PostgreSQL Source Code  git master
visibilitymap.c File Reference
#include "postgres.h"
#include "access/heapam_xlog.h"
#include "access/visibilitymap.h"
#include "access/xloginsert.h"
#include "access/xlogutils.h"
#include "miscadmin.h"
#include "port/pg_bitutils.h"
#include "storage/bufmgr.h"
#include "storage/smgr.h"
#include "utils/inval.h"
#include "utils/rel.h"
Include dependency graph for visibilitymap.c:

Go to the source code of this file.

Macros

#define MAPSIZE   (BLCKSZ - MAXALIGN(SizeOfPageHeaderData))
 
#define HEAPBLOCKS_PER_BYTE   (BITS_PER_BYTE / BITS_PER_HEAPBLOCK)
 
#define HEAPBLOCKS_PER_PAGE   (MAPSIZE * HEAPBLOCKS_PER_BYTE)
 
#define HEAPBLK_TO_MAPBLOCK(x)   ((x) / HEAPBLOCKS_PER_PAGE)
 
#define HEAPBLK_TO_MAPBYTE(x)   (((x) % HEAPBLOCKS_PER_PAGE) / HEAPBLOCKS_PER_BYTE)
 
#define HEAPBLK_TO_OFFSET(x)   (((x) % HEAPBLOCKS_PER_BYTE) * BITS_PER_HEAPBLOCK)
 
#define VISIBLE_MASK8   (0x55) /* The lower bit of each bit pair */
 
#define FROZEN_MASK8   (0xaa) /* The upper bit of each bit pair */
 

Functions

static Buffer vm_readbuf (Relation rel, BlockNumber blkno, bool extend)
 
static Buffer vm_extend (Relation rel, BlockNumber vm_nblocks)
 
bool visibilitymap_clear (Relation rel, BlockNumber heapBlk, Buffer vmbuf, uint8 flags)
 
void visibilitymap_pin (Relation rel, BlockNumber heapBlk, Buffer *vmbuf)
 
bool visibilitymap_pin_ok (BlockNumber heapBlk, Buffer vmbuf)
 
void visibilitymap_set (Relation rel, BlockNumber heapBlk, Buffer heapBuf, XLogRecPtr recptr, Buffer vmBuf, TransactionId cutoff_xid, uint8 flags)
 
uint8 visibilitymap_get_status (Relation rel, BlockNumber heapBlk, Buffer *vmbuf)
 
void visibilitymap_count (Relation rel, BlockNumber *all_visible, BlockNumber *all_frozen)
 
BlockNumber visibilitymap_prepare_truncate (Relation rel, BlockNumber nheapblocks)
 

Macro Definition Documentation

◆ FROZEN_MASK8

#define FROZEN_MASK8   (0xaa) /* The upper bit of each bit pair */

Definition at line 123 of file visibilitymap.c.

◆ HEAPBLK_TO_MAPBLOCK

#define HEAPBLK_TO_MAPBLOCK (   x)    ((x) / HEAPBLOCKS_PER_PAGE)

Definition at line 117 of file visibilitymap.c.

◆ HEAPBLK_TO_MAPBYTE

#define HEAPBLK_TO_MAPBYTE (   x)    (((x) % HEAPBLOCKS_PER_PAGE) / HEAPBLOCKS_PER_BYTE)

Definition at line 118 of file visibilitymap.c.

◆ HEAPBLK_TO_OFFSET

#define HEAPBLK_TO_OFFSET (   x)    (((x) % HEAPBLOCKS_PER_BYTE) * BITS_PER_HEAPBLOCK)

Definition at line 119 of file visibilitymap.c.

◆ HEAPBLOCKS_PER_BYTE

#define HEAPBLOCKS_PER_BYTE   (BITS_PER_BYTE / BITS_PER_HEAPBLOCK)

Definition at line 111 of file visibilitymap.c.

◆ HEAPBLOCKS_PER_PAGE

#define HEAPBLOCKS_PER_PAGE   (MAPSIZE * HEAPBLOCKS_PER_BYTE)

Definition at line 114 of file visibilitymap.c.

◆ MAPSIZE

#define MAPSIZE   (BLCKSZ - MAXALIGN(SizeOfPageHeaderData))

Definition at line 108 of file visibilitymap.c.

