Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * gistbuildbuffers.c
4 : * node buffer management functions for GiST buffering build algorithm.
5 : *
6 : *
7 : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
8 : * Portions Copyright (c) 1994, Regents of the University of California
9 : *
10 : * IDENTIFICATION
11 : * src/backend/access/gist/gistbuildbuffers.c
12 : *
13 : *-------------------------------------------------------------------------
14 : */
15 : #include "postgres.h"
16 :
17 : #include "access/gist_private.h"
18 : #include "storage/buffile.h"
19 : #include "storage/bufmgr.h"
20 : #include "utils/rel.h"
21 :
22 : static GISTNodeBufferPage *gistAllocateNewPageBuffer(GISTBuildBuffers *gfbb);
23 : static void gistAddLoadedBuffer(GISTBuildBuffers *gfbb,
24 : GISTNodeBuffer *nodeBuffer);
25 : static void gistLoadNodeBuffer(GISTBuildBuffers *gfbb,
26 : GISTNodeBuffer *nodeBuffer);
27 : static void gistUnloadNodeBuffer(GISTBuildBuffers *gfbb,
28 : GISTNodeBuffer *nodeBuffer);
29 : static void gistPlaceItupToPage(GISTNodeBufferPage *pageBuffer,
30 : IndexTuple itup);
31 : static void gistGetItupFromPage(GISTNodeBufferPage *pageBuffer,
32 : IndexTuple *itup);
33 : static long gistBuffersGetFreeBlock(GISTBuildBuffers *gfbb);
34 : static void gistBuffersReleaseBlock(GISTBuildBuffers *gfbb, long blocknum);
35 :
36 : static void ReadTempFileBlock(BufFile *file, long blknum, void *ptr);
37 : static void WriteTempFileBlock(BufFile *file, long blknum, const void *ptr);
38 :
39 :
40 : /*
41 : * Initialize GiST build buffers.
42 : */
43 : GISTBuildBuffers *
44 6 : gistInitBuildBuffers(int pagesPerBuffer, int levelStep, int maxLevel)
45 : {
46 : GISTBuildBuffers *gfbb;
47 : HASHCTL hashCtl;
48 :
49 6 : gfbb = palloc(sizeof(GISTBuildBuffers));
50 6 : gfbb->pagesPerBuffer = pagesPerBuffer;
51 6 : gfbb->levelStep = levelStep;
52 :
53 : /*
54 : * Create a temporary file to hold buffer pages that are swapped out of
55 : * memory.
56 : */
57 6 : gfbb->pfile = BufFileCreateTemp(false);
58 6 : gfbb->nFileBlocks = 0;
59 :
60 : /* Initialize free page management. */
61 6 : gfbb->nFreeBlocks = 0;
62 6 : gfbb->freeBlocksLen = 32;
63 6 : gfbb->freeBlocks = (long *) palloc(gfbb->freeBlocksLen * sizeof(long));
64 :
65 : /*
66 : * Current memory context will be used for all in-memory data structures
67 : * of buffers which are persistent during buffering build.
68 : */
69 6 : gfbb->context = CurrentMemoryContext;
70 :
71 : /*
72 : * nodeBuffersTab hash is association between index blocks and it's
73 : * buffers.
74 : */
75 6 : hashCtl.keysize = sizeof(BlockNumber);
76 6 : hashCtl.entrysize = sizeof(GISTNodeBuffer);
77 6 : hashCtl.hcxt = CurrentMemoryContext;
78 6 : gfbb->nodeBuffersTab = hash_create("gistbuildbuffers",
79 : 1024,
80 : &hashCtl,
81 : HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
82 :
83 6 : gfbb->bufferEmptyingQueue = NIL;
84 :
85 : /*
86 : * Per-level node buffers lists for final buffers emptying process. Node
87 : * buffers are inserted here when they are created.
