1/*-------------------------------------------------------------------------
2 *
3 * gistutil.c
4 * utilities routines for the postgres GiST index access method.
5 *
6 *
7 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
8 * Portions Copyright (c) 1994, Regents of the University of California
9 *
10 * IDENTIFICATION
11 * src/backend/access/gist/gistutil.c
12 *-------------------------------------------------------------------------
13 */
14#include "postgres.h"
15
16#include <math.h>
17
18#include "access/gist_private.h"
19#include "access/htup_details.h"
20#include "access/reloptions.h"
21#include "catalog/pg_opclass.h"
22#include "storage/indexfsm.h"
23#include "storage/lmgr.h"
24#include "utils/float.h"
25#include "utils/syscache.h"
26#include "utils/snapmgr.h"
27#include "utils/lsyscache.h"
28
29
30/*
31 * Write itup vector to page, has no control of free space.
32 */
33void
34gistfillbuffer(Page page, IndexTuple *itup, int len, OffsetNumber off)
35{
36 OffsetNumber l = InvalidOffsetNumber;
37 int i;
38
39 if (off == InvalidOffsetNumber)
40 off = (PageIsEmpty(page)) ? FirstOffsetNumber :
41 OffsetNumberNext(PageGetMaxOffsetNumber(page));
42
43 for (i = 0; i < len; i++)
44 {
45 Size sz = IndexTupleSize(itup[i]);
46
47 l = PageAddItem(page, (Item) itup[i], sz, off, false, false);
48 if (l == InvalidOffsetNumber)
49 elog(ERROR, "failed to add item to GiST index page, item %d out of %d, size %d bytes",
50 i, len, (int) sz);
51 off++;
52 }
53}
54
55/*
56 * Check space for itup vector on page
57 */
58bool
59gistnospace(Page page, IndexTuple *itvec, int len, OffsetNumber todelete, Size freespace)
60{
61 unsigned int size = freespace,
62 deleted = 0;
63 int i;
64
65 for (i = 0; i < len; i++)
66 size += IndexTupleSize(itvec[i]) + sizeof(ItemIdData);
67
68 if (todelete != InvalidOffsetNumber)
69 {
70 IndexTuple itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, todelete));
71
72 deleted = IndexTupleSize(itup) + sizeof(ItemIdData);
73 }
74
75 return (PageGetFreeSpace(page) + deleted < size);
76}
77
78bool
79gistfitpage(IndexTuple *itvec, int len)
80{
81 int i;
82 Size size = 0;
83
84 for (i = 0; i < len; i++)
85 size += IndexTupleSize(itvec[i]) + sizeof(ItemIdData);
86
87 /* TODO: Consider fillfactor */
88 return (size <= GiSTPageSize);
89}
90
91/*
92 * Read buffer into itup vector
93 */
94IndexTuple *
95gistextractpage(Page page, int *len /* out */ )
96{
97 OffsetNumber i,
98 maxoff;
99 IndexTuple *itvec;
100
101 maxoff = PageGetMaxOffsetNumber(page);
102 *len = maxoff;
103 itvec = palloc(sizeof(IndexTuple) * maxoff);
104 for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
105 itvec[i - FirstOffsetNumber] = (IndexTuple) PageGetItem(page, PageGetItemId(page, i));
106
107 return itvec;
108}
109
110/*
111 * join two vectors into one
112 */
113IndexTuple *
114gistjoinvector(IndexTuple *itvec, int *len, IndexTuple *additvec, int addlen)
115{
116 itvec = (IndexTuple *) repalloc((void *) itvec, sizeof(IndexTuple) * ((*len) + addlen));
117 memmove(&itvec[*len], additvec, sizeof(IndexTuple) * addlen);
118 *len += addlen;
119 return itvec;
120}
121
122/*
123 * make plain IndexTupleVector
124 */
125
126IndexTupleData *
127gistfillitupvec(IndexTuple *vec, int veclen, int *memlen)
128{
129 char *ptr,
130 *ret;
131 int i;
132
133 *memlen = 0;
134
135 for (i = 0; i < veclen; i++)
136 *memlen += IndexTupleSize(vec[i]);
137
138 ptr = ret = palloc(*memlen);
139
140 for (i = 0; i < veclen; i++)
141 {
142 memcpy(ptr, vec[i], IndexTupleSize(vec[i]));
143 ptr += IndexTupleSize(vec[i]);
144 }
145
146 return (IndexTupleData *) ret;
147}
148
149/*
150 * Make unions of keys in IndexTuple vector (one union datum per index column).