◆ VISIBLE_MASK8

#define VISIBLE_MASK8   (0x55) /* The lower bit of each bit pair */

Definition at line 122 of file visibilitymap.c.

Function Documentation

◆ visibilitymap_clear()

bool visibilitymap_clear ( Relation  rel,
BlockNumber  heapBlk,
Buffer  vmbuf,
uint8  flags 
)

Definition at line 138 of file visibilitymap.c.

139 {
140  BlockNumber mapBlock = HEAPBLK_TO_MAPBLOCK(heapBlk);
141  int mapByte = HEAPBLK_TO_MAPBYTE(heapBlk);
142  int mapOffset = HEAPBLK_TO_OFFSET(heapBlk);
143  uint8 mask = flags << mapOffset;
144  char *map;
145  bool cleared = false;
146 
147  /* Must never clear all_visible bit while leaving all_frozen bit set */
150 
151 #ifdef TRACE_VISIBILITYMAP
152  elog(DEBUG1, "vm_clear %s %d", RelationGetRelationName(rel), heapBlk);
153 #endif
154 
155  if (!BufferIsValid(vmbuf) || BufferGetBlockNumber(vmbuf) != mapBlock)
156  elog(ERROR, "wrong buffer passed to visibilitymap_clear");
157 
159  map = PageGetContents(BufferGetPage(vmbuf));
160 
161  if (map[mapByte] & mask)
162  {
163  map[mapByte] &= ~mask;
164 
165  MarkBufferDirty(vmbuf);
166  cleared = true;
167  }
168 
170 
171  return cleared;
172 }
uint32 BlockNumber
Definition: block.h:31
BlockNumber BufferGetBlockNumber(Buffer buffer)
Definition: bufmgr.c:3713
void MarkBufferDirty(Buffer buffer)
Definition: bufmgr.c:2520
void LockBuffer(Buffer buffer, int mode)
Definition: bufmgr.c:5131
#define BUFFER_LOCK_UNLOCK
Definition: bufmgr.h:193
static Page BufferGetPage(Buffer buffer)
Definition: bufmgr.h:404
#define BUFFER_LOCK_EXCLUSIVE
Definition: bufmgr.h:195
static bool BufferIsValid(Buffer bufnum)
Definition: bufmgr.h:355
static char * PageGetContents(Page page)
Definition: bufpage.h:254
#define Assert(condition)
Definition: c.h:858
unsigned char uint8
Definition: c.h:504
#define DEBUG1
Definition: elog.h:30
#define ERROR
Definition: elog.h:39
#define elog(elevel,...)
Definition: elog.h:224
#define RelationGetRelationName(relation)
Definition: rel.h:539
#define HEAPBLK_TO_OFFSET(x)
#define HEAPBLK_TO_MAPBLOCK(x)
#define HEAPBLK_TO_MAPBYTE(x)
#define VISIBILITYMAP_VALID_BITS
#define VISIBILITYMAP_ALL_VISIBLE

References Assert, BUFFER_LOCK_EXCLUSIVE, BUFFER_LOCK_UNLOCK, BufferGetBlockNumber(), BufferGetPage(), BufferIsValid(), DEBUG1, elog, ERROR, HEAPBLK_TO_MAPBLOCK, HEAPBLK_TO_MAPBYTE, HEAPBLK_TO_OFFSET, LockBuffer(), MarkBufferDirty(), PageGetContents(), RelationGetRelationName, VISIBILITYMAP_ALL_VISIBLE, and VISIBILITYMAP_VALID_BITS.

Referenced by heap_delete(), heap_force_common(), heap_insert(), heap_lock_tuple(), heap_lock_updated_tuple_rec(), heap_multi_insert(), heap_update(), heap_xlog_delete(), heap_xlog_insert(), heap_xlog_lock(), heap_xlog_lock_updated(), heap_xlog_multi_insert(), heap_xlog_update(), and lazy_scan_prune().

◆ visibilitymap_count()

void visibilitymap_count ( Relation  rel,
BlockNumber all_visible,
BlockNumber all_frozen 
)

Definition at line 384 of file visibilitymap.c.

