Coverage Report

Created: 2026-09-28 06:55

next uncovered line (L), next uncovered region (R), next uncovered branch (B)
/src/postgres/src/backend/access/gist/gistbuildbuffers.c
Line
Count
Source
1
/*-------------------------------------------------------------------------
2
 *
3
 * gistbuildbuffers.c
4
 *    node buffer management functions for GiST buffering build algorithm.
5
 *
6
 *
7
 * Portions Copyright (c) 1996-2026, 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
gistInitBuildBuffers(int pagesPerBuffer, int levelStep, int maxLevel)
45
0
{
46
0
  GISTBuildBuffers *gfbb;
47
0
  HASHCTL   hashCtl;
48
49
0
  gfbb = palloc_object(GISTBuildBuffers);
50
0
  gfbb->pagesPerBuffer = pagesPerBuffer;
51
0
  gfbb->levelStep = levelStep;
52
53
  /*
54
   * Create a temporary file to hold buffer pages that are swapped out of
55
   * memory.
56
   */
57
0
  gfbb->pfile = BufFileCreateTemp(false);
58
0
  gfbb->nFileBlocks = 0;
59
60
  /* Initialize free page management. */
61
0
  gfbb->nFreeBlocks = 0;
62
0
  gfbb->freeBlocksLen = 32;
63
0
  gfbb->freeBlocks = palloc_array(long, gfbb->freeBlocksLen);
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
0
  gfbb->context = CurrentMemoryContext;
70
71
  /*
72
   * nodeBuffersTab hash is association between index blocks and it's
73
   * buffers.
74
   */
75
0
  hashCtl.keysize = sizeof(BlockNumber);
76
0
  hashCtl.entrysize = sizeof(GISTNodeBuffer);
77
0
  hashCtl.hcxt = CurrentMemoryContext;
78
0
  gfbb->nodeBuffersTab = hash_create("gistbuildbuffers",
79
0
                     1024,
80
0
                     &hashCtl,
81
0
                     HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
82
83
0
  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
0
  gfbb->buffersOnLevelsLen = 1;
90
0
  gfbb->buffersOnLevels = palloc_array(List *, gfbb->buffersOnLevelsLen);
91
0
  gfbb->buffersOnLevels[0] = NIL;
92
93
  /*
94
   * Block numbers of node buffers which last pages are currently loaded
95
   * into main memory.
96
   */
97
0
  gfbb->loadedBuffersLen = 32;
98
0
  gfbb->loadedBuffers = palloc_array(GISTNodeBuffer *, gfbb->loadedBuffersLen);
99
0
  gfbb->loadedBuffersCount = 0;
100
101
0
  gfbb->rootlevel = maxLevel;
102
103
0
  return gfbb;
104
0
}
105
106
/*
107
 * Returns a node buffer for given block. The buffer is created if it
108
 * doesn't exist yet.
109
 */
110
GISTNodeBuffer *
111
gistGetNodeBuffer(GISTBuildBuffers *gfbb, GISTSTATE *giststate,
112
          BlockNumber nodeBlocknum, int level)
113
0
{
114
0
  GISTNodeBuffer *nodeBuffer;
115
0
  bool    found;
116
117
  /* Find node buffer in hash table */
118
0
  nodeBuffer = (GISTNodeBuffer *) hash_search(gfbb->nodeBuffersTab,
119
0
                        &nodeBlocknum,
120
0
                        HASH_ENTER,
121
0
                        &found);
122
0
  if (!found)
123
0
  {
124
    /*
125
     * Node buffer wasn't found. Initialize the new buffer as empty.
126
     */
127
0
    MemoryContext oldcxt = MemoryContextSwitchTo(gfbb->context);
128
129
    /* nodeBuffer->nodeBlocknum is the hash key and was filled in already */
130
0
    nodeBuffer->blocksCount = 0;
131
0
    nodeBuffer->pageBlocknum = InvalidBlockNumber;
132
0
    nodeBuffer->pageBuffer = NULL;
133
0
    nodeBuffer->queuedForEmptying = false;
134
0
    nodeBuffer->isTemp = false;
135
0
    nodeBuffer->level = level;
136
137
    /*
138
     * Add this buffer to the list of buffers on this level. Enlarge
139
     * buffersOnLevels array if needed.
