1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
/*-------------------------------------------------------------------------
*
* nbtree.c
* Implementation of Lehman and Yao's btree management algorithm for
* Postgres.
*
* NOTES
* This file contains only the public interface routines.
*
*
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.123 2004/12/01 19:00:37 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/genam.h"
#include "access/heapam.h"
#include "access/nbtree.h"
#include "catalog/index.h"
#include "commands/vacuum.h"
#include "miscadmin.h"
#include "storage/freespace.h"
#include "storage/smgr.h"
/* Working state for btbuild and its callback */
typedef struct
{
bool usefast;
bool isUnique;
bool haveDead;
Relation heapRel;
BTSpool *spool;
/*
* spool2 is needed only when the index is an unique index. Dead
* tuples are put into spool2 instead of spool in order to avoid
* uniqueness check.
*/
BTSpool *spool2;
double indtuples;
} BTBuildState;
bool FastBuild = true; /* use SORT instead of insertion build */
static void _bt_restscan(IndexScanDesc scan);
static void btbuildCallback(Relation index,
HeapTuple htup,
Datum *attdata,
char *nulls,
bool tupleIsAlive,
void *state);
/*
* btbuild() -- build a new btree index.
*/
Datum
btbuild(PG_FUNCTION_ARGS)
{
Relation heap = (Relation) PG_GETARG_POINTER(0);
Relation index = (Relation) PG_GETARG_POINTER(1);
IndexInfo *indexInfo = (IndexInfo *) PG_GETARG_POINTER(2);
double reltuples;
BTBuildState buildstate;
/*
* bootstrap processing does something strange, so don't use
* sort/build for initial catalog indices. at some point i need to
* look harder at this. (there is some kind of incremental processing
* going on there.) -- pma 08/29/95
*/
buildstate.usefast = (FastBuild && IsNormalProcessingMode());
buildstate.isUnique = indexInfo->ii_Unique;
buildstate.haveDead = false;
buildstate.heapRel = heap;
buildstate.spool = NULL;
buildstate.spool2 = NULL;
buildstate.indtuples = 0;
#ifdef BTREE_BUILD_STATS
if (log_btree_build_stats)
ResetUsage();
#endif /* BTREE_BUILD_STATS */
/*
* We expect to be called exactly once for any index relation. If
* that's not the case, big trouble's what we have.
*/
if (RelationGetNumberOfBlocks(index) != 0)
elog(ERROR, "index \"%s\" already contains data",
RelationGetRelationName(index));
if (buildstate.usefast)
{
buildstate.spool = _bt_spoolinit(index, indexInfo->ii_Unique, false);
/*
* If building a unique index, put dead tuples in a second spool
* to keep them out of the uniqueness check.
*/
if (indexInfo->ii_Unique)
buildstate.spool2 = _bt_spoolinit(index, false, true);
}
else
{
/* if using slow build, initialize the btree index metadata page */
_bt_metapinit(index);
}
/* do the heap scan */
reltuples = IndexBuildHeapScan(heap, index, indexInfo,
btbuildCallback, (void *) &buildstate);
/* okay, all heap tuples are indexed */
if (buildstate.spool2 && !buildstate.haveDead)
{
/* spool2 turns out to be unnecessary */
_bt_spooldestroy(buildstate.spool2);
buildstate.spool2 = NULL;
}
/*
* if we are doing bottom-up btree build, finish the build by (1)
* completing the sort of the spool file, (2) inserting the sorted
* tuples into btree pages and (3) building the upper levels.