88 : */
89 6 : gfbb->buffersOnLevelsLen = 1;
90 12 : gfbb->buffersOnLevels = (List **) palloc(sizeof(List *) *
91 6 : gfbb->buffersOnLevelsLen);
92 6 : gfbb->buffersOnLevels[0] = NIL;
93 :
94 : /*
95 : * Block numbers of node buffers which last pages are currently loaded
96 : * into main memory.
97 : */
98 6 : gfbb->loadedBuffersLen = 32;
99 6 : gfbb->loadedBuffers = (GISTNodeBuffer **) palloc(gfbb->loadedBuffersLen *
100 : sizeof(GISTNodeBuffer *));
101 6 : gfbb->loadedBuffersCount = 0;
102 :
103 6 : gfbb->rootlevel = maxLevel;
104 :
105 6 : return gfbb;
106 : }
107 :
108 : /*
109 : * Returns a node buffer for given block. The buffer is created if it
110 : * doesn't exist yet.
111 : */
112 : GISTNodeBuffer *
113 34356 : gistGetNodeBuffer(GISTBuildBuffers *gfbb, GISTSTATE *giststate,
114 : BlockNumber nodeBlocknum, int level)
115 : {
116 : GISTNodeBuffer *nodeBuffer;
117 : bool found;
118 :
119 : /* Find node buffer in hash table */
120 34356 : nodeBuffer = (GISTNodeBuffer *) hash_search(gfbb->nodeBuffersTab,
121 : &nodeBlocknum,
122 : HASH_ENTER,
123 : &found);
124 34356 : if (!found)
125 : {
126 : /*
127 : * Node buffer wasn't found. Initialize the new buffer as empty.
128 : */
129 18 : MemoryContext oldcxt = MemoryContextSwitchTo(gfbb->context);
130 :
131 : /* nodeBuffer->nodeBlocknum is the hash key and was filled in already */
132 18 : nodeBuffer->blocksCount = 0;
133 18 : nodeBuffer->pageBlocknum = InvalidBlockNumber;
134 18 : nodeBuffer->pageBuffer = NULL;
135 18 : nodeBuffer->queuedForEmptying = false;
136 18 : nodeBuffer->isTemp = false;
137 18 : nodeBuffer->level = level;
138 :
139 : /*
140 : * Add this buffer to the list of buffers on this level. Enlarge
141 : * buffersOnLevels array if needed.
142 : */
143 18 : if (level >= gfbb->buffersOnLevelsLen)
144 : {
145 : int i;
146 :
147 6 : gfbb->buffersOnLevels =
148 6 : (List **) repalloc(gfbb->buffersOnLevels,
149 6 : (level + 1) * sizeof(List *));
150 :
151 : /* initialize the enlarged portion */
152 12 : for (i = gfbb->buffersOnLevelsLen; i <= level; i++)
153 6 : gfbb->buffersOnLevels[i] = NIL;
154 6 : gfbb->buffersOnLevelsLen = level + 1;
155 : }
156 :
157 : /*
158 : * Prepend the new buffer to the list of buffers on this level. It's
159 : * not arbitrary that the new buffer is put to the beginning of the
160 : * list: in the final emptying phase we loop through all buffers at
161 : * each level, and flush them. If a page is split during the emptying,
162 : * it's more efficient to flush the new split pages first, before
163 : * moving on to pre-existing pages on the level. The buffers just
164 : * created during the page split are likely still in cache, so
165 : * flushing them immediately is more efficient than putting them to
166 : * the end of the queue.
167 : */
168 36 : gfbb->buffersOnLevels[level] = lcons(nodeBuffer,
169 18 : gfbb->buffersOnLevels[level]);
170 :
171 18 : MemoryContextSwitchTo(oldcxt);
172 : }
173 :
174 34356 : return nodeBuffer;
175 : }
176 :
177 : /*
178 : * Allocate memory for a buffer page.
