1 /*-------------------------------------------------------------------------
2 *
3 * gistutil.c
4 * utilities routines for the postgres GiST index access method.
5 *
6 *
7 * Portions Copyright (c) 1996-2020, 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/lsyscache.h"
26 #include "utils/snapmgr.h"
27 #include "utils/syscache.h"
28
29 /*
30 * Write itup vector to page, has no control of free space.
31 */
32 void
gistfillbuffer(Page page,IndexTuple * itup,int len,OffsetNumber off)33 gistfillbuffer(Page page, IndexTuple *itup, int len, OffsetNumber off)
34 {
35 OffsetNumber l = InvalidOffsetNumber;
36 int i;
37
38 if (off == InvalidOffsetNumber)
39 off = (PageIsEmpty(page)) ? FirstOffsetNumber :
40 OffsetNumberNext(PageGetMaxOffsetNumber(page));
41
42 for (i = 0; i < len; i++)
43 {
44 Size sz = IndexTupleSize(itup[i]);
45
46 l = PageAddItem(page, (Item) itup[i], sz, off, false, false);
47 if (l == InvalidOffsetNumber)
48 elog(ERROR, "failed to add item to GiST index page, item %d out of %d, size %d bytes",
49 i, len, (int) sz);
50 off++;
51 }
52 }
53
54 /*
55 * Check space for itup vector on page
56 */
57 bool
gistnospace(Page page,IndexTuple * itvec,int len,OffsetNumber todelete,Size freespace)58 gistnospace(Page page, IndexTuple *itvec, int len, OffsetNumber todelete, Size freespace)
59 {
60 unsigned int size = freespace,
61 deleted = 0;
62 int i;
63
64 for (i = 0; i < len; i++)
65 size += IndexTupleSize(itvec[i]) + sizeof(ItemIdData);
66
67 if (todelete != InvalidOffsetNumber)
68 {
69 IndexTuple itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, todelete));
70
71 deleted = IndexTupleSize(itup) + sizeof(ItemIdData);
72 }
73
74 return (PageGetFreeSpace(page) + deleted < size);
75 }
76
77 bool
gistfitpage(IndexTuple * itvec,int len)78 gistfitpage(IndexTuple *itvec, int len)
79 {
80 int i;
81 Size size = 0;
82
83 for (i = 0; i < len; i++)
84 size += IndexTupleSize(itvec[i]) + sizeof(ItemIdData);
85
86 /* TODO: Consider fillfactor */
87 return (size <= GiSTPageSize);
88 }
89
90 /*
91 * Read buffer into itup vector
92 */
93 IndexTuple *
gistextractpage(Page page,int * len)94 gistextractpage(Page page, int *len /* out */ )
95 {
96 OffsetNumber i,
97 maxoff;
98 IndexTuple *itvec;
99
100 maxoff = PageGetMaxOffsetNumber(page);
101 *len = maxoff;
102 itvec = palloc(sizeof(IndexTuple) * maxoff);
103 for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
104 itvec[i - FirstOffsetNumber] = (IndexTuple) PageGetItem(page, PageGetItemId(page, i));
105
106 return itvec;
107 }
108
109 /*
110 * join two vectors into one
111 */
112 IndexTuple *
gistjoinvector(IndexTuple * itvec,int * len,IndexTuple * additvec,int addlen)113 gistjoinvector(IndexTuple *itvec, int *len, IndexTuple *additvec, int addlen)
114 {
115 itvec = (IndexTuple *) repalloc((void *) itvec, sizeof(IndexTuple) * ((*len) + addlen));
116 memmove(&itvec[*len], additvec, sizeof(IndexTuple) * addlen);
117 *len += addlen;
118 return itvec;
119 }
120
121 /*
122 * make plain IndexTuple vector
123 */
124
125 IndexTupleData *
gistfillitupvec(IndexTuple * vec,int veclen,int * memlen)126 gistfillitupvec(IndexTuple *vec, int veclen, int *memlen)
127 {
128 char *ptr,
129 *ret;
130 int i;
131
132 *memlen = 0;
133
134 for (i = 0; i < veclen; i++)
135 *memlen += IndexTupleSize(vec[i]);
136
137 ptr = ret = palloc(*memlen);
138
139 for (i = 0; i < veclen; i++)
140 {
141 memcpy(ptr, vec[i], IndexTupleSize(vec[i]));
142 ptr += IndexTupleSize(vec[i]);
143 }
144
145 return (IndexTupleData *) ret;
146 }
147
148 /*
149 * Make unions of keys in IndexTuple vector (one union datum per index column).
150 * Union Datums are returned into the attr/isnull arrays.