*/
if (buildstate.usefast)
{
_bt_leafbuild(buildstate.spool, buildstate.spool2);
_bt_spooldestroy(buildstate.spool);
if (buildstate.spool2)
_bt_spooldestroy(buildstate.spool2);
}
#ifdef BTREE_BUILD_STATS
if (log_btree_build_stats)
{
ShowUsage("BTREE BUILD STATS");
ResetUsage();
}
#endif /* BTREE_BUILD_STATS */
/*
* Since we just counted the tuples in the heap, we update its stats
* in pg_class to guarantee that the planner takes advantage of the
* index we just created. But, only update statistics during normal
* index definitions, not for indices on system catalogs created
* during bootstrap processing. We must close the relations before
* updating statistics to guarantee that the relcache entries are
* flushed when we increment the command counter in UpdateStats(). But
* we do not release any locks on the relations; those will be held
* until end of transaction.
*/
if (IsNormalProcessingMode())
{
Oid hrelid = RelationGetRelid(heap);
Oid irelid = RelationGetRelid(index);
heap_close(heap, NoLock);
index_close(index);
UpdateStats(hrelid, reltuples);
UpdateStats(irelid, buildstate.indtuples);
}
PG_RETURN_VOID();
}
/*
* Per-tuple callback from IndexBuildHeapScan
*/
static void
btbuildCallback(Relation index,
HeapTuple htup,
Datum *attdata,
char *nulls,
bool tupleIsAlive,
void *state)
{
BTBuildState *buildstate = (BTBuildState *) state;
IndexTuple itup;
BTItem btitem;
InsertIndexResult res;
/* form an index tuple and point it at the heap tuple */
itup = index_formtuple(RelationGetDescr(index), attdata, nulls);
itup->t_tid = htup->t_self;
btitem = _bt_formitem(itup);
/*
* if we are doing bottom-up btree build, we insert the index into a
* spool file for subsequent processing. otherwise, we insert into
* the btree.
*/
if (buildstate->usefast)
{
if (tupleIsAlive || buildstate->spool2 == NULL)
_bt_spool(btitem, buildstate->spool);
else
{
/* dead tuples are put into spool2 */
buildstate->haveDead = true;
_bt_spool(btitem, buildstate->spool2);
}
}
else
{
res = _bt_doinsert(index, btitem,
buildstate->isUnique, buildstate->heapRel);
if (res)
pfree(res);
}
buildstate->indtuples += 1;
pfree(btitem);
pfree(itup);
}
/*
* btinsert() -- insert an index tuple into a btree.
*
* Descend the tree recursively, find the appropriate location for our
* new tuple, put it there, set its unique OID as appropriate, and
* return an InsertIndexResult to the caller.
*/
Datum
btinsert(PG_FUNCTION_ARGS)
{
Relation rel = (Relation) PG_GETARG_POINTER(0);
Datum *datum = (Datum *) PG_GETARG_POINTER(1);
char *nulls = (char *) PG_GETARG_POINTER(2);
ItemPointer ht_ctid = (ItemPointer) PG_GETARG_POINTER(3);
Relation heapRel = (Relation) PG_GETARG_POINTER(4);
bool checkUnique = PG_GETARG_BOOL(5);
InsertIndexResult res;
BTItem btitem;
IndexTuple itup;
/* generate an index tuple */
itup = index_formtuple(RelationGetDescr(rel), datum, nulls);
itup->t_tid = *ht_ctid;
btitem = _bt_formitem(itup);
res = _bt_doinsert(rel, btitem, checkUnique, heapRel);
pfree(btitem);
pfree(itup);
PG_RETURN_POINTER(res);
}
/*
* btgettuple() -- Get the next tuple in the scan.
*/
Datum
btgettuple(PG_FUNCTION_ARGS)
{
IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
ScanDirection dir = (ScanDirection) PG_GETARG_INT32(1);
BTScanOpaque so = (BTScanOpaque) scan->opaque;
Page page;
OffsetNumber offnum;
bool res;
/*
* If we've already initialized this scan, we can just advance it in
* the appropriate direction. If we haven't done so yet, we call a
* routine to get the first item in the scan.
*/
if (ItemPointerIsValid(&(scan->currentItemData)))
{
/*
* Restore scan position using heap TID returned by previous call
* to btgettuple(). _bt_restscan() re-grabs the read lock on the
* buffer, too.