179 : */
180 : static GISTNodeBufferPage *
181 48 : gistAllocateNewPageBuffer(GISTBuildBuffers *gfbb)
182 : {
183 : GISTNodeBufferPage *pageBuffer;
184 :
185 48 : pageBuffer = (GISTNodeBufferPage *) MemoryContextAllocZero(gfbb->context,
186 : BLCKSZ);
187 48 : pageBuffer->prev = InvalidBlockNumber;
188 :
189 : /* Set page free space */
190 48 : PAGE_FREE_SPACE(pageBuffer) = BLCKSZ - BUFFER_PAGE_DATA_OFFSET;
191 48 : return pageBuffer;
192 : }
193 :
194 : /*
195 : * Add specified buffer into loadedBuffers array.
196 : */
197 : static void
198 48 : gistAddLoadedBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer)
199 : {
200 : /* Never add a temporary buffer to the array */
201 48 : if (nodeBuffer->isTemp)
202 0 : return;
203 :
204 : /* Enlarge the array if needed */
205 48 : if (gfbb->loadedBuffersCount >= gfbb->loadedBuffersLen)
206 : {
207 0 : gfbb->loadedBuffersLen *= 2;
208 0 : gfbb->loadedBuffers = (GISTNodeBuffer **)
209 0 : repalloc(gfbb->loadedBuffers,
210 0 : gfbb->loadedBuffersLen * sizeof(GISTNodeBuffer *));
211 : }
212 :
213 48 : gfbb->loadedBuffers[gfbb->loadedBuffersCount] = nodeBuffer;
214 48 : gfbb->loadedBuffersCount++;
215 : }
216 :
217 : /*
218 : * Load last page of node buffer into main memory.
219 : */
220 : static void
221 18 : gistLoadNodeBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer)
222 : {
223 : /* Check if we really should load something */
224 18 : if (!nodeBuffer->pageBuffer && nodeBuffer->blocksCount > 0)
225 : {
226 : /* Allocate memory for page */
227 18 : nodeBuffer->pageBuffer = gistAllocateNewPageBuffer(gfbb);
228 :
229 : /* Read block from temporary file */
230 18 : ReadTempFileBlock(gfbb->pfile, nodeBuffer->pageBlocknum,
231 18 : nodeBuffer->pageBuffer);
232 :
233 : /* Mark file block as free */
234 18 : gistBuffersReleaseBlock(gfbb, nodeBuffer->pageBlocknum);
235 :
236 : /* Mark node buffer as loaded */
237 18 : gistAddLoadedBuffer(gfbb, nodeBuffer);
238 18 : nodeBuffer->pageBlocknum = InvalidBlockNumber;
239 : }
240 18 : }
241 :
242 : /*
243 : * Write last page of node buffer to the disk.
244 : */
245 : static void
246 42 : gistUnloadNodeBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer)
247 : {
248 : /* Check if we have something to write */
249 42 : if (nodeBuffer->pageBuffer)
250 : {
251 : BlockNumber blkno;
252 :
253 : /* Get free file block */
254 18 : blkno = gistBuffersGetFreeBlock(gfbb);
255 :
256 : /* Write block to the temporary file */
257 18 : WriteTempFileBlock(gfbb->pfile, blkno, nodeBuffer->pageBuffer);
258 :
259 : /* Free memory of that page */
260 18 : pfree(nodeBuffer->pageBuffer);
261 18 : nodeBuffer->pageBuffer = NULL;
262 :
263 : /* Save block number */
264 18 : nodeBuffer->pageBlocknum = blkno;
265 : }
266 42 : }
267 :
268 : /*
269 : * Write last pages of all node buffers to the disk.
270 : */
271 : void
272 18 : gistUnloadNodeBuffers(GISTBuildBuffers *gfbb)
273 : {
274 : int i;
275 :
276 : /* Unload all the buffers that have a page loaded in memory. */
277 60 : for (i = 0; i < gfbb->loadedBuffersCount; i++)
278 42 : gistUnloadNodeBuffer(gfbb, gfbb->loadedBuffers[i]);
279 :
280 : /* Now there are no node buffers with loaded last page */
281 18 : gfbb->loadedBuffersCount = 0;
282 18 : }
283 :
284 : /*
285 : * Add index tuple to buffer page.