151 * Resulting Datums aren't compressed.
152 */
153 void
gistMakeUnionItVec(GISTSTATE * giststate,IndexTuple * itvec,int len,Datum * attr,bool * isnull)154 gistMakeUnionItVec(GISTSTATE *giststate, IndexTuple *itvec, int len,
155 Datum *attr, bool *isnull)
156 {
157 int i;
158 GistEntryVector *evec;
159 int attrsize;
160
161 evec = (GistEntryVector *) palloc((len + 2) * sizeof(GISTENTRY) + GEVHDRSZ);
162
163 for (i = 0; i < giststate->nonLeafTupdesc->natts; i++)
164 {
165 int j;
166
167 /* Collect non-null datums for this column */
168 evec->n = 0;
169 for (j = 0; j < len; j++)
170 {
171 Datum datum;
172 bool IsNull;
173
174 datum = index_getattr(itvec[j], i + 1, giststate->leafTupdesc,
175 &IsNull);
176 if (IsNull)
177 continue;
178
179 gistdentryinit(giststate, i,
180 evec->vector + evec->n,
181 datum,
182 NULL, NULL, (OffsetNumber) 0,
183 false, IsNull);
184 evec->n++;
185 }
186
187 /* If this column was all NULLs, the union is NULL */
188 if (evec->n == 0)
189 {
190 attr[i] = (Datum) 0;
191 isnull[i] = true;
192 }
193 else
194 {
195 if (evec->n == 1)
196 {
197 /* unionFn may expect at least two inputs */
198 evec->n = 2;
199 evec->vector[1] = evec->vector[0];
200 }
201
202 /* Make union and store in attr array */
203 attr[i] = FunctionCall2Coll(&giststate->unionFn[i],
204 giststate->supportCollation[i],
205 PointerGetDatum(evec),
206 PointerGetDatum(&attrsize));
207
208 isnull[i] = false;
209 }
210 }
211 }
212
213 /*
214 * Return an IndexTuple containing the result of applying the "union"
215 * method to the specified IndexTuple vector.
216 */
217 IndexTuple
gistunion(Relation r,IndexTuple * itvec,int len,GISTSTATE * giststate)218 gistunion(Relation r, IndexTuple *itvec, int len, GISTSTATE *giststate)
219 {
220 Datum attr[INDEX_MAX_KEYS];
221 bool isnull[INDEX_MAX_KEYS];
222
223 gistMakeUnionItVec(giststate, itvec, len, attr, isnull);
224
225 return gistFormTuple(giststate, r, attr, isnull, false);
226 }
227
228 /*
229 * makes union of two key
230 */
231 void
gistMakeUnionKey(GISTSTATE * giststate,int attno,GISTENTRY * entry1,bool isnull1,GISTENTRY * entry2,bool isnull2,Datum * dst,bool * dstisnull)232 gistMakeUnionKey(GISTSTATE *giststate, int attno,
233 GISTENTRY *entry1, bool isnull1,
234 GISTENTRY *entry2, bool isnull2,
235 Datum *dst, bool *dstisnull)
236 {
237 /* we need a GistEntryVector with room for exactly 2 elements */
238 union
239 {
240 GistEntryVector gev;
241 char padding[2 * sizeof(GISTENTRY) + GEVHDRSZ];
242 } storage;
243 GistEntryVector *evec = &storage.gev;
244 int dstsize;
245
246 evec->n = 2;
247
248 if (isnull1 && isnull2)
249 {
250 *dstisnull = true;
251 *dst = (Datum) 0;
252 }
253 else
254 {
255 if (isnull1 == false && isnull2 == false)
256 {
257 evec->vector[0] = *entry1;
258 evec->vector[1] = *entry2;
259 }
260 else if (isnull1 == false)
261 {
262 evec->vector[0] = *entry1;
263 evec->vector[1] = *entry1;
264 }
265 else
266 {
267 evec->vector[0] = *entry2;
268 evec->vector[1] = *entry2;
269 }
270
271 *dstisnull = false;
272 *dst = FunctionCall2Coll(&giststate->unionFn[attno],
273 giststate->supportCollation[attno],
274 PointerGetDatum(evec),
275 PointerGetDatum(&dstsize));
276 }
277 }
278
279 bool
gistKeyIsEQ(GISTSTATE * giststate,int attno,Datum a,Datum b)280 gistKeyIsEQ(GISTSTATE *giststate, int attno, Datum a, Datum b)
281 {
282 bool result;
283
284 FunctionCall3Coll(&giststate->equalFn[attno],
285 giststate->supportCollation[attno],
286 a, b,
287 PointerGetDatum(&result));
288 return result;