*/
_bt_restscan(scan);
/*
* Check to see if we should kill the previously-fetched tuple.
*/
if (scan->kill_prior_tuple)
{
/*
* Yes, so mark it by setting the LP_DELETE bit in the item
* flags.
*/
offnum = ItemPointerGetOffsetNumber(&(scan->currentItemData));
page = BufferGetPage(so->btso_curbuf);
PageGetItemId(page, offnum)->lp_flags |= LP_DELETE;
/*
* Since this can be redone later if needed, it's treated the
* same as a commit-hint-bit status update for heap tuples: we
* mark the buffer dirty but don't make a WAL log entry.
*/
SetBufferCommitInfoNeedsSave(so->btso_curbuf);
}
/*
* Now continue the scan.
*/
res = _bt_next(scan, dir);
}
else
res = _bt_first(scan, dir);
/*
* Skip killed tuples if asked to.
*/
if (scan->ignore_killed_tuples)
{
while (res)
{
offnum = ItemPointerGetOffsetNumber(&(scan->currentItemData));
page = BufferGetPage(so->btso_curbuf);
if (!ItemIdDeleted(PageGetItemId(page, offnum)))
break;
res = _bt_next(scan, dir);
}
}
/*
* Save heap TID to use it in _bt_restscan. Then release the read
* lock on the buffer so that we aren't blocking other backends.
*
* NOTE: we do keep the pin on the buffer! This is essential to ensure
* that someone else doesn't delete the index entry we are stopped on.
*/
if (res)
{
((BTScanOpaque) scan->opaque)->curHeapIptr = scan->xs_ctup.t_self;
LockBuffer(((BTScanOpaque) scan->opaque)->btso_curbuf,
BUFFER_LOCK_UNLOCK);
}
PG_RETURN_BOOL(res);
}
/*
* btbeginscan() -- start a scan on a btree index
*/
Datum
btbeginscan(PG_FUNCTION_ARGS)
{
Relation rel = (Relation) PG_GETARG_POINTER(0);
int keysz = PG_GETARG_INT32(1);
ScanKey scankey = (ScanKey) PG_GETARG_POINTER(2);
IndexScanDesc scan;
/* get the scan */
scan = RelationGetIndexScan(rel, keysz, scankey);
PG_RETURN_POINTER(scan);
}
/*
* btrescan() -- rescan an index relation
*/
Datum
btrescan(PG_FUNCTION_ARGS)
{
IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
ScanKey scankey = (ScanKey) PG_GETARG_POINTER(1);
ItemPointer iptr;
BTScanOpaque so;
so = (BTScanOpaque) scan->opaque;
if (so == NULL) /* if called from btbeginscan */
{
so = (BTScanOpaque) palloc(sizeof(BTScanOpaqueData));
so->btso_curbuf = so->btso_mrkbuf = InvalidBuffer;
ItemPointerSetInvalid(&(so->curHeapIptr));
ItemPointerSetInvalid(&(so->mrkHeapIptr));
if (scan->numberOfKeys > 0)
so->keyData = (ScanKey) palloc(scan->numberOfKeys * sizeof(ScanKeyData));
else
so->keyData = NULL;
scan->opaque = so;
}
/* we aren't holding any read locks, but gotta drop the pins */
if (ItemPointerIsValid(iptr = &(scan->currentItemData)))
{
ReleaseBuffer(so->btso_curbuf);
so->btso_curbuf = InvalidBuffer;
ItemPointerSetInvalid(&(so->curHeapIptr));
ItemPointerSetInvalid(iptr);
}
if (ItemPointerIsValid(iptr = &(scan->currentMarkData)))
{
ReleaseBuffer(so->btso_mrkbuf);
so->btso_mrkbuf = InvalidBuffer;