151 * Union Datums are returned into the attr/isnull arrays.
152 * Resulting Datums aren't compressed.
153 */
154void
155gistMakeUnionItVec(GISTSTATE *giststate, IndexTuple *itvec, int len,
156 Datum *attr, bool *isnull)
157{
158 int i;
159 GistEntryVector *evec;
160 int attrsize;
161
162 evec = (GistEntryVector *) palloc((len + 2) * sizeof(GISTENTRY) + GEVHDRSZ);
163
164 for (i = 0; i < giststate->nonLeafTupdesc->natts; i++)
165 {
166 int j;
167
168 /* Collect non-null datums for this column */
169 evec->n = 0;
170 for (j = 0; j < len; j++)
171 {
172 Datum datum;
173 bool IsNull;
174
175 datum = index_getattr(itvec[j], i + 1, giststate->leafTupdesc,
176 &IsNull);
177 if (IsNull)
178 continue;
179
180 gistdentryinit(giststate, i,
181 evec->vector + evec->n,
182 datum,
183 NULL, NULL, (OffsetNumber) 0,
184 false, IsNull);
185 evec->n++;
186 }
187
188 /* If this column was all NULLs, the union is NULL */
189 if (evec->n == 0)
190 {
191 attr[i] = (Datum) 0;
192 isnull[i] = true;
193 }
194 else
195 {
196 if (evec->n == 1)
197 {
198 /* unionFn may expect at least two inputs */
199 evec->n = 2;
200 evec->vector[1] = evec->vector[0];
201 }
202
203 /* Make union and store in attr array */
204 attr[i] = FunctionCall2Coll(&giststate->unionFn[i],
205 giststate->supportCollation[i],
206 PointerGetDatum(evec),
207 PointerGetDatum(&attrsize));
208
209 isnull[i] = false;
210 }
211 }
212}
213
214/*
215 * Return an IndexTuple containing the result of applying the "union"
216 * method to the specified IndexTuple vector.
217 */
218IndexTuple
219gistunion(Relation r, IndexTuple *itvec, int len, GISTSTATE *giststate)
220{
221 Datum attr[INDEX_MAX_KEYS];
222 bool isnull[INDEX_MAX_KEYS];
223
224 gistMakeUnionItVec(giststate, itvec, len, attr, isnull);
225
226 return gistFormTuple(giststate, r, attr, isnull, false);
227}
228
229/*
230 * makes union of two key
231 */
232void
233gistMakeUnionKey(GISTSTATE *giststate, int attno,
234 GISTENTRY *entry1, bool isnull1,
235 GISTENTRY *entry2, bool isnull2,
236 Datum *dst, bool *dstisnull)
237{
238 /* we need a GistEntryVector with room for exactly 2 elements */
239 union
240 {
241 GistEntryVector gev;
242 char padding[2 * sizeof(GISTENTRY) + GEVHDRSZ];
243 } storage;
244 GistEntryVector *evec = &storage.gev;
245 int dstsize;
246
247 evec->n = 2;
248
249 if (isnull1 && isnull2)
250 {
251 *dstisnull = true;
252 *dst = (Datum) 0;
253 }
254 else
255 {
256 if (isnull1 == false && isnull2 == false)
257 {
258 evec->vector[0] = *entry1;
259 evec->vector[1] = *entry2;
260 }
261 else if (isnull1 == false)
262 {
263 evec->vector[0] = *entry1;
264 evec->vector[1] = *entry1;
265 }
266 else
267 {
268 evec->vector[0] = *entry2;
269 evec->vector[1] = *entry2;
270 }
271
272 *dstisnull = false;
273 *dst = FunctionCall2Coll(&giststate->unionFn[attno],
274 giststate->supportCollation[attno],
275 PointerGetDatum(evec),
276 PointerGetDatum(&dstsize));
277 }
278}
279
280bool
281gistKeyIsEQ(GISTSTATE *giststate, int attno, Datum a, Datum b)
282{
283 bool result;
284
285 FunctionCall3Coll(&giststate->equalFn[attno],
286 giststate->supportCollation[attno],
287 a, b,
288 PointerGetDatum(&result));
289 return result;
290}
291
292/*