140
     */
141
0
    if (level >= gfbb->buffersOnLevelsLen)
142
0
    {
143
0
      int     i;
144
145
0
      gfbb->buffersOnLevels = repalloc_array(gfbb->buffersOnLevels, List *, level + 1);
146
147
      /* initialize the enlarged portion */
148
0
      for (i = gfbb->buffersOnLevelsLen; i <= level; i++)
149
0
        gfbb->buffersOnLevels[i] = NIL;
150
0
      gfbb->buffersOnLevelsLen = level + 1;
151
0
    }
152
153
    /*
154
     * Prepend the new buffer to the list of buffers on this level. It's
155
     * not arbitrary that the new buffer is put to the beginning of the
156
     * list: in the final emptying phase we loop through all buffers at
157
     * each level, and flush them. If a page is split during the emptying,
158
     * it's more efficient to flush the new split pages first, before
159
     * moving on to pre-existing pages on the level. The buffers just
160
     * created during the page split are likely still in cache, so
161
     * flushing them immediately is more efficient than putting them to
162
     * the end of the queue.
163
     */
164
0
    gfbb->buffersOnLevels[level] = lcons(nodeBuffer,
165
0
                       gfbb->buffersOnLevels[level]);
166
167
0
    MemoryContextSwitchTo(oldcxt);
168
0
  }
169
170
0
  return nodeBuffer;
171
0
}
172
173
/*
174
 * Allocate memory for a buffer page.
175
 */
176
static GISTNodeBufferPage *
177
gistAllocateNewPageBuffer(GISTBuildBuffers *gfbb)
178
0
{
179
0
  GISTNodeBufferPage *pageBuffer;
180
181
0
  pageBuffer = (GISTNodeBufferPage *) MemoryContextAllocZero(gfbb->context,
182
0
                                 BLCKSZ);
183
0
  pageBuffer->prev = InvalidBlockNumber;
184
185
  /* Set page free space */
186
0
  PAGE_FREE_SPACE(pageBuffer) = BLCKSZ - BUFFER_PAGE_DATA_OFFSET;
187
0
  return pageBuffer;
188
0
}
189
190
/*
191
 * Add specified buffer into loadedBuffers array.
192
 */
193
static void
194
gistAddLoadedBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer)
195
0
{
196
  /* Never add a temporary buffer to the array */
197
0
  if (nodeBuffer->isTemp)
198
0
    return;
199
200
  /* Enlarge the array if needed */
201
0
  if (gfbb->loadedBuffersCount >= gfbb->loadedBuffersLen)
202
0
  {
203
0
    gfbb->loadedBuffersLen *= 2;
204
0
    gfbb->loadedBuffers = repalloc_array(gfbb->loadedBuffers,
205
0
                       GISTNodeBuffer *, gfbb->loadedBuffersLen);
206
0
  }
207
208
0
  gfbb->loadedBuffers[gfbb->loadedBuffersCount] = nodeBuffer;
209
0
  gfbb->loadedBuffersCount++;
210
0
}
211
212
/*
213
 * Load last page of node buffer into main memory.
214
 */
215
static void
216
gistLoadNodeBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer)
217
0
{
218
  /* Check if we really should load something */
219
0
  if (!nodeBuffer->pageBuffer && nodeBuffer->blocksCount > 0)
220
0
  {
221
    /* Allocate memory for page */
222
0
    nodeBuffer->pageBuffer = gistAllocateNewPageBuffer(gfbb);
223
224
    /* Read block from temporary file */
225
0
    ReadTempFileBlock(gfbb->pfile, nodeBuffer->pageBlocknum,
226
0
              nodeBuffer->pageBuffer);
227
228
    /* Mark file block as free */
229
0
    gistBuffersReleaseBlock(gfbb, nodeBuffer->pageBlocknum);
230
231
    /* Mark node buffer as loaded */
232
0
    gistAddLoadedBuffer(gfbb, nodeBuffer);
233
0
    nodeBuffer->pageBlocknum = InvalidBlockNumber;
234
0
  }
235
0
}
236
237
/*
238
 * Write last page of node buffer to the disk.
