapper.c:74
void RelationMapCopy(Oid dbid, Oid tsid, char *srcdbpath, char *dstdbpath)
Definition: relmapper.c:293
static void apply_map_update(RelMapFile *map, Oid relationId, RelFileNumber fileNumber, bool add_okay)
Definition: relmapper.c:383
static void write_relmap_file(RelMapFile *newmap, bool write_wal, bool send_sinval, bool preserve_files, Oid dbid, Oid tsid, const char *dbpath)
Definition: relmapper.c:887
Oid RelationMapFilenumberToOid(RelFileNumber filenumber, bool shared)
Definition: relmapper.c:219
void RelationMapInvalidateAll(void)
Definition: relmapper.c:490
void RestoreRelationMap(char *startAddress)
Definition: relmapper.c:739
#define MAX_MAPPINGS
Definition: relmapper.c:82
static RelMapFile shared_map
Definition: relmapper.c:113
static RelMapFile active_local_updates
Definition: relmapper.c:133
static void perform_relmap_update(bool shared, const RelMapFile *updates)
Definition: relmapper.c:1028
static void read_relmap_file(RelMapFile *map, char *dbpath, bool lock_held, int elevel)
Definition: relmapper.c:782
void RelationMapInitialize(void)
Definition: relmapper.c:649
void AtPrepare_RelationMap(void)
Definition: relmapper.c:588
static RelMapFile local_map
Definition: relmapper.c:114
#define RELMAPPER_TEMP_FILENAME
Definition: relmapper.c:72
void relmap_redo(XLogReaderState *record)
Definition: relmapper.c:1085
#define RELMAPPER_FILENAME
Definition: relmapper.c:71
void AtEOXact_RelationMap(bool isCommit, bool isParallelWorker)
Definition: relmapper.c:541
void RelationMapInvalidate(bool shared)
Definition: relmapper.c:468
static RelMapFile pending_shared_updates
Definition: relmapper.c:134
void RelationMapInitializePhase2(void)
Definition: relmapper.c:669
void RelationMapFinishBootstrap(void)
Definition: relmapper.c:625
struct SerializedActiveRelMaps SerializedActiveRelMaps
RelFileNumber RelationMapOidToFilenumber(Oid relationId, bool shared)
Definition: relmapper.c:166
void RelationMapUpdateMap(Oid relationId, RelFileNumber fileNumber, bool shared, bool immediate)
Definition: relmapper.c:325
void RelationMapInitializePhase3(void)
Definition: relmapper.c:690
struct RelMapFile RelMapFile
void AtCCI_RelationMap(void)
Definition: relmapper.c:504
static void merge_map_updates(RelMapFile *map, const RelMapFile *updates, bool add_okay)
Definition: relmapper.c:416
void CheckPointRelationMap(void)
Definition: relmapper.c:611
static RelMapFile active_shared_updates
Definition: relmapper.c:132
static void load_relmap_file(bool shared, bool lock_held)
Definition: relmapper.c:763
#define XLOG_RELMAP_UPDATE
Definition: relmapper.h:25
#define MinSizeOfRelmapUpdate
Definition: relmapper.h:35
char * GetDatabasePath(Oid dbOid, Oid spcOid)
Definition: relpath.c:110
Oid RelFileNumber
Definition: relpath.h:25
#define InvalidRelFileNumber
Definition: relpath.h:26
void RelationPreserveStorage(RelFileLocator rlocator, bool atCommit)
Definition: storage.c:250
RelFileNumber relNumber
RelMapping mappings[MAX_MAPPINGS]
Definition: relmapper.c:94
int32 magic
Definition: relmapper.c:92
pg_crc32c crc
Definition: relmapper.c:95
int32 num_mappings
Definition: relmapper.c:93
Oid mapoid
Definition: relmapper.c:86
RelFileNumber mapfilenumber
Definition: relmapper.c:87
RelMapFile active_local_updates
Definition: relmapper.c:105
RelMapFile active_shared_updates
Definition: relmapper.c:104
char data[FLEXIBLE_ARRAY_MEMBER]
Definition: relmapper.h:32
@ WAIT_EVENT_RELATION_MAP_WRITE
Definition: wait_event.h:199
@ WAIT_EVENT_RELATION_MAP_READ
Definition: wait_event.h:197
@ WAIT_EVENT_RELATION_MAP_REPLACE
Definition: wait_event.h:198
static void pgstat_report_wait_start(uint32 wait_event_info)
Definition: wait_event.h:268
static void pgstat_report_wait_end(void)
Definition: wait_event.h:284
int GetCurrentTransactionNestLevel(void)
Definition: xact.c:913
bool IsInParallelMode(void)
Definition: xact.c:1068
void XLogFlush(XLogRecPtr record)
Definition: xlog.c:2512
uint64 XLogRecPtr
Definition: xlogdefs.h:21
void XLogRegisterData(char *data, uint32 len)
Definition: xloginsert.c:351
XLogRecPtr XLogInsert(RmgrId rmid, uint8 info)
Definition: xloginsert.c:451
void XLogBeginInsert(void)
Definition: xloginsert.c:150
#define XLogRecGetInfo(decoder)
Definition: xlogreader.h:411
#define XLogRecGetData(decoder)
Definition: xlogreader.h:416
#define XLogRecHasAnyBlockRefs(decoder)
Definition: xlogreader.h:418
#define XLR_INFO_MASK
Definition: xlogrecord.h:62