293 * Decompress all keys in tuple
294 */
295void
296gistDeCompressAtt(GISTSTATE *giststate, Relation r, IndexTuple tuple, Page p,
297 OffsetNumber o, GISTENTRY *attdata, bool *isnull)
298{
299 int i;
300
301 for (i = 0; i < IndexRelationGetNumberOfKeyAttributes(r); i++)
302 {
303 Datum datum;
304
305 datum = index_getattr(tuple, i + 1, giststate->leafTupdesc, &isnull[i]);
306 gistdentryinit(giststate, i, &attdata[i],
307 datum, r, p, o,
308 false, isnull[i]);
309 }
310}
311
312/*
313 * Forms union of oldtup and addtup, if union == oldtup then return NULL
314 */
315IndexTuple
316gistgetadjusted(Relation r, IndexTuple oldtup, IndexTuple addtup, GISTSTATE *giststate)
317{
318 bool neednew = false;
319 GISTENTRY oldentries[INDEX_MAX_KEYS],
320 addentries[INDEX_MAX_KEYS];
321 bool oldisnull[INDEX_MAX_KEYS],
322 addisnull[INDEX_MAX_KEYS];
323 Datum attr[INDEX_MAX_KEYS];
324 bool isnull[INDEX_MAX_KEYS];
325 IndexTuple newtup = NULL;
326 int i;
327
328 gistDeCompressAtt(giststate, r, oldtup, NULL,
329 (OffsetNumber) 0, oldentries, oldisnull);
330
331 gistDeCompressAtt(giststate, r, addtup, NULL,
332 (OffsetNumber) 0, addentries, addisnull);
333
334 for (i = 0; i < IndexRelationGetNumberOfKeyAttributes(r); i++)
335 {
336 gistMakeUnionKey(giststate, i,
337 oldentries + i, oldisnull[i],
338 addentries + i, addisnull[i],
339 attr + i, isnull + i);
340
341 if (neednew)
342 /* we already need new key, so we can skip check */
343 continue;
344
345 if (isnull[i])
346 /* union of key may be NULL if and only if both keys are NULL */
347 continue;
348
349 if (!addisnull[i])
350 {
351 if (oldisnull[i] ||
352 !gistKeyIsEQ(giststate, i, oldentries[i].key, attr[i]))
353 neednew = true;
354 }
355 }
356
357 if (neednew)
358 {
359 /* need to update key */
360 newtup = gistFormTuple(giststate, r, attr, isnull, false);
361 newtup->t_tid = oldtup->t_tid;
362 }
363
364 return newtup;
365}
366
367/*
368 * Search an upper index page for the entry with lowest penalty for insertion
369 * of the new index key contained in "it".
370 *
371 * Returns the index of the page entry to insert into.
372 */
373OffsetNumber
374gistchoose(Relation r, Page p, IndexTuple it, /* it has compressed entry */
375 GISTSTATE *giststate)
376{
377 OffsetNumber result;
378 OffsetNumber maxoff;
379 OffsetNumber i;
380 float best_penalty[INDEX_MAX_KEYS];
381 GISTENTRY entry,
382 identry[INDEX_MAX_KEYS];
383 bool isnull[INDEX_MAX_KEYS];
384 int keep_current_best;
385
386 Assert(!GistPageIsLeaf(p));
387
388 gistDeCompressAtt(giststate, r,
389 it, NULL, (OffsetNumber) 0,
390 identry, isnull);
391
392 /* we'll return FirstOffsetNumber if page is empty (shouldn't happen) */
393 result = FirstOffsetNumber;
394
395 /*
396 * The index may have multiple columns, and there's a penalty value for
397 * each column. The penalty associated with a column that appears earlier
398 * in the index definition is strictly more important than the penalty of
399 * a column that appears later in the index definition.
400 *
401 * best_penalty[j] is the best penalty we have seen so far for column j,
402 * or -1 when we haven't yet examined column j. Array entries to the
403 * right of the first -1 are undefined.