286 : */
287 : static void
288 64074 : gistPlaceItupToPage(GISTNodeBufferPage *pageBuffer, IndexTuple itup)
289 : {
290 64074 : Size itupsz = IndexTupleSize(itup);
291 : char *ptr;
292 :
293 : /* There should be enough of space. */
294 : Assert(PAGE_FREE_SPACE(pageBuffer) >= MAXALIGN(itupsz));
295 :
296 : /* Reduce free space value of page to reserve a spot for the tuple. */
297 64074 : PAGE_FREE_SPACE(pageBuffer) -= MAXALIGN(itupsz);
298 :
299 : /* Get pointer to the spot we reserved (ie. end of free space). */
300 64074 : ptr = (char *) pageBuffer + BUFFER_PAGE_DATA_OFFSET
301 64074 : + PAGE_FREE_SPACE(pageBuffer);
302 :
303 : /* Copy the index tuple there. */
304 64074 : memcpy(ptr, itup, itupsz);
305 64074 : }
306 :
307 : /*
308 : * Get last item from buffer page and remove it from page.
309 : */
310 : static void
311 64074 : gistGetItupFromPage(GISTNodeBufferPage *pageBuffer, IndexTuple *itup)
312 : {
313 : IndexTuple ptr;
314 : Size itupsz;
315 :
316 : Assert(!PAGE_IS_EMPTY(pageBuffer)); /* Page shouldn't be empty */
317 :
318 : /* Get pointer to last index tuple */
319 64074 : ptr = (IndexTuple) ((char *) pageBuffer
320 : + BUFFER_PAGE_DATA_OFFSET
321 64074 : + PAGE_FREE_SPACE(pageBuffer));
322 64074 : itupsz = IndexTupleSize(ptr);
323 :
324 : /* Make a copy of the tuple */
325 64074 : *itup = (IndexTuple) palloc(itupsz);
326 64074 : memcpy(*itup, ptr, itupsz);
327 :
328 : /* Mark the space used by the tuple as free */
329 64074 : PAGE_FREE_SPACE(pageBuffer) += MAXALIGN(itupsz);
330 64074 : }
331 :
332 : /*
333 : * Push an index tuple to node buffer.
334 : */
335 : void
336 64074 : gistPushItupToNodeBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer,
337 : IndexTuple itup)
338 : {
339 : /*
340 : * Most part of memory operations will be in buffering build persistent
341 : * context. So, let's switch to it.
342 : */
343 64074 : MemoryContext oldcxt = MemoryContextSwitchTo(gfbb->context);
344 :
345 : /*
346 : * If the buffer is currently empty, create the first page.
347 : */
348 64074 : if (nodeBuffer->blocksCount == 0)
349 : {
350 30 : nodeBuffer->pageBuffer = gistAllocateNewPageBuffer(gfbb);
351 30 : nodeBuffer->blocksCount = 1;
352 30 : gistAddLoadedBuffer(gfbb, nodeBuffer);
353 : }
354 :
355 : /* Load last page of node buffer if it wasn't in memory already */
356 64074 : if (!nodeBuffer->pageBuffer)
357 0 : gistLoadNodeBuffer(gfbb, nodeBuffer);
358 :
359 : /*
360 : * Check if there is enough space on the last page for the tuple.
361 : */
362 64074 : if (PAGE_NO_SPACE(nodeBuffer->pageBuffer, itup))
363 : {
364 : /*
365 : * Nope. Swap previous block to disk and allocate a new one.
