Age Owner Branch data TLA Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * bufpage.c
4 : : * POSTGRES standard buffer page code.
5 : : *
6 : : * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
7 : : * Portions Copyright (c) 1994, Regents of the University of California
8 : : *
9 : : *
10 : : * IDENTIFICATION
11 : : * src/backend/storage/page/bufpage.c
12 : : *
13 : : *-------------------------------------------------------------------------
14 : : */
15 : : #include "postgres.h"
16 : :
17 : : #include "access/htup_details.h"
18 : : #include "access/itup.h"
19 : : #include "access/xlog.h"
20 : : #include "pgstat.h"
21 : : #include "storage/checksum.h"
22 : : #include "utils/memdebug.h"
23 : : #include "utils/memutils.h"
24 : :
25 : :
26 : : /* GUC variable */
27 : : bool ignore_checksum_failure = false;
28 : :
29 : :
30 : : /* ----------------------------------------------------------------
31 : : * Page support functions
32 : : * ----------------------------------------------------------------
33 : : */
34 : :
35 : : /*
36 : : * PageInit
37 : : * Initializes the contents of a page.
38 : : * Note that we don't calculate an initial checksum here; that's not done
39 : : * until it's time to write.
40 : : */
41 : : void
10753 scrappy@hub.org 42 :CBC 350959 : PageInit(Page page, Size pageSize, Size specialSize)
43 : : {
10327 bruce@momjian.us 44 : 350959 : PageHeader p = (PageHeader) page;
45 : :
8821 tgl@sss.pgh.pa.us 46 : 350959 : specialSize = MAXALIGN(specialSize);
47 : :
10328 bruce@momjian.us 48 [ - + ]: 350959 : Assert(pageSize == BLCKSZ);
8569 49 [ - + ]: 350959 : Assert(pageSize > specialSize + SizeOfPageHeaderData);
50 : :
51 : : /* Make sure all fields of page are zero, as well as unused space */
8737 tgl@sss.pgh.pa.us 52 [ + - + - : 350959 : MemSet(p, 0, pageSize);
+ - - + -
- ]
53 : :
4653 simon@2ndQuadrant.co 54 : 350959 : p->pd_flags = 0;
8569 bruce@momjian.us 55 : 350959 : p->pd_lower = SizeOfPageHeaderData;
10328 56 : 350959 : p->pd_upper = pageSize - specialSize;
57 : 350959 : p->pd_special = pageSize - specialSize;
8507 tgl@sss.pgh.pa.us 58 : 350959 : PageSetPageSizeAndVersion(page, pageSize, PG_PAGE_LAYOUT_VERSION);
59 : : /* p->pd_prune_xid = InvalidTransactionId; done by above MemSet */
9118 vadim4o@yahoo.com 60 : 350959 : }
61 : :
62 : :
63 : : /*
64 : : * PageIsVerified
65 : : * Check that the page header and checksum (if any) appear valid.
66 : : *
67 : : * This is called when a page has just been read in from disk. The idea is
68 : : * to cheaply detect trashed pages before we go nuts following bogus line
69 : : * pointers, testing invalid transaction identifiers, etc.
70 : : *
71 : : * It turns out to be necessary to allow zeroed pages here too. Even though
72 : : * this routine is *not* called when deliberately adding a page to a relation,
73 : : * there are scenarios in which a zeroed page might be found in a table.
74 : : * (Example: a backend extends a relation, then crashes before it can write
75 : : * any WAL entry about the new page. The kernel will already have the
76 : : * zeroed page in the file, and it will stay that way after restart.) So we
77 : : * allow zeroed pages here, and are careful that the page access macros
78 : : * treat such a page as empty and without free space. Eventually, VACUUM
79 : : * will clean up such a page and make it usable.
80 : : *
81 : : * If flag PIV_LOG_WARNING/PIV_LOG_LOG is set, a WARNING/LOG message is logged
82 : : * in the event of a checksum failure.
83 : : *
84 : : * If flag PIV_IGNORE_CHECKSUM_FAILURE is set, checksum failures will cause a
85 : : * message about the failure to be emitted, but will not cause
86 : : * PageIsVerified() to return false.
87 : : *
88 : : * To allow the caller to report statistics about checksum failures,
89 : : * *checksum_failure_p can be passed in. Note that there may be checksum
90 : : * failures even if this function returns true, due to
91 : : * PIV_IGNORE_CHECKSUM_FAILURE.
92 : : */
93 : : bool
263 andres@anarazel.de 94 : 1350302 : PageIsVerified(PageData *page, BlockNumber blkno, int flags, bool *checksum_failure_p)
95 : : {
331 peter@eisentraut.org 96 : 1350302 : const PageHeaderData *p = (const PageHeaderData *) page;
97 : : size_t *pagebytes;
4653 simon@2ndQuadrant.co 98 : 1350302 : bool checksum_failure = false;
99 : 1350302 : bool header_sane = false;
tgl@sss.pgh.pa.us 100 : 1350302 : uint16 checksum = 0;
101 : :
263 andres@anarazel.de 102 [ + - ]: 1350302 : if (checksum_failure_p)
103 : 1350302 : *checksum_failure_p = false;
104 : :
105 : : /*
106 : : * Don't verify page data unless the page passes basic non-zero test
107 : : */
4653 simon@2ndQuadrant.co 108 [ + + ]: 1350302 : if (!PageIsNew(page))
109 : : {
2809 magnus@hagander.net 110 [ + + ]: 1345944 : if (DataChecksumsEnabled())
111 : : {
308 peter@eisentraut.org 112 : 1335724 : checksum = pg_checksum_page(page, blkno);
113 : :
4653 simon@2ndQuadrant.co 114 [ + + ]: 1335724 : if (checksum != p->pd_checksum)
115 : : {
116 : 48 : checksum_failure = true;
263 andres@anarazel.de 117 [ + - ]: 48 : if (checksum_failure_p)
118 : 48 : *checksum_failure_p = true;
119 : : }
120 : : }
121 : :
122 : : /*
123 : : * The following checks don't prove the header is correct, only that
124 : : * it looks sane enough to allow into the buffer pool. Later usage of
125 : : * the block can still reveal problems, which is why we offer the
126 : : * checksum option.
127 : : */
4653 simon@2ndQuadrant.co 128 [ + - ]: 1345944 : if ((p->pd_flags & ~PD_VALID_FLAG_BITS) == 0 &&
4585 bruce@momjian.us 129 [ + - ]: 1345944 : p->pd_lower <= p->pd_upper &&
130 [ + - ]: 1345944 : p->pd_upper <= p->pd_special &&
131 [ + + ]: 1345944 : p->pd_special <= BLCKSZ &&
132 [ + - ]: 1345824 : p->pd_special == MAXALIGN(p->pd_special))
4653 simon@2ndQuadrant.co 133 : 1345824 : header_sane = true;
134 : :
135 [ + + + + ]: 1345944 : if (header_sane && !checksum_failure)
136 : 1345785 : return true;
137 : : }
138 : :
139 : : /* Check all-zeroes case */
3387 andres@anarazel.de 140 : 4517 : pagebytes = (size_t *) page;
141 : :
394 michael@paquier.xyz 142 [ + + ]: 4517 : if (pg_memory_is_all_zeros(pagebytes, BLCKSZ))
4653 simon@2ndQuadrant.co 143 : 4358 : return true;
144 : :
145 : : /*
146 : : * Throw a WARNING/LOG, as instructed by PIV_LOG_*, if the checksum fails,
147 : : * but only after we've checked for the all-zeroes case.
148 : : */
149 [ + + ]: 159 : if (checksum_failure)
150 : : {
262 andres@anarazel.de 151 [ + - ]: 48 : if ((flags & (PIV_LOG_WARNING | PIV_LOG_LOG)) != 0)
152 [ - + + - ]: 48 : ereport(flags & PIV_LOG_WARNING ? WARNING : LOG,
153 : : (errcode(ERRCODE_DATA_CORRUPTED),
154 : : errmsg("page verification failed, calculated checksum %u but expected %u",
155 : : checksum, p->pd_checksum)));
156 : :
157 [ + + + + ]: 48 : if (header_sane && (flags & PIV_IGNORE_CHECKSUM_FAILURE))
4653 simon@2ndQuadrant.co 158 : 18 : return true;
159 : : }
160 : :
161 : 141 : return false;
162 : : }
163 : :
164 : :
165 : : /*
166 : : * PageAddItemExtended
167 : : *
168 : : * Add an item to a page. Return value is the offset at which it was
169 : : * inserted, or InvalidOffsetNumber if the item is not inserted for any
170 : : * reason. A WARNING is issued indicating the reason for the refusal.
171 : : *
172 : : * offsetNumber must be either InvalidOffsetNumber to specify finding a
173 : : * free line pointer, or a value between FirstOffsetNumber and one past
174 : : * the last existing item, to specify using that particular line pointer.
175 : : *
176 : : * If offsetNumber is valid and flag PAI_OVERWRITE is set, we just store
177 : : * the item at the specified offsetNumber, which must be either a
178 : : * currently-unused line pointer, or one past the last existing item.
179 : : *
180 : : * If offsetNumber is valid and flag PAI_OVERWRITE is not set, insert
181 : : * the item at the specified offsetNumber, moving existing items later
182 : : * in the array to make room.
183 : : *
184 : : * If offsetNumber is not valid, then assign a slot by finding the first
185 : : * one that is both unused and deallocated.
186 : : *
187 : : * If flag PAI_IS_HEAP is set, we enforce that there can't be more than
188 : : * MaxHeapTuplesPerPage line pointers on the page.
189 : : *
190 : : * !!! EREPORT(ERROR) IS DISALLOWED HERE !!!
