Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * pruneheap.c
4 : * heap page pruning and HOT-chain management code
5 : *
6 : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : *
10 : * IDENTIFICATION
11 : * src/backend/access/heap/pruneheap.c
12 : *
13 : *-------------------------------------------------------------------------
14 : */
15 : #include "postgres.h"
16 :
17 : #include "access/heapam.h"
18 : #include "access/heapam_xlog.h"
19 : #include "access/htup_details.h"
20 : #include "access/multixact.h"
21 : #include "access/transam.h"
22 : #include "access/xlog.h"
23 : #include "access/xloginsert.h"
24 : #include "commands/vacuum.h"
25 : #include "executor/instrument.h"
26 : #include "miscadmin.h"
27 : #include "pgstat.h"
28 : #include "storage/bufmgr.h"
29 : #include "utils/rel.h"
30 : #include "utils/snapmgr.h"
31 :
32 : /* Working data for heap_page_prune_and_freeze() and subroutines */
33 : typedef struct
34 : {
35 : /*-------------------------------------------------------
36 : * Arguments passed to heap_page_prune_and_freeze()
37 : *-------------------------------------------------------
38 : */
39 :
40 : /* tuple visibility test, initialized for the relation */
41 : GlobalVisState *vistest;
42 : /* whether or not dead items can be set LP_UNUSED during pruning */
43 : bool mark_unused_now;
44 : /* whether to attempt freezing tuples */
45 : bool freeze;
46 : struct VacuumCutoffs *cutoffs;
47 :
48 : /*-------------------------------------------------------
49 : * Fields describing what to do to the page
50 : *-------------------------------------------------------
51 : */
52 : TransactionId new_prune_xid; /* new prune hint value */
53 : TransactionId latest_xid_removed;
54 : int nredirected; /* numbers of entries in arrays below */
55 : int ndead;
56 : int nunused;
57 : int nfrozen;
58 : /* arrays that accumulate indexes of items to be changed */
59 : OffsetNumber redirected[MaxHeapTuplesPerPage * 2];
60 : OffsetNumber nowdead[MaxHeapTuplesPerPage];
61 : OffsetNumber nowunused[MaxHeapTuplesPerPage];
62 : HeapTupleFreeze frozen[MaxHeapTuplesPerPage];
63 :
64 : /*-------------------------------------------------------
65 : * Working state for HOT chain processing
66 : *-------------------------------------------------------
67 : */
68 :
69 : /*
70 : * 'root_items' contains offsets of all LP_REDIRECT line pointers and
71 : * normal non-HOT tuples. They can be stand-alone items or the first item
72 : * in a HOT chain. 'heaponly_items' contains heap-only tuples which can
73 : * only be removed as part of a HOT chain.
74 : */
75 : int nroot_items;
76 : OffsetNumber root_items[MaxHeapTuplesPerPage];
77 : int nheaponly_items;
78 : OffsetNumber heaponly_items[MaxHeapTuplesPerPage];
79 :
80 : /*
81 : * processed[offnum] is true if item at offnum has been processed.
82 : *
83 : * This needs to be MaxHeapTuplesPerPage + 1 long as FirstOffsetNumber is
84 : * 1. Otherwise every access would need to subtract 1.
85 : */
86 : bool processed[MaxHeapTuplesPerPage + 1];
87 :
88 : /*
89 : * Tuple visibility is only computed once for each tuple, for correctness
90 : * and efficiency reasons; see comment in heap_page_prune_and_freeze() for
91 : * details. This is of type int8[], instead of HTSV_Result[], so we can
92 : * use -1 to indicate no visibility has been computed, e.g. for LP_DEAD
93 : * items.
94 : *
95 : * This needs to be MaxHeapTuplesPerPage + 1 long as FirstOffsetNumber is
96 : * 1. Otherwise every access would need to subtract 1.
97 : */
98 : int8 htsv[MaxHeapTuplesPerPage + 1];
99 :
100 : /*
101 : * Freezing-related state.
102 : */
103 : HeapPageFreeze pagefrz;
104 :
105 : /*-------------------------------------------------------
106 : * Information about what was done
107 : *
108 : * These fields are not used by pruning itself for the most part, but are
109 : * used to collect information about what was pruned and what state the
110 : * page is in after pruning, for the benefit of the caller. They are
111 : * copied to the caller's PruneFreezeResult at the end.
112 : * -------------------------------------------------------
113 : */
114 :
115 : int ndeleted; /* Number of tuples deleted from the page */
116 :
117 : /* Number of live and recently dead tuples, after pruning */
118 : int live_tuples;
119 : int recently_dead_tuples;
120 :
121 : /* Whether or not the page makes rel truncation unsafe */
122 : bool hastup;
123 :
124 : /*
125 : * LP_DEAD items on the page after pruning. Includes existing LP_DEAD
126 : * items
127 : */
128 : int lpdead_items; /* number of items in the array */
129 : OffsetNumber *deadoffsets; /* points directly to presult->deadoffsets */
130 :
131 : /*
132 : * all_visible and all_frozen indicate if the all-visible and all-frozen
133 : * bits in the visibility map can be set for this page after pruning.
134 : *
135 : * visibility_cutoff_xid is the newest xmin of live tuples on the page.
136 : * The caller can use it as the conflict horizon, when setting the VM
137 : * bits. It is only valid if we froze some tuples, and all_frozen is
138 : * true.
139 : *
140 : * NOTE: all_visible and all_frozen don't include LP_DEAD items. That's
141 : * convenient for heap_page_prune_and_freeze(), to use them to decide
142 : * whether to freeze the page or not. The all_visible and all_frozen
143 : * values returned to the caller are adjusted to include LP_DEAD items at
144 : * the end.
145 : *
146 : * all_frozen should only be considered valid if all_visible is also set;
147 : * we don't bother to clear the all_frozen flag every time we clear the
148 : * all_visible flag.
149 : */
150 : bool all_visible;
151 : bool all_frozen;
152 : TransactionId visibility_cutoff_xid;
153 : } PruneState;
154 :
155 : /* Local functions */
156 : static HTSV_Result heap_prune_satisfies_vacuum(PruneState *prstate,
157 : HeapTuple tup,
158 : Buffer buffer);
159 : static inline HTSV_Result htsv_get_valid_status(int status);
160 : static void heap_prune_chain(Page page, BlockNumber blockno, OffsetNumber maxoff,
161 : OffsetNumber rootoffnum, PruneState *prstate);
162 : static void heap_prune_record_prunable(PruneState *prstate, TransactionId xid);
163 : static void heap_prune_record_redirect(PruneState *prstate,
164 : OffsetNumber offnum, OffsetNumber rdoffnum,
165 : bool was_normal);
166 : static void heap_prune_record_dead(PruneState *prstate, OffsetNumber offnum,
167 : bool was_normal);
168 : static void heap_prune_record_dead_or_unused(PruneState *prstate, OffsetNumber offnum,
169 : bool was_normal);
170 : static void heap_prune_record_unused(PruneState *prstate, OffsetNumber offnum, bool was_normal);
171 :
172 : static void heap_prune_record_unchanged_lp_unused(Page page, PruneState *prstate, OffsetNumber offnum);
173 : static void heap_prune_record_unchanged_lp_normal(Page page, PruneState *prstate, OffsetNumber offnum);
174 : static void heap_prune_record_unchanged_lp_dead(Page page, PruneState *prstate, OffsetNumber offnum);
175 : static void heap_prune_record_unchanged_lp_redirect(PruneState *prstate, OffsetNumber offnum);
176 :
177 : static void page_verify_redirects(Page page);
178 :
179 :
180 : /*
181 : * Optionally prune and repair fragmentation in the specified page.
182 : *
183 : * This is an opportunistic function. It will perform housekeeping
184 : * only if the page heuristically looks like a candidate for pruning and we
185 : * can acquire buffer cleanup lock without blocking.
186 : *
187 : * Note: this is called quite often. It's important that it fall out quickly
188 : * if there's not any use in pruning.
189 : *
190 : * Caller must have pin on the buffer, and must *not* have a lock on it.
191 : */
192 : void
193 28196368 : heap_page_prune_opt(Relation relation, Buffer buffer)
194 : {
195 28196368 : Page page = BufferGetPage(buffer);
196 : TransactionId prune_xid;
197 : GlobalVisState *vistest;
198 : Size minfree;
199 :
200 : /*
201 : * We can't write WAL in recovery mode, so there's no point trying to
202 : * clean the page. The primary will likely issue a cleaning WAL record
203 : * soon anyway, so this is no particular loss.
204 : */
205 28196368 : if (RecoveryInProgress())
206 425750 : return;
207 :
208 : /*
209 : * First check whether there's any chance there's something to prune,
210 : * determining the appropriate horizon is a waste if there's no prune_xid
211 : * (i.e. no updates/deletes left potentially dead tuples around).
212 : */
213 27770618 : prune_xid = ((PageHeader) page)->pd_prune_xid;
214 27770618 : if (!TransactionIdIsValid(prune_xid))
215 12900316 : return;
216 :
217 : /*
218 : * Check whether prune_xid indicates that there may be dead rows that can
219 : * be cleaned up.
220 : */
221 14870302 : vistest = GlobalVisTestFor(relation);
222 :
223 14870302 : if (!GlobalVisTestIsRemovableXid(vistest, prune_xid))
224 12668554 : return;
225 :
226 : /*
227 : * We prune when a previous UPDATE failed to find enough space on the page
228 : * for a new tuple version, or when free space falls below the relation's
229 : * fill-factor target (but not less than 10%).
230 : *
231 : * Checking free space here is questionable since we aren't holding any
232 : * lock on the buffer; in the worst case we could get a bogus answer. It's
233 : * unlikely to be *seriously* wrong, though, since reading either pd_lower
234 : * or pd_upper is probably atomic. Avoiding taking a lock seems more
235 : * important than sometimes getting a wrong answer in what is after all
236 : * just a heuristic estimate.
237 : */
238 2201748 : minfree = RelationGetTargetPageFreeSpace(relation,
239 : HEAP_DEFAULT_FILLFACTOR);
240 2201748 : minfree = Max(minfree, BLCKSZ / 10);
241 :
242 2201748 : if (PageIsFull(page) || PageGetHeapFreeSpace(page) < minfree)
243 : {
244 : /* OK, try to get exclusive buffer lock */
245 77118 : if (!ConditionalLockBufferForCleanup(buffer))
246 570 : return;
247 :
248 : /*
249 : * Now that we have buffer lock, get accurate information about the
250 : * page's free space, and recheck the heuristic about whether to
251 : * prune.
252 : */
253 76548 : if (PageIsFull(page) || PageGetHeapFreeSpace(page) < minfree)
254 : {
255 : OffsetNumber dummy_off_loc;
256 : PruneFreezeResult presult;
257 :
258 : /*
259 : * For now, pass mark_unused_now as false regardless of whether or
260 : * not the relation has indexes, since we cannot safely determine
261 : * that during on-access pruning with the current implementation.
262 : */
263 76548 : heap_page_prune_and_freeze(relation, buffer, vistest, 0,
264 : NULL, &presult, PRUNE_ON_ACCESS, &dummy_off_loc, NULL, NULL);
265 :
266 : /*
267 : * Report the number of tuples reclaimed to pgstats. This is
268 : * presult.ndeleted minus the number of newly-LP_DEAD-set items.
269 : *
270 : * We derive the number of dead tuples like this to avoid totally
271 : * forgetting about items that were set to LP_DEAD, since they
272 : * still need to be cleaned up by VACUUM. We only want to count
273 : * heap-only tuples that just became LP_UNUSED in our report,
274 : * which don't.
275 : *
276 : * VACUUM doesn't have to compensate in the same way when it
277 : * tracks ndeleted, since it will set the same LP_DEAD items to
278 : * LP_UNUSED separately.