404 */
405 best_penalty[0] = -1;
406
407 /*
408 * If we find a tuple that's exactly as good as the currently best one, we
409 * could use either one. When inserting a lot of tuples with the same or
410 * similar keys, it's preferable to descend down the same path when
411 * possible, as that's more cache-friendly. On the other hand, if all
412 * inserts land on the same leaf page after a split, we're never going to
413 * insert anything to the other half of the split, and will end up using
414 * only 50% of the available space. Distributing the inserts evenly would
415 * lead to better space usage, but that hurts cache-locality during
416 * insertion. To get the best of both worlds, when we find a tuple that's
417 * exactly as good as the previous best, choose randomly whether to stick
418 * to the old best, or use the new one. Once we decide to stick to the
419 * old best, we keep sticking to it for any subsequent equally good tuples
420 * we might find. This favors tuples with low offsets, but still allows
421 * some inserts to go to other equally-good subtrees.
422 *
423 * keep_current_best is -1 if we haven't yet had to make a random choice
424 * whether to keep the current best tuple. If we have done so, and
425 * decided to keep it, keep_current_best is 1; if we've decided to
426 * replace, keep_current_best is 0. (This state will be reset to -1 as
427 * soon as we've made the replacement, but sometimes we make the choice in
428 * advance of actually finding a replacement best tuple.)
429 */
430 keep_current_best = -1;
431
432 /*
433 * Loop over tuples on page.
434 */
435 maxoff = PageGetMaxOffsetNumber(p);
436 Assert(maxoff >= FirstOffsetNumber);
437
438 for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
439 {
440 IndexTuple itup = (IndexTuple) PageGetItem(p, PageGetItemId(p, i));
441 bool zero_penalty;
442 int j;
443
444 zero_penalty = true;
445
446 /* Loop over index attributes. */
447 for (j = 0; j < IndexRelationGetNumberOfKeyAttributes(r); j++)
448 {
449 Datum datum;
450 float usize;
451 bool IsNull;
452
453 /* Compute penalty for this column. */
454 datum = index_getattr(itup, j + 1, giststate->leafTupdesc,
455 &IsNull);
456 gistdentryinit(giststate, j, &entry, datum, r, p, i,
457 false, IsNull);
458 usize = gistpenalty(giststate, j, &entry, IsNull,
459 &identry[j], isnull[j]);
460 if (usize > 0)
461 zero_penalty = false;
462
463 if (best_penalty[j] < 0 || usize < best_penalty[j])
464 {
465 /*
466 * New best penalty for column. Tentatively select this tuple
467 * as the target, and record the best penalty. Then reset the
468 * next column's penalty to "unknown" (and indirectly, the
469 * same for all the ones to its right). This will force us to
470 * adopt this tuple's penalty values as the best for all the
471 * remaining columns during subsequent loop iterations.
472 */
473 result = i;
474 best_penalty[j] = usize;
475
476 if (j < IndexRelationGetNumberOfKeyAttributes(r) - 1)
477 best_penalty[j + 1] = -1;
478
479 /* we have new best, so reset keep-it decision */
480 keep_current_best = -1;
481 }
482 else if (best_penalty[j] == usize)
483 {
484 /*
485 * The current tuple is exactly as good for this column as the
486 * best tuple seen so far. The next iteration of this loop
487 * will compare the next column.
488 */
489 }
490 else
491 {
492 /*
493 * The current tuple is worse for this column than the best
494 * tuple seen so far. Skip the remaining columns and move on
495 * to the next tuple, if any.
496 */
497 zero_penalty = false; /* so outer loop won't exit */
498 break;
499 }
500 }
501
502 /*
503 * If we looped past the last column, and did not update "result",
504 * then this tuple is exactly as good as the prior best tuple.
505 */
506 if (j == IndexRelationGetNumberOfKeyAttributes(r) && result != i)
507 {
508 if (keep_current_best == -1)
509 {
510 /* we didn't make the random choice yet for this old best */
511 keep_current_best = (random() <= (MAX_RANDOM_VALUE / 2)) ? 1 : 0;
512 }
513 if (keep_current_best == 0)
514 {
515 /* we choose to use the new tuple */
516 result = i;
517 /* choose again if there are even more exactly-as-good ones */
518 keep_current_best = -1;
519 }
520 }
521
522 /*
523 * If we find a tuple with zero penalty for all columns, and we've
524 * decided we don't want to search for another tuple with equal
525 * penalty, there's no need to examine remaining tuples; just break
526 * out of the loop and return it.