191 : : */
192 : : OffsetNumber
3488 alvherre@alvh.no-ip. 193 : 34861722 : PageAddItemExtended(Page page,
194 : : const void *item,
195 : : Size size,
196 : : OffsetNumber offsetNumber,
197 : : int flags)
198 : : {
8737 tgl@sss.pgh.pa.us 199 : 34861722 : PageHeader phdr = (PageHeader) page;
200 : : Size alignedSize;
201 : : int lower;
202 : : int upper;
203 : : ItemId itemId;
204 : : OffsetNumber limit;
9280 205 : 34861722 : bool needshuffle = false;
206 : :
207 : : /*
208 : : * Be wary about corrupted page pointers
209 : : */
8569 bruce@momjian.us 210 [ + - ]: 34861722 : if (phdr->pd_lower < SizeOfPageHeaderData ||
8737 tgl@sss.pgh.pa.us 211 [ + - ]: 34861722 : phdr->pd_lower > phdr->pd_upper ||
212 [ + - ]: 34861722 : phdr->pd_upper > phdr->pd_special ||
213 [ - + ]: 34861722 : phdr->pd_special > BLCKSZ)
8182 tgl@sss.pgh.pa.us 214 [ # # ]:UBC 0 : ereport(PANIC,
215 : : (errcode(ERRCODE_DATA_CORRUPTED),
216 : : errmsg("corrupted page pointers: lower = %u, upper = %u, special = %u",
217 : : phdr->pd_lower, phdr->pd_upper, phdr->pd_special)));
218 : :
219 : : /*
220 : : * Select offsetNumber to place the new item at
221 : : */
10328 bruce@momjian.us 222 :CBC 34861722 : limit = OffsetNumberNext(PageGetMaxOffsetNumber(page));
223 : :
224 : : /* was offsetNumber passed in? */
225 [ + + + - : 34861722 : if (OffsetNumberIsValid(offsetNumber))
+ + ]
226 : : {
227 : : /* yes, check it */
3488 alvherre@alvh.no-ip. 228 [ + + ]: 23071901 : if ((flags & PAI_OVERWRITE) != 0)
229 : : {
9080 vadim4o@yahoo.com 230 [ + + ]: 1598154 : if (offsetNumber < limit)
231 : : {
1255 peter@eisentraut.org 232 : 21461 : itemId = PageGetItemId(page, offsetNumber);
6671 tgl@sss.pgh.pa.us 233 [ + - - + ]: 21461 : if (ItemIdIsUsed(itemId) || ItemIdHasStorage(itemId))
234 : : {
8182 tgl@sss.pgh.pa.us 235 [ # # ]:UBC 0 : elog(WARNING, "will not overwrite a used ItemId");
9080 vadim4o@yahoo.com 236 : 0 : return InvalidOffsetNumber;
237 : : }
238 : : }
239 : : }
240 : : else
241 : : {
8534 tgl@sss.pgh.pa.us 242 [ + + ]:CBC 21473747 : if (offsetNumber < limit)
3101 243 : 3436850 : needshuffle = true; /* need to move existing linp's */
244 : : }
245 : : }
246 : : else
247 : : {
248 : : /* offsetNumber was not passed in, so find a free slot */
249 : : /* if no free slot, we'll put it at limit (1st open slot) */
1255 peter@eisentraut.org 250 [ + + ]: 11789821 : if (PageHasFreeLinePointers(page))
251 : : {
252 : : /*
253 : : * Scan line pointer array to locate a "recyclable" (unused)
254 : : * ItemId.
255 : : *
256 : : * Always use earlier items first. PageTruncateLinePointerArray
257 : : * can only truncate unused items when they appear as a contiguous
258 : : * group at the end of the line pointer array.
259 : : */
1715 pg@bowt.ie 260 : 163059 : for (offsetNumber = FirstOffsetNumber;
1680 tgl@sss.pgh.pa.us 261 [ + + ]: 9915388 : offsetNumber < limit; /* limit is maxoff+1 */
1715 pg@bowt.ie 262 : 9752329 : offsetNumber++)
263 : : {
1255 peter@eisentraut.org 264 : 9906715 : itemId = PageGetItemId(page, offsetNumber);
265 : :
266 : : /*
267 : : * We check for no storage as well, just to be paranoid;
268 : : * unused items should never have storage. Assert() that the
269 : : * invariant is respected too.
270 : : */
1725 pg@bowt.ie 271 [ + + - + ]: 9906715 : Assert(ItemIdIsUsed(itemId) || !ItemIdHasStorage(itemId));
272 : :
6671 tgl@sss.pgh.pa.us 273 [ + + + - ]: 9906715 : if (!ItemIdIsUsed(itemId) && !ItemIdHasStorage(itemId))
6865 274 : 154386 : break;
275 : : }
276 [ + + ]: 163059 : if (offsetNumber >= limit)
277 : : {
278 : : /* the hint is wrong, so reset it */
1255 peter@eisentraut.org 279 : 8673 : PageClearHasFreeLinePointers(page);
280 : : }
281 : : }
282 : : else
283 : : {
284 : : /* don't bother searching if hint says there's no free slot */
6865 tgl@sss.pgh.pa.us 285 : 11626762 : offsetNumber = limit;
286 : : }
287 : : }
288 : :
289 : : /* Reject placing items beyond the first unused line pointer */
3386 290 [ - + ]: 34861722 : if (offsetNumber > limit)
291 : : {
8182 tgl@sss.pgh.pa.us 292 [ # # ]:UBC 0 : elog(WARNING, "specified item offset is too large");
8534 293 : 0 : return InvalidOffsetNumber;
294 : : }
295 : :
296 : : /* Reject placing items beyond heap boundary, if heap */
3488 alvherre@alvh.no-ip. 297 [ + + - + ]:CBC 34861722 : if ((flags & PAI_IS_HEAP) != 0 && offsetNumber > MaxHeapTuplesPerPage)
298 : : {
6663 tgl@sss.pgh.pa.us 299 [ # # ]:UBC 0 : elog(WARNING, "can't put more than MaxHeapTuplesPerPage items in a heap page");
300 : 0 : return InvalidOffsetNumber;
301 : : }
302 : :
303 : : /*
304 : : * Compute new lower and upper pointers for page, see if it'll fit.
305 : : *
306 : : * Note: do arithmetic as signed ints, to avoid mistakes if, say,
307 : : * alignedSize > pd_upper.
308 : : */
3386 tgl@sss.pgh.pa.us 309 [ + + + + ]:CBC 34861722 : if (offsetNumber == limit || needshuffle)
8737 310 : 34685875 : lower = phdr->pd_lower + sizeof(ItemIdData);
311 : : else
312 : 175847 : lower = phdr->pd_lower;
313 : :
9648 bruce@momjian.us 314 : 34861722 : alignedSize = MAXALIGN(size);
315 : :
8737 tgl@sss.pgh.pa.us 316 : 34861722 : upper = (int) phdr->pd_upper - (int) alignedSize;
317 : :
10328 bruce@momjian.us 318 [ - + ]: 34861722 : if (lower > upper)
9969 bruce@momjian.us 319 :UBC 0 : return InvalidOffsetNumber;
320 : :
321 : : /*
322 : : * OK to insert the item. First, shuffle the existing pointers if needed.
323 : : */
1255 peter@eisentraut.org 324 :CBC 34861722 : itemId = PageGetItemId(page, offsetNumber);
325 : :
8534 tgl@sss.pgh.pa.us 326 [ + + ]: 34861722 : if (needshuffle)
327 : 3436850 : memmove(itemId + 1, itemId,
328 : 3436850 : (limit - offsetNumber) * sizeof(ItemIdData));
329 : :
330 : : /* set the line pointer */
6671 331 : 34861722 : ItemIdSetNormal(itemId, upper, size);
332 : :
333 : : /*
334 : : * Items normally contain no uninitialized bytes. Core bufpage consumers
335 : : * conform, but this is not a necessary coding rule; a new index AM could
336 : : * opt to depart from it. However, data type input functions and other
337 : : * C-language functions that synthesize datums should initialize all
338 : : * bytes; datumIsEqual() relies on this. Testing here, along with the
339 : : * similar check in printtup(), helps to catch such mistakes.
340 : : *
341 : : * Values of the "name" type retrieved via index-only scans may contain
342 : : * uninitialized bytes; see comment in btrescan(). Valgrind will report
343 : : * this as an error, but it is safe to ignore.
344 : : */
345 : : VALGRIND_CHECK_MEM_IS_DEFINED(item, size);
346 : :
347 : : /* copy the item's data onto the page */
8534 348 : 34861722 : memcpy((char *) page + upper, item, size);
349 : :
350 : : /* adjust page header */
8737 351 : 34861722 : phdr->pd_lower = (LocationIndex) lower;
352 : 34861722 : phdr->pd_upper = (LocationIndex) upper;
353 : :
9969 bruce@momjian.us 354 : 34861722 : return offsetNumber;
355 : : }
356 : :
357 : :
358 : : /*
359 : : * PageGetTempPage
360 : : * Get a temporary page in local memory for special processing.
361 : : * The returned page is not initialized at all; caller must do that.
362 : : */
363 : : Page
331 peter@eisentraut.org 364 : 120 : PageGetTempPage(const PageData *page)
365 : : {
366 : : Size pageSize;
367 : : Page temp;
368 : :
6253 tgl@sss.pgh.pa.us 369 : 120 : pageSize = PageGetPageSize(page);
370 : 120 : temp = (Page) palloc(pageSize);
371 : :
372 : 120 : return temp;
373 : : }
374 : :
375 : : /*
376 : : * PageGetTempPageCopy
377 : : * Get a temporary page in local memory for special processing.
378 : : * The page is initialized by copying the contents of the given page.
379 : : */
380 : : Page
331 peter@eisentraut.org 381 : 4648 : PageGetTempPageCopy(const PageData *page)
382 : : {
383 : : Size pageSize;
384 : : Page temp;
385 : :
10328 bruce@momjian.us 386 : 4648 : pageSize = PageGetPageSize(page);
9280 tgl@sss.pgh.pa.us 387 : 4648 : temp = (Page) palloc(pageSize);
388 : :
8821 389 : 4648 : memcpy(temp, page, pageSize);
390 : :
6253 391 : 4648 : return temp;
392 : : }
393 : :
394 : : /*
395 : : * PageGetTempPageCopySpecial
396 : : * Get a temporary page in local memory for special processing.