289 }
290
291 /*
292 * Decompress all keys in tuple
293 */
294 void
gistDeCompressAtt(GISTSTATE * giststate,Relation r,IndexTuple tuple,Page p,OffsetNumber o,GISTENTRY * attdata,bool * isnull)295 gistDeCompressAtt(GISTSTATE *giststate, Relation r, IndexTuple tuple, Page p,
296 OffsetNumber o, GISTENTRY *attdata, bool *isnull)
297 {
298 int i;
299
300 for (i = 0; i < IndexRelationGetNumberOfKeyAttributes(r); i++)
301 {
302 Datum datum;
303
304 datum = index_getattr(tuple, i + 1, giststate->leafTupdesc, &isnull[i]);
305 gistdentryinit(giststate, i, &attdata[i],
306 datum, r, p, o,
307 false, isnull[i]);
308 }
309 }
310
311 /*
312 * Forms union of oldtup and addtup, if union == oldtup then return NULL
313 */
314 IndexTuple
gistgetadjusted(Relation r,IndexTuple oldtup,IndexTuple addtup,GISTSTATE * giststate)315 gistgetadjusted(Relation r, IndexTuple oldtup, IndexTuple addtup, GISTSTATE *giststate)
316 {
317 bool neednew = false;
318 GISTENTRY oldentries[INDEX_MAX_KEYS],
319 addentries[INDEX_MAX_KEYS];
320 bool oldisnull[INDEX_MAX_KEYS],
321 addisnull[INDEX_MAX_KEYS];
322 Datum attr[INDEX_MAX_KEYS];
323 bool isnull[INDEX_MAX_KEYS];
324 IndexTuple newtup = NULL;
325 int i;
326
327 gistDeCompressAtt(giststate, r, oldtup, NULL,
328 (OffsetNumber) 0, oldentries, oldisnull);
329
330 gistDeCompressAtt(giststate, r, addtup, NULL,
331 (OffsetNumber) 0, addentries, addisnull);
332
333 for (i = 0; i < IndexRelationGetNumberOfKeyAttributes(r); i++)
334 {
335 gistMakeUnionKey(giststate, i,
336 oldentries + i, oldisnull[i],
337 addentries + i, addisnull[i],
338 attr + i, isnull + i);
339
340 if (neednew)
341 /* we already need new key, so we can skip check */
342 continue;
343
344 if (isnull[i])
345 /* union of key may be NULL if and only if both keys are NULL */
346 continue;
347
348 if (!addisnull[i])
349 {
350 if (oldisnull[i] ||
351 !gistKeyIsEQ(giststate, i, oldentries[i].key, attr[i]))
352 neednew = true;
353 }
354 }
355
356 if (neednew)
357 {
358 /* need to update key */
359 newtup = gistFormTuple(giststate, r, attr, isnull, false);
360 newtup->t_tid = oldtup->t_tid;
361 }
362
363 return newtup;
364 }
365
366 /*
367 * Search an upper index page for the entry with lowest penalty for insertion
368 * of the new index key contained in "it".
369 *
370 * Returns the index of the page entry to insert into.
371 */
372 OffsetNumber
gistchoose(Relation r,Page p,IndexTuple it,GISTSTATE * giststate)373 gistchoose(Relation r, Page p, IndexTuple it, /* it has compressed entry */
374 GISTSTATE *giststate)
375 {
376 OffsetNumber result;
377 OffsetNumber maxoff;
378 OffsetNumber i;
379 float best_penalty[INDEX_MAX_KEYS];
380 GISTENTRY entry,
381 identry[INDEX_MAX_KEYS];
382 bool isnull[INDEX_MAX_KEYS];
383 int keep_current_best;
384
385 Assert(!GistPageIsLeaf(p));
386
387 gistDeCompressAtt(giststate, r,
388 it, NULL, (OffsetNumber) 0,
389 identry, isnull);
390
391 /* we'll return FirstOffsetNumber if page is empty (shouldn't happen) */
392 result = FirstOffsetNumber;
393
394 /*
395 * The index may have multiple columns, and there's a penalty value for
396 * each column. The penalty associated with a column that appears earlier
397 * in the index definition is strictly more important than the penalty of
398 * a column that appears later in the index definition.
399 *
400 * best_penalty[j] is the best penalty we have seen so far for column j,
401 * or -1 when we haven't yet examined column j. Array entries to the
402 * right of the first -1 are undefined.