527 */
528 if (zero_penalty)
529 {
530 if (keep_current_best == -1)
531 {
532 /* we didn't make the random choice yet for this old best */
533 keep_current_best = (random() <= (MAX_RANDOM_VALUE / 2)) ? 1 : 0;
534 }
535 if (keep_current_best == 1)
536 break;
537 }
538 }
539
540 return result;
541}
542
543/*
544 * initialize a GiST entry with a decompressed version of key
545 */
546void
547gistdentryinit(GISTSTATE *giststate, int nkey, GISTENTRY *e,
548 Datum k, Relation r, Page pg, OffsetNumber o,
549 bool l, bool isNull)
550{
551 if (!isNull)
552 {
553 GISTENTRY *dep;
554
555 gistentryinit(*e, k, r, pg, o, l);
556
557 /* there may not be a decompress function in opclass */
558 if (!OidIsValid(giststate->decompressFn[nkey].fn_oid))
559 return;
560
561 dep = (GISTENTRY *)
562 DatumGetPointer(FunctionCall1Coll(&giststate->decompressFn[nkey],
563 giststate->supportCollation[nkey],
564 PointerGetDatum(e)));
565 /* decompressFn may just return the given pointer */
566 if (dep != e)
567 gistentryinit(*e, dep->key, dep->rel, dep->page, dep->offset,
568 dep->leafkey);
569 }
570 else
571 gistentryinit(*e, (Datum) 0, r, pg, o, l);
572}
573
574IndexTuple
575gistFormTuple(GISTSTATE *giststate, Relation r,
576 Datum attdata[], bool isnull[], bool isleaf)
577{
578 Datum compatt[INDEX_MAX_KEYS];
579 int i;
580 IndexTuple res;
581
582 /*
583 * Call the compress method on each attribute.
584 */
585 for (i = 0; i < IndexRelationGetNumberOfKeyAttributes(r); i++)
586 {
587 if (isnull[i])
588 compatt[i] = (Datum) 0;
589 else
590 {
591 GISTENTRY centry;
592 GISTENTRY *cep;
593
594 gistentryinit(centry, attdata[i], r, NULL, (OffsetNumber) 0,
595 isleaf);
596 /* there may not be a compress function in opclass */
597 if (OidIsValid(giststate->compressFn[i].fn_oid))
598 cep = (GISTENTRY *)
599 DatumGetPointer(FunctionCall1Coll(&giststate->compressFn[i],
600 giststate->supportCollation[i],
601 PointerGetDatum(&centry)));
602 else
603 cep = &centry;
604 compatt[i] = cep->key;
605 }
606 }
607
608 if (isleaf)
609 {
610 /*
611 * Emplace each included attribute if any.
612 */
613 for (; i < r->rd_att->natts; i++)
614 {
615 if (isnull[i])
616 compatt[i] = (Datum) 0;
617 else
618 compatt[i] = attdata[i];
619 }
620 }
621
622 res = index_form_tuple(isleaf ? giststate->leafTupdesc :
623 giststate->nonLeafTupdesc,
624 compatt, isnull);
625
626 /*
627 * The offset number on tuples on internal pages is unused. For historical
628 * reasons, it is set to 0xffff.
629 */
630 ItemPointerSetOffsetNumber(&(res->t_tid), 0xffff);
631 return res;
632}
633
634/*
635 * initialize a GiST entry with fetched value in key field
636 */
637static Datum
638gistFetchAtt(GISTSTATE *giststate, int nkey, Datum k, Relation r)
639{
640 GISTENTRY fentry;
641 GISTENTRY *fep;
642
643 gistentryinit(fentry, k, r, NULL, (OffsetNumber) 0, false);
644
645 fep = (GISTENTRY *)
646 DatumGetPointer(FunctionCall1Coll(&giststate->fetchFn[nkey],
647 giststate->supportCollation[nkey],
648 PointerGetDatum(&fentry)));
649
650 /* fetchFn set 'key', return it to the caller */
651 return fep->key;
652}
653
654/*
655 * Fetch all keys in tuple.
656 * Returns a new HeapTuple containing the originally-indexed data.