397 : : * The page is PageInit'd with the same special-space size as the
398 : : * given page, and the special space is copied from the given page.
399 : : */
400 : : Page
331 peter@eisentraut.org 401 : 30469 : PageGetTempPageCopySpecial(const PageData *page)
402 : : {
403 : : Size pageSize;
404 : : Page temp;
405 : :
6253 tgl@sss.pgh.pa.us 406 : 30469 : pageSize = PageGetPageSize(page);
407 : 30469 : temp = (Page) palloc(pageSize);
408 : :
409 : 30469 : PageInit(temp, pageSize, PageGetSpecialSize(page));
410 : 91407 : memcpy(PageGetSpecialPointer(temp),
411 : 30469 : PageGetSpecialPointer(page),
412 : 30469 : PageGetSpecialSize(page));
413 : :
9969 bruce@momjian.us 414 : 30469 : return temp;
415 : : }
416 : :
417 : : /*
418 : : * PageRestoreTempPage
419 : : * Copy temporary page back to permanent page after special processing
420 : : * and release the temporary page.
421 : : */
422 : : void
10753 scrappy@hub.org 423 : 28993 : PageRestoreTempPage(Page tempPage, Page oldPage)
424 : : {
425 : : Size pageSize;
426 : :
10328 bruce@momjian.us 427 : 28993 : pageSize = PageGetPageSize(tempPage);
308 peter@eisentraut.org 428 : 28993 : memcpy(oldPage, tempPage, pageSize);
429 : :
10328 bruce@momjian.us 430 : 28993 : pfree(tempPage);
10753 scrappy@hub.org 431 : 28993 : }
432 : :
433 : : /*
434 : : * Tuple defrag support for PageRepairFragmentation and PageIndexMultiDelete
435 : : */
436 : : typedef struct itemIdCompactData
437 : : {
438 : : uint16 offsetindex; /* linp array index */
439 : : int16 itemoff; /* page offset of item data */
440 : : uint16 alignedlen; /* MAXALIGN(item data len) */
441 : : } itemIdCompactData;
442 : : typedef itemIdCompactData *itemIdCompact;
443 : :
444 : : /*
445 : : * After removing or marking some line pointers unused, move the tuples to
446 : : * remove the gaps caused by the removed items and reorder them back into
447 : : * reverse line pointer order in the page.
448 : : *
449 : : * This function can often be fairly hot, so it pays to take some measures to
450 : : * make it as optimal as possible.
451 : : *
452 : : * Callers may pass 'presorted' as true if the 'itemidbase' array is sorted in
453 : : * descending order of itemoff. When this is true we can just memmove()
454 : : * tuples towards the end of the page. This is quite a common case as it's
455 : : * the order that tuples are initially inserted into pages. When we call this
456 : : * function to defragment the tuples in the page then any new line pointers
457 : : * added to the page will keep that presorted order, so hitting this case is
458 : : * still very common for tables that are commonly updated.
459 : : *
460 : : * When the 'itemidbase' array is not presorted then we're unable to just
461 : : * memmove() tuples around freely. Doing so could cause us to overwrite the
462 : : * memory belonging to a tuple we've not moved yet. In this case, we copy all
463 : : * the tuples that need to be moved into a temporary buffer. We can then
464 : : * simply memcpy() out of that temp buffer back into the page at the correct
465 : : * location. Tuples are copied back into the page in the same order as the
466 : : * 'itemidbase' array, so we end up reordering the tuples back into reverse
467 : : * line pointer order. This will increase the chances of hitting the
468 : : * presorted case the next time around.
469 : : *
470 : : * Callers must ensure that nitems is > 0
471 : : */
472 : : static void
1918 drowley@postgresql.o 473 : 69034 : compactify_tuples(itemIdCompact itemidbase, int nitems, Page page, bool presorted)
474 : : {
3970 heikki.linnakangas@i 475 : 69034 : PageHeader phdr = (PageHeader) page;
476 : : Offset upper;
477 : : Offset copy_tail;
478 : : Offset copy_head;
479 : : itemIdCompact itemidptr;
480 : : int i;
481 : :
482 : : /* Code within will not work correctly if nitems == 0 */
1918 drowley@postgresql.o 483 [ - + ]: 69034 : Assert(nitems > 0);
484 : :
485 [ + + ]: 69034 : if (presorted)
486 : : {
487 : :
488 : : #ifdef USE_ASSERT_CHECKING
489 : : {
490 : : /*
491 : : * Verify we've not gotten any new callers that are incorrectly
492 : : * passing a true presorted value.
493 : : */
494 : 50610 : Offset lastoff = phdr->pd_special;
495 : :
496 [ + + ]: 1807460 : for (i = 0; i < nitems; i++)
497 : : {
498 : 1756850 : itemidptr = &itemidbase[i];
499 : :
500 [ - + ]: 1756850 : Assert(lastoff > itemidptr->itemoff);
501 : :
502 : 1756850 : lastoff = itemidptr->itemoff;
503 : : }
504 : : }
505 : : #endif /* USE_ASSERT_CHECKING */
506 : :
507 : : /*
508 : : * 'itemidbase' is already in the optimal order, i.e, lower item
509 : : * pointers have a higher offset. This allows us to memmove() the
510 : : * tuples up to the end of the page without having to worry about
511 : : * overwriting other tuples that have not been moved yet.
512 : : *
513 : : * There's a good chance that there are tuples already right at the
514 : : * end of the page that we can simply skip over because they're
515 : : * already in the correct location within the page. We'll do that
516 : : * first...
517 : : */
518 : 50610 : upper = phdr->pd_special;
519 : 50610 : i = 0;
520 : : do
521 : : {
522 : 735393 : itemidptr = &itemidbase[i];
523 [ + + ]: 735393 : if (upper != itemidptr->itemoff + itemidptr->alignedlen)
524 : 44787 : break;
525 : 690606 : upper -= itemidptr->alignedlen;
526 : :
527 : 690606 : i++;
528 [ + + ]: 690606 : } while (i < nitems);
529 : :
530 : : /*
531 : : * Now that we've found the first tuple that needs to be moved, we can
532 : : * do the tuple compactification. We try and make the least number of
533 : : * memmove() calls and only call memmove() when there's a gap. When
534 : : * we see a gap we just move all tuples after the gap up until the
535 : : * point of the last move operation.
536 : : */
537 : 50610 : copy_tail = copy_head = itemidptr->itemoff + itemidptr->alignedlen;
538 [ + + ]: 1116854 : for (; i < nitems; i++)
539 : : {
540 : : ItemId lp;
541 : :
542 : 1066244 : itemidptr = &itemidbase[i];
543 : 1066244 : lp = PageGetItemId(page, itemidptr->offsetindex + 1);
544 : :
545 [ + + ]: 1066244 : if (copy_head != itemidptr->itemoff + itemidptr->alignedlen)
546 : : {
547 : 122231 : memmove((char *) page + upper,
548 : 122231 : page + copy_head,
549 : 122231 : copy_tail - copy_head);
550 : :
551 : : /*
552 : : * We've now moved all tuples already seen, but not the
553 : : * current tuple, so we set the copy_tail to the end of this
554 : : * tuple so it can be moved in another iteration of the loop.
555 : : */
556 : 122231 : copy_tail = itemidptr->itemoff + itemidptr->alignedlen;
557 : : }
558 : : /* shift the target offset down by the length of this tuple */
559 : 1066244 : upper -= itemidptr->alignedlen;
560 : : /* point the copy_head to the start of this tuple */
561 : 1066244 : copy_head = itemidptr->itemoff;
562 : :
563 : : /* update the line pointer to reference the new offset */
564 : 1066244 : lp->lp_off = upper;
565 : : }
566 : :
567 : : /* move the remaining tuples. */
3970 heikki.linnakangas@i 568 : 50610 : memmove((char *) page + upper,
1918 drowley@postgresql.o 569 : 50610 : page + copy_head,
570 : 50610 : copy_tail - copy_head);
571 : : }
572 : : else
573 : : {
574 : : PGAlignedBlock scratch;
575 : 18424 : char *scratchptr = scratch.data;
576 : :
577 : : /*
578 : : * Non-presorted case: The tuples in the itemidbase array may be in
579 : : * any order. So, in order to move these to the end of the page we
580 : : * must make a temp copy of each tuple that needs to be moved before
581 : : * we copy them back into the page at the new offset.
582 : : *
583 : : * If a large percentage of tuples have been pruned (>75%) then we'll
584 : : * copy these into the temp buffer tuple-by-tuple, otherwise, we'll
585 : : * just do a single memcpy() for all tuples that need to be moved.
586 : : * When so many tuples have been removed there's likely to be a lot of
587 : : * gaps and it's unlikely that many non-movable tuples remain at the
588 : : * end of the page.
589 : : */
590 [ + + ]: 18424 : if (nitems < PageGetMaxOffsetNumber(page) / 4)
591 : : {
592 : 1070 : i = 0;
593 : : do
594 : : {
595 : 20835 : itemidptr = &itemidbase[i];
596 : 20835 : memcpy(scratchptr + itemidptr->itemoff, page + itemidptr->itemoff,
597 : 20835 : itemidptr->alignedlen);
598 : 20835 : i++;
599 [ + + ]: 20835 : } while (i < nitems);
600 : :
601 : : /* Set things up for the compactification code below */
602 : 1070 : i = 0;
603 : 1070 : itemidptr = &itemidbase[0];
604 : 1070 : upper = phdr->pd_special;
605 : : }
606 : : else
607 : : {
608 : 17354 : upper = phdr->pd_special;
609 : :
610 : : /*
611 : : * Many tuples are likely to already be in the correct location.