403 */
404 best_penalty[0] = -1;
405
406 /*
407 * If we find a tuple that's exactly as good as the currently best one, we
408 * could use either one. When inserting a lot of tuples with the same or
409 * similar keys, it's preferable to descend down the same path when
410 * possible, as that's more cache-friendly. On the other hand, if all
411 * inserts land on the same leaf page after a split, we're never going to
412 * insert anything to the other half of the split, and will end up using
413 * only 50% of the available space. Distributing the inserts evenly would
414 * lead to better space usage, but that hurts cache-locality during
415 * insertion. To get the best of both worlds, when we find a tuple that's
416 * exactly as good as the previous best, choose randomly whether to stick
417 * to the old best, or use the new one. Once we decide to stick to the
418 * old best, we keep sticking to it for any subsequent equally good tuples
419 * we might find. This favors tuples with low offsets, but still allows
420 * some inserts to go to other equally-good subtrees.
421 *
422 * keep_current_best is -1 if we haven't yet had to make a random choice
423 * whether to keep the current best tuple. If we have done so, and
424 * decided to keep it, keep_current_best is 1; if we've decided to
425 * replace, keep_current_best is 0. (This state will be reset to -1 as
426 * soon as we've made the replacement, but sometimes we make the choice in
427 * advance of actually finding a replacement best tuple.)
428 */
429 keep_current_best = -1;
430
431 /*
432 * Loop over tuples on page.
433 */
434 maxoff = PageGetMaxOffsetNumber(p);
435 Assert(maxoff >= FirstOffsetNumber);
436
437 for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
438 {
439 IndexTuple itup = (IndexTuple) PageGetItem(p, PageGetItemId(p, i));
440 bool zero_penalty;
441 int j;
442
443 zero_penalty = true;
444
445 /* Loop over index attributes. */
446 for (j = 0; j < IndexRelationGetNumberOfKeyAttributes(r); j++)
447 {
448 Datum datum;
449 float usize;
450 bool IsNull;
451
452 /* Compute penalty for this column. */
453 datum = index_getattr(itup, j + 1, giststate->leafTupdesc,
454 &IsNull);
455 gistdentryinit(giststate, j, &entry, datum, r, p, i,
456 false, IsNull);
457 usize = gistpenalty(giststate, j, &entry, IsNull,
458 &identry[j], isnull[j]);
459 if (usize > 0)
460 zero_penalty = false;
461
462 if (best_penalty[j] < 0 || usize < best_penalty[j])
463 {
464 /*
465 * New best penalty for column. Tentatively select this tuple
466 * as the target, and record the best penalty. Then reset the
467 * next column's penalty to "unknown" (and indirectly, the
468 * same for all the ones to its right). This will force us to
469 * adopt this tuple's penalty values as the best for all the
470 * remaining columns during subsequent loop iterations.
471 */
472 result = i;
473 best_penalty[j] = usize;
474
475 if (j < IndexRelationGetNumberOfKeyAttributes(r) - 1)
476 best_penalty[j + 1] = -1;
477
478 /* we have new best, so reset keep-it decision */
479 keep_current_best = -1;
480 }
481 else if (best_penalty[j] == usize)
482 {
483 /*
484 * The current tuple is exactly as good for this column as the
485 * best tuple seen so far. The next iteration of this loop
486 * will compare the next column.
487 */
488 }
489 else
490 {
491 /*
492 * The current tuple is worse for this column than the best
493 * tuple seen so far. Skip the remaining columns and move on
494 * to the next tuple, if any.
495 */
496 zero_penalty = false; /* so outer loop won't exit */
497 break;
498 }
499 }
500
501 /*
502 * If we looped past the last column, and did not update "result",
503 * then this tuple is exactly as good as the prior best tuple.
504 */
505 if (j == IndexRelationGetNumberOfKeyAttributes(r) && result != i)
506 {
507 if (keep_current_best == -1)
508 {
509 /* we didn't make the random choice yet for this old best */
510 keep_current_best = (random() <= (MAX_RANDOM_VALUE / 2)) ? 1 : 0;
511 }
512 if (keep_current_best == 0)
513 {
514 /* we choose to use the new tuple */
515 result = i;
516 /* choose again if there are even more exactly-as-good ones */
517 keep_current_best = -1;
518 }
519 }
520
521 /*
522 * If we find a tuple with zero penalty for all columns, and we've
523 * decided we don't want to search for another tuple with equal
524 * penalty, there's no need to examine remaining tuples; just break
525 * out of the loop and return it.