385 {
386  BlockNumber mapBlock;
387  BlockNumber nvisible = 0;
388  BlockNumber nfrozen = 0;
389 
390  /* all_visible must be specified */
391  Assert(all_visible);
392 
393  for (mapBlock = 0;; mapBlock++)
394  {
395  Buffer mapBuffer;
396  uint64 *map;
397 
398  /*
399  * Read till we fall off the end of the map. We assume that any extra
400  * bytes in the last page are zeroed, so we don't bother excluding
401  * them from the count.
402  */
403  mapBuffer = vm_readbuf(rel, mapBlock, false);
404  if (!BufferIsValid(mapBuffer))
405  break;
406 
407  /*
408  * We choose not to lock the page, since the result is going to be
409  * immediately stale anyway if anyone is concurrently setting or
410  * clearing bits, and we only really need an approximate value.
411  */
412  map = (uint64 *) PageGetContents(BufferGetPage(mapBuffer));
413 
414  nvisible += pg_popcount_masked((const char *) map, MAPSIZE, VISIBLE_MASK8);
415  if (all_frozen)
416  nfrozen += pg_popcount_masked((const char *) map, MAPSIZE, FROZEN_MASK8);
417 
418  ReleaseBuffer(mapBuffer);
419  }
420 
421  *all_visible = nvisible;
422  if (all_frozen)
423  *all_frozen = nfrozen;
424 }
int Buffer
Definition: buf.h:23
void ReleaseBuffer(Buffer buffer)
Definition: bufmgr.c:4896
static uint64 pg_popcount_masked(const char *buf, int bytes, bits8 mask)
Definition: pg_bitutils.h:370
#define MAPSIZE
#define FROZEN_MASK8
#define VISIBLE_MASK8
static Buffer vm_readbuf(Relation rel, BlockNumber blkno, bool extend)

References Assert, BufferGetPage(), BufferIsValid(), FROZEN_MASK8, MAPSIZE, PageGetContents(), pg_popcount_masked(), ReleaseBuffer(), VISIBLE_MASK8, and vm_readbuf().

Referenced by do_analyze_rel(), heap_vacuum_rel(), and index_update_stats().

◆ visibilitymap_get_status()

uint8 visibilitymap_get_status ( Relation  rel,
BlockNumber  heapBlk,
Buffer vmbuf 
)

Definition at line 336 of file visibilitymap.c.

337 {
338  BlockNumber mapBlock = HEAPBLK_TO_MAPBLOCK(heapBlk);
339  uint32 mapByte = HEAPBLK_TO_MAPBYTE(heapBlk);
340  uint8 mapOffset = HEAPBLK_TO_OFFSET(heapBlk);
341  char *map;
342  uint8 result;
343 
344 #ifdef TRACE_VISIBILITYMAP
345  elog(DEBUG1, "vm_get_status %s %d", RelationGetRelationName(rel), heapBlk);
346 #endif
347 
348  /* Reuse the old pinned buffer if possible */
349  if (BufferIsValid(*vmbuf))
350  {
351  if (BufferGetBlockNumber(*vmbuf) != mapBlock)
352  {
353  ReleaseBuffer(*vmbuf);
354  *vmbuf = InvalidBuffer;
355  }
356  }
357 
358  if (!BufferIsValid(*vmbuf))
359  {
360  *vmbuf = vm_readbuf(rel, mapBlock, false);
361  if (!BufferIsValid(*vmbuf))
362  return false;
363  }
364 
365  map = PageGetContents(BufferGetPage(*vmbuf));
366 
367  /*
368  * A single byte read is atomic. There could be memory-ordering effects
369  * here, but for performance reasons we make it the caller's job to worry
370  * about that.
371  */
372  result = ((map[mapByte] >> mapOffset) & VISIBILITYMAP_VALID_BITS);
373  return result;
374 }
#define InvalidBuffer
Definition: buf.h:25
unsigned int uint32
Definition: c.h:506

References BufferGetBlockNumber(), BufferGetPage(), BufferIsValid(), DEBUG1, elog, HEAPBLK_TO_MAPBLOCK, HEAPBLK_TO_MAPBYTE, HEAPBLK_TO_OFFSET, InvalidBuffer, PageGetContents(), RelationGetRelationName, ReleaseBuffer(), VISIBILITYMAP_VALID_BITS, and vm_readbuf().