612 : : * There's no need to copy these into the temp buffer. Instead
613 : : * we'll just skip forward in the itemidbase array to the position
614 : : * that we do need to move tuples from so that the code below just
615 : : * leaves these ones alone.
616 : : */
617 : 17354 : i = 0;
618 : : do
619 : : {
620 : 407918 : itemidptr = &itemidbase[i];
621 [ + + ]: 407918 : if (upper != itemidptr->itemoff + itemidptr->alignedlen)
622 : 17354 : break;
623 : 390564 : upper -= itemidptr->alignedlen;
624 : :
625 : 390564 : i++;
626 [ + - ]: 390564 : } while (i < nitems);
627 : :
628 : : /* Copy all tuples that need to be moved into the temp buffer */
629 : 17354 : memcpy(scratchptr + phdr->pd_upper,
630 : 17354 : page + phdr->pd_upper,
631 : 17354 : upper - phdr->pd_upper);
632 : : }
633 : :
634 : : /*
635 : : * Do the tuple compactification. itemidptr is already pointing to
636 : : * the first tuple that we're going to move. Here we collapse the
637 : : * memcpy calls for adjacent tuples into a single call. This is done
638 : : * by delaying the memcpy call until we find a gap that needs to be
639 : : * closed.
640 : : */
641 : 18424 : copy_tail = copy_head = itemidptr->itemoff + itemidptr->alignedlen;
642 [ + + ]: 1909927 : for (; i < nitems; i++)
643 : : {
644 : : ItemId lp;
645 : :
646 : 1891503 : itemidptr = &itemidbase[i];
647 : 1891503 : lp = PageGetItemId(page, itemidptr->offsetindex + 1);
648 : :
649 : : /* copy pending tuples when we detect a gap */
650 [ + + ]: 1891503 : if (copy_head != itemidptr->itemoff + itemidptr->alignedlen)
651 : : {
652 : 548366 : memcpy((char *) page + upper,
653 : 548366 : scratchptr + copy_head,
654 : 548366 : copy_tail - copy_head);
655 : :
656 : : /*
657 : : * We've now copied all tuples already seen, but not the
658 : : * current tuple, so we set the copy_tail to the end of this
659 : : * tuple.
660 : : */
661 : 548366 : copy_tail = itemidptr->itemoff + itemidptr->alignedlen;
662 : : }
663 : : /* shift the target offset down by the length of this tuple */
664 : 1891503 : upper -= itemidptr->alignedlen;
665 : : /* point the copy_head to the start of this tuple */
666 : 1891503 : copy_head = itemidptr->itemoff;
667 : :
668 : : /* update the line pointer to reference the new offset */
669 : 1891503 : lp->lp_off = upper;
670 : : }
671 : :
672 : : /* Copy the remaining chunk */
673 : 18424 : memcpy((char *) page + upper,
674 : 18424 : scratchptr + copy_head,
675 : 18424 : copy_tail - copy_head);
676 : : }
677 : :
3970 heikki.linnakangas@i 678 : 69034 : phdr->pd_upper = upper;
679 : 69034 : }
680 : :
681 : : /*
682 : : * PageRepairFragmentation
683 : : *
684 : : * Frees fragmented space on a heap page following pruning.
685 : : *
686 : : * This routine is usable for heap pages only, but see PageIndexMultiDelete.
687 : : *
688 : : * This routine removes unused line pointers from the end of the line pointer
689 : : * array. This is possible when dead heap-only tuples get removed by pruning,
690 : : * especially when there were HOT chains with several tuples each beforehand.
691 : : *
692 : : * Caller had better have a full cleanup lock on page's buffer. As a side
693 : : * effect the page's PD_HAS_FREE_LINES hint bit will be set or unset as
694 : : * needed. Caller might also need to account for a reduction in the length of
695 : : * the line pointer array following array truncation.
696 : : */
697 : : void
6663 tgl@sss.pgh.pa.us 698 : 60776 : PageRepairFragmentation(Page page)
699 : : {
8821 700 : 60776 : Offset pd_lower = ((PageHeader) page)->pd_lower;
701 : 60776 : Offset pd_upper = ((PageHeader) page)->pd_upper;
702 : 60776 : Offset pd_special = ((PageHeader) page)->pd_special;
703 : : Offset last_offset;
704 : : itemIdCompactData itemidbase[MaxHeapTuplesPerPage];
705 : : itemIdCompact itemidptr;
706 : : ItemId lp;
707 : : int nline,
708 : : nstorage,
709 : : nunused;
1350 pg@bowt.ie 710 : 60776 : OffsetNumber finalusedlp = InvalidOffsetNumber;
711 : : int i;
712 : : Size totallen;
1918 drowley@postgresql.o 713 : 60776 : bool presorted = true; /* For now */
714 : :
715 : : /*
716 : : * It's worth the trouble to be more paranoid here than in most places,
717 : : * because we are about to reshuffle data in (what is usually) a shared
718 : : * disk buffer. If we aren't careful then corrupted pointers, lengths,
719 : : * etc could cause us to clobber adjacent disk buffers, spreading the data
720 : : * loss further. So, check everything.
721 : : */
8569 bruce@momjian.us 722 [ + - + - ]: 60776 : if (pd_lower < SizeOfPageHeaderData ||
8821 tgl@sss.pgh.pa.us 723 [ + - ]: 60776 : pd_lower > pd_upper ||
724 [ + - ]: 60776 : pd_upper > pd_special ||
725 : 60776 : pd_special > BLCKSZ ||
726 [ - + ]: 60776 : pd_special != MAXALIGN(pd_special))
8182 tgl@sss.pgh.pa.us 727 [ # # ]:UBC 0 : ereport(ERROR,
728 : : (errcode(ERRCODE_DATA_CORRUPTED),
729 : : errmsg("corrupted page pointers: lower = %u, upper = %u, special = %u",
730 : : pd_lower, pd_upper, pd_special)));
731 : :
732 : : /*
733 : : * Run through the line pointer array and collect data about live items.
734 : : */
8821 tgl@sss.pgh.pa.us 735 :CBC 60776 : nline = PageGetMaxOffsetNumber(page);
2966 736 : 60776 : itemidptr = itemidbase;
737 : 60776 : nunused = totallen = 0;
1918 drowley@postgresql.o 738 : 60776 : last_offset = pd_special;
6663 tgl@sss.pgh.pa.us 739 [ + + ]: 4928197 : for (i = FirstOffsetNumber; i <= nline; i++)
740 : : {
741 : 4867421 : lp = PageGetItemId(page, i);
7391 bruce@momjian.us 742 [ + + ]: 4867421 : if (ItemIdIsUsed(lp))
743 : : {
6671 tgl@sss.pgh.pa.us 744 [ + + ]: 4639944 : if (ItemIdHasStorage(lp))
745 : : {
2966 746 : 1762151 : itemidptr->offsetindex = i - 1;
747 : 1762151 : itemidptr->itemoff = ItemIdGetOffset(lp);
748 : :
1918 drowley@postgresql.o 749 [ + + ]: 1762151 : if (last_offset > itemidptr->itemoff)
750 : 1483799 : last_offset = itemidptr->itemoff;
751 : : else
752 : 278352 : presorted = false;
753 : :
2966 tgl@sss.pgh.pa.us 754 [ + - - + : 1762151 : if (unlikely(itemidptr->itemoff < (int) pd_upper ||
- + ]
755 : : itemidptr->itemoff >= (int) pd_special))
2966 tgl@sss.pgh.pa.us 756 [ # # ]:UBC 0 : ereport(ERROR,
757 : : (errcode(ERRCODE_DATA_CORRUPTED),
758 : : errmsg("corrupted line pointer: %u",
759 : : itemidptr->itemoff)));
2966 tgl@sss.pgh.pa.us 760 :CBC 1762151 : itemidptr->alignedlen = MAXALIGN(ItemIdGetLength(lp));
761 : 1762151 : totallen += itemidptr->alignedlen;
762 : 1762151 : itemidptr++;
763 : : }
764 : :
1350 pg@bowt.ie 765 : 4639944 : finalusedlp = i; /* Could be the final non-LP_UNUSED item */
766 : : }
767 : : else
768 : : {
769 : : /* Unused entries should have lp_len = 0, but make sure */
770 [ - + ]: 227477 : Assert(!ItemIdHasStorage(lp));
6671 tgl@sss.pgh.pa.us 771 : 227477 : ItemIdSetUnused(lp);
6663 772 : 227477 : nunused++;
773 : : }
774 : : }
775 : :
2966 776 : 60776 : nstorage = itemidptr - itemidbase;
6671 777 [ + + ]: 60776 : if (nstorage == 0)
778 : : {
779 : : /* Page is completely empty, so just reset it quickly */
7499 780 : 11736 : ((PageHeader) page)->pd_upper = pd_special;
781 : : }
782 : : else
783 : : {
784 : : /* Need to compact the page the hard way */
8821 785 [ - + ]: 49040 : if (totallen > (Size) (pd_special - pd_lower))
8182 tgl@sss.pgh.pa.us 786 [ # # ]:UBC 0 : ereport(ERROR,
787 : : (errcode(ERRCODE_DATA_CORRUPTED),
788 : : errmsg("corrupted item lengths: total %zu, available space %u",
789 : : totallen, pd_special - pd_lower)));
790 : :
1918 drowley@postgresql.o 791 :CBC 49040 : compactify_tuples(itemidbase, nstorage, page, presorted);
792 : : }
793 : :
1350 pg@bowt.ie 794 [ + + ]: 60776 : if (finalusedlp != nline)
795 : : {
796 : : /* The last line pointer is not the last used line pointer */
1315 tgl@sss.pgh.pa.us 797 : 2067 : int nunusedend = nline - finalusedlp;
798 : :
1350 pg@bowt.ie 799 [ + - - + ]: 2067 : Assert(nunused >= nunusedend && nunusedend > 0);
800 : :
801 : : /* remove trailing unused line pointers from the count */
802 : 2067 : nunused -= nunusedend;
803 : : /* truncate the line pointer array */
804 : 2067 : ((PageHeader) page)->pd_lower -= (sizeof(ItemIdData) * nunusedend);
805 : : }
806 : :
807 : : /* Set hint bit for PageAddItemExtended */
6663 tgl@sss.pgh.pa.us 808 [ + + ]: 60776 : if (nunused > 0)
6865 809 : 15493 : PageSetHasFreeLinePointers(page);
810 : : else
811 : 45283 : PageClearHasFreeLinePointers(page);
10753 scrappy@hub.org 812 : 60776 : }
813 : :
814 : : /*
815 : : * PageTruncateLinePointerArray
816 : : *
817 : : * Removes unused line pointers at the end of the line pointer array.