526 */
527 if (zero_penalty)
528 {
529 if (keep_current_best == -1)
530 {
531 /* we didn't make the random choice yet for this old best */
532 keep_current_best = (random() <= (MAX_RANDOM_VALUE / 2)) ? 1 : 0;
533 }
534 if (keep_current_best == 1)
535 break;
536 }
537 }
538
539 return result;
540 }
541
542 /*
543 * initialize a GiST entry with a decompressed version of key
544 */
545 void
gistdentryinit(GISTSTATE * giststate,int nkey,GISTENTRY * e,Datum k,Relation r,Page pg,OffsetNumber o,bool l,bool isNull)546 gistdentryinit(GISTSTATE *giststate, int nkey, GISTENTRY *e,
547 Datum k, Relation r, Page pg, OffsetNumber o,
548 bool l, bool isNull)
549 {
550 if (!isNull)
551 {
552 GISTENTRY *dep;
553
554 gistentryinit(*e, k, r, pg, o, l);
555
556 /* there may not be a decompress function in opclass */
557 if (!OidIsValid(giststate->decompressFn[nkey].fn_oid))
558 return;
559
560 dep = (GISTENTRY *)
561 DatumGetPointer(FunctionCall1Coll(&giststate->decompressFn[nkey],
562 giststate->supportCollation[nkey],
563 PointerGetDatum(e)));
564 /* decompressFn may just return the given pointer */
565 if (dep != e)
566 gistentryinit(*e, dep->key, dep->rel, dep->page, dep->offset,
567 dep->leafkey);
568 }
569 else
570 gistentryinit(*e, (Datum) 0, r, pg, o, l);
571 }
572
573 IndexTuple
gistFormTuple(GISTSTATE * giststate,Relation r,Datum attdata[],bool isnull[],bool isleaf)574 gistFormTuple(GISTSTATE *giststate, Relation r,
575 Datum attdata[], bool isnull[], bool isleaf)
576 {
577 Datum compatt[INDEX_MAX_KEYS];
578 int i;
579 IndexTuple res;
580
581 /*
582 * Call the compress method on each attribute.
583 */
584 for (i = 0; i < IndexRelationGetNumberOfKeyAttributes(r); i++)
585 {
586 if (isnull[i])
587 compatt[i] = (Datum) 0;
588 else
589 {
590 GISTENTRY centry;
591 GISTENTRY *cep;
592
593 gistentryinit(centry, attdata[i], r, NULL, (OffsetNumber) 0,
594 isleaf);
595 /* there may not be a compress function in opclass */
596 if (OidIsValid(giststate->compressFn[i].fn_oid))
597 cep = (GISTENTRY *)
598 DatumGetPointer(FunctionCall1Coll(&giststate->compressFn[i],
599 giststate->supportCollation[i],
600 PointerGetDatum(¢ry)));
601 else
602 cep = ¢ry;
603 compatt[i] = cep->key;
604 }
605 }
606
607 if (isleaf)
608 {
609 /*
610 * Emplace each included attribute if any.
611 */
612 for (; i < r->rd_att->natts; i++)
613 {
614 if (isnull[i])
615 compatt[i] = (Datum) 0;
616 else
617 compatt[i] = attdata[i];
618 }
619 }
620
621 res = index_form_tuple(isleaf ? giststate->leafTupdesc :
622 giststate->nonLeafTupdesc,
623 compatt, isnull);
624
625 /*
626 * The offset number on tuples on internal pages is unused. For historical
627 * reasons, it is set to 0xffff.
628 */
629 ItemPointerSetOffsetNumber(&(res->t_tid), 0xffff);
630 return res;
631 }
632
633 /*
634 * initialize a GiST entry with fetched value in key field
635 */
636 static Datum
gistFetchAtt(GISTSTATE * giststate,int nkey,Datum k,Relation r)637 gistFetchAtt(GISTSTATE *giststate, int nkey, Datum k, Relation r)
638 {
639 GISTENTRY fentry;
640 GISTENTRY *fep;
641
642 gistentryinit(fentry, k, r, NULL, (OffsetNumber) 0, false);
643
644 fep = (GISTENTRY *)
645 DatumGetPointer(FunctionCall1Coll(&giststate->fetchFn[nkey],
646 giststate->supportCollation[nkey],
647 PointerGetDatum(&fentry)));
648
649 /* fetchFn set 'key', return it to the caller */
650 return fep->key;
651 }
652
653 /*
654 * Fetch all keys in tuple.
655 * Returns a new HeapTuple containing the originally-indexed data.