657 */
658HeapTuple
659gistFetchTuple(GISTSTATE *giststate, Relation r, IndexTuple tuple)
660{
661 MemoryContext oldcxt = MemoryContextSwitchTo(giststate->tempCxt);
662 Datum fetchatt[INDEX_MAX_KEYS];
663 bool isnull[INDEX_MAX_KEYS];
664 int i;
665
666 for (i = 0; i < IndexRelationGetNumberOfKeyAttributes(r); i++)
667 {
668 Datum datum;
669
670 datum = index_getattr(tuple, i + 1, giststate->leafTupdesc, &isnull[i]);
671
672 if (giststate->fetchFn[i].fn_oid != InvalidOid)
673 {
674 if (!isnull[i])
675 fetchatt[i] = gistFetchAtt(giststate, i, datum, r);
676 else
677 fetchatt[i] = (Datum) 0;
678 }
679 else if (giststate->compressFn[i].fn_oid == InvalidOid)
680 {
681 /*
682 * If opclass does not provide compress method that could change
683 * original value, att is necessarily stored in original form.
684 */
685 if (!isnull[i])
686 fetchatt[i] = datum;
687 else
688 fetchatt[i] = (Datum) 0;
689 }
690 else
691 {
692 /*
693 * Index-only scans not supported for this column. Since the
694 * planner chose an index-only scan anyway, it is not interested
695 * in this column, and we can replace it with a NULL.
696 */
697 isnull[i] = true;
698 fetchatt[i] = (Datum) 0;
699 }
700 }
701
702 /*
703 * Get each included attribute.
704 */
705 for (; i < r->rd_att->natts; i++)
706 {
707 fetchatt[i] = index_getattr(tuple, i + 1, giststate->leafTupdesc,
708 &isnull[i]);
709 }
710 MemoryContextSwitchTo(oldcxt);
711
712 return heap_form_tuple(giststate->fetchTupdesc, fetchatt, isnull);
713}
714
715float
716gistpenalty(GISTSTATE *giststate, int attno,
717 GISTENTRY *orig, bool isNullOrig,
718 GISTENTRY *add, bool isNullAdd)
719{
720 float penalty = 0.0;
721
722 if (giststate->penaltyFn[attno].fn_strict == false ||
723 (isNullOrig == false && isNullAdd == false))
724 {
725 FunctionCall3Coll(&giststate->penaltyFn[attno],
726 giststate->supportCollation[attno],
727 PointerGetDatum(orig),
728 PointerGetDatum(add),
729 PointerGetDatum(&penalty));
730 /* disallow negative or NaN penalty */
731 if (isnan(penalty) || penalty < 0.0)
732 penalty = 0.0;
733 }
734 else if (isNullOrig && isNullAdd)
735 penalty = 0.0;
736 else
737 {
738 /* try to prevent mixing null and non-null values */
739 penalty = get_float4_infinity();
740 }
741
742 return penalty;
743}
744
745/*
746 * Initialize a new index page
747 */
748void
749GISTInitBuffer(Buffer b, uint32 f)
750{
751 GISTPageOpaque opaque;
752 Page page;
753 Size pageSize;
754
755 pageSize = BufferGetPageSize(b);
756 page = BufferGetPage(b);
757 PageInit(page, pageSize, sizeof(GISTPageOpaqueData));
758
759 opaque = GistPageGetOpaque(page);
760 /* page was already zeroed by PageInit, so this is not needed: */
761 /* memset(&(opaque->nsn), 0, sizeof(GistNSN)); */
762 opaque->rightlink = InvalidBlockNumber;
763 opaque->flags = f;
764 opaque->gist_page_id = GIST_PAGE_ID;
765}
766
767/*
768 * Verify that a freshly-read page looks sane.
769 */
770void
771gistcheckpage(Relation rel, Buffer buf)
772{
773 Page page = BufferGetPage(buf);
774
775 /*
776 * ReadBuffer verifies that every newly-read page passes
777 * PageHeaderIsValid, which means it either contains a reasonably sane
778 * page header or is all-zero. We have to defend against the all-zero
779 * case, however.
780 */
781 if (PageIsNew(page))
782 ereport(ERROR,
783 (errcode(ERRCODE_INDEX_CORRUPTED),
784 errmsg("index \"%s\" contains unexpected zero page at block %u",
785 RelationGetRelationName(rel),
786 BufferGetBlockNumber(buf)),
787 errhint("Please REINDEX it.")));
788
789 /*
790 * Additionally check that the special area looks sane.