Referenced by collect_visibility_data(), find_next_unskippable_block(), lazy_scan_prune(), pg_visibility(), pg_visibility_map(), pg_visibility_map_summary(), and verify_heapam().

◆ visibilitymap_pin()

void visibilitymap_pin ( Relation  rel,
BlockNumber  heapBlk,
Buffer vmbuf 
)

Definition at line 191 of file visibilitymap.c.

192 {
193  BlockNumber mapBlock = HEAPBLK_TO_MAPBLOCK(heapBlk);
194 
195  /* Reuse the old pinned buffer if possible */
196  if (BufferIsValid(*vmbuf))
197  {
198  if (BufferGetBlockNumber(*vmbuf) == mapBlock)
199  return;
200 
201  ReleaseBuffer(*vmbuf);
202  }
203  *vmbuf = vm_readbuf(rel, mapBlock, true);
204 }

References BufferGetBlockNumber(), BufferIsValid(), HEAPBLK_TO_MAPBLOCK, ReleaseBuffer(), and vm_readbuf().

Referenced by GetVisibilityMapPins(), heap_delete(), heap_force_common(), heap_lock_tuple(), heap_lock_updated_tuple_rec(), heap_update(), heap_xlog_delete(), heap_xlog_insert(), heap_xlog_lock(), heap_xlog_lock_updated(), heap_xlog_multi_insert(), heap_xlog_update(), heap_xlog_visible(), lazy_scan_heap(), lazy_vacuum_heap_rel(), and RelationGetBufferForTuple().

◆ visibilitymap_pin_ok()

bool visibilitymap_pin_ok ( BlockNumber  heapBlk,
Buffer  vmbuf 
)

Definition at line 215 of file visibilitymap.c.

216 {
217  BlockNumber mapBlock = HEAPBLK_TO_MAPBLOCK(heapBlk);
218 
219  return BufferIsValid(vmbuf) && BufferGetBlockNumber(vmbuf) == mapBlock;
220 }

References BufferGetBlockNumber(), BufferIsValid(), and HEAPBLK_TO_MAPBLOCK.

Referenced by GetVisibilityMapPins(), heap_multi_insert(), and RelationGetBufferForTuple().

◆ visibilitymap_prepare_truncate()

BlockNumber visibilitymap_prepare_truncate ( Relation  rel,
BlockNumber  nheapblocks 
)

Definition at line 438 of file visibilitymap.c.