ItemPointerSetInvalid(&(so->mrkHeapIptr));
ItemPointerSetInvalid(iptr);
}
/*
* Reset the scan keys. Note that keys ordering stuff moved to
* _bt_first. - vadim 05/05/97
*/
if (scankey && scan->numberOfKeys > 0)
memmove(scan->keyData,
scankey,
scan->numberOfKeys * sizeof(ScanKeyData));
so->numberOfKeys = 0; /* until _bt_preprocess_keys sets it */
PG_RETURN_VOID();
}
/*
* btendscan() -- close down a scan
*/
Datum
btendscan(PG_FUNCTION_ARGS)
{
IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
ItemPointer iptr;
BTScanOpaque so;
so = (BTScanOpaque) scan->opaque;
/* we aren't holding any read locks, but gotta drop the pins */
if (ItemPointerIsValid(iptr = &(scan->currentItemData)))
{
if (BufferIsValid(so->btso_curbuf))
ReleaseBuffer(so->btso_curbuf);
so->btso_curbuf = InvalidBuffer;
ItemPointerSetInvalid(iptr);
}
if (ItemPointerIsValid(iptr = &(scan->currentMarkData)))
{
if (BufferIsValid(so->btso_mrkbuf))
ReleaseBuffer(so->btso_mrkbuf);
so->btso_mrkbuf = InvalidBuffer;
ItemPointerSetInvalid(iptr);
}
if (so->keyData != NULL)
pfree(so->keyData);
pfree(so);
PG_RETURN_VOID();
}
/*
* btmarkpos() -- save current scan position
*/
Datum
btmarkpos(PG_FUNCTION_ARGS)
{
IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
ItemPointer iptr;
BTScanOpaque so;
so = (BTScanOpaque) scan->opaque;
/* we aren't holding any read locks, but gotta drop the pin */
if (ItemPointerIsValid(iptr = &(scan->currentMarkData)))
{
ReleaseBuffer(so->btso_mrkbuf);
so->btso_mrkbuf = InvalidBuffer;
ItemPointerSetInvalid(iptr);
}
/* bump pin on current buffer for assignment to mark buffer */
if (ItemPointerIsValid(&(scan->currentItemData)))
{
IncrBufferRefCount(so->btso_curbuf);
so->btso_mrkbuf = so->btso_curbuf;
scan->currentMarkData = scan->currentItemData;
so->mrkHeapIptr = so->curHeapIptr;
}
PG_RETURN_VOID();
}
/*
* btrestrpos() -- restore scan to last saved position
*/
Datum
btrestrpos(PG_FUNCTION_ARGS)
{
IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
ItemPointer iptr;
BTScanOpaque so;
so = (BTScanOpaque) scan->opaque;
/* we aren't holding any read locks, but gotta drop the pin */
if (ItemPointerIsValid(iptr = &(scan->currentItemData)))
{
ReleaseBuffer(so->btso_curbuf);
so->btso_curbuf = InvalidBuffer;
ItemPointerSetInvalid(iptr);
}
/* bump pin on marked buffer */
if (ItemPointerIsValid(&(scan->currentMarkData)))
{
IncrBufferRefCount(so->btso_mrkbuf);
so->btso_curbuf = so->btso_mrkbuf;
scan->currentItemData = scan->currentMarkData;
so->curHeapIptr = so->mrkHeapIptr;
}
PG_RETURN_VOID();
}
/*
* Bulk deletion of all index entries pointing to a set of heap tuples.
* The set of target tuples is specified via a callback routine that tells
* whether any given heap tuple (identified by ItemPointer) is being deleted.
*
* Result: a palloc'd struct containing statistical info for VACUUM displays.