279 : */
280 76548 : if (presult.ndeleted > presult.nnewlpdead)
281 33486 : pgstat_update_heap_dead_tuples(relation,
282 33486 : presult.ndeleted - presult.nnewlpdead);
283 : }
284 :
285 : /* And release buffer lock */
286 76548 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
287 :
288 : /*
289 : * We avoid reuse of any free space created on the page by unrelated
290 : * UPDATEs/INSERTs by opting to not update the FSM at this point. The
291 : * free space should be reused by UPDATEs to *this* page.
292 : */
293 : }
294 : }
295 :
296 :
297 : /*
298 : * Prune and repair fragmentation and potentially freeze tuples on the
299 : * specified page.
300 : *
301 : * Caller must have pin and buffer cleanup lock on the page. Note that we
302 : * don't update the FSM information for page on caller's behalf. Caller might
303 : * also need to account for a reduction in the length of the line pointer
304 : * array following array truncation by us.
305 : *
306 : * If the HEAP_PRUNE_FREEZE option is set, we will also freeze tuples if it's
307 : * required in order to advance relfrozenxid / relminmxid, or if it's
308 : * considered advantageous for overall system performance to do so now. The
309 : * 'cutoffs', 'presult', 'new_relfrozen_xid' and 'new_relmin_mxid' arguments
310 : * are required when freezing. When HEAP_PRUNE_FREEZE option is set, we also
311 : * set presult->all_visible and presult->all_frozen on exit, to indicate if
312 : * the VM bits can be set. They are always set to false when the
313 : * HEAP_PRUNE_FREEZE option is not set, because at the moment only callers
314 : * that also freeze need that information.
315 : *
316 : * vistest is used to distinguish whether tuples are DEAD or RECENTLY_DEAD
317 : * (see heap_prune_satisfies_vacuum).
318 : *
319 : * options:
320 : * MARK_UNUSED_NOW indicates that dead items can be set LP_UNUSED during
321 : * pruning.
322 : *
323 : * FREEZE indicates that we will also freeze tuples, and will return
324 : * 'all_visible', 'all_frozen' flags to the caller.
325 : *
326 : * cutoffs contains the freeze cutoffs, established by VACUUM at the beginning
327 : * of vacuuming the relation. Required if HEAP_PRUNE_FREEZE option is set.
328 : * cutoffs->OldestXmin is also used to determine if dead tuples are
329 : * HEAPTUPLE_RECENTLY_DEAD or HEAPTUPLE_DEAD.
330 : *
331 : * presult contains output parameters needed by callers, such as the number of
332 : * tuples removed and the offsets of dead items on the page after pruning.
333 : * heap_page_prune_and_freeze() is responsible for initializing it. Required
334 : * by all callers.
335 : *
336 : * reason indicates why the pruning is performed. It is included in the WAL
337 : * record for debugging and analysis purposes, but otherwise has no effect.
338 : *
339 : * off_loc is the offset location required by the caller to use in error
340 : * callback.
341 : *
342 : * new_relfrozen_xid and new_relmin_mxid must provided by the caller if the
343 : * HEAP_PRUNE_FREEZE option is set. On entry, they contain the oldest XID and
344 : * multi-XID seen on the relation so far. They will be updated with oldest
345 : * values present on the page after pruning. After processing the whole
346 : * relation, VACUUM can use these values as the new relfrozenxid/relminmxid
347 : * for the relation.
348 : */
349 : void
350 485872 : heap_page_prune_and_freeze(Relation relation, Buffer buffer,
351 : GlobalVisState *vistest,
352 : int options,
353 : struct VacuumCutoffs *cutoffs,
354 : PruneFreezeResult *presult,
355 : PruneReason reason,
356 : OffsetNumber *off_loc,
357 : TransactionId *new_relfrozen_xid,
358 : MultiXactId *new_relmin_mxid)
359 : {
360 485872 : Page page = BufferGetPage(buffer);
361 485872 : BlockNumber blockno = BufferGetBlockNumber(buffer);
362 : OffsetNumber offnum,
363 : maxoff;
364 : PruneState prstate;
365 : HeapTupleData tup;
366 : bool do_freeze;
367 : bool do_prune;
368 : bool do_hint;
369 : bool hint_bit_fpi;
370 485872 : int64 fpi_before = pgWalUsage.wal_fpi;
371 :
372 : /* Copy parameters to prstate */
373 485872 : prstate.vistest = vistest;
374 485872 : prstate.mark_unused_now = (options & HEAP_PAGE_PRUNE_MARK_UNUSED_NOW) != 0;
375 485872 : prstate.freeze = (options & HEAP_PAGE_PRUNE_FREEZE) != 0;
376 485872 : prstate.cutoffs = cutoffs;
377 :
378 : /*
379 : * Our strategy is to scan the page and make lists of items to change,
380 : * then apply the changes within a critical section. This keeps as much
381 : * logic as possible out of the critical section, and also ensures that
382 : * WAL replay will work the same as the normal case.
383 : *
384 : * First, initialize the new pd_prune_xid value to zero (indicating no
385 : * prunable tuples). If we find any tuples which may soon become
386 : * prunable, we will save the lowest relevant XID in new_prune_xid. Also
387 : * initialize the rest of our working state.
388 : */
389 485872 : prstate.new_prune_xid = InvalidTransactionId;
390 485872 : prstate.latest_xid_removed = InvalidTransactionId;
391 485872 : prstate.nredirected = prstate.ndead = prstate.nunused = prstate.nfrozen = 0;
392 485872 : prstate.nroot_items = 0;
393 485872 : prstate.nheaponly_items = 0;
394 :
395 : /* initialize page freezing working state */
396 485872 : prstate.pagefrz.freeze_required = false;
397 485872 : if (prstate.freeze)
398 : {
399 : Assert(new_relfrozen_xid && new_relmin_mxid);
400 409324 : prstate.pagefrz.FreezePageRelfrozenXid = *new_relfrozen_xid;
401 409324 : prstate.pagefrz.NoFreezePageRelfrozenXid = *new_relfrozen_xid;
402 409324 : prstate.pagefrz.FreezePageRelminMxid = *new_relmin_mxid;
403 409324 : prstate.pagefrz.NoFreezePageRelminMxid = *new_relmin_mxid;
404 : }
405 : else
406 : {
407 : Assert(new_relfrozen_xid == NULL && new_relmin_mxid == NULL);
408 76548 : prstate.pagefrz.FreezePageRelminMxid = InvalidMultiXactId;
409 76548 : prstate.pagefrz.NoFreezePageRelminMxid = InvalidMultiXactId;
410 76548 : prstate.pagefrz.FreezePageRelfrozenXid = InvalidTransactionId;
411 76548 : prstate.pagefrz.NoFreezePageRelfrozenXid = InvalidTransactionId;
412 : }
413 :
414 485872 : prstate.ndeleted = 0;
415 485872 : prstate.live_tuples = 0;
416 485872 : prstate.recently_dead_tuples = 0;
417 485872 : prstate.hastup = false;
418 485872 : prstate.lpdead_items = 0;
419 485872 : prstate.deadoffsets = presult->deadoffsets;
420 :
421 : /*
422 : * Caller may update the VM after we're done. We can keep track of
423 : * whether the page will be all-visible and all-frozen after pruning and
424 : * freezing to help the caller to do that.
425 : *
426 : * Currently, only VACUUM sets the VM bits. To save the effort, only do
427 : * the bookkeeping if the caller needs it. Currently, that's tied to
428 : * HEAP_PAGE_PRUNE_FREEZE, but it could be a separate flag if you wanted
429 : * to update the VM bits without also freezing or freeze without also
430 : * setting the VM bits.
431 : *
432 : * In addition to telling the caller whether it can set the VM bit, we
433 : * also use 'all_visible' and 'all_frozen' for our own decision-making. If
434 : * the whole page would become frozen, we consider opportunistically
435 : * freezing tuples. We will not be able to freeze the whole page if there
436 : * are tuples present that are not visible to everyone or if there are
437 : * dead tuples which are not yet removable. However, dead tuples which
438 : * will be removed by the end of vacuuming should not preclude us from
439 : * opportunistically freezing. Because of that, we do not clear
440 : * all_visible when we see LP_DEAD items. We fix that at the end of the
441 : * function, when we return the value to the caller, so that the caller
442 : * doesn't set the VM bit incorrectly.
443 : */
444 485872 : if (prstate.freeze)
445 : {
446 409324 : prstate.all_visible = true;
447 409324 : prstate.all_frozen = true;
448 : }
449 : else
450 : {
451 : /*
452 : * Initializing to false allows skipping the work to update them in
453 : * heap_prune_record_unchanged_lp_normal().
454 : */
455 76548 : prstate.all_visible = false;
456 76548 : prstate.all_frozen = false;
457 : }
458 :
459 : /*
460 : * The visibility cutoff xid is the newest xmin of live tuples on the
461 : * page. In the common case, this will be set as the conflict horizon the
462 : * caller can use for updating the VM. If, at the end of freezing and
463 : * pruning, the page is all-frozen, there is no possibility that any
464 : * running transaction on the standby does not see tuples on the page as
465 : * all-visible, so the conflict horizon remains InvalidTransactionId.
466 : */
467 485872 : prstate.visibility_cutoff_xid = InvalidTransactionId;
468 :
469 485872 : maxoff = PageGetMaxOffsetNumber(page);
470 485872 : tup.t_tableOid = RelationGetRelid(relation);
471 :
472 : /*
473 : * Determine HTSV for all tuples, and queue them up for processing as HOT
474 : * chain roots or as heap-only items.
475 : *
476 : * Determining HTSV only once for each tuple is required for correctness,
477 : * to deal with cases where running HTSV twice could result in different
478 : * results. For example, RECENTLY_DEAD can turn to DEAD if another
479 : * checked item causes GlobalVisTestIsRemovableFullXid() to update the
480 : * horizon, or INSERT_IN_PROGRESS can change to DEAD if the inserting
481 : * transaction aborts.
482 : *
483 : * It's also good for performance. Most commonly tuples within a page are
484 : * stored at decreasing offsets (while the items are stored at increasing
485 : * offsets). When processing all tuples on a page this leads to reading
486 : * memory at decreasing offsets within a page, with a variable stride.
487 : * That's hard for CPU prefetchers to deal with. Processing the items in
488 : * reverse order (and thus the tuples in increasing order) increases
489 : * prefetching efficiency significantly / decreases the number of cache
490 : * misses.
491 : */
492 27703466 : for (offnum = maxoff;
493 : offnum >= FirstOffsetNumber;
494 27217594 : offnum = OffsetNumberPrev(offnum))
495 : {
496 27217594 : ItemId itemid = PageGetItemId(page, offnum);
497 : HeapTupleHeader htup;
498 :
499 : /*
500 : * Set the offset number so that we can display it along with any
501 : * error that occurred while processing this tuple.
502 : */
503 27217594 : *off_loc = offnum;
504 :
505 27217594 : prstate.processed[offnum] = false;
506 27217594 : prstate.htsv[offnum] = -1;
507 :
508 : /* Nothing to do if slot doesn't contain a tuple */
509 27217594 : if (!ItemIdIsUsed(itemid))
510 : {
511 265104 : heap_prune_record_unchanged_lp_unused(page, &prstate, offnum);
512 265104 : continue;
513 : }
514 :
515 26952490 : if (ItemIdIsDead(itemid))
516 : {
517 : /*
518 : * If the caller set mark_unused_now true, we can set dead line
519 : * pointers LP_UNUSED now.
520 : */
521 1926776 : if (unlikely(prstate.mark_unused_now))
522 1504 : heap_prune_record_unused(&prstate, offnum, false);
523 : else
524 1925272 : heap_prune_record_unchanged_lp_dead(page, &prstate, offnum);
525 1926776 : continue;
526 : }
527 :
528 25025714 : if (ItemIdIsRedirected(itemid))
529 : {
530 : /* This is the start of a HOT chain */
531 380142 : prstate.root_items[prstate.nroot_items++] = offnum;
532 380142 : continue;
533 : }
534 :
535 : Assert(ItemIdIsNormal(itemid));
536 :
537 : /*
538 : * Get the tuple's visibility status and queue it up for processing.