366 : */
367 : BlockNumber blkno;
368 :
369 : /* Write filled page to the disk */
370 306 : blkno = gistBuffersGetFreeBlock(gfbb);
371 306 : WriteTempFileBlock(gfbb->pfile, blkno, nodeBuffer->pageBuffer);
372 :
373 : /*
374 : * Reset the in-memory page as empty, and link the previous block to
375 : * the new page by storing its block number in the prev-link.
376 : */
377 306 : PAGE_FREE_SPACE(nodeBuffer->pageBuffer) =
378 : BLCKSZ - MAXALIGN(offsetof(GISTNodeBufferPage, tupledata));
379 306 : nodeBuffer->pageBuffer->prev = blkno;
380 :
381 : /* We've just added one more page */
382 306 : nodeBuffer->blocksCount++;
383 : }
384 :
385 64074 : gistPlaceItupToPage(nodeBuffer->pageBuffer, itup);
386 :
387 : /*
388 : * If the buffer just overflowed, add it to the emptying queue.
389 : */
390 64074 : if (BUFFER_HALF_FILLED(nodeBuffer, gfbb) && !nodeBuffer->queuedForEmptying)
391 : {
392 0 : gfbb->bufferEmptyingQueue = lcons(nodeBuffer,
393 : gfbb->bufferEmptyingQueue);
394 0 : nodeBuffer->queuedForEmptying = true;
395 : }
396 :
397 : /* Restore memory context */
398 64074 : MemoryContextSwitchTo(oldcxt);
399 64074 : }
400 :
401 : /*
402 : * Removes one index tuple from node buffer. Returns true if success and false
403 : * if node buffer is empty.
404 : */
405 : bool
406 64104 : gistPopItupFromNodeBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer,
407 : IndexTuple *itup)
408 : {
409 : /*
410 : * If node buffer is empty then return false.
411 : */
412 64104 : if (nodeBuffer->blocksCount <= 0)
413 30 : return false;
414 :
415 : /* Load last page of node buffer if needed */
416 64074 : if (!nodeBuffer->pageBuffer)
417 18 : gistLoadNodeBuffer(gfbb, nodeBuffer);
418 :
419 : /*
420 : * Get index tuple from last non-empty page.
421 : */
422 64074 : gistGetItupFromPage(nodeBuffer->pageBuffer, itup);
423 :
424 : /*
425 : * If we just removed the last tuple from the page, fetch previous page on
426 : * this node buffer (if any).
427 : */
428 64074 : if (PAGE_IS_EMPTY(nodeBuffer->pageBuffer))
429 : {
430 : BlockNumber prevblkno;
431 :
432 : /*
433 : * blocksCount includes the page in pageBuffer, so decrease it now.
434 : */
435 336 : nodeBuffer->blocksCount--;
436 :
437 : /*
438 : * If there's more pages, fetch previous one.
439 : */
440 336 : prevblkno = nodeBuffer->pageBuffer->prev;
441 336 : if (prevblkno != InvalidBlockNumber)
442 : {
443 : /* There is a previous page. Fetch it. */
444 : Assert(nodeBuffer->blocksCount > 0);
445 306 : ReadTempFileBlock(gfbb->pfile, prevblkno, nodeBuffer->pageBuffer);
446 :
447 : /*
448 : * Now that we've read the block in memory, we can release its
449 : * on-disk block for reuse.
450 : */
451 306 : gistBuffersReleaseBlock(gfbb, prevblkno);
452 : }
453 : else
454 : {
455 : /* No more pages. Free memory. */
456 : Assert(nodeBuffer->blocksCount == 0);
457 30 : pfree(nodeBuffer->pageBuffer);
458 30 : nodeBuffer->pageBuffer = NULL;
459 : }
460 : }
461 64074 : return true;
462 : }
463 :
464 : /*
465 : * Select a currently unused block for writing to.
466 : */
467 : static long
468 324 : gistBuffersGetFreeBlock(GISTBuildBuffers *gfbb)
469 : {
470 : /*
471 : * If there are multiple free blocks, we select the one appearing last in
472 : * freeBlocks[]. If there are none, assign the next block at the end of
473 : * the file (causing the file to be extended).