239
 */
240
static void
241
gistUnloadNodeBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer)
242
0
{
243
  /* Check if we have something to write */
244
0
  if (nodeBuffer->pageBuffer)
245
0
  {
246
0
    BlockNumber blkno;
247
248
    /* Get free file block */
249
0
    blkno = gistBuffersGetFreeBlock(gfbb);
250
251
    /* Write block to the temporary file */
252
0
    WriteTempFileBlock(gfbb->pfile, blkno, nodeBuffer->pageBuffer);
253
254
    /* Free memory of that page */
255
0
    pfree(nodeBuffer->pageBuffer);
256
0
    nodeBuffer->pageBuffer = NULL;
257
258
    /* Save block number */
259
0
    nodeBuffer->pageBlocknum = blkno;
260
0
  }
261
0
}
262
263
/*
264
 * Write last pages of all node buffers to the disk.
265
 */
266
void
267
gistUnloadNodeBuffers(GISTBuildBuffers *gfbb)
268
0
{
269
0
  int     i;
270
271
  /* Unload all the buffers that have a page loaded in memory. */
272
0
  for (i = 0; i < gfbb->loadedBuffersCount; i++)
273
0
    gistUnloadNodeBuffer(gfbb, gfbb->loadedBuffers[i]);
274
275
  /* Now there are no node buffers with loaded last page */
276
0
  gfbb->loadedBuffersCount = 0;
277
0
}
278
279
/*
280
 * Add index tuple to buffer page.
281
 */
282
static void
283
gistPlaceItupToPage(GISTNodeBufferPage *pageBuffer, IndexTuple itup)
284
0
{
285
0
  Size    itupsz = IndexTupleSize(itup);
286
0
  char     *ptr;
287
288
  /* There should be enough of space. */
289
0
  Assert(PAGE_FREE_SPACE(pageBuffer) >= MAXALIGN(itupsz));
290
291
  /* Reduce free space value of page to reserve a spot for the tuple. */
292
0
  PAGE_FREE_SPACE(pageBuffer) -= MAXALIGN(itupsz);
293
294
  /* Get pointer to the spot we reserved (ie. end of free space). */
295
0
  ptr = (char *) pageBuffer + BUFFER_PAGE_DATA_OFFSET
296
0
    + PAGE_FREE_SPACE(pageBuffer);
297
298
  /* Copy the index tuple there. */
299
0
  memcpy(ptr, itup, itupsz);
300
0
}
301
302
/*
303
 * Get last item from buffer page and remove it from page.
304
 */
305
static void
306
gistGetItupFromPage(GISTNodeBufferPage *pageBuffer, IndexTuple *itup)
307
0
{
308
0
  IndexTuple  ptr;
309
0
  Size    itupsz;
310
311
0
  Assert(!PAGE_IS_EMPTY(pageBuffer)); /* Page shouldn't be empty */
312
313
  /* Get pointer to last index tuple */
314
0
  ptr = (IndexTuple) ((char *) pageBuffer
315
0
            + BUFFER_PAGE_DATA_OFFSET
316
0
            + PAGE_FREE_SPACE(pageBuffer));
317
0
  itupsz = IndexTupleSize(ptr);
318
319
  /* Make a copy of the tuple */
320
0
  *itup = (IndexTuple) palloc(itupsz);
321
0
  memcpy(*itup, ptr, itupsz);
322
323
  /* Mark the space used by the tuple as free */
324
0
  PAGE_FREE_SPACE(pageBuffer) += MAXALIGN(itupsz);
325
0
}
326
327
/*
328
 * Push an index tuple to node buffer.
329
 */
330
void
331
gistPushItupToNodeBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer,
332
             IndexTuple itup)
333
0
{
334
  /*
335
   * Most part of memory operations will be in buffering build persistent
336
   * context. So, let's switch to it.
337
   */
338
0
  MemoryContext oldcxt = MemoryContextSwitchTo(gfbb->context);
339
340
  /*
341
   * If the buffer is currently empty, create the first page.
342
   */
343
0
  if (nodeBuffer->blocksCount == 0)
344
0
  {
345
0
    nodeBuffer->pageBuffer = gistAllocateNewPageBuffer(gfbb);
346
0
    nodeBuffer->blocksCount = 1;
347
0
    gistAddLoadedBuffer(gfbb, nodeBuffer);
348
0
  }
349
350
  /* Load last page of node buffer if it wasn't in memory already */
351
0
  if (!nodeBuffer->pageBuffer)
352
0
    gistLoadNodeBuffer(gfbb, nodeBuffer);
353
354
  /*
355
   * Check if there is enough space on the last page for the tuple.