656 */
657 HeapTuple
gistFetchTuple(GISTSTATE * giststate,Relation r,IndexTuple tuple)658 gistFetchTuple(GISTSTATE *giststate, Relation r, IndexTuple tuple)
659 {
660 MemoryContext oldcxt = MemoryContextSwitchTo(giststate->tempCxt);
661 Datum fetchatt[INDEX_MAX_KEYS];
662 bool isnull[INDEX_MAX_KEYS];
663 int i;
664
665 for (i = 0; i < IndexRelationGetNumberOfKeyAttributes(r); i++)
666 {
667 Datum datum;
668
669 datum = index_getattr(tuple, i + 1, giststate->leafTupdesc, &isnull[i]);
670
671 if (giststate->fetchFn[i].fn_oid != InvalidOid)
672 {
673 if (!isnull[i])
674 fetchatt[i] = gistFetchAtt(giststate, i, datum, r);
675 else
676 fetchatt[i] = (Datum) 0;
677 }
678 else if (giststate->compressFn[i].fn_oid == InvalidOid)
679 {
680 /*
681 * If opclass does not provide compress method that could change
682 * original value, att is necessarily stored in original form.
683 */
684 if (!isnull[i])
685 fetchatt[i] = datum;
686 else
687 fetchatt[i] = (Datum) 0;
688 }
689 else
690 {
691 /*
692 * Index-only scans not supported for this column. Since the
693 * planner chose an index-only scan anyway, it is not interested
694 * in this column, and we can replace it with a NULL.
695 */
696 isnull[i] = true;
697 fetchatt[i] = (Datum) 0;
698 }
699 }
700
701 /*
702 * Get each included attribute.
703 */
704 for (; i < r->rd_att->natts; i++)
705 {
706 fetchatt[i] = index_getattr(tuple, i + 1, giststate->leafTupdesc,
707 &isnull[i]);
708 }
709 MemoryContextSwitchTo(oldcxt);
710
711 return heap_form_tuple(giststate->fetchTupdesc, fetchatt, isnull);
712 }
713
714 float
gistpenalty(GISTSTATE * giststate,int attno,GISTENTRY * orig,bool isNullOrig,GISTENTRY * add,bool isNullAdd)715 gistpenalty(GISTSTATE *giststate, int attno,
716 GISTENTRY *orig, bool isNullOrig,
717 GISTENTRY *add, bool isNullAdd)
718 {
719 float penalty = 0.0;
720
721 if (giststate->penaltyFn[attno].fn_strict == false ||
722 (isNullOrig == false && isNullAdd == false))
723 {
724 FunctionCall3Coll(&giststate->penaltyFn[attno],
725 giststate->supportCollation[attno],
726 PointerGetDatum(orig),
727 PointerGetDatum(add),
728 PointerGetDatum(&penalty));
729 /* disallow negative or NaN penalty */
730 if (isnan(penalty) || penalty < 0.0)
731 penalty = 0.0;
732 }
733 else if (isNullOrig && isNullAdd)
734 penalty = 0.0;
735 else
736 {
737 /* try to prevent mixing null and non-null values */
738 penalty = get_float4_infinity();
739 }
740
741 return penalty;
742 }
743
744 /*
745 * Initialize a new index page
746 */
747 void
GISTInitBuffer(Buffer b,uint32 f)748 GISTInitBuffer(Buffer b, uint32 f)
749 {
750 GISTPageOpaque opaque;
751 Page page;
752 Size pageSize;
753
754 pageSize = BufferGetPageSize(b);
755 page = BufferGetPage(b);
756 PageInit(page, pageSize, sizeof(GISTPageOpaqueData));
757
758 opaque = GistPageGetOpaque(page);
759 /* page was already zeroed by PageInit, so this is not needed: */
760 /* memset(&(opaque->nsn), 0, sizeof(GistNSN)); */
761 opaque->rightlink = InvalidBlockNumber;
762 opaque->flags = f;
763 opaque->gist_page_id = GIST_PAGE_ID;
764 }
765
766 /*
767 * Verify that a freshly-read page looks sane.
768 */
769 void
gistcheckpage(Relation rel,Buffer buf)770 gistcheckpage(Relation rel, Buffer buf)
771 {
772 Page page = BufferGetPage(buf);
773
774 /*
775 * ReadBuffer verifies that every newly-read page passes
776 * PageHeaderIsValid, which means it either contains a reasonably sane
777 * page header or is all-zero. We have to defend against the all-zero
778 * case, however.
779 */
780 if (PageIsNew(page))
781 ereport(ERROR,
782 (errcode(ERRCODE_INDEX_CORRUPTED),
783 errmsg("index \"%s\" contains unexpected zero page at block %u",
784 RelationGetRelationName(rel),
785 BufferGetBlockNumber(buf)),
786 errhint("Please REINDEX it.")));
787
788 /*
789 * Additionally check that the special area looks sane.