439 {
440  BlockNumber newnblocks;
441 
442  /* last remaining block, byte, and bit */
443  BlockNumber truncBlock = HEAPBLK_TO_MAPBLOCK(nheapblocks);
444  uint32 truncByte = HEAPBLK_TO_MAPBYTE(nheapblocks);
445  uint8 truncOffset = HEAPBLK_TO_OFFSET(nheapblocks);
446 
447 #ifdef TRACE_VISIBILITYMAP
448  elog(DEBUG1, "vm_truncate %s %d", RelationGetRelationName(rel), nheapblocks);
449 #endif
450 
451  /*
452  * If no visibility map has been created yet for this relation, there's
453  * nothing to truncate.
454  */
456  return InvalidBlockNumber;
457 
458  /*
459  * Unless the new size is exactly at a visibility map page boundary, the
460  * tail bits in the last remaining map page, representing truncated heap
461  * blocks, need to be cleared. This is not only tidy, but also necessary
462  * because we don't get a chance to clear the bits if the heap is extended
463  * again.
464  */
465  if (truncByte != 0 || truncOffset != 0)
466  {
467  Buffer mapBuffer;
468  Page page;
469  char *map;
470 
471  newnblocks = truncBlock + 1;
472 
473  mapBuffer = vm_readbuf(rel, truncBlock, false);
474  if (!BufferIsValid(mapBuffer))
475  {
476  /* nothing to do, the file was already smaller */
477  return InvalidBlockNumber;
478  }
479 
480  page = BufferGetPage(mapBuffer);
481  map = PageGetContents(page);
482 
483  LockBuffer(mapBuffer, BUFFER_LOCK_EXCLUSIVE);
484 
485  /* NO EREPORT(ERROR) from here till changes are logged */
487 
488  /* Clear out the unwanted bytes. */
489  MemSet(&map[truncByte + 1], 0, MAPSIZE - (truncByte + 1));
490 
491  /*----
492  * Mask out the unwanted bits of the last remaining byte.
493  *
494  * ((1 << 0) - 1) = 00000000
495  * ((1 << 1) - 1) = 00000001
496  * ...
497  * ((1 << 6) - 1) = 00111111
498  * ((1 << 7) - 1) = 01111111
499  *----
500  */
501  map[truncByte] &= (1 << truncOffset) - 1;
502 
503  /*
504  * Truncation of a relation is WAL-logged at a higher-level, and we
505  * will be called at WAL replay. But if checksums are enabled, we need
506  * to still write a WAL record to protect against a torn page, if the
507  * page is flushed to disk before the truncation WAL record. We cannot
508  * use MarkBufferDirtyHint here, because that will not dirty the page
509  * during recovery.
510  */
511  MarkBufferDirty(mapBuffer);
513  log_newpage_buffer(mapBuffer, false);
514 
516 
517  UnlockReleaseBuffer(mapBuffer);
518  }
519  else
520  newnblocks = truncBlock;
521 
522  if (smgrnblocks(RelationGetSmgr(rel), VISIBILITYMAP_FORKNUM) <= newnblocks)
523  {
524  /* nothing to do, the file was already smaller than requested size */
525  return InvalidBlockNumber;
526  }
527 
528  return newnblocks;
529 }
#define InvalidBlockNumber
Definition: block.h:33
void UnlockReleaseBuffer(Buffer buffer)
Definition: bufmgr.c:4913
Pointer Page
Definition: bufpage.h:78
#define MemSet(start, val, len)
Definition: c.h:1020
#define START_CRIT_SECTION()
Definition: miscadmin.h:149
#define END_CRIT_SECTION()
Definition: miscadmin.h:151
static SMgrRelation RelationGetSmgr(Relation rel)
Definition: rel.h:567
#define RelationNeedsWAL(relation)
Definition: rel.h:628
@ VISIBILITYMAP_FORKNUM
Definition: relpath.h:52
BlockNumber smgrnblocks(SMgrRelation reln, ForkNumber forknum)
Definition: smgr.c:655
bool smgrexists(SMgrRelation reln, ForkNumber forknum)
Definition: smgr.c:398
#define XLogHintBitIsNeeded()
Definition: xlog.h:118
XLogRecPtr log_newpage_buffer(Buffer buffer, bool page_std)
Definition: xloginsert.c:1237
bool InRecovery
Definition: xlogutils.c:50

References BUFFER_LOCK_EXCLUSIVE, BufferGetPage(), BufferIsValid(), DEBUG1, elog, END_CRIT_SECTION, HEAPBLK_TO_MAPBLOCK, HEAPBLK_TO_MAPBYTE, HEAPBLK_TO_OFFSET, InRecovery, InvalidBlockNumber, LockBuffer(), log_newpage_buffer(), MAPSIZE, MarkBufferDirty(), MemSet, PageGetContents(), RelationGetRelationName, RelationGetSmgr(), RelationNeedsWAL, smgrexists(), smgrnblocks(), START_CRIT_SECTION, UnlockReleaseBuffer(), VISIBILITYMAP_FORKNUM, vm_readbuf(), and XLogHintBitIsNeeded.

Referenced by pg_truncate_visibility_map(), RelationTruncate(), and smgr_redo().

◆ visibilitymap_set()

void visibilitymap_set ( Relation  rel,
BlockNumber  heapBlk,
Buffer  heapBuf,
XLogRecPtr  recptr,
Buffer  vmBuf,
TransactionId  cutoff_xid,
uint8  flags 
)

Definition at line 244 of file visibilitymap.c.