818 : : *
819 : : * This routine is usable for heap pages only. It is called by VACUUM during
820 : : * its second pass over the heap. We expect at least one LP_UNUSED line
821 : : * pointer on the page (if VACUUM didn't have an LP_DEAD item on the page that
822 : : * it just set to LP_UNUSED then it should not call here).
823 : : *
824 : : * We avoid truncating the line pointer array to 0 items, if necessary by
825 : : * leaving behind a single remaining LP_UNUSED item. This is a little
826 : : * arbitrary, but it seems like a good idea to avoid leaving a PageIsEmpty()
827 : : * page behind.
828 : : *
829 : : * Caller can have either an exclusive lock or a full cleanup lock on page's
830 : : * buffer. The page's PD_HAS_FREE_LINES hint bit will be set or unset based
831 : : * on whether or not we leave behind any remaining LP_UNUSED items.
832 : : */
833 : : void
1715 pg@bowt.ie 834 : 18394 : PageTruncateLinePointerArray(Page page)
835 : : {
836 : 18394 : PageHeader phdr = (PageHeader) page;
837 : 18394 : bool countdone = false,
838 : 18394 : sethint = false;
839 : 18394 : int nunusedend = 0;
840 : :
841 : : /* Scan line pointer array back-to-front */
842 [ + + ]: 1080193 : for (int i = PageGetMaxOffsetNumber(page); i >= FirstOffsetNumber; i--)
843 : : {
844 : 1079418 : ItemId lp = PageGetItemId(page, i);
845 : :
846 [ + + + + ]: 1079418 : if (!countdone && i > FirstOffsetNumber)
847 : : {
848 : : /*
849 : : * Still determining which line pointers from the end of the array
850 : : * will be truncated away. Either count another line pointer as
851 : : * safe to truncate, or notice that it's not safe to truncate
852 : : * additional line pointers (stop counting line pointers).
853 : : */
854 [ + + ]: 960831 : if (!ItemIdIsUsed(lp))
855 : 951411 : nunusedend++;
856 : : else
857 : 9420 : countdone = true;
858 : : }
859 : : else
860 : : {
861 : : /*
862 : : * Once we've stopped counting we still need to figure out if
863 : : * there are any remaining LP_UNUSED line pointers somewhere more
864 : : * towards the front of the array.
865 : : */
866 [ + + ]: 118587 : if (!ItemIdIsUsed(lp))
867 : : {
868 : : /*
869 : : * This is an unused line pointer that we won't be truncating
870 : : * away -- so there is at least one. Set hint on page.
871 : : */
872 : 17619 : sethint = true;
873 : 17619 : break;
874 : : }
875 : : }
876 : : }
877 : :
878 [ + + ]: 18394 : if (nunusedend > 0)
879 : : {
880 : 12132 : phdr->pd_lower -= sizeof(ItemIdData) * nunusedend;
881 : :
882 : : #ifdef CLOBBER_FREED_MEMORY
883 : 12132 : memset((char *) page + phdr->pd_lower, 0x7F,
884 : : sizeof(ItemIdData) * nunusedend);
885 : : #endif
886 : : }
887 : : else
888 [ - + ]: 6262 : Assert(sethint);
889 : :
890 : : /* Set hint bit for PageAddItemExtended */
891 [ + + ]: 18394 : if (sethint)
892 : 17619 : PageSetHasFreeLinePointers(page);
893 : : else
894 : 775 : PageClearHasFreeLinePointers(page);
895 : 18394 : }
896 : :
897 : : /*
898 : : * PageGetFreeSpace
899 : : * Returns the size of the free (allocatable) space on a page,
900 : : * reduced by the space needed for a new line pointer.
901 : : *
902 : : * Note: this should usually only be used on index pages. Use
903 : : * PageGetHeapFreeSpace on heap pages.
904 : : */
905 : : Size
331 peter@eisentraut.org 906 : 29106049 : PageGetFreeSpace(const PageData *page)
907 : : {
908 : 29106049 : const PageHeaderData *phdr = (const PageHeaderData *) page;
909 : : int space;
910 : :
911 : : /*
912 : : * Use signed arithmetic here so that we behave sensibly if pd_lower >
913 : : * pd_upper.
914 : : */
915 : 29106049 : space = (int) phdr->pd_upper - (int) phdr->pd_lower;
916 : :
8737 tgl@sss.pgh.pa.us 917 [ + + ]: 29106049 : if (space < (int) sizeof(ItemIdData))
9969 bruce@momjian.us 918 : 5924 : return 0;
6874 919 : 29100125 : space -= sizeof(ItemIdData);
920 : :
921 : 29100125 : return (Size) space;
922 : : }
923 : :
924 : : /*
925 : : * PageGetFreeSpaceForMultipleTuples
926 : : * Returns the size of the free (allocatable) space on a page,
927 : : * reduced by the space needed for multiple new line pointers.
928 : : *
929 : : * Note: this should usually only be used on index pages. Use
930 : : * PageGetHeapFreeSpace on heap pages.
931 : : */
932 : : Size
331 peter@eisentraut.org 933 : 65654 : PageGetFreeSpaceForMultipleTuples(const PageData *page, int ntups)
934 : : {
935 : 65654 : const PageHeaderData *phdr = (const PageHeaderData *) page;
936 : : int space;
937 : :
938 : : /*
939 : : * Use signed arithmetic here so that we behave sensibly if pd_lower >
940 : : * pd_upper.
941 : : */
942 : 65654 : space = (int) phdr->pd_upper - (int) phdr->pd_lower;
943 : :
3215 rhaas@postgresql.org 944 [ - + ]: 65654 : if (space < (int) (ntups * sizeof(ItemIdData)))
3215 rhaas@postgresql.org 945 :UBC 0 : return 0;
3215 rhaas@postgresql.org 946 :CBC 65654 : space -= ntups * sizeof(ItemIdData);
947 : :
948 : 65654 : return (Size) space;
949 : : }
950 : :
951 : : /*
952 : : * PageGetExactFreeSpace
953 : : * Returns the size of the free (allocatable) space on a page,
954 : : * without any consideration for adding/removing line pointers.
955 : : */
956 : : Size
331 peter@eisentraut.org 957 : 1632076 : PageGetExactFreeSpace(const PageData *page)
958 : : {
959 : 1632076 : const PageHeaderData *phdr = (const PageHeaderData *) page;
960 : : int space;
961 : :
962 : : /*
963 : : * Use signed arithmetic here so that we behave sensibly if pd_lower >
964 : : * pd_upper.
965 : : */
966 : 1632076 : space = (int) phdr->pd_upper - (int) phdr->pd_lower;
967 : :
6520 tgl@sss.pgh.pa.us 968 [ - + ]: 1632076 : if (space < 0)
6520 tgl@sss.pgh.pa.us 969 :UBC 0 : return 0;
970 : :
8737 tgl@sss.pgh.pa.us 971 :CBC 1632076 : return (Size) space;
972 : : }
973 : :
974 : :
975 : : /*
976 : : * PageGetHeapFreeSpace
977 : : * Returns the size of the free (allocatable) space on a page,
978 : : * reduced by the space needed for a new line pointer.
979 : : *
980 : : * The difference between this and PageGetFreeSpace is that this will return
981 : : * zero if there are already MaxHeapTuplesPerPage line pointers in the page
982 : : * and none are free. We use this to enforce that no more than
983 : : * MaxHeapTuplesPerPage line pointers are created on a heap page. (Although
984 : : * no more tuples than that could fit anyway, in the presence of redirected
985 : : * or dead line pointers it'd be possible to have too many line pointers.
986 : : * To avoid breaking code that assumes MaxHeapTuplesPerPage is a hard limit
987 : : * on the number of line pointers, we make this extra check.)
988 : : */
989 : : Size
331 peter@eisentraut.org 990 : 13838387 : PageGetHeapFreeSpace(const PageData *page)
991 : : {
992 : : Size space;
993 : :
6663 tgl@sss.pgh.pa.us 994 : 13838387 : space = PageGetFreeSpace(page);
995 [ + + ]: 13838387 : if (space > 0)
996 : : {
997 : : OffsetNumber offnum,
998 : : nline;
999 : :
1000 : : /*
1001 : : * Are there already MaxHeapTuplesPerPage line pointers in the page?
1002 : : */
1003 : 13827379 : nline = PageGetMaxOffsetNumber(page);
1004 [ + + ]: 13827379 : if (nline >= MaxHeapTuplesPerPage)
1005 : : {
1255 peter@eisentraut.org 1006 [ + + ]: 2428 : if (PageHasFreeLinePointers(page))
1007 : : {
1008 : : /*
1009 : : * Since this is just a hint, we must confirm that there is
1010 : : * indeed a free line pointer
1011 : : */
6427 bruce@momjian.us 1012 [ + + ]: 289884 : for (offnum = FirstOffsetNumber; offnum <= nline; offnum = OffsetNumberNext(offnum))
1013 : : {
331 peter@eisentraut.org 1014 : 289823 : ItemId lp = PageGetItemId(unconstify(PageData *, page), offnum);
1015 : :
6663 tgl@sss.pgh.pa.us 1016 [ + + ]: 289823 : if (!ItemIdIsUsed(lp))
1017 : 1097 : break;
1018 : : }
1019 : :
1020 [ + + ]: 1158 : if (offnum > nline)
1021 : : {
1022 : : /*
1023 : : * The hint is wrong, but we can't clear it here since we
1024 : : * don't have the ability to mark the page dirty.