790 */
791 if (PageGetSpecialSize(page) != MAXALIGN(sizeof(GISTPageOpaqueData)))
792 ereport(ERROR,
793 (errcode(ERRCODE_INDEX_CORRUPTED),
794 errmsg("index \"%s\" contains corrupted page at block %u",
795 RelationGetRelationName(rel),
796 BufferGetBlockNumber(buf)),
797 errhint("Please REINDEX it.")));
798 }
799
800
801 /*
802 * Allocate a new page (either by recycling, or by extending the index file)
803 *
804 * The returned buffer is already pinned and exclusive-locked
805 *
806 * Caller is responsible for initializing the page by calling GISTInitBuffer
807 */
808 Buffer
gistNewBuffer(Relation r)809 gistNewBuffer(Relation r)
810 {
811 Buffer buffer;
812 bool needLock;
813
814 /* First, try to get a page from FSM */
815 for (;;)
816 {
817 BlockNumber blkno = GetFreeIndexPage(r);
818
819 if (blkno == InvalidBlockNumber)
820 break; /* nothing left in FSM */
821
822 buffer = ReadBuffer(r, blkno);
823
824 /*
825 * We have to guard against the possibility that someone else already
826 * recycled this page; the buffer may be locked if so.
827 */
828 if (ConditionalLockBuffer(buffer))
829 {
830 Page page = BufferGetPage(buffer);
831
832 /*
833 * If the page was never initialized, it's OK to use.
834 */
835 if (PageIsNew(page))
836 return buffer;
837
838 gistcheckpage(r, buffer);
839
840 /*
841 * Otherwise, recycle it if deleted, and too old to have any
842 * processes interested in it.
843 */
844 if (gistPageRecyclable(page))
845 {
846 /*
847 * If we are generating WAL for Hot Standby then create a WAL
848 * record that will allow us to conflict with queries running
849 * on standby, in case they have snapshots older than the
850 * page's deleteXid.
851 */
852 if (XLogStandbyInfoActive() && RelationNeedsWAL(r))
853 gistXLogPageReuse(r, blkno, GistPageGetDeleteXid(page));
854
855 return buffer;
856 }
857
858 LockBuffer(buffer, GIST_UNLOCK);
859 }
860
861 /* Can't use it, so release buffer and try again */
862 ReleaseBuffer(buffer);
863 }
864
865 /* Must extend the file */
866 needLock = !RELATION_IS_LOCAL(r);
867
868 if (needLock)
869 LockRelationForExtension(r, ExclusiveLock);
870
871 buffer = ReadBuffer(r, P_NEW);
872 LockBuffer(buffer, GIST_EXCLUSIVE);
873
874 if (needLock)
875 UnlockRelationForExtension(r, ExclusiveLock);
876
877 return buffer;
878 }
879
880 /* Can this page be recycled yet? */
881 bool
gistPageRecyclable(Page page)882 gistPageRecyclable(Page page)
883 {
884 if (PageIsNew(page))
885 return true;
886 if (GistPageIsDeleted(page))
887 {
888 /*
889 * The page was deleted, but when? If it was just deleted, a scan
890 * might have seen the downlink to it, and will read the page later.
891 * As long as that can happen, we must keep the deleted page around as
892 * a tombstone.
893 *
894 * Compare the deletion XID with RecentGlobalXmin. If deleteXid <
895 * RecentGlobalXmin, then no scan that's still in progress could have
896 * seen its downlink, and we can recycle it.
897 */
898 FullTransactionId deletexid_full = GistPageGetDeleteXid(page);
899 FullTransactionId recentxmin_full = GetFullRecentGlobalXmin();
900
901 if (FullTransactionIdPrecedes(deletexid_full, recentxmin_full))
902 return true;
903 }
904 return false;
905 }
906
907 bytea *
gistoptions(Datum reloptions,bool validate)908 gistoptions(Datum reloptions, bool validate)
909 {
910 static const relopt_parse_elt tab[] = {
911 {"fillfactor", RELOPT_TYPE_INT, offsetof(GiSTOptions, fillfactor)},
912 {"buffering", RELOPT_TYPE_ENUM, offsetof(GiSTOptions, buffering_mode)}
913 };
914
915 return (bytea *) build_reloptions(reloptions, validate,
916 RELOPT_KIND_GIST,
917 sizeof(GiSTOptions),
918 tab, lengthof(tab));
919 }
920
921 /*
922 * gistproperty() -- Check boolean properties of indexes.
923 *
924 * This is optional for most AMs, but is required for GiST because the core
925 * property code doesn't support AMPROP_DISTANCE_ORDERABLE. We also handle
926 * AMPROP_RETURNABLE here to save opening the rel to call gistcanreturn.