791 */
792 if (PageGetSpecialSize(page) != MAXALIGN(sizeof(GISTPageOpaqueData)))
793 ereport(ERROR,
794 (errcode(ERRCODE_INDEX_CORRUPTED),
795 errmsg("index \"%s\" contains corrupted page at block %u",
796 RelationGetRelationName(rel),
797 BufferGetBlockNumber(buf)),
798 errhint("Please REINDEX it.")));
799}
800
801
802/*
803 * Allocate a new page (either by recycling, or by extending the index file)
804 *
805 * The returned buffer is already pinned and exclusive-locked
806 *
807 * Caller is responsible for initializing the page by calling GISTInitBuffer
808 */
809Buffer
810gistNewBuffer(Relation r)
811{
812 Buffer buffer;
813 bool needLock;
814
815 /* First, try to get a page from FSM */
816 for (;;)
817 {
818 BlockNumber blkno = GetFreeIndexPage(r);
819
820 if (blkno == InvalidBlockNumber)
821 break; /* nothing left in FSM */
822
823 buffer = ReadBuffer(r, blkno);
824
825 /*
826 * We have to guard against the possibility that someone else already
827 * recycled this page; the buffer may be locked if so.
828 */
829 if (ConditionalLockBuffer(buffer))
830 {
831 Page page = BufferGetPage(buffer);
832
833 /*
834 * If the page was never initialized, it's OK to use.
835 */
836 if (PageIsNew(page))
837 return buffer;
838
839 gistcheckpage(r, buffer);
840
841 /*
842 * Otherwise, recycle it if deleted, and too old to have any
843 * processes interested in it.
844 */
845 if (gistPageRecyclable(page))
846 {
847 /*
848 * If we are generating WAL for Hot Standby then create a WAL
849 * record that will allow us to conflict with queries running
850 * on standby, in case they have snapshots older than the
851 * page's deleteXid.
852 */
853 if (XLogStandbyInfoActive() && RelationNeedsWAL(r))
854 gistXLogPageReuse(r, blkno, GistPageGetDeleteXid(page));
855
856 return buffer;
857 }
858
859 LockBuffer(buffer, GIST_UNLOCK);
860 }
861
862 /* Can't use it, so release buffer and try again */
863 ReleaseBuffer(buffer);
864 }
865
866 /* Must extend the file */
867 needLock = !RELATION_IS_LOCAL(r);
868
869 if (needLock)
870 LockRelationForExtension(r, ExclusiveLock);
871
872 buffer = ReadBuffer(r, P_NEW);
873 LockBuffer(buffer, GIST_EXCLUSIVE);
874
875 if (needLock)
876 UnlockRelationForExtension(r, ExclusiveLock);
877
878 return buffer;
879}
880
881/* Can this page be recycled yet? */
882bool
883gistPageRecyclable(Page page)
884{
885 if (PageIsNew(page))
886 return true;
887 if (GistPageIsDeleted(page))
888 {
889 /*
890 * The page was deleted, but when? If it was just deleted, a scan
891 * might have seen the downlink to it, and will read the page later.
892 * As long as that can happen, we must keep the deleted page around as
893 * a tombstone.
894 *
895 * Compare the deletion XID with RecentGlobalXmin. If deleteXid <
896 * RecentGlobalXmin, then no scan that's still in progress could have
897 * seen its downlink, and we can recycle it.
898 */
899 FullTransactionId deletexid_full = GistPageGetDeleteXid(page);
900 FullTransactionId recentxmin_full = GetFullRecentGlobalXmin();
901
902 if (FullTransactionIdPrecedes(deletexid_full, recentxmin_full))
903 return true;
904 }
905 return false;
906}
907
908bytea *
909gistoptions(Datum reloptions, bool validate)
910{
911 relopt_value *options;
912 GiSTOptions *rdopts;
913 int numoptions;
914 static const relopt_parse_elt tab[] = {
915 {"fillfactor", RELOPT_TYPE_INT, offsetof(GiSTOptions, fillfactor)},
916 {"buffering", RELOPT_TYPE_STRING, offsetof(GiSTOptions, bufferingModeOffset)}
917 };
918
919 options = parseRelOptions(reloptions, validate, RELOPT_KIND_GIST,
920 &numoptions);
921
922 /* if none set, we're done */
923 if (numoptions == 0)
924 return NULL;
925
926 rdopts = allocateReloptStruct(sizeof(GiSTOptions), options, numoptions);
927
928 fillRelOptions((void *) rdopts, sizeof(GiSTOptions), options, numoptions,
929 validate, tab, lengthof(tab));
930
931 pfree(options);
932
933 return (bytea *) rdopts;
934}
935
936/*
937 * gistproperty() -- Check boolean properties of indexes.