539 : */
540 24645572 : htup = (HeapTupleHeader) PageGetItem(page, itemid);
541 24645572 : tup.t_data = htup;
542 24645572 : tup.t_len = ItemIdGetLength(itemid);
543 24645572 : ItemPointerSet(&tup.t_self, blockno, offnum);
544 :
545 24645572 : prstate.htsv[offnum] = heap_prune_satisfies_vacuum(&prstate, &tup,
546 : buffer);
547 :
548 24645572 : if (!HeapTupleHeaderIsHeapOnly(htup))
549 24049476 : prstate.root_items[prstate.nroot_items++] = offnum;
550 : else
551 596096 : prstate.heaponly_items[prstate.nheaponly_items++] = offnum;
552 : }
553 :
554 : /*
555 : * If checksums are enabled, heap_prune_satisfies_vacuum() may have caused
556 : * an FPI to be emitted.
557 : */
558 485872 : hint_bit_fpi = fpi_before != pgWalUsage.wal_fpi;
559 :
560 : /*
561 : * Process HOT chains.
562 : *
563 : * We added the items to the array starting from 'maxoff', so by
564 : * processing the array in reverse order, we process the items in
565 : * ascending offset number order. The order doesn't matter for
566 : * correctness, but some quick micro-benchmarking suggests that this is
567 : * faster. (Earlier PostgreSQL versions, which scanned all the items on
568 : * the page instead of using the root_items array, also did it in
569 : * ascending offset number order.)
570 : */
571 24915490 : for (int i = prstate.nroot_items - 1; i >= 0; i--)
572 : {
573 24429618 : offnum = prstate.root_items[i];
574 :
575 : /* Ignore items already processed as part of an earlier chain */
576 24429618 : if (prstate.processed[offnum])
577 0 : continue;
578 :
579 : /* see preceding loop */
580 24429618 : *off_loc = offnum;
581 :
582 : /* Process this item or chain of items */
583 24429618 : heap_prune_chain(page, blockno, maxoff, offnum, &prstate);
584 : }
585 :
586 : /*
587 : * Process any heap-only tuples that were not already processed as part of
588 : * a HOT chain.
589 : */
590 1081968 : for (int i = prstate.nheaponly_items - 1; i >= 0; i--)
591 : {
592 596096 : offnum = prstate.heaponly_items[i];
593 :
594 596096 : if (prstate.processed[offnum])
595 571260 : continue;
596 :
597 : /* see preceding loop */
598 24836 : *off_loc = offnum;
599 :
600 : /*
601 : * If the tuple is DEAD and doesn't chain to anything else, mark it
602 : * unused. (If it does chain, we can only remove it as part of
603 : * pruning its chain.)
604 : *
605 : * We need this primarily to handle aborted HOT updates, that is,
606 : * XMIN_INVALID heap-only tuples. Those might not be linked to by any
607 : * chain, since the parent tuple might be re-updated before any
608 : * pruning occurs. So we have to be able to reap them separately from
609 : * chain-pruning. (Note that HeapTupleHeaderIsHotUpdated will never
610 : * return true for an XMIN_INVALID tuple, so this code will work even
611 : * when there were sequential updates within the aborted transaction.)
612 : */
613 24836 : if (prstate.htsv[offnum] == HEAPTUPLE_DEAD)
614 : {
615 3368 : ItemId itemid = PageGetItemId(page, offnum);
616 3368 : HeapTupleHeader htup = (HeapTupleHeader) PageGetItem(page, itemid);
617 :
618 3368 : if (likely(!HeapTupleHeaderIsHotUpdated(htup)))
619 : {
620 3368 : HeapTupleHeaderAdvanceConflictHorizon(htup,
621 : &prstate.latest_xid_removed);
622 3368 : heap_prune_record_unused(&prstate, offnum, true);
623 : }
624 : else
625 : {
626 : /*
627 : * This tuple should've been processed and removed as part of
628 : * a HOT chain, so something's wrong. To preserve evidence,
629 : * we don't dare to remove it. We cannot leave behind a DEAD
630 : * tuple either, because that will cause VACUUM to error out.
631 : * Throwing an error with a distinct error message seems like
632 : * the least bad option.
633 : */
634 0 : elog(ERROR, "dead heap-only tuple (%u, %d) is not linked to from any HOT chain",
635 : blockno, offnum);
636 : }
637 : }
638 : else
639 21468 : heap_prune_record_unchanged_lp_normal(page, &prstate, offnum);
640 : }
641 :
642 : /* We should now have processed every tuple exactly once */
643 : #ifdef USE_ASSERT_CHECKING
644 : for (offnum = FirstOffsetNumber;
645 : offnum <= maxoff;
646 : offnum = OffsetNumberNext(offnum))
647 : {
648 : *off_loc = offnum;
649 :
650 : Assert(prstate.processed[offnum]);
651 : }
652 : #endif
653 :
654 : /* Clear the offset information once we have processed the given page. */
655 485872 : *off_loc = InvalidOffsetNumber;
656 :
657 1428574 : do_prune = prstate.nredirected > 0 ||
658 877898 : prstate.ndead > 0 ||
659 392026 : prstate.nunused > 0;
660 :
661 : /*
662 : * Even if we don't prune anything, if we found a new value for the
663 : * pd_prune_xid field or the page was marked full, we will update the hint
664 : * bit.
665 : */
666 877278 : do_hint = ((PageHeader) page)->pd_prune_xid != prstate.new_prune_xid ||
667 391406 : PageIsFull(page);
668 :
669 : /*
670 : * Decide if we want to go ahead with freezing according to the freeze
671 : * plans we prepared, or not.
672 : */
673 485872 : do_freeze = false;
674 485872 : if (prstate.freeze)
675 : {
676 409324 : if (prstate.pagefrz.freeze_required)
677 : {
678 : /*
679 : * heap_prepare_freeze_tuple indicated that at least one XID/MXID
680 : * from before FreezeLimit/MultiXactCutoff is present. Must
681 : * freeze to advance relfrozenxid/relminmxid.
682 : */
683 29906 : do_freeze = true;
684 : }
685 : else
686 : {
687 : /*
688 : * Opportunistically freeze the page if we are generating an FPI
689 : * anyway and if doing so means that we can set the page
690 : * all-frozen afterwards (might not happen until VACUUM's final
691 : * heap pass).
692 : *
693 : * XXX: Previously, we knew if pruning emitted an FPI by checking
694 : * pgWalUsage.wal_fpi before and after pruning. Once the freeze
695 : * and prune records were combined, this heuristic couldn't be
696 : * used anymore. The opportunistic freeze heuristic must be
697 : * improved; however, for now, try to approximate the old logic.
698 : */
699 379418 : if (prstate.all_visible && prstate.all_frozen && prstate.nfrozen > 0)
700 : {
701 : /*
702 : * Freezing would make the page all-frozen. Have already
703 : * emitted an FPI or will do so anyway?
704 : */
705 21648 : if (RelationNeedsWAL(relation))
706 : {
707 21624 : if (hint_bit_fpi)
708 1716 : do_freeze = true;
709 19908 : else if (do_prune)
710 : {
711 1692 : if (XLogCheckBufferNeedsBackup(buffer))
712 696 : do_freeze = true;
713 : }
714 18216 : else if (do_hint)
715 : {
716 6 : if (XLogHintBitIsNeeded() && XLogCheckBufferNeedsBackup(buffer))
717 0 : do_freeze = true;
718 : }
719 : }
720 : }
721 : }
722 : }
723 :
724 485872 : if (do_freeze)
725 : {
726 : /*
727 : * Validate the tuples we will be freezing before entering the
728 : * critical section.
729 : */
730 32318 : heap_pre_freeze_checks(buffer, prstate.frozen, prstate.nfrozen);
731 : }
732 453554 : else if (prstate.nfrozen > 0)
733 : {
734 : /*
735 : * The page contained some tuples that were not already frozen, and we
736 : * chose not to freeze them now. The page won't be all-frozen then.
737 : */
738 : Assert(!prstate.pagefrz.freeze_required);
739 :
740 20640 : prstate.all_frozen = false;
741 20640 : prstate.nfrozen = 0; /* avoid miscounts in instrumentation */
742 : }
743 : else
744 : {
745 : /*
746 : * We have no freeze plans to execute. The page might already be
747 : * all-frozen (perhaps only following pruning), though. Such pages
748 : * can be marked all-frozen in the VM by our caller, even though none
749 : * of its tuples were newly frozen here.
750 : */
751 : }
752 :
753 : /* Any error while applying the changes is critical */
754 485872 : START_CRIT_SECTION();
755 :
756 485872 : if (do_hint)
757 : {
758 : /*
759 : * Update the page's pd_prune_xid field to either zero, or the lowest
760 : * XID of any soon-prunable tuple.
761 : */
762 94562 : ((PageHeader) page)->pd_prune_xid = prstate.new_prune_xid;
763 :
764 : /*
765 : * Also clear the "page is full" flag, since there's no point in
766 : * repeating the prune/defrag process until something else happens to
767 : * the page.
768 : */
769 94562 : PageClearFull(page);
770 :
771 : /*
772 : * If that's all we had to do to the page, this is a non-WAL-logged
773 : * hint. If we are going to freeze or prune the page, we will mark
774 : * the buffer dirty below.
775 : */
776 94562 : if (!do_freeze && !do_prune)
777 302 : MarkBufferDirtyHint(buffer, true);
778 : }
779 :
780 485872 : if (do_prune || do_freeze)
781 : {
782 : /* Apply the planned item changes and repair page fragmentation. */
783 125142 : if (do_prune)
784 : {
785 94566 : heap_page_prune_execute(buffer, false,
786 : prstate.redirected, prstate.nredirected,
787 : prstate.nowdead, prstate.ndead,
788 : prstate.nowunused, prstate.nunused);
789 : }
790 :
791 125142 : if (do_freeze)
792 32318 : heap_freeze_prepared_tuples(buffer, prstate.frozen, prstate.nfrozen);
793 :
794 125142 : MarkBufferDirty(buffer);
795 :
796 : /*
797 : * Emit a WAL XLOG_HEAP2_PRUNE_FREEZE record showing what we did
798 : */
799 125142 : if (RelationNeedsWAL(relation))
800 : {
801 : /*
802 : * The snapshotConflictHorizon for the whole record should be the
803 : * most conservative of all the horizons calculated for any of the
804 : * possible modifications. If this record will prune tuples, any
805 : * transactions on the standby older than the youngest xmax of the
806 : * most recently removed tuple this record will prune will
807 : * conflict. If this record will freeze tuples, any transactions
808 : * on the standby with xids older than the youngest tuple this
809 : * record will freeze will conflict.
810 : */
811 123502 : TransactionId frz_conflict_horizon = InvalidTransactionId;
812 : TransactionId conflict_xid;
813 :
814 : /*
815 : * We can use the visibility_cutoff_xid as our cutoff for
816 : * conflicts when the whole page is eligible to become all-frozen
817 : * in the VM once we're done with it. Otherwise we generate a
818 : * conservative cutoff by stepping back from OldestXmin.