1025 : : */
1026 : 61 : space = 0;
1027 : : }
1028 : : }
1029 : : else
1030 : : {
1031 : : /*
1032 : : * Although the hint might be wrong, PageAddItem will believe
1033 : : * it anyway, so we must believe it too.
1034 : : */
1035 : 1270 : space = 0;
1036 : : }
1037 : : }
1038 : : }
1039 : 13838387 : return space;
1040 : : }
1041 : :
1042 : :
1043 : : /*
1044 : : * PageIndexTupleDelete
1045 : : *
1046 : : * This routine does the work of removing a tuple from an index page.
1047 : : *
1048 : : * Unlike heap pages, we compact out the line pointer for the removed tuple.
1049 : : */
1050 : : void
10753 scrappy@hub.org 1051 : 504309 : PageIndexTupleDelete(Page page, OffsetNumber offnum)
1052 : : {
8737 tgl@sss.pgh.pa.us 1053 : 504309 : PageHeader phdr = (PageHeader) page;
1054 : : char *addr;
1055 : : ItemId tup;
1056 : : Size size;
1057 : : unsigned offset;
1058 : : int nbytes;
1059 : : int offidx;
1060 : : int nline;
1061 : :
1062 : : /*
1063 : : * As with PageRepairFragmentation, paranoia seems justified.
1064 : : */
8569 bruce@momjian.us 1065 [ + - ]: 504309 : if (phdr->pd_lower < SizeOfPageHeaderData ||
8737 tgl@sss.pgh.pa.us 1066 [ + - ]: 504309 : phdr->pd_lower > phdr->pd_upper ||
1067 [ + - ]: 504309 : phdr->pd_upper > phdr->pd_special ||
3386 1068 [ + - ]: 504309 : phdr->pd_special > BLCKSZ ||
1069 [ - + ]: 504309 : phdr->pd_special != MAXALIGN(phdr->pd_special))
8182 tgl@sss.pgh.pa.us 1070 [ # # ]:UBC 0 : ereport(ERROR,
1071 : : (errcode(ERRCODE_DATA_CORRUPTED),
1072 : : errmsg("corrupted page pointers: lower = %u, upper = %u, special = %u",
1073 : : phdr->pd_lower, phdr->pd_upper, phdr->pd_special)));
1074 : :
8737 tgl@sss.pgh.pa.us 1075 :CBC 504309 : nline = PageGetMaxOffsetNumber(page);
1076 [ + - - + ]: 504309 : if ((int) offnum <= 0 || (int) offnum > nline)
8182 tgl@sss.pgh.pa.us 1077 [ # # ]:UBC 0 : elog(ERROR, "invalid index offnum: %u", offnum);
1078 : :
1079 : : /* change offset number to offset index */
10328 bruce@momjian.us 1080 :CBC 504309 : offidx = offnum - 1;
1081 : :
1082 : 504309 : tup = PageGetItemId(page, offnum);
6671 tgl@sss.pgh.pa.us 1083 [ - + ]: 504309 : Assert(ItemIdHasStorage(tup));
10328 bruce@momjian.us 1084 : 504309 : size = ItemIdGetLength(tup);
8737 tgl@sss.pgh.pa.us 1085 : 504309 : offset = ItemIdGetOffset(tup);
1086 : :
1087 [ + - + - ]: 504309 : if (offset < phdr->pd_upper || (offset + size) > phdr->pd_special ||
3386 1088 [ - + ]: 504309 : offset != MAXALIGN(offset))
8182 tgl@sss.pgh.pa.us 1089 [ # # ]:UBC 0 : ereport(ERROR,
1090 : : (errcode(ERRCODE_DATA_CORRUPTED),
1091 : : errmsg("corrupted line pointer: offset = %u, size = %zu",
1092 : : offset, size)));
1093 : :
1094 : : /* Amount of space to actually be deleted */
3386 tgl@sss.pgh.pa.us 1095 :CBC 504309 : size = MAXALIGN(size);
1096 : :
1097 : : /*
1098 : : * First, we want to get rid of the pd_linp entry for the index tuple. We
1099 : : * copy all subsequent linp's back one slot in the array. We don't use
1100 : : * PageGetItemId, because we are manipulating the _array_, not individual
1101 : : * linp's.
1102 : : */
10328 bruce@momjian.us 1103 : 504309 : nbytes = phdr->pd_lower -
1104 : 504309 : ((char *) &phdr->pd_linp[offidx + 1] - (char *) phdr);
1105 : :
8534 tgl@sss.pgh.pa.us 1106 [ + + ]: 504309 : if (nbytes > 0)
308 peter@eisentraut.org 1107 : 490628 : memmove(&(phdr->pd_linp[offidx]),
1108 : 490628 : &(phdr->pd_linp[offidx + 1]),
1109 : : nbytes);
1110 : :
1111 : : /*
1112 : : * Now move everything between the old upper bound (beginning of tuple
1113 : : * space) and the beginning of the deleted tuple forward, so that space in
1114 : : * the middle of the page is left free. If we've just deleted the tuple
1115 : : * at the beginning of tuple space, then there's no need to do the copy.
1116 : : */
1117 : :
1118 : : /* beginning of tuple space */
8737 tgl@sss.pgh.pa.us 1119 : 504309 : addr = (char *) page + phdr->pd_upper;
1120 : :
1121 [ + + ]: 504309 : if (offset > phdr->pd_upper)
3386 1122 : 491199 : memmove(addr + size, addr, offset - phdr->pd_upper);
1123 : :
1124 : : /* adjust free space boundary pointers */
10328 bruce@momjian.us 1125 : 504309 : phdr->pd_upper += size;
1126 : 504309 : phdr->pd_lower -= sizeof(ItemIdData);
1127 : :
1128 : : /*
1129 : : * Finally, we need to adjust the linp entries that remain.
1130 : : *
1131 : : * Anything that used to be before the deleted tuple's data was moved
1132 : : * forward by the size of the deleted tuple.
1133 : : */
1134 [ + + ]: 504309 : if (!PageIsEmpty(page))
1135 : : {
1136 : : int i;
1137 : :
8737 tgl@sss.pgh.pa.us 1138 : 503520 : nline--; /* there's one less than when we started */
8376 bruce@momjian.us 1139 [ + + ]: 74679513 : for (i = 1; i <= nline; i++)
1140 : : {
1255 peter@eisentraut.org 1141 : 74175993 : ItemId ii = PageGetItemId(page, i);
1142 : :
6671 tgl@sss.pgh.pa.us 1143 [ - + ]: 74175993 : Assert(ItemIdHasStorage(ii));
7391 bruce@momjian.us 1144 [ + + ]: 74175993 : if (ItemIdGetOffset(ii) <= offset)
7862 1145 : 48105757 : ii->lp_off += size;
1146 : : }
1147 : : }
10753 scrappy@hub.org 1148 : 504309 : }
1149 : :
1150 : :
1151 : : /*
1152 : : * PageIndexMultiDelete
1153 : : *
1154 : : * This routine handles the case of deleting multiple tuples from an
1155 : : * index page at once. It is considerably faster than a loop around
1156 : : * PageIndexTupleDelete ... however, the caller *must* supply the array
1157 : : * of item numbers to be deleted in item number order!
1158 : : */
1159 : : void
7575 tgl@sss.pgh.pa.us 1160 : 22807 : PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
1161 : : {
1162 : 22807 : PageHeader phdr = (PageHeader) page;
1163 : 22807 : Offset pd_lower = phdr->pd_lower;
1164 : 22807 : Offset pd_upper = phdr->pd_upper;
1165 : 22807 : Offset pd_special = phdr->pd_special;
1166 : : Offset last_offset;
1167 : : itemIdCompactData itemidbase[MaxIndexTuplesPerPage];
1168 : : ItemIdData newitemids[MaxIndexTuplesPerPage];
1169 : : itemIdCompact itemidptr;
1170 : : ItemId lp;
1171 : : int nline,
1172 : : nused;
1173 : : Size totallen;
1174 : : Size size;
1175 : : unsigned offset;
1176 : : int nextitm;
1177 : : OffsetNumber offnum;
1918 drowley@postgresql.o 1178 : 22807 : bool presorted = true; /* For now */
1179 : :
3865 heikki.linnakangas@i 1180 [ - + ]: 22807 : Assert(nitems <= MaxIndexTuplesPerPage);
1181 : :
1182 : : /*
1183 : : * If there aren't very many items to delete, then retail
1184 : : * PageIndexTupleDelete is the best way. Delete the items in reverse
1185 : : * order so we don't have to think about adjusting item numbers for
1186 : : * previous deletions.
1187 : : *
1188 : : * TODO: tune the magic number here
1189 : : */
7575 tgl@sss.pgh.pa.us 1190 [ + + ]: 22807 : if (nitems <= 2)
1191 : : {
1192 [ + + ]: 5517 : while (--nitems >= 0)
1193 : 3108 : PageIndexTupleDelete(page, itemnos[nitems]);
1194 : 2409 : return;
1195 : : }
1196 : :
1197 : : /*
1198 : : * As with PageRepairFragmentation, paranoia seems justified.
1199 : : */
1200 [ + - + - ]: 20398 : if (pd_lower < SizeOfPageHeaderData ||
1201 [ + - ]: 20398 : pd_lower > pd_upper ||
1202 [ + - ]: 20398 : pd_upper > pd_special ||
1203 : 20398 : pd_special > BLCKSZ ||
1204 [ - + ]: 20398 : pd_special != MAXALIGN(pd_special))
7575 tgl@sss.pgh.pa.us 1205 [ # # ]:UBC 0 : ereport(ERROR,
1206 : : (errcode(ERRCODE_DATA_CORRUPTED),
1207 : : errmsg("corrupted page pointers: lower = %u, upper = %u, special = %u",
1208 : : pd_lower, pd_upper, pd_special)));
1209 : :
1210 : : /*
1211 : : * Scan the line pointer array and build a list of just the ones we are
1212 : : * going to keep. Notice we do not modify the page yet, since we are
1213 : : * still validity-checking.