356
   */
357
0
  if (PAGE_NO_SPACE(nodeBuffer->pageBuffer, itup))
358
0
  {
359
    /*
360
     * Nope. Swap previous block to disk and allocate a new one.
361
     */
362
0
    BlockNumber blkno;
363
364
    /* Write filled page to the disk */
365
0
    blkno = gistBuffersGetFreeBlock(gfbb);
366
0
    WriteTempFileBlock(gfbb->pfile, blkno, nodeBuffer->pageBuffer);
367
368
    /*
369
     * Reset the in-memory page as empty, and link the previous block to
370
     * the new page by storing its block number in the prev-link.
371
     */
372
0
    PAGE_FREE_SPACE(nodeBuffer->pageBuffer) =
373
0
      BLCKSZ - MAXALIGN(offsetof(GISTNodeBufferPage, tupledata));
374
0
    nodeBuffer->pageBuffer->prev = blkno;
375
376
    /* We've just added one more page */
377
0
    nodeBuffer->blocksCount++;
378
0
  }
379
380
0
  gistPlaceItupToPage(nodeBuffer->pageBuffer, itup);
381
382
  /*
383
   * If the buffer just overflowed, add it to the emptying queue.
384
   */
385
0
  if (BUFFER_HALF_FILLED(nodeBuffer, gfbb) && !nodeBuffer->queuedForEmptying)
386
0
  {
387
0
    gfbb->bufferEmptyingQueue = lcons(nodeBuffer,
388
0
                      gfbb->bufferEmptyingQueue);
389
0
    nodeBuffer->queuedForEmptying = true;
390
0
  }
391
392
  /* Restore memory context */
393
0
  MemoryContextSwitchTo(oldcxt);
394
0
}
395
396
/*
397
 * Removes one index tuple from node buffer. Returns true if success and false
398
 * if node buffer is empty.
399
 */
400
bool
401
gistPopItupFromNodeBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer,
402
              IndexTuple *itup)
403
0
{
404
  /*
405
   * If node buffer is empty then return false.
406
   */
407
0
  if (nodeBuffer->blocksCount <= 0)
408
0
    return false;
409
410
  /* Load last page of node buffer if needed */
411
0
  if (!nodeBuffer->pageBuffer)
412
0
    gistLoadNodeBuffer(gfbb, nodeBuffer);
413
414
  /*
415
   * Get index tuple from last non-empty page.
416
   */
417
0
  gistGetItupFromPage(nodeBuffer->pageBuffer, itup);
418
419
  /*
420
   * If we just removed the last tuple from the page, fetch previous page on
421
   * this node buffer (if any).
422
   */
423
0
  if (PAGE_IS_EMPTY(nodeBuffer->pageBuffer))
424
0
  {
425
0
    BlockNumber prevblkno;
426
427
    /*
428
     * blocksCount includes the page in pageBuffer, so decrease it now.
429
     */
430
0
    nodeBuffer->blocksCount--;
431
432
    /*
433
     * If there's more pages, fetch previous one.
434
     */
435
0
    prevblkno = nodeBuffer->pageBuffer->prev;
436
0
    if (prevblkno != InvalidBlockNumber)
437
0
    {
438
      /* There is a previous page. Fetch it. */
439
0
      Assert(nodeBuffer->blocksCount > 0);
440
0
      ReadTempFileBlock(gfbb->pfile, prevblkno, nodeBuffer->pageBuffer);
441
442
      /*
443
       * Now that we've read the block in memory, we can release its
444
       * on-disk block for reuse.
445
       */
446
0
      gistBuffersReleaseBlock(gfbb, prevblkno);
447
0
    }
448
0
    else
449
0
    {
450
      /* No more pages. Free memory. */
451
0
      Assert(nodeBuffer->blocksCount == 0);
452
0
      pfree(nodeBuffer->pageBuffer);
453
0
      nodeBuffer->pageBuffer = NULL;
454
0
    }
455
0
  }
456
0
  return true;
457
0
}
458
459
/*
460
 * Select a currently unused block for writing to.