474 : */
475 324 : if (gfbb->nFreeBlocks > 0)
476 150 : return gfbb->freeBlocks[--gfbb->nFreeBlocks];
477 : else
478 174 : return gfbb->nFileBlocks++;
479 : }
480 :
481 : /*
482 : * Return a block# to the freelist.
483 : */
484 : static void
485 324 : gistBuffersReleaseBlock(GISTBuildBuffers *gfbb, long blocknum)
486 : {
487 : int ndx;
488 :
489 : /* Enlarge freeBlocks array if full. */
490 324 : if (gfbb->nFreeBlocks >= gfbb->freeBlocksLen)
491 : {
492 0 : gfbb->freeBlocksLen *= 2;
493 0 : gfbb->freeBlocks = (long *) repalloc(gfbb->freeBlocks,
494 0 : gfbb->freeBlocksLen *
495 : sizeof(long));
496 : }
497 :
498 : /* Add blocknum to array */
499 324 : ndx = gfbb->nFreeBlocks++;
500 324 : gfbb->freeBlocks[ndx] = blocknum;
501 324 : }
502 :
503 : /*
504 : * Free buffering build data structure.
505 : */
506 : void
507 6 : gistFreeBuildBuffers(GISTBuildBuffers *gfbb)
508 : {
509 : /* Close buffers file. */
510 6 : BufFileClose(gfbb->pfile);
511 :
512 : /* All other things will be freed on memory context release */
513 6 : }
514 :
515 : /*
516 : * Data structure representing information about node buffer for index tuples
517 : * relocation from split node buffer.
518 : */
519 : typedef struct
520 : {
521 : GISTENTRY entry[INDEX_MAX_KEYS];
522 : bool isnull[INDEX_MAX_KEYS];
523 : GISTPageSplitInfo *splitinfo;
524 : GISTNodeBuffer *nodeBuffer;
525 : } RelocationBufferInfo;
526 :
527 : /*
528 : * At page split, distribute tuples from the buffer of the split page to
529 : * new buffers for the created page halves. This also adjusts the downlinks
530 : * in 'splitinfo' to include the tuples in the buffers.
531 : */
532 : void
533 768 : gistRelocateBuildBuffersOnSplit(GISTBuildBuffers *gfbb, GISTSTATE *giststate,
534 : Relation r, int level,
535 : Buffer buffer, List *splitinfo)
536 : {
537 : RelocationBufferInfo *relocationBuffersInfos;
538 : bool found;
539 : GISTNodeBuffer *nodeBuffer;
540 : BlockNumber blocknum;
541 : IndexTuple itup;
542 768 : int splitPagesCount = 0;
543 : GISTENTRY entry[INDEX_MAX_KEYS];
544 : bool isnull[INDEX_MAX_KEYS];
545 : GISTNodeBuffer oldBuf;
546 : ListCell *lc;
547 :
548 : /* If the split page doesn't have buffers, we have nothing to do. */
549 768 : if (!LEVEL_HAS_BUFFERS(level, gfbb))
550 756 : return;
551 :
552 : /*
553 : * Get the node buffer of the split page.
554 : */
555 12 : blocknum = BufferGetBlockNumber(buffer);
556 12 : nodeBuffer = hash_search(gfbb->nodeBuffersTab, &blocknum,
557 : HASH_FIND, &found);
558 12 : if (!found)
559 : {
560 : /* The page has no buffer, so we have nothing to do. */
561 0 : return;
562 : }
563 :
564 : /*
565 : * Make a copy of the old buffer, as we're going reuse it as the buffer
566 : * for the new left page, which is on the same block as the old page.
567 : * That's not true for the root page, but that's fine because we never
568 : * have a buffer on the root page anyway. The original algorithm as
569 : * described by Arge et al did, but it's of no use, as you might as well
570 : * read the tuples straight from the heap instead of the root buffer.