247 {
248  BlockNumber mapBlock = HEAPBLK_TO_MAPBLOCK(heapBlk);
249  uint32 mapByte = HEAPBLK_TO_MAPBYTE(heapBlk);
250  uint8 mapOffset = HEAPBLK_TO_OFFSET(heapBlk);
251  Page page;
252  uint8 *map;
253 
254 #ifdef TRACE_VISIBILITYMAP
255  elog(DEBUG1, "vm_set %s %d", RelationGetRelationName(rel), heapBlk);
256 #endif
257 
260  Assert((flags & VISIBILITYMAP_VALID_BITS) == flags);
261 
262  /* Must never set all_frozen bit without also setting all_visible bit */
264 
265  /* Check that we have the right heap page pinned, if present */
266  if (BufferIsValid(heapBuf) && BufferGetBlockNumber(heapBuf) != heapBlk)
267  elog(ERROR, "wrong heap buffer passed to visibilitymap_set");
268 
269  /* Check that we have the right VM page pinned */
270  if (!BufferIsValid(vmBuf) || BufferGetBlockNumber(vmBuf) != mapBlock)
271  elog(ERROR, "wrong VM buffer passed to visibilitymap_set");
272 
273  page = BufferGetPage(vmBuf);
274  map = (uint8 *) PageGetContents(page);
276 
277  if (flags != (map[mapByte] >> mapOffset & VISIBILITYMAP_VALID_BITS))
278  {
280 
281  map[mapByte] |= (flags << mapOffset);
282  MarkBufferDirty(vmBuf);
283 
284  if (RelationNeedsWAL(rel))
285  {
286  if (XLogRecPtrIsInvalid(recptr))
287  {
288  Assert(!InRecovery);
289  recptr = log_heap_visible(rel, heapBuf, vmBuf, cutoff_xid, flags);
290 
291  /*
292  * If data checksums are enabled (or wal_log_hints=on), we
293  * need to protect the heap page from being torn.
294  *
295  * If not, then we must *not* update the heap page's LSN. In
296  * this case, the FPI for the heap page was omitted from the
297  * WAL record inserted above, so it would be incorrect to
298  * update the heap page's LSN.
299  */
300  if (XLogHintBitIsNeeded())
301  {
302  Page heapPage = BufferGetPage(heapBuf);
303 
304  PageSetLSN(heapPage, recptr);
305  }
306  }
307  PageSetLSN(page, recptr);
308  }
309 
311  }
312 
314 }
static bool PageIsAllVisible(Page page)
Definition: bufpage.h:426
static void PageSetLSN(Page page, XLogRecPtr lsn)
Definition: bufpage.h:388
XLogRecPtr log_heap_visible(Relation rel, Buffer heap_buffer, Buffer vm_buffer, TransactionId snapshotConflictHorizon, uint8 vmflags)
Definition: heapam.c:8321
#define VISIBILITYMAP_ALL_FROZEN
#define XLogRecPtrIsInvalid(r)
Definition: xlogdefs.h:29

References Assert, BUFFER_LOCK_EXCLUSIVE, BUFFER_LOCK_UNLOCK, BufferGetBlockNumber(), BufferGetPage(), BufferIsValid(), DEBUG1, elog, END_CRIT_SECTION, ERROR, HEAPBLK_TO_MAPBLOCK, HEAPBLK_TO_MAPBYTE, HEAPBLK_TO_OFFSET, InRecovery, LockBuffer(), log_heap_visible(), MarkBufferDirty(), PageGetContents(), PageIsAllVisible(), PageSetLSN(), RelationGetRelationName, RelationNeedsWAL, START_CRIT_SECTION, VISIBILITYMAP_ALL_FROZEN, VISIBILITYMAP_VALID_BITS, XLogHintBitIsNeeded, and XLogRecPtrIsInvalid.

Referenced by heap_multi_insert(), heap_xlog_visible(), lazy_scan_new_or_empty(), lazy_scan_prune(), and lazy_vacuum_heap_page().

◆ vm_extend()

static Buffer vm_extend ( Relation  rel,
BlockNumber  vm_nblocks 
)
static

Definition at line 612 of file visibilitymap.c.

613 {
614  Buffer buf;
615 
619  vm_nblocks,
621 
622  /*
623  * Send a shared-inval message to force other backends to close any smgr
624  * references they may have for this rel, which we are about to change.
625  * This is a useful optimization because it means that backends don't have
626  * to keep checking for creation or extension of the file, which happens
627  * infrequently.
628  */
629  CacheInvalidateSmgr(RelationGetSmgr(rel)->smgr_rlocator);
630 
631  return buf;
632 }
Buffer ExtendBufferedRelTo(BufferManagerRelation bmr, ForkNumber fork, BufferAccessStrategy strategy, uint32 flags, BlockNumber extend_to, ReadBufferMode mode)
Definition: bufmgr.c:909
@ EB_CLEAR_SIZE_CACHE
Definition: bufmgr.h:89
@ EB_CREATE_FORK_IF_NEEDED
Definition: bufmgr.h:83
@ RBM_ZERO_ON_ERROR
Definition: bufmgr.h:50
#define BMR_REL(p_rel)
Definition: bufmgr.h:107
void CacheInvalidateSmgr(RelFileLocatorBackend rlocator)
Definition: inval.c:1459
static char * buf
Definition: pg_test_fsync.c:73