*/
Datum
btbulkdelete(PG_FUNCTION_ARGS)
{
Relation rel = (Relation) PG_GETARG_POINTER(0);
IndexBulkDeleteCallback callback = (IndexBulkDeleteCallback) PG_GETARG_POINTER(1);
void *callback_state = (void *) PG_GETARG_POINTER(2);
IndexBulkDeleteResult *result;
double tuples_removed;
double num_index_tuples;
OffsetNumber deletable[BLCKSZ / sizeof(OffsetNumber)];
int ndeletable;
Buffer buf;
BlockNumber num_pages;
tuples_removed = 0;
num_index_tuples = 0;
/*
* The outer loop iterates over index leaf pages, the inner over items
* on a leaf page. We issue just one _bt_delitems() call per page, so
* as to minimize WAL traffic.
*
* Note that we exclusive-lock every leaf page containing data items, in
* sequence left to right. It sounds attractive to only
* exclusive-lock those containing items we need to delete, but
* unfortunately that is not safe: we could then pass a stopped
* indexscan, which could in rare cases lead to deleting the item it
* needs to find when it resumes. (See _bt_restscan --- this could
* only happen if an indexscan stops on a deletable item and then a
* page split moves that item into a page further to its right, which
* the indexscan will have no pin on.) We can skip obtaining
* exclusive lock on empty pages though, since no indexscan could be
* stopped on those.
*/
buf = _bt_get_endpoint(rel, 0, false);
if (BufferIsValid(buf)) /* check for empty index */
{
for (;;)
{
Page page;
BTPageOpaque opaque;
OffsetNumber offnum,
minoff,
maxoff;
BlockNumber nextpage;
vacuum_delay_point();
ndeletable = 0;
page = BufferGetPage(buf);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
minoff = P_FIRSTDATAKEY(opaque);
maxoff = PageGetMaxOffsetNumber(page);
/* We probably cannot see deleted pages, but skip 'em if so */
if (minoff <= maxoff && !P_ISDELETED(opaque))
{
/*
* Trade in the initial read lock for a super-exclusive
* write lock on this page.
*/
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
LockBufferForCleanup(buf);
/*
* Recompute minoff/maxoff, both of which could have
* changed while we weren't holding the lock.
*/
minoff = P_FIRSTDATAKEY(opaque);
maxoff = PageGetMaxOffsetNumber(page);
/*
* Scan over all items to see which ones need deleted
* according to the callback function.
*/
for (offnum = minoff;
offnum <= maxoff;
offnum = OffsetNumberNext(offnum))
{
BTItem btitem;
ItemPointer htup;
btitem = (BTItem) PageGetItem(page,
PageGetItemId(page, offnum));
htup = &(btitem->bti_itup.t_tid);
if (callback(htup, callback_state))
{
deletable[ndeletable++] = offnum;
tuples_removed += 1;
}
else
num_index_tuples += 1;
}
}
/*
* If we need to delete anything, do it and write the buffer;
* else just release the buffer.
*/
nextpage = opaque->btpo_next;
if (ndeletable > 0)
{
_bt_delitems(rel, buf, deletable, ndeletable);
_bt_wrtbuf(rel, buf);
}
else
_bt_relbuf(rel, buf);
/* And advance to next page, if any */
if (nextpage == P_NONE)
break;
buf = _bt_getbuf(rel, nextpage, BT_READ);
}
}
/* return statistics */
num_pages = RelationGetNumberOfBlocks(rel);
result = (IndexBulkDeleteResult *) palloc0(sizeof(IndexBulkDeleteResult));
result->num_pages = num_pages;
result->num_index_tuples = num_index_tuples;
result->tuples_removed = tuples_removed;
PG_RETURN_POINTER(result);
}
/*
* Post-VACUUM cleanup.
*
* Here, we scan looking for pages we can delete or return to the freelist.
*
* Result: a palloc'd struct containing statistical info for VACUUM displays.