1214 : : */
7575 tgl@sss.pgh.pa.us 1215 :CBC 20398 : nline = PageGetMaxOffsetNumber(page);
1216 : 20398 : itemidptr = itemidbase;
1217 : 20398 : totallen = 0;
1218 : 20398 : nused = 0;
1219 : 20398 : nextitm = 0;
1918 drowley@postgresql.o 1220 : 20398 : last_offset = pd_special;
6427 bruce@momjian.us 1221 [ + + ]: 4518324 : for (offnum = FirstOffsetNumber; offnum <= nline; offnum = OffsetNumberNext(offnum))
1222 : : {
7575 tgl@sss.pgh.pa.us 1223 : 4497926 : lp = PageGetItemId(page, offnum);
6671 1224 [ - + ]: 4497926 : Assert(ItemIdHasStorage(lp));
7575 1225 : 4497926 : size = ItemIdGetLength(lp);
1226 : 4497926 : offset = ItemIdGetOffset(lp);
1227 [ + - ]: 4497926 : if (offset < pd_upper ||
1228 [ + - ]: 4497926 : (offset + size) > pd_special ||
1229 [ - + ]: 4497926 : offset != MAXALIGN(offset))
7575 tgl@sss.pgh.pa.us 1230 [ # # ]:UBC 0 : ereport(ERROR,
1231 : : (errcode(ERRCODE_DATA_CORRUPTED),
1232 : : errmsg("corrupted line pointer: offset = %u, size = %zu",
1233 : : offset, size)));
1234 : :
7575 tgl@sss.pgh.pa.us 1235 [ + + + + ]:CBC 4497926 : if (nextitm < nitems && offnum == itemnos[nextitm])
1236 : : {
1237 : : /* skip item to be deleted */
1238 : 2221160 : nextitm++;
1239 : : }
1240 : : else
1241 : : {
3101 1242 : 2276766 : itemidptr->offsetindex = nused; /* where it will go */
7575 1243 : 2276766 : itemidptr->itemoff = offset;
1244 : :
1918 drowley@postgresql.o 1245 [ + + ]: 2276766 : if (last_offset > itemidptr->itemoff)
1246 : 1152210 : last_offset = itemidptr->itemoff;
1247 : : else
1248 : 1124556 : presorted = false;
1249 : :
7575 tgl@sss.pgh.pa.us 1250 : 2276766 : itemidptr->alignedlen = MAXALIGN(size);
1251 : 2276766 : totallen += itemidptr->alignedlen;
3970 heikki.linnakangas@i 1252 : 2276766 : newitemids[nused] = *lp;
7575 tgl@sss.pgh.pa.us 1253 : 2276766 : itemidptr++;
1254 : 2276766 : nused++;
1255 : : }
1256 : : }
1257 : :
1258 : : /* this will catch invalid or out-of-order itemnos[] */
1259 [ - + ]: 20398 : if (nextitm != nitems)
7575 tgl@sss.pgh.pa.us 1260 [ # # ]:UBC 0 : elog(ERROR, "incorrect index offsets supplied");
1261 : :
7575 tgl@sss.pgh.pa.us 1262 [ - + ]:CBC 20398 : if (totallen > (Size) (pd_special - pd_lower))
7575 tgl@sss.pgh.pa.us 1263 [ # # ]:UBC 0 : ereport(ERROR,
1264 : : (errcode(ERRCODE_DATA_CORRUPTED),
1265 : : errmsg("corrupted item lengths: total %zu, available space %u",
1266 : : totallen, pd_special - pd_lower)));
1267 : :
1268 : : /*
1269 : : * Looks good. Overwrite the line pointers with the copy, from which we've
1270 : : * removed all the unused items.
1271 : : */
3970 heikki.linnakangas@i 1272 :CBC 20398 : memcpy(phdr->pd_linp, newitemids, nused * sizeof(ItemIdData));
7499 tgl@sss.pgh.pa.us 1273 : 20398 : phdr->pd_lower = SizeOfPageHeaderData + nused * sizeof(ItemIdData);
1274 : :
1275 : : /* and compactify the tuple data */
1918 drowley@postgresql.o 1276 [ + + ]: 20398 : if (nused > 0)
1277 : 19994 : compactify_tuples(itemidbase, nused, page, presorted);
1278 : : else
1279 : 404 : phdr->pd_upper = pd_special;
1280 : : }
1281 : :
1282 : :
1283 : : /*
1284 : : * PageIndexTupleDeleteNoCompact
1285 : : *
1286 : : * Remove the specified tuple from an index page, but set its line pointer
1287 : : * to "unused" instead of compacting it out, except that it can be removed
1288 : : * if it's the last line pointer on the page.
1289 : : *
1290 : : * This is used for index AMs that require that existing TIDs of live tuples
1291 : : * remain unchanged, and are willing to allow unused line pointers instead.
1292 : : */
1293 : : void
3386 tgl@sss.pgh.pa.us 1294 : 338 : PageIndexTupleDeleteNoCompact(Page page, OffsetNumber offnum)
1295 : : {
4058 alvherre@alvh.no-ip. 1296 : 338 : PageHeader phdr = (PageHeader) page;
1297 : : char *addr;
1298 : : ItemId tup;
1299 : : Size size;
1300 : : unsigned offset;
1301 : : int nline;
1302 : :
1303 : : /*
1304 : : * As with PageRepairFragmentation, paranoia seems justified.
1305 : : */
3386 tgl@sss.pgh.pa.us 1306 [ + - ]: 338 : if (phdr->pd_lower < SizeOfPageHeaderData ||
1307 [ + - ]: 338 : phdr->pd_lower > phdr->pd_upper ||
1308 [ + - ]: 338 : phdr->pd_upper > phdr->pd_special ||
1309 [ + - ]: 338 : phdr->pd_special > BLCKSZ ||
1310 [ - + ]: 338 : phdr->pd_special != MAXALIGN(phdr->pd_special))
4058 alvherre@alvh.no-ip. 1311 [ # # ]:UBC 0 : ereport(ERROR,
1312 : : (errcode(ERRCODE_DATA_CORRUPTED),
1313 : : errmsg("corrupted page pointers: lower = %u, upper = %u, special = %u",
1314 : : phdr->pd_lower, phdr->pd_upper, phdr->pd_special)));
1315 : :
3386 tgl@sss.pgh.pa.us 1316 :CBC 338 : nline = PageGetMaxOffsetNumber(page);
1317 [ + - - + ]: 338 : if ((int) offnum <= 0 || (int) offnum > nline)
3386 tgl@sss.pgh.pa.us 1318 [ # # ]:UBC 0 : elog(ERROR, "invalid index offnum: %u", offnum);
1319 : :
3386 tgl@sss.pgh.pa.us 1320 :CBC 338 : tup = PageGetItemId(page, offnum);
1321 [ - + ]: 338 : Assert(ItemIdHasStorage(tup));
1322 : 338 : size = ItemIdGetLength(tup);
1323 : 338 : offset = ItemIdGetOffset(tup);
1324 : :
1325 [ + - + - ]: 338 : if (offset < phdr->pd_upper || (offset + size) > phdr->pd_special ||
1326 [ - + ]: 338 : offset != MAXALIGN(offset))
3386 tgl@sss.pgh.pa.us 1327 [ # # ]:UBC 0 : ereport(ERROR,
1328 : : (errcode(ERRCODE_DATA_CORRUPTED),
1329 : : errmsg("corrupted line pointer: offset = %u, size = %zu",
1330 : : offset, size)));
1331 : :
1332 : : /* Amount of space to actually be deleted */
3386 tgl@sss.pgh.pa.us 1333 :CBC 338 : size = MAXALIGN(size);
1334 : :
1335 : : /*
1336 : : * Either set the line pointer to "unused", or zap it if it's the last
1337 : : * one. (Note: it's possible that the next-to-last one(s) are already
1338 : : * unused, but we do not trouble to try to compact them out if so.)
1339 : : */
1340 [ + + ]: 338 : if ((int) offnum < nline)
1341 : 304 : ItemIdSetUnused(tup);
1342 : : else
1343 : : {
1344 : 34 : phdr->pd_lower -= sizeof(ItemIdData);
1345 : 34 : nline--; /* there's one less than when we started */
1346 : : }
1347 : :
1348 : : /*
1349 : : * Now move everything between the old upper bound (beginning of tuple
1350 : : * space) and the beginning of the deleted tuple forward, so that space in
1351 : : * the middle of the page is left free. If we've just deleted the tuple
1352 : : * at the beginning of tuple space, then there's no need to do the copy.
1353 : : */
1354 : :
1355 : : /* beginning of tuple space */
1356 : 338 : addr = (char *) page + phdr->pd_upper;
1357 : :
1358 [ + + ]: 338 : if (offset > phdr->pd_upper)
1359 : 304 : memmove(addr + size, addr, offset - phdr->pd_upper);
1360 : :
1361 : : /* adjust free space boundary pointer */
1362 : 338 : phdr->pd_upper += size;
1363 : :
1364 : : /*
1365 : : * Finally, we need to adjust the linp entries that remain.
1366 : : *
1367 : : * Anything that used to be before the deleted tuple's data was moved
1368 : : * forward by the size of the deleted tuple.