References BMR_REL, buf, CacheInvalidateSmgr(), EB_CLEAR_SIZE_CACHE, EB_CREATE_FORK_IF_NEEDED, ExtendBufferedRelTo(), RBM_ZERO_ON_ERROR, RelationGetSmgr(), and VISIBILITYMAP_FORKNUM.

Referenced by vm_readbuf().

◆ vm_readbuf()

static Buffer vm_readbuf ( Relation  rel,
BlockNumber  blkno,
bool  extend 
)
static

Definition at line 538 of file visibilitymap.c.

539 {
540  Buffer buf;
541  SMgrRelation reln;
542 
543  /*
544  * Caution: re-using this smgr pointer could fail if the relcache entry
545  * gets closed. It's safe as long as we only do smgr-level operations
546  * between here and the last use of the pointer.
547  */
548  reln = RelationGetSmgr(rel);
549 
550  /*
551  * If we haven't cached the size of the visibility map fork yet, check it
552  * first.
553  */
555  {
558  else
560  }
561 
562  /*
563  * For reading we use ZERO_ON_ERROR mode, and initialize the page if
564  * necessary. It's always safe to clear bits, so it's better to clear
565  * corrupt pages than error out.
566  *
567  * We use the same path below to initialize pages when extending the
568  * relation, as a concurrent extension can end up with vm_extend()
569  * returning an already-initialized page.
570  */
571  if (blkno >= reln->smgr_cached_nblocks[VISIBILITYMAP_FORKNUM])
572  {
573  if (extend)
574  buf = vm_extend(rel, blkno + 1);
575  else
576  return InvalidBuffer;
577  }
578  else
580  RBM_ZERO_ON_ERROR, NULL);
581 
582  /*
583  * Initializing the page when needed is trickier than it looks, because of
584  * the possibility of multiple backends doing this concurrently, and our
585  * desire to not uselessly take the buffer lock in the normal path where
586  * the page is OK. We must take the lock to initialize the page, so
587  * recheck page newness after we have the lock, in case someone else
588  * already did it. Also, because we initially check PageIsNew with no
589  * lock, it's possible to fall through and return the buffer while someone
590  * else is still initializing the page (i.e., we might see pd_upper as set
591  * but other page header fields are still zeroes). This is harmless for
592  * callers that will take a buffer lock themselves, but some callers
593  * inspect the page without any lock at all. The latter is OK only so
594  * long as it doesn't depend on the page header having correct contents.
595  * Current usage is safe because PageGetContents() does not require that.
596  */
598  {
601  PageInit(BufferGetPage(buf), BLCKSZ, 0);
603  }
604  return buf;
605 }
Buffer ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum, ReadBufferMode mode, BufferAccessStrategy strategy)
Definition: bufmgr.c:792
void PageInit(Page page, Size pageSize, Size specialSize)
Definition: bufpage.c:42
static bool PageIsNew(Page page)
Definition: bufpage.h:230
BlockNumber smgr_cached_nblocks[MAX_FORKNUM+1]
Definition: smgr.h:46
static Buffer vm_extend(Relation rel, BlockNumber vm_nblocks)

References buf, BUFFER_LOCK_EXCLUSIVE, BUFFER_LOCK_UNLOCK, BufferGetPage(), InvalidBlockNumber, InvalidBuffer, LockBuffer(), PageInit(), PageIsNew(), RBM_ZERO_ON_ERROR, ReadBufferExtended(), RelationGetSmgr(), SMgrRelationData::smgr_cached_nblocks, smgrexists(), smgrnblocks(), VISIBILITYMAP_FORKNUM, and vm_extend().

Referenced by visibilitymap_count(), visibilitymap_get_status(), visibilitymap_pin(), and visibilitymap_prepare_truncate().