571 : */
572 : Assert(blocknum != GIST_ROOT_BLKNO);
573 12 : memcpy(&oldBuf, nodeBuffer, sizeof(GISTNodeBuffer));
574 12 : oldBuf.isTemp = true;
575 :
576 : /* Reset the old buffer, used for the new left page from now on */
577 12 : nodeBuffer->blocksCount = 0;
578 12 : nodeBuffer->pageBuffer = NULL;
579 12 : nodeBuffer->pageBlocknum = InvalidBlockNumber;
580 :
581 : /*
582 : * Allocate memory for information about relocation buffers.
583 : */
584 12 : splitPagesCount = list_length(splitinfo);
585 : relocationBuffersInfos =
586 12 : (RelocationBufferInfo *) palloc(sizeof(RelocationBufferInfo) *
587 : splitPagesCount);
588 :
589 : /*
590 : * Fill relocation buffers information for node buffers of pages produced
591 : * by split.
592 : */
593 36 : foreach(lc, splitinfo)
594 : {
595 24 : GISTPageSplitInfo *si = (GISTPageSplitInfo *) lfirst(lc);
596 : GISTNodeBuffer *newNodeBuffer;
597 24 : int i = foreach_current_index(lc);
598 :
599 : /* Decompress parent index tuple of node buffer page. */
600 24 : gistDeCompressAtt(giststate, r,
601 : si->downlink, NULL, (OffsetNumber) 0,
602 24 : relocationBuffersInfos[i].entry,
603 24 : relocationBuffersInfos[i].isnull);
604 :
605 : /*
606 : * Create a node buffer for the page. The leftmost half is on the same
607 : * block as the old page before split, so for the leftmost half this
608 : * will return the original buffer. The tuples on the original buffer
609 : * were relinked to the temporary buffer, so the original one is now
610 : * empty.
611 : */
612 24 : newNodeBuffer = gistGetNodeBuffer(gfbb, giststate, BufferGetBlockNumber(si->buf), level);
613 :
614 24 : relocationBuffersInfos[i].nodeBuffer = newNodeBuffer;
615 24 : relocationBuffersInfos[i].splitinfo = si;
616 : }
617 :
618 : /*
619 : * Loop through all index tuples in the buffer of the page being split,
620 : * moving them to buffers for the new pages. We try to move each tuple to
621 : * the page that will result in the lowest penalty for the leading column
622 : * or, in the case of a tie, the lowest penalty for the earliest column
623 : * that is not tied.
624 : *
625 : * The page searching logic is very similar to gistchoose().
626 : */
627 29754 : while (gistPopItupFromNodeBuffer(gfbb, &oldBuf, &itup))
628 : {
629 : float best_penalty[INDEX_MAX_KEYS];
630 : int i,
631 : which;
632 : IndexTuple newtup;
633 : RelocationBufferInfo *targetBufferInfo;
634 :
635 29742 : gistDeCompressAtt(giststate, r,
636 : itup, NULL, (OffsetNumber) 0, entry, isnull);
637 :
638 : /* default to using first page (shouldn't matter) */
639 29742 : which = 0;
640 :
641 : /*
642 : * best_penalty[j] is the best penalty we have seen so far for column
643 : * j, or -1 when we haven't yet examined column j. Array entries to
644 : * the right of the first -1 are undefined.
645 : */
646 29742 : best_penalty[0] = -1;
647 :
648 : /*
649 : * Loop over possible target pages, looking for one to move this tuple
650 : * to.