819 : */
820 123502 : if (do_freeze)
821 : {
822 32314 : if (prstate.all_visible && prstate.all_frozen)
823 27688 : frz_conflict_horizon = prstate.visibility_cutoff_xid;
824 : else
825 : {
826 : /* Avoids false conflicts when hot_standby_feedback in use */
827 4626 : frz_conflict_horizon = prstate.cutoffs->OldestXmin;
828 4626 : TransactionIdRetreat(frz_conflict_horizon);
829 : }
830 : }
831 :
832 123502 : if (TransactionIdFollows(frz_conflict_horizon, prstate.latest_xid_removed))
833 31058 : conflict_xid = frz_conflict_horizon;
834 : else
835 92444 : conflict_xid = prstate.latest_xid_removed;
836 :
837 123502 : log_heap_prune_and_freeze(relation, buffer,
838 : conflict_xid,
839 : true, reason,
840 : prstate.frozen, prstate.nfrozen,
841 : prstate.redirected, prstate.nredirected,
842 : prstate.nowdead, prstate.ndead,
843 : prstate.nowunused, prstate.nunused);
844 : }
845 : }
846 :
847 485872 : END_CRIT_SECTION();
848 :
849 : /* Copy information back for caller */
850 485872 : presult->ndeleted = prstate.ndeleted;
851 485872 : presult->nnewlpdead = prstate.ndead;
852 485872 : presult->nfrozen = prstate.nfrozen;
853 485872 : presult->live_tuples = prstate.live_tuples;
854 485872 : presult->recently_dead_tuples = prstate.recently_dead_tuples;
855 :
856 : /*
857 : * It was convenient to ignore LP_DEAD items in all_visible earlier on to
858 : * make the choice of whether or not to freeze the page unaffected by the
859 : * short-term presence of LP_DEAD items. These LP_DEAD items were
860 : * effectively assumed to be LP_UNUSED items in the making. It doesn't
861 : * matter which vacuum heap pass (initial pass or final pass) ends up
862 : * setting the page all-frozen, as long as the ongoing VACUUM does it.
863 : *
864 : * Now that freezing has been finalized, unset all_visible if there are
865 : * any LP_DEAD items on the page. It needs to reflect the present state
866 : * of the page, as expected by our caller.
867 : */
868 485872 : if (prstate.all_visible && prstate.lpdead_items == 0)
869 : {
870 193240 : presult->all_visible = prstate.all_visible;
871 193240 : presult->all_frozen = prstate.all_frozen;
872 : }
873 : else
874 : {
875 292632 : presult->all_visible = false;
876 292632 : presult->all_frozen = false;
877 : }
878 :
879 485872 : presult->hastup = prstate.hastup;
880 :
881 : /*
882 : * For callers planning to update the visibility map, the conflict horizon
883 : * for that record must be the newest xmin on the page. However, if the
884 : * page is completely frozen, there can be no conflict and the
885 : * vm_conflict_horizon should remain InvalidTransactionId. This includes
886 : * the case that we just froze all the tuples; the prune-freeze record
887 : * included the conflict XID already so the caller doesn't need it.
888 : */
889 485872 : if (presult->all_frozen)
890 179046 : presult->vm_conflict_horizon = InvalidTransactionId;
891 : else
892 306826 : presult->vm_conflict_horizon = prstate.visibility_cutoff_xid;
893 :
894 485872 : presult->lpdead_items = prstate.lpdead_items;
895 : /* the presult->deadoffsets array was already filled in */
896 :
897 485872 : if (prstate.freeze)
898 : {
899 409324 : if (presult->nfrozen > 0)
900 : {
901 32318 : *new_relfrozen_xid = prstate.pagefrz.FreezePageRelfrozenXid;
902 32318 : *new_relmin_mxid = prstate.pagefrz.FreezePageRelminMxid;
903 : }
904 : else
905 : {
906 377006 : *new_relfrozen_xid = prstate.pagefrz.NoFreezePageRelfrozenXid;
907 377006 : *new_relmin_mxid = prstate.pagefrz.NoFreezePageRelminMxid;
908 : }
909 : }
910 485872 : }
911 :
912 :
913 : /*
914 : * Perform visibility checks for heap pruning.
915 : */
916 : static HTSV_Result
917 24645572 : heap_prune_satisfies_vacuum(PruneState *prstate, HeapTuple tup, Buffer buffer)
918 : {
919 : HTSV_Result res;
920 : TransactionId dead_after;
921 :
922 24645572 : res = HeapTupleSatisfiesVacuumHorizon(tup, buffer, &dead_after);
923 :
924 24645572 : if (res != HEAPTUPLE_RECENTLY_DEAD)
925 21392356 : return res;
926 :
927 : /*
928 : * For VACUUM, we must be sure to prune tuples with xmax older than
929 : * OldestXmin -- a visibility cutoff determined at the beginning of
930 : * vacuuming the relation. OldestXmin is used for freezing determination
931 : * and we cannot freeze dead tuples' xmaxes.
932 : */
933 3253216 : if (prstate->cutoffs &&
934 1633352 : TransactionIdIsValid(prstate->cutoffs->OldestXmin) &&
935 1633352 : NormalTransactionIdPrecedes(dead_after, prstate->cutoffs->OldestXmin))
936 1148080 : return HEAPTUPLE_DEAD;
937 :
938 : /*
939 : * Determine whether or not the tuple is considered dead when compared
940 : * with the provided GlobalVisState. On-access pruning does not provide
941 : * VacuumCutoffs. And for vacuum, even if the tuple's xmax is not older
942 : * than OldestXmin, GlobalVisTestIsRemovableXid() could find the row dead
943 : * if the GlobalVisState has been updated since the beginning of vacuuming
944 : * the relation.
945 : */
946 2105136 : if (GlobalVisTestIsRemovableXid(prstate->vistest, dead_after))
947 1568104 : return HEAPTUPLE_DEAD;
948 :
949 537032 : return res;
950 : }
951 :
952 :
953 : /*
954 : * Pruning calculates tuple visibility once and saves the results in an array
955 : * of int8. See PruneState.htsv for details. This helper function is meant
956 : * to guard against examining visibility status array members which have not
957 : * yet been computed.
958 : */
959 : static inline HTSV_Result
960 24620736 : htsv_get_valid_status(int status)
961 : {
962 : Assert(status >= HEAPTUPLE_DEAD &&
963 : status <= HEAPTUPLE_DELETE_IN_PROGRESS);
964 24620736 : return (HTSV_Result) status;
965 : }
966 :
967 : /*
968 : * Prune specified line pointer or a HOT chain originating at line pointer.
969 : *
970 : * Tuple visibility information is provided in prstate->htsv.
971 : *
972 : * If the item is an index-referenced tuple (i.e. not a heap-only tuple),
973 : * the HOT chain is pruned by removing all DEAD tuples at the start of the HOT
974 : * chain. We also prune any RECENTLY_DEAD tuples preceding a DEAD tuple.
975 : * This is OK because a RECENTLY_DEAD tuple preceding a DEAD tuple is really
976 : * DEAD, our visibility test is just too coarse to detect it.
977 : *
978 : * Pruning must never leave behind a DEAD tuple that still has tuple storage.
979 : * VACUUM isn't prepared to deal with that case.
980 : *
981 : * The root line pointer is redirected to the tuple immediately after the
982 : * latest DEAD tuple. If all tuples in the chain are DEAD, the root line
983 : * pointer is marked LP_DEAD. (This includes the case of a DEAD simple
984 : * tuple, which we treat as a chain of length 1.)
985 : *
986 : * We don't actually change the page here. We just add entries to the arrays in
987 : * prstate showing the changes to be made. Items to be redirected are added
988 : * to the redirected[] array (two entries per redirection); items to be set to
989 : * LP_DEAD state are added to nowdead[]; and items to be set to LP_UNUSED
990 : * state are added to nowunused[]. We perform bookkeeping of live tuples,
991 : * visibility etc. based on what the page will look like after the changes
992 : * applied. All that bookkeeping is performed in the heap_prune_record_*()
993 : * subroutines. The division of labor is that heap_prune_chain() decides the
994 : * fate of each tuple, ie. whether it's going to be removed, redirected or
995 : * left unchanged, and the heap_prune_record_*() subroutines update PruneState
996 : * based on that outcome.
997 : */
998 : static void
999 24429618 : heap_prune_chain(Page page, BlockNumber blockno, OffsetNumber maxoff,
1000 : OffsetNumber rootoffnum, PruneState *prstate)
1001 : {
1002 24429618 : TransactionId priorXmax = InvalidTransactionId;
1003 : ItemId rootlp;
1004 : OffsetNumber offnum;
1005 : OffsetNumber chainitems[MaxHeapTuplesPerPage];
1006 :
1007 : /*
1008 : * After traversing the HOT chain, ndeadchain is the index in chainitems
1009 : * of the first live successor after the last dead item.
1010 : */
1011 24429618 : int ndeadchain = 0,
1012 24429618 : nchain = 0;
1013 :
1014 24429618 : rootlp = PageGetItemId(page, rootoffnum);
1015 :
1016 : /* Start from the root tuple */
1017 24429618 : offnum = rootoffnum;
1018 :
1019 : /* while not end of the chain */
1020 : for (;;)
1021 571260 : {
1022 : HeapTupleHeader htup;
1023 : ItemId lp;
1024 :
1025 : /* Sanity check (pure paranoia) */
1026 25000878 : if (offnum < FirstOffsetNumber)
1027 0 : break;
1028 :
1029 : /*
1030 : * An offset past the end of page's line pointer array is possible
1031 : * when the array was truncated (original item must have been unused)
1032 : */
1033 25000878 : if (offnum > maxoff)
1034 0 : break;
1035 :
1036 : /* If item is already processed, stop --- it must not be same chain */
1037 25000878 : if (prstate->processed[offnum])
1038 0 : break;
1039 :
1040 25000878 : lp = PageGetItemId(page, offnum);
1041 :
1042 : /*
1043 : * Unused item obviously isn't part of the chain. Likewise, a dead
1044 : * line pointer can't be part of the chain. Both of those cases were
1045 : * already marked as processed.
1046 : */
1047 : Assert(ItemIdIsUsed(lp));
1048 : Assert(!ItemIdIsDead(lp));
1049 :
1050 : /*
1051 : * If we are looking at the redirected root line pointer, jump to the
1052 : * first normal tuple in the chain. If we find a redirect somewhere
1053 : * else, stop --- it must not be same chain.
1054 : */
1055 25000878 : if (ItemIdIsRedirected(lp))
1056 : {
1057 380142 : if (nchain > 0)
1058 0 : break; /* not at start of chain */
1059 380142 : chainitems[nchain++] = offnum;
1060 380142 : offnum = ItemIdGetRedirect(rootlp);
1061 380142 : continue;
1062 : }
1063 :
1064 : Assert(ItemIdIsNormal(lp));
1065 :
1066 24620736 : htup = (HeapTupleHeader) PageGetItem(page, lp);
1067 :
1068 : /*
1069 : * Check the tuple XMIN against prior XMAX, if any
1070 : */
1071 24811854 : if (TransactionIdIsValid(priorXmax) &&
1072 191118 : !TransactionIdEquals(HeapTupleHeaderGetXmin(htup), priorXmax))
1073 0 : break;
1074 :
1075 : /*
1076 : * OK, this tuple is indeed a member of the chain.
1077 : */
1078 24620736 : chainitems[nchain++] = offnum;
1079 :
1080 24620736 : switch (htsv_get_valid_status(prstate->htsv[offnum]))
1081 : {
1082 2790742 : case HEAPTUPLE_DEAD:
1083 :
1084 : /* Remember the last DEAD tuple seen */
1085 2790742 : ndeadchain = nchain;
1086 2790742 : HeapTupleHeaderAdvanceConflictHorizon(htup,
1087 : &prstate->latest_xid_removed);
1088 : /* Advance to next chain member */
1089 2790742 : break;
1090 :
1091 537032 : case HEAPTUPLE_RECENTLY_DEAD:
1092 :
1093 : /*
1094 : * We don't need to advance the conflict horizon for
1095 : * RECENTLY_DEAD tuples, even if we are removing them. This
1096 : * is because we only remove RECENTLY_DEAD tuples if they
1097 : * precede a DEAD tuple, and the DEAD tuple must have been
1098 : * inserted by a newer transaction than the RECENTLY_DEAD
1099 : * tuple by virtue of being later in the chain. We will have
1100 : * advanced the conflict horizon for the DEAD tuple.