461
 */
462
static long
463
gistBuffersGetFreeBlock(GISTBuildBuffers *gfbb)
464
0
{
465
  /*
466
   * If there are multiple free blocks, we select the one appearing last in
467
   * freeBlocks[].  If there are none, assign the next block at the end of
468
   * the file (causing the file to be extended).
469
   */
470
0
  if (gfbb->nFreeBlocks > 0)
471
0
    return gfbb->freeBlocks[--gfbb->nFreeBlocks];
472
0
  else
473
0
    return gfbb->nFileBlocks++;
474
0
}
475
476
/*
477
 * Return a block# to the freelist.
478
 */
479
static void
480
gistBuffersReleaseBlock(GISTBuildBuffers *gfbb, long blocknum)
481
0
{
482
0
  int     ndx;
483
484
  /* Enlarge freeBlocks array if full. */
485
0
  if (gfbb->nFreeBlocks >= gfbb->freeBlocksLen)
486
0
  {
487
0
    gfbb->freeBlocksLen *= 2;
488
0
    gfbb->freeBlocks = repalloc_array(gfbb->freeBlocks,
489
0
                      long, gfbb->freeBlocksLen);
490
0
  }
491
492
  /* Add blocknum to array */
493
0
  ndx = gfbb->nFreeBlocks++;
494
0
  gfbb->freeBlocks[ndx] = blocknum;
495
0
}
496
497
/*
498
 * Free buffering build data structure.
499
 */
500
void
501
gistFreeBuildBuffers(GISTBuildBuffers *gfbb)
502
0
{
503
  /* Close buffers file. */
504
0
  BufFileClose(gfbb->pfile);
505
506
  /* All other things will be freed on memory context release */
507
0
}
508
509
/*
510
 * Data structure representing information about node buffer for index tuples
511
 * relocation from split node buffer.
512
 */
513
typedef struct
514
{
515
  GISTENTRY entry[INDEX_MAX_KEYS];
516
  bool    isnull[INDEX_MAX_KEYS];
517
  GISTPageSplitInfo *splitinfo;
518
  GISTNodeBuffer *nodeBuffer;
519
} RelocationBufferInfo;
520
521
/*
522
 * At page split, distribute tuples from the buffer of the split page to
523
 * new buffers for the created page halves. This also adjusts the downlinks
524
 * in 'splitinfo' to include the tuples in the buffers.
525
 */
526
void
527
gistRelocateBuildBuffersOnSplit(GISTBuildBuffers *gfbb, GISTSTATE *giststate,
528
                Relation r, int level,
529
                Buffer buffer, List *splitinfo)
530
0
{
531
0
  RelocationBufferInfo *relocationBuffersInfos;
532
0
  bool    found;
533
0
  GISTNodeBuffer *nodeBuffer;
534
0
  BlockNumber blocknum;
535
0
  IndexTuple  itup;
536
0
  int     splitPagesCount = 0;
537
0
  GISTENTRY entry[INDEX_MAX_KEYS];
538
0
  bool    isnull[INDEX_MAX_KEYS];
539
0
  GISTNodeBuffer oldBuf;
540
0
  ListCell   *lc;
541
542
  /* If the split page doesn't have buffers, we have nothing to do. */
543
0
  if (!LEVEL_HAS_BUFFERS(level, gfbb))
544
0
    return;
545
546
  /*
547
   * Get the node buffer of the split page.
548
   */
549
0
  blocknum = BufferGetBlockNumber(buffer);
550
0
  nodeBuffer = hash_search(gfbb->nodeBuffersTab, &blocknum,
551
0
               HASH_FIND, &found);
552
0
  if (!found)
553
0
  {
554
    /* The page has no buffer, so we have nothing to do. */
555
0
    return;
556
0
  }
557
558
  /*
559
   * Make a copy of the old buffer, as we're going reuse it as the buffer
560
   * for the new left page, which is on the same block as the old page.
561
   * That's not true for the root page, but that's fine because we never
562
   * have a buffer on the root page anyway. The original algorithm as
563
   * described by Arge et al did, but it's of no use, as you might as well
564
   * read the tuples straight from the heap instead of the root buffer.