*/
Datum
btvacuumcleanup(PG_FUNCTION_ARGS)
{
Relation rel = (Relation) PG_GETARG_POINTER(0);
IndexVacuumCleanupInfo *info = (IndexVacuumCleanupInfo *) PG_GETARG_POINTER(1);
IndexBulkDeleteResult *stats = (IndexBulkDeleteResult *) PG_GETARG_POINTER(2);
BlockNumber num_pages;
BlockNumber blkno;
BlockNumber *freePages;
int nFreePages,
maxFreePages;
BlockNumber pages_deleted = 0;
MemoryContext mycontext;
MemoryContext oldcontext;
Assert(stats != NULL);
num_pages = RelationGetNumberOfBlocks(rel);
/* No point in remembering more than MaxFSMPages pages */
maxFreePages = MaxFSMPages;
if ((BlockNumber) maxFreePages > num_pages)
maxFreePages = (int) num_pages;
freePages = (BlockNumber *) palloc(maxFreePages * sizeof(BlockNumber));
nFreePages = 0;
/* Create a temporary memory context to run _bt_pagedel in */
mycontext = AllocSetContextCreate(CurrentMemoryContext,
"_bt_pagedel",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
/*
* Scan through all pages of index, except metapage. (Any pages added
* after we start the scan will not be examined; this should be fine,
* since they can't possibly be empty.)
*/
for (blkno = BTREE_METAPAGE + 1; blkno < num_pages; blkno++)
{
Buffer buf;
Page page;
BTPageOpaque opaque;
buf = _bt_getbuf(rel, blkno, BT_READ);
page = BufferGetPage(buf);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
if (_bt_page_recyclable(page))
{
/* Okay to recycle this page */
if (nFreePages < maxFreePages)
freePages[nFreePages++] = blkno;
pages_deleted++;
}
else if (P_ISDELETED(opaque))
{
/* Already deleted, but can't recycle yet */
pages_deleted++;
}
else if ((opaque->btpo_flags & BTP_HALF_DEAD) ||
P_FIRSTDATAKEY(opaque) > PageGetMaxOffsetNumber(page))
{
/* Empty, try to delete */
int ndel;
/* Run pagedel in a temp context to avoid memory leakage */
MemoryContextReset(mycontext);
oldcontext = MemoryContextSwitchTo(mycontext);
ndel = _bt_pagedel(rel, buf, info->vacuum_full);
/* count only this page, else may double-count parent */
if (ndel)
pages_deleted++;
/*
* During VACUUM FULL it's okay to recycle deleted pages
* immediately, since there can be no other transactions
* scanning the index. Note that we will only recycle the
* current page and not any parent pages that _bt_pagedel
* might have recursed to; this seems reasonable in the name
* of simplicity. (Trying to do otherwise would mean we'd
* have to sort the list of recyclable pages we're building.)
*/
if (ndel && info->vacuum_full)
{
if (nFreePages < maxFreePages)
freePages[nFreePages++] = blkno;
}
MemoryContextSwitchTo(oldcontext);
continue; /* pagedel released buffer */
}
_bt_relbuf(rel, buf);
}
/*
* During VACUUM FULL, we truncate off any recyclable pages at the end
* of the index. In a normal vacuum it'd be unsafe to do this except
* by acquiring exclusive lock on the index and then rechecking all
* the pages; doesn't seem worth it.
*/
if (info->vacuum_full && nFreePages > 0)
{
BlockNumber new_pages = num_pages;
while (nFreePages > 0 && freePages[nFreePages - 1] == new_pages - 1)
{
new_pages--;
pages_deleted--;
nFreePages--;
}
if (new_pages != num_pages)
{
/*
* Okay to truncate.
*
* First, flush any shared buffers for the blocks we intend to
* delete. FlushRelationBuffers is a bit more than we need
* for this, since it will also write out dirty buffers for
* blocks we aren't deleting, but it's the closest thing in
* bufmgr's API.
*/
FlushRelationBuffers(rel, new_pages);
/*
* Do the physical truncation.
*/
RelationTruncate(rel, new_pages);
/* update statistics */
stats->pages_removed = num_pages - new_pages;
num_pages = new_pages;
}
}
/*
* Update the shared Free Space Map with the info we now have about
* free pages in the index, discarding any old info the map may have.