938 *
939 * This is optional for most AMs, but is required for GiST because the core
940 * property code doesn't support AMPROP_DISTANCE_ORDERABLE. We also handle
941 * AMPROP_RETURNABLE here to save opening the rel to call gistcanreturn.
942 */
943bool
944gistproperty(Oid index_oid, int attno,
945 IndexAMProperty prop, const char *propname,
946 bool *res, bool *isnull)
947{
948 Oid opclass,
949 opfamily,
950 opcintype;
951 int16 procno;
952
953 /* Only answer column-level inquiries */
954 if (attno == 0)
955 return false;
956
957 /*
958 * Currently, GiST distance-ordered scans require that there be a distance
959 * function in the opclass with the default types (i.e. the one loaded
960 * into the relcache entry, see initGISTstate). So we assume that if such
961 * a function exists, then there's a reason for it (rather than grubbing
962 * through all the opfamily's operators to find an ordered one).
963 *
964 * Essentially the same code can test whether we support returning the
965 * column data, since that's true if the opclass provides a fetch proc.
966 */
967
968 switch (prop)
969 {
970 case AMPROP_DISTANCE_ORDERABLE:
971 procno = GIST_DISTANCE_PROC;
972 break;
973 case AMPROP_RETURNABLE:
974 procno = GIST_FETCH_PROC;
975 break;
976 default:
977 return false;
978 }
979
980 /* First we need to know the column's opclass. */
981 opclass = get_index_column_opclass(index_oid, attno);
982 if (!OidIsValid(opclass))
983 {
984 *isnull = true;
985 return true;
986 }
987
988 /* Now look up the opclass family and input datatype. */
989 if (!get_opclass_opfamily_and_input_type(opclass, &opfamily, &opcintype))
990 {
991 *isnull = true;
992 return true;
993 }
994
995 /* And now we can check whether the function is provided. */
996
997 *res = SearchSysCacheExists4(AMPROCNUM,
998 ObjectIdGetDatum(opfamily),
999 ObjectIdGetDatum(opcintype),
1000 ObjectIdGetDatum(opcintype),
1001 Int16GetDatum(procno));
1002
1003 /*
1004 * Special case: even without a fetch function, AMPROP_RETURNABLE is true
1005 * if the opclass has no compress function.
1006 */
1007 if (prop == AMPROP_RETURNABLE && !*res)
1008 {
1009 *res = !SearchSysCacheExists4(AMPROCNUM,
1010 ObjectIdGetDatum(opfamily),
1011 ObjectIdGetDatum(opcintype),
1012 ObjectIdGetDatum(opcintype),
1013 Int16GetDatum(GIST_COMPRESS_PROC));
1014 }
1015
1016 *isnull = false;
1017
1018 return true;
1019}
1020
1021/*
1022 * Temporary and unlogged GiST indexes are not WAL-logged, but we need LSNs
1023 * to detect concurrent page splits anyway. This function provides a fake
1024 * sequence of LSNs for that purpose.
1025 */
1026XLogRecPtr
1027gistGetFakeLSN(Relation rel)
1028{
1029 static XLogRecPtr counter = FirstNormalUnloggedLSN;
1030
1031 if (rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP)
1032 {
1033 /*
1034 * Temporary relations are only accessible in our session, so a simple
1035 * backend-local counter will do.
1036 */
1037 return counter++;
1038 }
1039 else
1040 {
1041 /*
1042 * Unlogged relations are accessible from other backends, and survive
1043 * (clean) restarts. GetFakeLSNForUnloggedRel() handles that for us.
1044 */
1045 Assert(rel->rd_rel->relpersistence == RELPERSISTENCE_UNLOGGED);
1046 return GetFakeLSNForUnloggedRel();
1047 }
1048}
1049