1369 : : */
1370 [ + + ]: 338 : if (!PageIsEmpty(page))
1371 : : {
1372 : : int i;
1373 : :
1374 [ + + ]: 86507 : for (i = 1; i <= nline; i++)
1375 : : {
1255 peter@eisentraut.org 1376 : 86174 : ItemId ii = PageGetItemId(page, i);
1377 : :
3386 tgl@sss.pgh.pa.us 1378 [ + + + + ]: 86174 : if (ItemIdHasStorage(ii) && ItemIdGetOffset(ii) <= offset)
1379 : 42279 : ii->lp_off += size;
1380 : : }
1381 : : }
4058 alvherre@alvh.no-ip. 1382 : 338 : }
1383 : :
1384 : :
1385 : : /*
1386 : : * PageIndexTupleOverwrite
1387 : : *
1388 : : * Replace a specified tuple on an index page.
1389 : : *
1390 : : * The new tuple is placed exactly where the old one had been, shifting
1391 : : * other tuples' data up or down as needed to keep the page compacted.
1392 : : * This is better than deleting and reinserting the tuple, because it
1393 : : * avoids any data shifting when the tuple size doesn't change; and
1394 : : * even when it does, we avoid moving the line pointers around.
1395 : : * This could be used by an index AM that doesn't want to unset the
1396 : : * LP_DEAD bit when it happens to be set. It could conceivably also be
1397 : : * used by an index AM that cares about the physical order of tuples as
1398 : : * well as their logical/ItemId order.
1399 : : *
1400 : : * If there's insufficient space for the new tuple, return false. Other
1401 : : * errors represent data-corruption problems, so we just elog.
1402 : : */
1403 : : bool
3386 tgl@sss.pgh.pa.us 1404 : 447044 : PageIndexTupleOverwrite(Page page, OffsetNumber offnum,
1405 : : const void *newtup, Size newsize)
1406 : : {
1407 : 447044 : PageHeader phdr = (PageHeader) page;
1408 : : ItemId tupid;
1409 : : int oldsize;
1410 : : unsigned offset;
1411 : : Size alignednewsize;
1412 : : int size_diff;
1413 : : int itemcount;
1414 : :
1415 : : /*
1416 : : * As with PageRepairFragmentation, paranoia seems justified.
1417 : : */
1418 [ + - ]: 447044 : if (phdr->pd_lower < SizeOfPageHeaderData ||
1419 [ + - ]: 447044 : phdr->pd_lower > phdr->pd_upper ||
1420 [ + - ]: 447044 : phdr->pd_upper > phdr->pd_special ||
1421 [ + - ]: 447044 : phdr->pd_special > BLCKSZ ||
1422 [ - + ]: 447044 : phdr->pd_special != MAXALIGN(phdr->pd_special))
3386 tgl@sss.pgh.pa.us 1423 [ # # ]:UBC 0 : ereport(ERROR,
1424 : : (errcode(ERRCODE_DATA_CORRUPTED),
1425 : : errmsg("corrupted page pointers: lower = %u, upper = %u, special = %u",
1426 : : phdr->pd_lower, phdr->pd_upper, phdr->pd_special)));
1427 : :
3386 tgl@sss.pgh.pa.us 1428 :CBC 447044 : itemcount = PageGetMaxOffsetNumber(page);
1429 [ + - - + ]: 447044 : if ((int) offnum <= 0 || (int) offnum > itemcount)
3386 tgl@sss.pgh.pa.us 1430 [ # # ]:UBC 0 : elog(ERROR, "invalid index offnum: %u", offnum);
1431 : :
3386 tgl@sss.pgh.pa.us 1432 :CBC 447044 : tupid = PageGetItemId(page, offnum);
1433 [ - + ]: 447044 : Assert(ItemIdHasStorage(tupid));
1434 : 447044 : oldsize = ItemIdGetLength(tupid);
1435 : 447044 : offset = ItemIdGetOffset(tupid);
1436 : :
1437 [ + - + - ]: 447044 : if (offset < phdr->pd_upper || (offset + oldsize) > phdr->pd_special ||
1438 [ - + ]: 447044 : offset != MAXALIGN(offset))
3386 tgl@sss.pgh.pa.us 1439 [ # # ]:UBC 0 : ereport(ERROR,
1440 : : (errcode(ERRCODE_DATA_CORRUPTED),
1441 : : errmsg("corrupted line pointer: offset = %u, size = %d",
1442 : : offset, oldsize)));
1443 : :
1444 : : /*
1445 : : * Determine actual change in space requirement, check for page overflow.
1446 : : */
3386 tgl@sss.pgh.pa.us 1447 :CBC 447044 : oldsize = MAXALIGN(oldsize);
1448 : 447044 : alignednewsize = MAXALIGN(newsize);
1449 [ - + ]: 447044 : if (alignednewsize > oldsize + (phdr->pd_upper - phdr->pd_lower))
3386 tgl@sss.pgh.pa.us 1450 :UBC 0 : return false;
1451 : :
1452 : : /*
1453 : : * Relocate existing data and update line pointers, unless the new tuple
1454 : : * is the same size as the old (after alignment), in which case there's
1455 : : * nothing to do. Notice that what we have to relocate is data before the
1456 : : * target tuple, not data after, so it's convenient to express size_diff
1457 : : * as the amount by which the tuple's size is decreasing, making it the
1458 : : * delta to add to pd_upper and affected line pointers.
1459 : : */
3386 tgl@sss.pgh.pa.us 1460 :CBC 447044 : size_diff = oldsize - (int) alignednewsize;
1461 [ + + ]: 447044 : if (size_diff != 0)
1462 : : {
1463 : 49244 : char *addr = (char *) page + phdr->pd_upper;
1464 : : int i;
1465 : :
1466 : : /* relocate all tuple data before the target tuple */
1467 : 49244 : memmove(addr + size_diff, addr, offset - phdr->pd_upper);
1468 : :
1469 : : /* adjust free space boundary pointer */
1470 : 49244 : phdr->pd_upper += size_diff;
1471 : :
1472 : : /* adjust affected line pointers too */
1473 [ + + ]: 7992017 : for (i = FirstOffsetNumber; i <= itemcount; i++)
1474 : : {
1255 peter@eisentraut.org 1475 : 7942773 : ItemId ii = PageGetItemId(page, i);
1476 : :
1477 : : /* Allow items without storage; currently only BRIN needs that */
3386 tgl@sss.pgh.pa.us 1478 [ + + + + ]: 7942773 : if (ItemIdHasStorage(ii) && ItemIdGetOffset(ii) <= offset)
1479 : 3843016 : ii->lp_off += size_diff;
1480 : : }
1481 : : }
1482 : :
1483 : : /* Update the item's tuple length without changing its lp_flags field */
2121 pg@bowt.ie 1484 : 447044 : tupid->lp_off = offset + size_diff;
1485 : 447044 : tupid->lp_len = newsize;
1486 : :
1487 : : /* Copy new tuple data onto page */
3386 tgl@sss.pgh.pa.us 1488 : 447044 : memcpy(PageGetItem(page, tupid), newtup, newsize);
1489 : :
1490 : 447044 : return true;
1491 : : }
1492 : :
1493 : :
1494 : : /*
1495 : : * Set checksum for a page in shared buffers.
1496 : : *
1497 : : * If checksums are disabled, or if the page is not initialized, just return
1498 : : * the input. Otherwise, we must make a copy of the page before calculating
1499 : : * the checksum, to prevent concurrent modifications (e.g. setting hint bits)
1500 : : * from making the final checksum invalid. It doesn't matter if we include or
1501 : : * exclude hints during the copy, as long as we write a valid page and
1502 : : * associated checksum.
1503 : : *
1504 : : * Returns a pointer to the block-sized data that needs to be written. Uses
1505 : : * statically-allocated memory, so the caller must immediately write the
1506 : : * returned page and not refer to it again.
1507 : : */
1508 : : char *
4653 simon@2ndQuadrant.co 1509 : 573020 : PageSetChecksumCopy(Page page, BlockNumber blkno)
1510 : : {
1511 : : static char *pageCopy = NULL;
1512 : :
1513 : : /* If we don't need a checksum, just return the passed-in data */
2809 magnus@hagander.net 1514 [ + + + + ]: 573020 : if (PageIsNew(page) || !DataChecksumsEnabled())
300 peter@eisentraut.org 1515 : 12290 : return page;
1516 : :
1517 : : /*
1518 : : * We allocate the copy space once and use it over on each subsequent
1519 : : * call. The point of palloc'ing here, rather than having a static char
1520 : : * array, is first to ensure adequate alignment for the checksumming code
1521 : : * and second to avoid wasting space in processes that never call this.
1522 : : */
4570 tgl@sss.pgh.pa.us 1523 [ + + ]: 560730 : if (pageCopy == NULL)
984 tmunro@postgresql.or 1524 : 2699 : pageCopy = MemoryContextAllocAligned(TopMemoryContext,
1525 : : BLCKSZ,
1526 : : PG_IO_ALIGN_SIZE,
1527 : : 0);
1528 : :
308 peter@eisentraut.org 1529 : 560730 : memcpy(pageCopy, page, BLCKSZ);
4570 tgl@sss.pgh.pa.us 1530 : 560730 : ((PageHeader) pageCopy)->pd_checksum = pg_checksum_page(pageCopy, blkno);
1531 : 560730 : return pageCopy;
1532 : : }
1533 : :
1534 : : /*
1535 : : * Set checksum for a page in private memory.
1536 : : *
1537 : : * This must only be used when we know that no other process can be modifying
1538 : : * the page buffer.
1539 : : */
1540 : : void
4653 simon@2ndQuadrant.co 1541 : 63949 : PageSetChecksumInplace(Page page, BlockNumber blkno)
1542 : : {
1543 : : /* If we don't need a checksum, just return */
2809 magnus@hagander.net 1544 [ + + + + ]: 63949 : if (PageIsNew(page) || !DataChecksumsEnabled())
4653 simon@2ndQuadrant.co 1545 : 2171 : return;
1546 : :
308 peter@eisentraut.org 1547 : 61778 : ((PageHeader) page)->pd_checksum = pg_checksum_page(page, blkno);
1548 : : }
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