1101 : */
1102 :
1103 : /*
1104 : * Advance past RECENTLY_DEAD tuples just in case there's a
1105 : * DEAD one after them. We have to make sure that we don't
1106 : * miss any DEAD tuples, since DEAD tuples that still have
1107 : * tuple storage after pruning will confuse VACUUM.
1108 : */
1109 537032 : break;
1110 :
1111 21292962 : case HEAPTUPLE_DELETE_IN_PROGRESS:
1112 : case HEAPTUPLE_LIVE:
1113 : case HEAPTUPLE_INSERT_IN_PROGRESS:
1114 21292962 : goto process_chain;
1115 :
1116 0 : default:
1117 0 : elog(ERROR, "unexpected HeapTupleSatisfiesVacuum result");
1118 : goto process_chain;
1119 : }
1120 :
1121 : /*
1122 : * If the tuple is not HOT-updated, then we are at the end of this
1123 : * HOT-update chain.
1124 : */
1125 3327774 : if (!HeapTupleHeaderIsHotUpdated(htup))
1126 3136656 : goto process_chain;
1127 :
1128 : /* HOT implies it can't have moved to different partition */
1129 : Assert(!HeapTupleHeaderIndicatesMovedPartitions(htup));
1130 :
1131 : /*
1132 : * Advance to next chain member.
1133 : */
1134 : Assert(ItemPointerGetBlockNumber(&htup->t_ctid) == blockno);
1135 191118 : offnum = ItemPointerGetOffsetNumber(&htup->t_ctid);
1136 191118 : priorXmax = HeapTupleHeaderGetUpdateXid(htup);
1137 : }
1138 :
1139 0 : if (ItemIdIsRedirected(rootlp) && nchain < 2)
1140 : {
1141 : /*
1142 : * We found a redirect item that doesn't point to a valid follow-on
1143 : * item. This can happen if the loop in heap_page_prune_and_freeze()
1144 : * caused us to visit the dead successor of a redirect item before
1145 : * visiting the redirect item. We can clean up by setting the
1146 : * redirect item to LP_DEAD state or LP_UNUSED if the caller
1147 : * indicated.
1148 : */
1149 0 : heap_prune_record_dead_or_unused(prstate, rootoffnum, false);
1150 0 : return;
1151 : }
1152 :
1153 0 : process_chain:
1154 :
1155 24429618 : if (ndeadchain == 0)
1156 : {
1157 : /*
1158 : * No DEAD tuple was found, so the chain is entirely composed of
1159 : * normal, unchanged tuples. Leave it alone.
1160 : */
1161 21700898 : int i = 0;
1162 :
1163 21700898 : if (ItemIdIsRedirected(rootlp))
1164 : {
1165 350500 : heap_prune_record_unchanged_lp_redirect(prstate, rootoffnum);
1166 350500 : i++;
1167 : }
1168 43409122 : for (; i < nchain; i++)
1169 21708224 : heap_prune_record_unchanged_lp_normal(page, prstate, chainitems[i]);
1170 : }
1171 2728720 : else if (ndeadchain == nchain)
1172 : {
1173 : /*
1174 : * The entire chain is dead. Mark the root line pointer LP_DEAD, and
1175 : * fully remove the other tuples in the chain.
1176 : */
1177 2610716 : heap_prune_record_dead_or_unused(prstate, rootoffnum, ItemIdIsNormal(rootlp));
1178 2670076 : for (int i = 1; i < nchain; i++)
1179 59360 : heap_prune_record_unused(prstate, chainitems[i], true);
1180 : }
1181 : else
1182 : {
1183 : /*
1184 : * We found a DEAD tuple in the chain. Redirect the root line pointer
1185 : * to the first non-DEAD tuple, and mark as unused each intermediate
1186 : * item that we are able to remove from the chain.
1187 : */
1188 118004 : heap_prune_record_redirect(prstate, rootoffnum, chainitems[ndeadchain],
1189 118004 : ItemIdIsNormal(rootlp));
1190 150308 : for (int i = 1; i < ndeadchain; i++)
1191 32304 : heap_prune_record_unused(prstate, chainitems[i], true);
1192 :
1193 : /* the rest of tuples in the chain are normal, unchanged tuples */
1194 239774 : for (int i = ndeadchain; i < nchain; i++)
1195 121770 : heap_prune_record_unchanged_lp_normal(page, prstate, chainitems[i]);
1196 : }
1197 : }
1198 :
1199 : /* Record lowest soon-prunable XID */
1200 : static void
1201 5085488 : heap_prune_record_prunable(PruneState *prstate, TransactionId xid)
1202 : {
1203 : /*
1204 : * This should exactly match the PageSetPrunable macro. We can't store
1205 : * directly into the page header yet, so we update working state.
1206 : */
1207 : Assert(TransactionIdIsNormal(xid));
1208 9975114 : if (!TransactionIdIsValid(prstate->new_prune_xid) ||
1209 4889626 : TransactionIdPrecedes(xid, prstate->new_prune_xid))
1210 197660 : prstate->new_prune_xid = xid;
1211 5085488 : }
1212 :
1213 : /* Record line pointer to be redirected */
1214 : static void
1215 118004 : heap_prune_record_redirect(PruneState *prstate,
1216 : OffsetNumber offnum, OffsetNumber rdoffnum,
1217 : bool was_normal)
1218 : {
1219 : Assert(!prstate->processed[offnum]);
1220 118004 : prstate->processed[offnum] = true;
1221 :
1222 : /*
1223 : * Do not mark the redirect target here. It needs to be counted
1224 : * separately as an unchanged tuple.
1225 : */
1226 :
1227 : Assert(prstate->nredirected < MaxHeapTuplesPerPage);
1228 118004 : prstate->redirected[prstate->nredirected * 2] = offnum;
1229 118004 : prstate->redirected[prstate->nredirected * 2 + 1] = rdoffnum;
1230 :
1231 118004 : prstate->nredirected++;
1232 :
1233 : /*
1234 : * If the root entry had been a normal tuple, we are deleting it, so count
1235 : * it in the result. But changing a redirect (even to DEAD state) doesn't
1236 : * count.
1237 : */
1238 118004 : if (was_normal)
1239 104698 : prstate->ndeleted++;
1240 :
1241 118004 : prstate->hastup = true;
1242 118004 : }
1243 :
1244 : /* Record line pointer to be marked dead */
1245 : static void
1246 2542096 : heap_prune_record_dead(PruneState *prstate, OffsetNumber offnum,
1247 : bool was_normal)
1248 : {
1249 : Assert(!prstate->processed[offnum]);
1250 2542096 : prstate->processed[offnum] = true;
1251 :
1252 : Assert(prstate->ndead < MaxHeapTuplesPerPage);
1253 2542096 : prstate->nowdead[prstate->ndead] = offnum;
1254 2542096 : prstate->ndead++;
1255 :
1256 : /*
1257 : * Deliberately delay unsetting all_visible until later during pruning.
1258 : * Removable dead tuples shouldn't preclude freezing the page.
1259 : */
1260 :
1261 : /* Record the dead offset for vacuum */
1262 2542096 : prstate->deadoffsets[prstate->lpdead_items++] = offnum;
1263 :
1264 : /*
1265 : * If the root entry had been a normal tuple, we are deleting it, so count
1266 : * it in the result. But changing a redirect (even to DEAD state) doesn't
1267 : * count.
1268 : */
1269 2542096 : if (was_normal)
1270 2525760 : prstate->ndeleted++;
1271 2542096 : }
1272 :
1273 : /*
1274 : * Depending on whether or not the caller set mark_unused_now to true, record that a
1275 : * line pointer should be marked LP_DEAD or LP_UNUSED. There are other cases in
1276 : * which we will mark line pointers LP_UNUSED, but we will not mark line
1277 : * pointers LP_DEAD if mark_unused_now is true.
1278 : */
1279 : static void
1280 2610716 : heap_prune_record_dead_or_unused(PruneState *prstate, OffsetNumber offnum,
1281 : bool was_normal)
1282 : {
1283 : /*
1284 : * If the caller set mark_unused_now to true, we can remove dead tuples
1285 : * during pruning instead of marking their line pointers dead. Set this
1286 : * tuple's line pointer LP_UNUSED. We hint that this option is less
1287 : * likely.
1288 : */
1289 2610716 : if (unlikely(prstate->mark_unused_now))
1290 68620 : heap_prune_record_unused(prstate, offnum, was_normal);
1291 : else
1292 2542096 : heap_prune_record_dead(prstate, offnum, was_normal);
1293 2610716 : }
1294 :
1295 : /* Record line pointer to be marked unused */
1296 : static void
1297 165156 : heap_prune_record_unused(PruneState *prstate, OffsetNumber offnum, bool was_normal)
1298 : {
1299 : Assert(!prstate->processed[offnum]);
1300 165156 : prstate->processed[offnum] = true;
1301 :
1302 : Assert(prstate->nunused < MaxHeapTuplesPerPage);
1303 165156 : prstate->nowunused[prstate->nunused] = offnum;
1304 165156 : prstate->nunused++;
1305 :
1306 : /*
1307 : * If the root entry had been a normal tuple, we are deleting it, so count
1308 : * it in the result. But changing a redirect (even to DEAD state) doesn't
1309 : * count.
1310 : */
1311 165156 : if (was_normal)
1312 163652 : prstate->ndeleted++;
1313 165156 : }
1314 :
1315 : /*
1316 : * Record an unused line pointer that is left unchanged.
1317 : */
1318 : static void
1319 265104 : heap_prune_record_unchanged_lp_unused(Page page, PruneState *prstate, OffsetNumber offnum)
1320 : {
1321 : Assert(!prstate->processed[offnum]);
1322 265104 : prstate->processed[offnum] = true;
1323 265104 : }
1324 :
1325 : /*
1326 : * Record line pointer that is left unchanged. We consider freezing it, and
1327 : * update bookkeeping of tuple counts and page visibility.
1328 : */
1329 : static void
1330 21851462 : heap_prune_record_unchanged_lp_normal(Page page, PruneState *prstate, OffsetNumber offnum)
1331 : {
1332 : HeapTupleHeader htup;
1333 :
1334 : Assert(!prstate->processed[offnum]);
1335 21851462 : prstate->processed[offnum] = true;
1336 :
1337 21851462 : prstate->hastup = true; /* the page is not empty */
1338 :
1339 : /*
1340 : * The criteria for counting a tuple as live in this block need to match
1341 : * what analyze.c's acquire_sample_rows() does, otherwise VACUUM and
1342 : * ANALYZE may produce wildly different reltuples values, e.g. when there
1343 : * are many recently-dead tuples.
1344 : *
1345 : * The logic here is a bit simpler than acquire_sample_rows(), as VACUUM
1346 : * can't run inside a transaction block, which makes some cases impossible
1347 : * (e.g. in-progress insert from the same transaction).
1348 : *
1349 : * HEAPTUPLE_DEAD are handled by the other heap_prune_record_*()
1350 : * subroutines. They don't count dead items like acquire_sample_rows()
1351 : * does, because we assume that all dead items will become LP_UNUSED
1352 : * before VACUUM finishes. This difference is only superficial. VACUUM
1353 : * effectively agrees with ANALYZE about DEAD items, in the end. VACUUM
1354 : * won't remember LP_DEAD items, but only because they're not supposed to
1355 : * be left behind when it is done. (Cases where we bypass index vacuuming
1356 : * will violate this optimistic assumption, but the overall impact of that
1357 : * should be negligible.)