* We do not need to sort the page numbers; they're in order already.
*/
RecordIndexFreeSpace(&rel->rd_node, nFreePages, freePages);
pfree(freePages);
MemoryContextDelete(mycontext);
/* update statistics */
stats->num_pages = num_pages;
stats->pages_deleted = pages_deleted;
stats->pages_free = nFreePages;
PG_RETURN_POINTER(stats);
}
/*
* Restore scan position when btgettuple is called to continue a scan.
*
* This is nontrivial because concurrent insertions might have moved the
* index tuple we stopped on. We assume the tuple can only have moved to
* the right from our stop point, because we kept a pin on the buffer,
* and so no deletion can have occurred on that page.
*
* On entry, we have a pin but no read lock on the buffer that contained
* the index tuple we stopped the scan on. On exit, we have pin and read
* lock on the buffer that now contains that index tuple, and the scandesc's
* current position is updated to point at it.
*/
static void
_bt_restscan(IndexScanDesc scan)
{
Relation rel = scan->indexRelation;
BTScanOpaque so = (BTScanOpaque) scan->opaque;
Buffer buf = so->btso_curbuf;
Page page;
ItemPointer current = &(scan->currentItemData);
OffsetNumber offnum = ItemPointerGetOffsetNumber(current),
maxoff;
BTPageOpaque opaque;
Buffer nextbuf;
ItemPointer target = &(so->curHeapIptr);
BTItem item;
BlockNumber blkno;
/*
* Reacquire read lock on the buffer. (We should still have a
* reference-count pin on it, so need not get that.)
*/
LockBuffer(buf, BT_READ);
page = BufferGetPage(buf);
maxoff = PageGetMaxOffsetNumber(page);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
/*
* We use this as flag when first index tuple on page is deleted but
* we do not move left (this would slowdown vacuum) - so we set
* current->ip_posid before first index tuple on the current page
* (_bt_step will move it right)... XXX still needed?
*/
if (!ItemPointerIsValid(target))
{
ItemPointerSetOffsetNumber(current,
OffsetNumberPrev(P_FIRSTDATAKEY(opaque)));
return;
}
/*
* The item we were on may have moved right due to insertions. Find it
* again. We use the heap TID to identify the item uniquely.
*/
for (;;)
{
/* Check for item on this page */
for (;
offnum <= maxoff;
offnum = OffsetNumberNext(offnum))
{
item = (BTItem) PageGetItem(page, PageGetItemId(page, offnum));
if (BTTidSame(item->bti_itup.t_tid, *target))
{
/* Found it */
current->ip_posid = offnum;
return;
}
}
/*
* The item we're looking for moved right at least one page, so
* move right. We are careful here to pin and read-lock the next
* non-dead page before releasing the current one. This ensures
* that a concurrent btbulkdelete scan cannot pass our position
* --- if it did, it might be able to reach and delete our target
* item before we can find it again.
*/
if (P_RIGHTMOST(opaque))
elog(ERROR, "failed to re-find previous key in \"%s\"",
RelationGetRelationName(rel));
/* Advance to next non-dead page --- there must be one */
nextbuf = InvalidBuffer;
for (;;)
{
blkno = opaque->btpo_next;
nextbuf = _bt_relandgetbuf(rel, nextbuf, blkno, BT_READ);
page = BufferGetPage(nextbuf);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
if (!P_IGNORE(opaque))
break;
if (P_RIGHTMOST(opaque))
elog(ERROR, "fell off the end of \"%s\"",
RelationGetRelationName(rel));
}
_bt_relbuf(rel, buf);
so->btso_curbuf = buf = nextbuf;
maxoff = PageGetMaxOffsetNumber(page);
offnum = P_FIRSTDATAKEY(opaque);
ItemPointerSet(current, blkno, offnum);
}
}