927 */
928 bool
gistproperty(Oid index_oid,int attno,IndexAMProperty prop,const char * propname,bool * res,bool * isnull)929 gistproperty(Oid index_oid, int attno,
930 IndexAMProperty prop, const char *propname,
931 bool *res, bool *isnull)
932 {
933 Oid opclass,
934 opfamily,
935 opcintype;
936 int16 procno;
937
938 /* Only answer column-level inquiries */
939 if (attno == 0)
940 return false;
941
942 /*
943 * Currently, GiST distance-ordered scans require that there be a distance
944 * function in the opclass with the default types (i.e. the one loaded
945 * into the relcache entry, see initGISTstate). So we assume that if such
946 * a function exists, then there's a reason for it (rather than grubbing
947 * through all the opfamily's operators to find an ordered one).
948 *
949 * Essentially the same code can test whether we support returning the
950 * column data, since that's true if the opclass provides a fetch proc.
951 */
952
953 switch (prop)
954 {
955 case AMPROP_DISTANCE_ORDERABLE:
956 procno = GIST_DISTANCE_PROC;
957 break;
958 case AMPROP_RETURNABLE:
959 procno = GIST_FETCH_PROC;
960 break;
961 default:
962 return false;
963 }
964
965 /* First we need to know the column's opclass. */
966 opclass = get_index_column_opclass(index_oid, attno);
967 if (!OidIsValid(opclass))
968 {
969 *isnull = true;
970 return true;
971 }
972
973 /* Now look up the opclass family and input datatype. */
974 if (!get_opclass_opfamily_and_input_type(opclass, &opfamily, &opcintype))
975 {
976 *isnull = true;
977 return true;
978 }
979
980 /* And now we can check whether the function is provided. */
981
982 *res = SearchSysCacheExists4(AMPROCNUM,
983 ObjectIdGetDatum(opfamily),
984 ObjectIdGetDatum(opcintype),
985 ObjectIdGetDatum(opcintype),
986 Int16GetDatum(procno));
987
988 /*
989 * Special case: even without a fetch function, AMPROP_RETURNABLE is true
990 * if the opclass has no compress function.
991 */
992 if (prop == AMPROP_RETURNABLE && !*res)
993 {
994 *res = !SearchSysCacheExists4(AMPROCNUM,
995 ObjectIdGetDatum(opfamily),
996 ObjectIdGetDatum(opcintype),
997 ObjectIdGetDatum(opcintype),
998 Int16GetDatum(GIST_COMPRESS_PROC));
999 }
1000
1001 *isnull = false;
1002
1003 return true;
1004 }
1005
1006 /*
1007 * Some indexes are not WAL-logged, but we need LSNs to detect concurrent page
1008 * splits anyway. This function provides a fake sequence of LSNs for that
1009 * purpose.
1010 */
1011 XLogRecPtr
gistGetFakeLSN(Relation rel)1012 gistGetFakeLSN(Relation rel)
1013 {
1014 if (rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP)
1015 {
1016 /*
1017 * Temporary relations are only accessible in our session, so a simple
1018 * backend-local counter will do.
1019 */
1020 static XLogRecPtr counter = FirstNormalUnloggedLSN;
1021
1022 return counter++;
1023 }
1024 else if (rel->rd_rel->relpersistence == RELPERSISTENCE_PERMANENT)
1025 {
1026 /*
1027 * WAL-logging on this relation will start after commit, so its LSNs
1028 * must be distinct numbers smaller than the LSN at the next commit.
1029 * Emit a dummy WAL record if insert-LSN hasn't advanced after the
1030 * last call.
1031 */
1032 static XLogRecPtr lastlsn = InvalidXLogRecPtr;
1033 XLogRecPtr currlsn = GetXLogInsertRecPtr();
1034
1035 /* Shouldn't be called for WAL-logging relations */
1036 Assert(!RelationNeedsWAL(rel));
1037
1038 /* No need for an actual record if we already have a distinct LSN */
1039 if (!XLogRecPtrIsInvalid(lastlsn) && lastlsn == currlsn)
1040 currlsn = gistXLogAssignLSN();
1041
1042 lastlsn = currlsn;
1043 return currlsn;
1044 }
1045 else
1046 {
1047 /*
1048 * Unlogged relations are accessible from other backends, and survive
1049 * (clean) restarts. GetFakeLSNForUnloggedRel() handles that for us.
1050 */
1051 Assert(rel->rd_rel->relpersistence == RELPERSISTENCE_UNLOGGED);
1052 return GetFakeLSNForUnloggedRel();
1053 }
1054 }
1055