1358 : */
1359 21851462 : htup = (HeapTupleHeader) PageGetItem(page, PageGetItemId(page, offnum));
1360 :
1361 21851462 : switch (prstate->htsv[offnum])
1362 : {
1363 16650428 : case HEAPTUPLE_LIVE:
1364 :
1365 : /*
1366 : * Count it as live. Not only is this natural, but it's also what
1367 : * acquire_sample_rows() does.
1368 : */
1369 16650428 : prstate->live_tuples++;
1370 :
1371 : /*
1372 : * Is the tuple definitely visible to all transactions?
1373 : *
1374 : * NB: Like with per-tuple hint bits, we can't set the
1375 : * PD_ALL_VISIBLE flag if the inserter committed asynchronously.
1376 : * See SetHintBits for more info. Check that the tuple is hinted
1377 : * xmin-committed because of that.
1378 : */
1379 16650428 : if (prstate->all_visible)
1380 : {
1381 : TransactionId xmin;
1382 :
1383 11738098 : if (!HeapTupleHeaderXminCommitted(htup))
1384 : {
1385 208 : prstate->all_visible = false;
1386 208 : break;
1387 : }
1388 :
1389 : /*
1390 : * The inserter definitely committed. But is it old enough
1391 : * that everyone sees it as committed? A FrozenTransactionId
1392 : * is seen as committed to everyone. Otherwise, we check if
1393 : * there is a snapshot that considers this xid to still be
1394 : * running, and if so, we don't consider the page all-visible.
1395 : */
1396 11737890 : xmin = HeapTupleHeaderGetXmin(htup);
1397 :
1398 : /*
1399 : * For now always use prstate->cutoffs for this test, because
1400 : * we only update 'all_visible' when freezing is requested. We
1401 : * could use GlobalVisTestIsRemovableXid instead, if a
1402 : * non-freezing caller wanted to set the VM bit.
1403 : */
1404 : Assert(prstate->cutoffs);
1405 11737890 : if (!TransactionIdPrecedes(xmin, prstate->cutoffs->OldestXmin))
1406 : {
1407 4250 : prstate->all_visible = false;
1408 4250 : break;
1409 : }
1410 :
1411 : /* Track newest xmin on page. */
1412 11733640 : if (TransactionIdFollows(xmin, prstate->visibility_cutoff_xid) &&
1413 : TransactionIdIsNormal(xmin))
1414 177070 : prstate->visibility_cutoff_xid = xmin;
1415 : }
1416 16645970 : break;
1417 :
1418 537032 : case HEAPTUPLE_RECENTLY_DEAD:
1419 537032 : prstate->recently_dead_tuples++;
1420 537032 : prstate->all_visible = false;
1421 :
1422 : /*
1423 : * This tuple will soon become DEAD. Update the hint field so
1424 : * that the page is reconsidered for pruning in future.
1425 : */
1426 537032 : heap_prune_record_prunable(prstate,
1427 537032 : HeapTupleHeaderGetUpdateXid(htup));
1428 537032 : break;
1429 :
1430 115546 : case HEAPTUPLE_INSERT_IN_PROGRESS:
1431 :
1432 : /*
1433 : * We do not count these rows as live, because we expect the
1434 : * inserting transaction to update the counters at commit, and we
1435 : * assume that will happen only after we report our results. This
1436 : * assumption is a bit shaky, but it is what acquire_sample_rows()
1437 : * does, so be consistent.
1438 : */
1439 115546 : prstate->all_visible = false;
1440 :
1441 : /*
1442 : * If we wanted to optimize for aborts, we might consider marking
1443 : * the page prunable when we see INSERT_IN_PROGRESS. But we
1444 : * don't. See related decisions about when to mark the page
1445 : * prunable in heapam.c.
1446 : */
1447 115546 : break;
1448 :
1449 4548456 : case HEAPTUPLE_DELETE_IN_PROGRESS:
1450 :
1451 : /*
1452 : * This an expected case during concurrent vacuum. Count such
1453 : * rows as live. As above, we assume the deleting transaction
1454 : * will commit and update the counters after we report.
1455 : */
1456 4548456 : prstate->live_tuples++;
1457 4548456 : prstate->all_visible = false;
1458 :
1459 : /*
1460 : * This tuple may soon become DEAD. Update the hint field so that
1461 : * the page is reconsidered for pruning in future.
1462 : */
1463 4548456 : heap_prune_record_prunable(prstate,
1464 4548456 : HeapTupleHeaderGetUpdateXid(htup));
1465 4548456 : break;
1466 :
1467 0 : default:
1468 :
1469 : /*
1470 : * DEAD tuples should've been passed to heap_prune_record_dead()
1471 : * or heap_prune_record_unused() instead.
1472 : */
1473 0 : elog(ERROR, "unexpected HeapTupleSatisfiesVacuum result %d",
1474 : prstate->htsv[offnum]);
1475 : break;
1476 : }
1477 :
1478 : /* Consider freezing any normal tuples which will not be removed */
1479 21851462 : if (prstate->freeze)
1480 : {
1481 : bool totally_frozen;
1482 :
1483 19062312 : if ((heap_prepare_freeze_tuple(htup,
1484 19062312 : prstate->cutoffs,
1485 : &prstate->pagefrz,
1486 19062312 : &prstate->frozen[prstate->nfrozen],
1487 : &totally_frozen)))
1488 : {
1489 : /* Save prepared freeze plan for later */
1490 3241736 : prstate->frozen[prstate->nfrozen++].offset = offnum;
1491 : }
1492 :
1493 : /*
1494 : * If any tuple isn't either totally frozen already or eligible to
1495 : * become totally frozen (according to its freeze plan), then the page
1496 : * definitely cannot be set all-frozen in the visibility map later on.
1497 : */
1498 19062312 : if (!totally_frozen)
1499 5568894 : prstate->all_frozen = false;
1500 : }
1501 21851462 : }
1502 :
1503 :
1504 : /*
1505 : * Record line pointer that was already LP_DEAD and is left unchanged.
1506 : */
1507 : static void
1508 1925272 : heap_prune_record_unchanged_lp_dead(Page page, PruneState *prstate, OffsetNumber offnum)
1509 : {
1510 : Assert(!prstate->processed[offnum]);
1511 1925272 : prstate->processed[offnum] = true;
1512 :
1513 : /*
1514 : * Deliberately don't set hastup for LP_DEAD items. We make the soft
1515 : * assumption that any LP_DEAD items encountered here will become
1516 : * LP_UNUSED later on, before count_nondeletable_pages is reached. If we
1517 : * don't make this assumption then rel truncation will only happen every
1518 : * other VACUUM, at most. Besides, VACUUM must treat
1519 : * hastup/nonempty_pages as provisional no matter how LP_DEAD items are
1520 : * handled (handled here, or handled later on).
1521 : *
1522 : * Similarly, don't unset all_visible until later, at the end of
1523 : * heap_page_prune_and_freeze(). This will allow us to attempt to freeze
1524 : * the page after pruning. As long as we unset it before updating the
1525 : * visibility map, this will be correct.
1526 : */
1527 :
1528 : /* Record the dead offset for vacuum */
1529 1925272 : prstate->deadoffsets[prstate->lpdead_items++] = offnum;
1530 1925272 : }
1531 :
1532 : /*
1533 : * Record LP_REDIRECT that is left unchanged.
1534 : */
1535 : static void
1536 350500 : heap_prune_record_unchanged_lp_redirect(PruneState *prstate, OffsetNumber offnum)
1537 : {
1538 : /*
1539 : * A redirect line pointer doesn't count as a live tuple.
1540 : *
1541 : * If we leave a redirect line pointer in place, there will be another
1542 : * tuple on the page that it points to. We will do the bookkeeping for
1543 : * that separately. So we have nothing to do here, except remember that
1544 : * we processed this item.
1545 : */
1546 : Assert(!prstate->processed[offnum]);
1547 350500 : prstate->processed[offnum] = true;
1548 350500 : }
1549 :
1550 : /*
1551 : * Perform the actual page changes needed by heap_page_prune_and_freeze().
1552 : *
1553 : * If 'lp_truncate_only' is set, we are merely marking LP_DEAD line pointers
1554 : * as unused, not redirecting or removing anything else. The
1555 : * PageRepairFragmentation() call is skipped in that case.
1556 : *
1557 : * If 'lp_truncate_only' is not set, the caller must hold a cleanup lock on
1558 : * the buffer. If it is set, an ordinary exclusive lock suffices.
1559 : */
1560 : void
1561 109178 : heap_page_prune_execute(Buffer buffer, bool lp_truncate_only,
1562 : OffsetNumber *redirected, int nredirected,
1563 : OffsetNumber *nowdead, int ndead,
1564 : OffsetNumber *nowunused, int nunused)
1565 : {
1566 109178 : Page page = (Page) BufferGetPage(buffer);
1567 : OffsetNumber *offnum;
1568 : HeapTupleHeader htup PG_USED_FOR_ASSERTS_ONLY;
1569 :
1570 : /* Shouldn't be called unless there's something to do */
1571 : Assert(nredirected > 0 || ndead > 0 || nunused > 0);
1572 :
1573 : /* If 'lp_truncate_only', we can only remove already-dead line pointers */
1574 : Assert(!lp_truncate_only || (nredirected == 0 && ndead == 0));
1575 :
1576 : /* Update all redirected line pointers */
1577 109178 : offnum = redirected;
1578 264182 : for (int i = 0; i < nredirected; i++)
1579 : {
1580 155004 : OffsetNumber fromoff = *offnum++;
1581 155004 : OffsetNumber tooff = *offnum++;
1582 155004 : ItemId fromlp = PageGetItemId(page, fromoff);
1583 : ItemId tolp PG_USED_FOR_ASSERTS_ONLY;
1584 :
1585 : #ifdef USE_ASSERT_CHECKING
1586 :
1587 : /*
1588 : * Any existing item that we set as an LP_REDIRECT (any 'from' item)
1589 : * must be the first item from a HOT chain. If the item has tuple
1590 : * storage then it can't be a heap-only tuple. Otherwise we are just
1591 : * maintaining an existing LP_REDIRECT from an existing HOT chain that
1592 : * has been pruned at least once before now.
1593 : */
1594 : if (!ItemIdIsRedirected(fromlp))
1595 : {
1596 : Assert(ItemIdHasStorage(fromlp) && ItemIdIsNormal(fromlp));
1597 :
1598 : htup = (HeapTupleHeader) PageGetItem(page, fromlp);
1599 : Assert(!HeapTupleHeaderIsHeapOnly(htup));
1600 : }
1601 : else
1602 : {
1603 : /* We shouldn't need to redundantly set the redirect */
1604 : Assert(ItemIdGetRedirect(fromlp) != tooff);
1605 : }
1606 :
1607 : /*
1608 : * The item that we're about to set as an LP_REDIRECT (the 'from'
1609 : * item) will point to an existing item (the 'to' item) that is
1610 : * already a heap-only tuple. There can be at most one LP_REDIRECT
1611 : * item per HOT chain.
1612 : *
1613 : * We need to keep around an LP_REDIRECT item (after original
1614 : * non-heap-only root tuple gets pruned away) so that it's always
1615 : * possible for VACUUM to easily figure out what TID to delete from
1616 : * indexes when an entire HOT chain becomes dead. A heap-only tuple
1617 : * can never become LP_DEAD; an LP_REDIRECT item or a regular heap
1618 : * tuple can.
1619 : *
1620 : * This check may miss problems, e.g. the target of a redirect could
1621 : * be marked as unused subsequently. The page_verify_redirects() check
1622 : * below will catch such problems.