651 : */
652 89214 : for (i = 0; i < splitPagesCount; i++)
653 : {
654 59478 : RelocationBufferInfo *splitPageInfo = &relocationBuffersInfos[i];
655 : bool zero_penalty;
656 : int j;
657 :
658 59478 : zero_penalty = true;
659 :
660 : /* Loop over index attributes. */
661 110580 : for (j = 0; j < IndexRelationGetNumberOfKeyAttributes(r); j++)
662 : {
663 : float usize;
664 :
665 : /* Compute penalty for this column. */
666 59478 : usize = gistpenalty(giststate, j,
667 : &splitPageInfo->entry[j],
668 59478 : splitPageInfo->isnull[j],
669 59478 : &entry[j], isnull[j]);
670 59478 : if (usize > 0)
671 59472 : zero_penalty = false;
672 :
673 59478 : if (best_penalty[j] < 0 || usize < best_penalty[j])
674 : {
675 : /*
676 : * New best penalty for column. Tentatively select this
677 : * page as the target, and record the best penalty. Then
678 : * reset the next column's penalty to "unknown" (and
679 : * indirectly, the same for all the ones to its right).
680 : * This will force us to adopt this page's penalty values
681 : * as the best for all the remaining columns during
682 : * subsequent loop iterations.
683 : */
684 51102 : which = i;
685 51102 : best_penalty[j] = usize;
686 :
687 51102 : if (j < IndexRelationGetNumberOfKeyAttributes(r) - 1)
688 0 : best_penalty[j + 1] = -1;
689 : }
690 8376 : else if (best_penalty[j] == usize)
691 : {
692 : /*
693 : * The current page is exactly as good for this column as
694 : * the best page seen so far. The next iteration of this
695 : * loop will compare the next column.
696 : */
697 : }
698 : else
699 : {
700 : /*
701 : * The current page is worse for this column than the best
702 : * page seen so far. Skip the remaining columns and move
703 : * on to the next page, if any.
704 : */
705 8376 : zero_penalty = false; /* so outer loop won't exit */
706 8376 : break;
707 : }
708 : }
709 :
710 : /*
711 : * If we find a page with zero penalty for all columns, there's no
712 : * need to examine remaining pages; just break out of the loop and
713 : * return it.
714 : */
715 59478 : if (zero_penalty)
716 6 : break;
717 : }
718 :
719 : /* OK, "which" is the page index to push the tuple to */
720 29742 : targetBufferInfo = &relocationBuffersInfos[which];
721 :
722 : /* Push item to selected node buffer */
723 29742 : gistPushItupToNodeBuffer(gfbb, targetBufferInfo->nodeBuffer, itup);
724 :
725 : /* Adjust the downlink for this page, if needed. */
726 29742 : newtup = gistgetadjusted(r, targetBufferInfo->splitinfo->downlink,
727 : itup, giststate);
728 29742 : if (newtup)
729 : {
730 29736 : gistDeCompressAtt(giststate, r,
731 : newtup, NULL, (OffsetNumber) 0,
732 29736 : targetBufferInfo->entry,
733 29736 : targetBufferInfo->isnull);
734 :
735 29736 : targetBufferInfo->splitinfo->downlink = newtup;
736 : }
737 : }
738 :
739 12 : pfree(relocationBuffersInfos);
740 : }
741 :
742 :
743 : /*
744 : * Wrappers around BufFile operations. The main difference is that these
745 : * wrappers report errors with ereport(), so that the callers don't need
746 : * to check the return code.
747 : */
748 :
749 : static void
750 324 : ReadTempFileBlock(BufFile *file, long blknum, void *ptr)
751 : {
752 324 : if (BufFileSeekBlock(file, blknum) != 0)
753 0 : elog(ERROR, "could not seek to block %ld in temporary file", blknum);
754 324 : BufFileReadExact(file, ptr, BLCKSZ);
755 324 : }
756 :
757 : static void
758 324 : WriteTempFileBlock(BufFile *file, long blknum, const void *ptr)
759 : {
760 324 : if (BufFileSeekBlock(file, blknum) != 0)
761 0 : elog(ERROR, "could not seek to block %ld in temporary file", blknum);
762 324 : BufFileWrite(file, ptr, BLCKSZ);
763 324 : }
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