1623 : */
1624 : tolp = PageGetItemId(page, tooff);
1625 : Assert(ItemIdHasStorage(tolp) && ItemIdIsNormal(tolp));
1626 : htup = (HeapTupleHeader) PageGetItem(page, tolp);
1627 : Assert(HeapTupleHeaderIsHeapOnly(htup));
1628 : #endif
1629 :
1630 155004 : ItemIdSetRedirect(fromlp, tooff);
1631 : }
1632 :
1633 : /* Update all now-dead line pointers */
1634 109178 : offnum = nowdead;
1635 3165948 : for (int i = 0; i < ndead; i++)
1636 : {
1637 3056770 : OffsetNumber off = *offnum++;
1638 3056770 : ItemId lp = PageGetItemId(page, off);
1639 :
1640 : #ifdef USE_ASSERT_CHECKING
1641 :
1642 : /*
1643 : * An LP_DEAD line pointer must be left behind when the original item
1644 : * (which is dead to everybody) could still be referenced by a TID in
1645 : * an index. This should never be necessary with any individual
1646 : * heap-only tuple item, though. (It's not clear how much of a problem
1647 : * that would be, but there is no reason to allow it.)
1648 : */
1649 : if (ItemIdHasStorage(lp))
1650 : {
1651 : Assert(ItemIdIsNormal(lp));
1652 : htup = (HeapTupleHeader) PageGetItem(page, lp);
1653 : Assert(!HeapTupleHeaderIsHeapOnly(htup));
1654 : }
1655 : else
1656 : {
1657 : /* Whole HOT chain becomes dead */
1658 : Assert(ItemIdIsRedirected(lp));
1659 : }
1660 : #endif
1661 :
1662 3056770 : ItemIdSetDead(lp);
1663 : }
1664 :
1665 : /* Update all now-unused line pointers */
1666 109178 : offnum = nowunused;
1667 553266 : for (int i = 0; i < nunused; i++)
1668 : {
1669 444088 : OffsetNumber off = *offnum++;
1670 444088 : ItemId lp = PageGetItemId(page, off);
1671 :
1672 : #ifdef USE_ASSERT_CHECKING
1673 :
1674 : if (lp_truncate_only)
1675 : {
1676 : /* Setting LP_DEAD to LP_UNUSED in vacuum's second pass */
1677 : Assert(ItemIdIsDead(lp) && !ItemIdHasStorage(lp));
1678 : }
1679 : else
1680 : {
1681 : /*
1682 : * When heap_page_prune_and_freeze() was called, mark_unused_now
1683 : * may have been passed as true, which allows would-be LP_DEAD
1684 : * items to be made LP_UNUSED instead. This is only possible if
1685 : * the relation has no indexes. If there are any dead items, then
1686 : * mark_unused_now was not true and every item being marked
1687 : * LP_UNUSED must refer to a heap-only tuple.
1688 : */
1689 : if (ndead > 0)
1690 : {
1691 : Assert(ItemIdHasStorage(lp) && ItemIdIsNormal(lp));
1692 : htup = (HeapTupleHeader) PageGetItem(page, lp);
1693 : Assert(HeapTupleHeaderIsHeapOnly(htup));
1694 : }
1695 : else
1696 : Assert(ItemIdIsUsed(lp));
1697 : }
1698 :
1699 : #endif
1700 :
1701 444088 : ItemIdSetUnused(lp);
1702 : }
1703 :
1704 109178 : if (lp_truncate_only)
1705 2156 : PageTruncateLinePointerArray(page);
1706 : else
1707 : {
1708 : /*
1709 : * Finally, repair any fragmentation, and update the page's hint bit
1710 : * about whether it has free pointers.
1711 : */
1712 107022 : PageRepairFragmentation(page);
1713 :
1714 : /*
1715 : * Now that the page has been modified, assert that redirect items
1716 : * still point to valid targets.
1717 : */
1718 107022 : page_verify_redirects(page);
1719 : }
1720 109178 : }
1721 :
1722 :
1723 : /*
1724 : * If built with assertions, verify that all LP_REDIRECT items point to a
1725 : * valid item.
1726 : *
1727 : * One way that bugs related to HOT pruning show is redirect items pointing to
1728 : * removed tuples. It's not trivial to reliably check that marking an item
1729 : * unused will not orphan a redirect item during heap_prune_chain() /
1730 : * heap_page_prune_execute(), so we additionally check the whole page after
1731 : * pruning. Without this check such bugs would typically only cause asserts
1732 : * later, potentially well after the corruption has been introduced.
1733 : *
1734 : * Also check comments in heap_page_prune_execute()'s redirection loop.
1735 : */
1736 : static void
1737 107022 : page_verify_redirects(Page page)
1738 : {
1739 : #ifdef USE_ASSERT_CHECKING
1740 : OffsetNumber offnum;
1741 : OffsetNumber maxoff;
1742 :
1743 : maxoff = PageGetMaxOffsetNumber(page);
1744 : for (offnum = FirstOffsetNumber;
1745 : offnum <= maxoff;
1746 : offnum = OffsetNumberNext(offnum))
1747 : {
1748 : ItemId itemid = PageGetItemId(page, offnum);
1749 : OffsetNumber targoff;
1750 : ItemId targitem;
1751 : HeapTupleHeader htup;
1752 :
1753 : if (!ItemIdIsRedirected(itemid))
1754 : continue;
1755 :
1756 : targoff = ItemIdGetRedirect(itemid);
1757 : targitem = PageGetItemId(page, targoff);
1758 :
1759 : Assert(ItemIdIsUsed(targitem));
1760 : Assert(ItemIdIsNormal(targitem));
1761 : Assert(ItemIdHasStorage(targitem));
1762 : htup = (HeapTupleHeader) PageGetItem(page, targitem);
1763 : Assert(HeapTupleHeaderIsHeapOnly(htup));
1764 : }
1765 : #endif
1766 107022 : }
1767 :
1768 :
1769 : /*
1770 : * For all items in this page, find their respective root line pointers.
1771 : * If item k is part of a HOT-chain with root at item j, then we set
1772 : * root_offsets[k - 1] = j.
1773 : *
1774 : * The passed-in root_offsets array must have MaxHeapTuplesPerPage entries.
1775 : * Unused entries are filled with InvalidOffsetNumber (zero).
1776 : *
1777 : * The function must be called with at least share lock on the buffer, to
1778 : * prevent concurrent prune operations.
1779 : *
1780 : * Note: The information collected here is valid only as long as the caller
1781 : * holds a pin on the buffer. Once pin is released, a tuple might be pruned
1782 : * and reused by a completely unrelated tuple.
1783 : */
1784 : void
1785 207870 : heap_get_root_tuples(Page page, OffsetNumber *root_offsets)
1786 : {
1787 : OffsetNumber offnum,
1788 : maxoff;
1789 :
1790 207870 : MemSet(root_offsets, InvalidOffsetNumber,
1791 : MaxHeapTuplesPerPage * sizeof(OffsetNumber));
1792 :
1793 207870 : maxoff = PageGetMaxOffsetNumber(page);
1794 17166114 : for (offnum = FirstOffsetNumber; offnum <= maxoff; offnum = OffsetNumberNext(offnum))
1795 : {
1796 16958244 : ItemId lp = PageGetItemId(page, offnum);
1797 : HeapTupleHeader htup;
1798 : OffsetNumber nextoffnum;
1799 : TransactionId priorXmax;
1800 :
1801 : /* skip unused and dead items */
1802 16958244 : if (!ItemIdIsUsed(lp) || ItemIdIsDead(lp))
1803 22204 : continue;
1804 :
1805 16936040 : if (ItemIdIsNormal(lp))
1806 : {
1807 16927918 : htup = (HeapTupleHeader) PageGetItem(page, lp);
1808 :
1809 : /*
1810 : * Check if this tuple is part of a HOT-chain rooted at some other
1811 : * tuple. If so, skip it for now; we'll process it when we find
1812 : * its root.
1813 : */
1814 16927918 : if (HeapTupleHeaderIsHeapOnly(htup))
1815 8860 : continue;
1816 :
1817 : /*
1818 : * This is either a plain tuple or the root of a HOT-chain.
1819 : * Remember it in the mapping.
1820 : */
1821 16919058 : root_offsets[offnum - 1] = offnum;
1822 :
1823 : /* If it's not the start of a HOT-chain, we're done with it */
1824 16919058 : if (!HeapTupleHeaderIsHotUpdated(htup))
1825 16918544 : continue;
1826 :
1827 : /* Set up to scan the HOT-chain */
1828 514 : nextoffnum = ItemPointerGetOffsetNumber(&htup->t_ctid);
1829 514 : priorXmax = HeapTupleHeaderGetUpdateXid(htup);
1830 : }
1831 : else
1832 : {
1833 : /* Must be a redirect item. We do not set its root_offsets entry */
1834 : Assert(ItemIdIsRedirected(lp));
1835 : /* Set up to scan the HOT-chain */
1836 8122 : nextoffnum = ItemIdGetRedirect(lp);
1837 8122 : priorXmax = InvalidTransactionId;
1838 : }
1839 :
1840 : /*
1841 : * Now follow the HOT-chain and collect other tuples in the chain.
1842 : *
1843 : * Note: Even though this is a nested loop, the complexity of the
1844 : * function is O(N) because a tuple in the page should be visited not
1845 : * more than twice, once in the outer loop and once in HOT-chain
1846 : * chases.
1847 : */
1848 : for (;;)
1849 : {
1850 : /* Sanity check (pure paranoia) */
1851 8860 : if (offnum < FirstOffsetNumber)
1852 0 : break;
1853 :
1854 : /*
1855 : * An offset past the end of page's line pointer array is possible
1856 : * when the array was truncated
1857 : */
1858 8860 : if (offnum > maxoff)
1859 0 : break;
1860 :
1861 8860 : lp = PageGetItemId(page, nextoffnum);
1862 :
1863 : /* Check for broken chains */
1864 8860 : if (!ItemIdIsNormal(lp))
1865 0 : break;
1866 :
1867 8860 : htup = (HeapTupleHeader) PageGetItem(page, lp);
1868 :
1869 9598 : if (TransactionIdIsValid(priorXmax) &&
1870 738 : !TransactionIdEquals(priorXmax, HeapTupleHeaderGetXmin(htup)))
1871 0 : break;
1872 :
1873 : /* Remember the root line pointer for this item */
1874 8860 : root_offsets[nextoffnum - 1] = offnum;
1875 :
1876 : /* Advance to next chain member, if any */
1877 8860 : if (!HeapTupleHeaderIsHotUpdated(htup))
1878 : break;
1879 :
1880 : /* HOT implies it can't have moved to different partition */
1881 : Assert(!HeapTupleHeaderIndicatesMovedPartitions(htup));
1882 :
1883 224 : nextoffnum = ItemPointerGetOffsetNumber(&htup->t_ctid);
1884 224 : priorXmax = HeapTupleHeaderGetUpdateXid(htup);
1885 : }
1886 : }
1887 207870 : }
1888 :
1889 :
1890 : /*
1891 : * Compare fields that describe actions required to freeze tuple with caller's
1892 : * open plan. If everything matches then the frz tuple plan is equivalent to
1893 : * caller's plan.
1894 : */
1895 : static inline bool
1896 1313934 : heap_log_freeze_eq(xlhp_freeze_plan *plan, HeapTupleFreeze *frz)
1897 : {
1898 1313934 : if (plan->xmax == frz->xmax &&
1899 1311346 : plan->t_infomask2 == frz->t_infomask2 &&
1900 1310126 : plan->t_infomask == frz->t_infomask &&
1901 1306006 : plan->frzflags == frz->frzflags)
1902 1306006 : return true;
1903 :
1904 : /* Caller must call heap_log_freeze_new_plan again for frz */
1905 7928 : return false;
1906 : }
1907 :
1908 : /*
1909 : * Comparator used to deduplicate XLOG_HEAP2_FREEZE_PAGE freeze plans
1910 : */
1911 : static int
1912 1979686 : heap_log_freeze_cmp(const void *arg1, const void *arg2)
1913 : {
1914 1979686 : HeapTupleFreeze *frz1 = (HeapTupleFreeze *) arg1;
1915 1979686 : HeapTupleFreeze *frz2 = (HeapTupleFreeze *) arg2;
1916 :
1917 1979686 : if (frz1->xmax < frz2->xmax)
1918 26354 : return -1;
1919 1953332 : else if (frz1->xmax > frz2->xmax)
1920 28726 : return 1;
1921 :
1922 1924606 : if (frz1->t_infomask2 < frz2->t_infomask2)
1923 6080 : return -1;
1924 1918526 : else if (frz1->t_infomask2 > frz2->t_infomask2)
1925 6986 : return 1;
1926 :
1927 1911540 : if (frz1->t_infomask < frz2->t_infomask)
1928 18046 : return -1;
1929 1893494 : else if (frz1->t_infomask > frz2->t_infomask)
1930 22246 : return 1;
1931 :
1932 1871248 : if (frz1->frzflags < frz2->frzflags)
1933 0 : return -1;
1934 1871248 : else if (frz1->frzflags > frz2->frzflags)
1935 0 : return 1;
1936 :
1937 : /*
1938 : * heap_log_freeze_eq would consider these tuple-wise plans to be equal.
1939 : * (So the tuples will share a single canonical freeze plan.)
1940 : *
1941 : * We tiebreak on page offset number to keep each freeze plan's page
1942 : * offset number array individually sorted. (Unnecessary, but be tidy.)
1943 : */
1944 1871248 : if (frz1->offset < frz2->offset)
1945 1508956 : return -1;
1946 362292 : else if (frz1->offset > frz2->offset)
1947 362292 : return 1;
1948 :
1949 : Assert(false);
1950 0 : return 0;
1951 : }
1952 :
1953 : /*
1954 : * Start new plan initialized using tuple-level actions. At least one tuple
1955 : * will have steps required to freeze described by caller's plan during REDO.
1956 : */
1957 : static inline void
1958 40242 : heap_log_freeze_new_plan(xlhp_freeze_plan *plan, HeapTupleFreeze *frz)
1959 : {
1960 40242 : plan->xmax = frz->xmax;
1961 40242 : plan->t_infomask2 = frz->t_infomask2;
1962 40242 : plan->t_infomask = frz->t_infomask;
1963 40242 : plan->frzflags = frz->frzflags;
1964 40242 : plan->ntuples = 1; /* for now */
1965 40242 : }
1966 :
1967 : /*
1968 : * Deduplicate tuple-based freeze plans so that each distinct set of
1969 : * processing steps is only stored once in XLOG_HEAP2_FREEZE_PAGE records.
1970 : * Called during original execution of freezing (for logged relations).
1971 : *
1972 : * Return value is number of plans set in *plans_out for caller. Also writes
1973 : * an array of offset numbers into *offsets_out output argument for caller
1974 : * (actually there is one array per freeze plan, but that's not of immediate
1975 : * concern to our caller).
1976 : */
1977 : static int
1978 32314 : heap_log_freeze_plan(HeapTupleFreeze *tuples, int ntuples,
1979 : xlhp_freeze_plan *plans_out,
1980 : OffsetNumber *offsets_out)
1981 : {
1982 32314 : int nplans = 0;
1983 :
1984 : /* Sort tuple-based freeze plans in the order required to deduplicate */
1985 32314 : qsort(tuples, ntuples, sizeof(HeapTupleFreeze), heap_log_freeze_cmp);
1986 :
1987 1378562 : for (int i = 0; i < ntuples; i++)
1988 : {
1989 1346248 : HeapTupleFreeze *frz = tuples + i;
1990 :
1991 1346248 : if (i == 0)
1992 : {
1993 : /* New canonical freeze plan starting with first tup */
1994 32314 : heap_log_freeze_new_plan(plans_out, frz);
1995 32314 : nplans++;
1996 : }
1997 1313934 : else if (heap_log_freeze_eq(plans_out, frz))
1998 : {
1999 : /* tup matches open canonical plan -- include tup in it */
2000 : Assert(offsets_out[i - 1] < frz->offset);
2001 1306006 : plans_out->ntuples++;
2002 : }
2003 : else
2004 : {
2005 : /* Tup doesn't match current plan -- done with it now */
2006 7928 : plans_out++;
2007 :
2008 : /* New canonical freeze plan starting with this tup */
2009 7928 : heap_log_freeze_new_plan(plans_out, frz);
2010 7928 : nplans++;
2011 : }
2012 :
2013 : /*
2014 : * Save page offset number in dedicated buffer in passing.
2015 : *
2016 : * REDO routine relies on the record's offset numbers array grouping
2017 : * offset numbers by freeze plan. The sort order within each grouping
2018 : * is ascending offset number order, just to keep things tidy.
2019 : */
2020 1346248 : offsets_out[i] = frz->offset;
2021 : }
2022 :
2023 : Assert(nplans > 0 && nplans <= ntuples);
2024 :
2025 32314 : return nplans;
2026 : }
2027 :
2028 : /*
2029 : * Write an XLOG_HEAP2_PRUNE_FREEZE WAL record
2030 : *
2031 : * This is used for several different page maintenance operations:
2032 : *
2033 : * - Page pruning, in VACUUM's 1st pass or on access: Some items are
2034 : * redirected, some marked dead, and some removed altogether.
2035 : *
2036 : * - Freezing: Items are marked as 'frozen'.
2037 : *
2038 : * - Vacuum, 2nd pass: Items that are already LP_DEAD are marked as unused.
2039 : *
2040 : * They have enough commonalities that we use a single WAL record for them
2041 : * all.
2042 : *
2043 : * If replaying the record requires a cleanup lock, pass cleanup_lock = true.
2044 : * Replaying 'redirected' or 'dead' items always requires a cleanup lock, but
2045 : * replaying 'unused' items depends on whether they were all previously marked
2046 : * as dead.
2047 : *
2048 : * Note: This function scribbles on the 'frozen' array.
2049 : *
2050 : * Note: This is called in a critical section, so careful what you do here.
2051 : */
2052 : void
2053 144048 : log_heap_prune_and_freeze(Relation relation, Buffer buffer,
2054 : TransactionId conflict_xid,
2055 : bool cleanup_lock,
2056 : PruneReason reason,
2057 : HeapTupleFreeze *frozen, int nfrozen,
2058 : OffsetNumber *redirected, int nredirected,
2059 : OffsetNumber *dead, int ndead,
2060 : OffsetNumber *unused, int nunused)
2061 : {
2062 : xl_heap_prune xlrec;
2063 : XLogRecPtr recptr;
2064 : uint8 info;
2065 :
2066 : /* The following local variables hold data registered in the WAL record: */
2067 : xlhp_freeze_plan plans[MaxHeapTuplesPerPage];
2068 : xlhp_freeze_plans freeze_plans;
2069 : xlhp_prune_items redirect_items;
2070 : xlhp_prune_items dead_items;
2071 : xlhp_prune_items unused_items;
2072 : OffsetNumber frz_offsets[MaxHeapTuplesPerPage];
2073 :
2074 144048 : xlrec.flags = 0;
2075 :
2076 : /*
2077 : * Prepare data for the buffer. The arrays are not actually in the
2078 : * buffer, but we pretend that they are. When XLogInsert stores a full
2079 : * page image, the arrays can be omitted.
2080 : */
2081 144048 : XLogBeginInsert();
2082 144048 : XLogRegisterBuffer(0, buffer, REGBUF_STANDARD);
2083 144048 : if (nfrozen > 0)
2084 : {
2085 : int nplans;
2086 :
2087 32314 : xlrec.flags |= XLHP_HAS_FREEZE_PLANS;
2088 :
2089 : /*
2090 : * Prepare deduplicated representation for use in the WAL record. This
2091 : * destructively sorts frozen tuples array in-place.
2092 : */
2093 32314 : nplans = heap_log_freeze_plan(frozen, nfrozen, plans, frz_offsets);
2094 :
2095 32314 : freeze_plans.nplans = nplans;
2096 32314 : XLogRegisterBufData(0, (char *) &freeze_plans,
2097 : offsetof(xlhp_freeze_plans, plans));
2098 32314 : XLogRegisterBufData(0, (char *) plans,
2099 : sizeof(xlhp_freeze_plan) * nplans);
2100 : }
2101 144048 : if (nredirected > 0)
2102 : {
2103 29030 : xlrec.flags |= XLHP_HAS_REDIRECTIONS;
2104 :
2105 29030 : redirect_items.ntargets = nredirected;
2106 29030 : XLogRegisterBufData(0, (char *) &redirect_items,
2107 : offsetof(xlhp_prune_items, data));
2108 29030 : XLogRegisterBufData(0, (char *) redirected,
2109 : sizeof(OffsetNumber[2]) * nredirected);
2110 : }
2111 144048 : if (ndead > 0)
2112 : {
2113 70068 : xlrec.flags |= XLHP_HAS_DEAD_ITEMS;
2114 :
2115 70068 : dead_items.ntargets = ndead;
2116 70068 : XLogRegisterBufData(0, (char *) &dead_items,
2117 : offsetof(xlhp_prune_items, data));
2118 70068 : XLogRegisterBufData(0, (char *) dead,
2119 : sizeof(OffsetNumber) * ndead);
2120 : }
2121 144048 : if (nunused > 0)
2122 : {
2123 39820 : xlrec.flags |= XLHP_HAS_NOW_UNUSED_ITEMS;
2124 :
2125 39820 : unused_items.ntargets = nunused;
2126 39820 : XLogRegisterBufData(0, (char *) &unused_items,
2127 : offsetof(xlhp_prune_items, data));
2128 39820 : XLogRegisterBufData(0, (char *) unused,
2129 : sizeof(OffsetNumber) * nunused);
2130 : }
2131 144048 : if (nfrozen > 0)
2132 32314 : XLogRegisterBufData(0, (char *) frz_offsets,
2133 : sizeof(OffsetNumber) * nfrozen);
2134 :
2135 : /*
2136 : * Prepare the main xl_heap_prune record. We already set the XLPH_HAS_*
2137 : * flag above.
2138 : */
2139 144048 : if (RelationIsAccessibleInLogicalDecoding(relation))
2140 1190 : xlrec.flags |= XLHP_IS_CATALOG_REL;
2141 144048 : if (TransactionIdIsValid(conflict_xid))
2142 114694 : xlrec.flags |= XLHP_HAS_CONFLICT_HORIZON;
2143 144048 : if (cleanup_lock)
2144 123502 : xlrec.flags |= XLHP_CLEANUP_LOCK;
2145 : else
2146 : {
2147 : Assert(nredirected == 0 && ndead == 0);
2148 : /* also, any items in 'unused' must've been LP_DEAD previously */
2149 : }
2150 144048 : XLogRegisterData((char *) &xlrec, SizeOfHeapPrune);
2151 144048 : if (TransactionIdIsValid(conflict_xid))
2152 114694 : XLogRegisterData((char *) &conflict_xid, sizeof(TransactionId));
2153 :
2154 144048 : switch (reason)
2155 : {
2156 76216 : case PRUNE_ON_ACCESS:
2157 76216 : info = XLOG_HEAP2_PRUNE_ON_ACCESS;
2158 76216 : break;
2159 47286 : case PRUNE_VACUUM_SCAN:
2160 47286 : info = XLOG_HEAP2_PRUNE_VACUUM_SCAN;
2161 47286 : break;
2162 20546 : case PRUNE_VACUUM_CLEANUP:
2163 20546 : info = XLOG_HEAP2_PRUNE_VACUUM_CLEANUP;
2164 20546 : break;
2165 0 : default:
2166 0 : elog(ERROR, "unrecognized prune reason: %d", (int) reason);
2167 : break;
2168 : }
2169 144048 : recptr = XLogInsert(RM_HEAP2_ID, info);
2170 :
2171 144048 : PageSetLSN(BufferGetPage(buffer), recptr);
2172 144048 : }
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