565
   */
566
0
  Assert(blocknum != GIST_ROOT_BLKNO);
567
0
  memcpy(&oldBuf, nodeBuffer, sizeof(GISTNodeBuffer));
568
0
  oldBuf.isTemp = true;
569
570
  /* Reset the old buffer, used for the new left page from now on */
571
0
  nodeBuffer->blocksCount = 0;
572
0
  nodeBuffer->pageBuffer = NULL;
573
0
  nodeBuffer->pageBlocknum = InvalidBlockNumber;
574
575
  /*
576
   * Allocate memory for information about relocation buffers.
577
   */
578
0
  splitPagesCount = list_length(splitinfo);
579
0
  relocationBuffersInfos = palloc_array(RelocationBufferInfo, splitPagesCount);
580
581
  /*
582
   * Fill relocation buffers information for node buffers of pages produced
583
   * by split.
584
   */
585
0
  foreach(lc, splitinfo)
586
0
  {
587
0
    GISTPageSplitInfo *si = (GISTPageSplitInfo *) lfirst(lc);
588
0
    GISTNodeBuffer *newNodeBuffer;
589
0
    int     i = foreach_current_index(lc);
590
591
    /* Decompress parent index tuple of node buffer page. */
592
0
    gistDeCompressAtt(giststate, r,
593
0
              si->downlink, NULL, (OffsetNumber) 0,
594
0
              relocationBuffersInfos[i].entry,
595
0
              relocationBuffersInfos[i].isnull);
596
597
    /*
598
     * Create a node buffer for the page. The leftmost half is on the same
599
     * block as the old page before split, so for the leftmost half this
600
     * will return the original buffer. The tuples on the original buffer
601
     * were relinked to the temporary buffer, so the original one is now
602
     * empty.
603
     */
604
0
    newNodeBuffer = gistGetNodeBuffer(gfbb, giststate, BufferGetBlockNumber(si->buf), level);
605
606
0
    relocationBuffersInfos[i].nodeBuffer = newNodeBuffer;
607
0
    relocationBuffersInfos[i].splitinfo = si;
608
0
  }
609
610
  /*
611
   * Loop through all index tuples in the buffer of the page being split,
612
   * moving them to buffers for the new pages.  We try to move each tuple to
613
   * the page that will result in the lowest penalty for the leading column
614
   * or, in the case of a tie, the lowest penalty for the earliest column
615
   * that is not tied.
616
   *
617
   * The page searching logic is very similar to gistchoose().
618
   */
619
0
  while (gistPopItupFromNodeBuffer(gfbb, &oldBuf, &itup))
620
0
  {
621
0
    float   best_penalty[INDEX_MAX_KEYS];
622
0
    int     i,
623
0
          which;
624
0
    IndexTuple  newtup;
625
0
    RelocationBufferInfo *targetBufferInfo;
626
627
0
    gistDeCompressAtt(giststate, r,
628
0
              itup, NULL, (OffsetNumber) 0, entry, isnull);
629
630
    /* default to using first page (shouldn't matter) */
631
0
    which = 0;
632
633
    /*
634
     * best_penalty[j] is the best penalty we have seen so far for column
635
     * j, or -1 when we haven't yet examined column j.  Array entries to
636
     * the right of the first -1 are undefined.
637
     */
638
0
    best_penalty[0] = -1;
639
640
    /*
641
     * Loop over possible target pages, looking for one to move this tuple
642
     * to.
643
     */
644
0
    for (i = 0; i < splitPagesCount; i++)
645
0
    {
646
0
      RelocationBufferInfo *splitPageInfo = &relocationBuffersInfos[i];
647
0
      bool    zero_penalty;
648
0
      int     j;
649
650
0
      zero_penalty = true;
651
652
      /* Loop over index attributes. */
653
0
      for (j = 0; j < IndexRelationGetNumberOfKeyAttributes(r); j++)
654
0
      {
655
0
        float   usize;
656
657
        /* Compute penalty for this column. */
658
0
        usize = gistpenalty(giststate, j,
659
0
                  &splitPageInfo->entry[j],
660
0
                  splitPageInfo->isnull[j],
661
0
                  &entry[j], isnull[j]);
662
0
        if (usize > 0)
663
0
          zero_penalty = false;
664
665
0
        if (best_penalty[j] < 0 || usize < best_penalty[j])
666
0
        {
667
          /*
668
           * New best penalty for column.  Tentatively select this
669
           * page as the target, and record the best penalty.  Then
670
           * reset the next column's penalty to "unknown" (and
671
           * indirectly, the same for all the ones to its right).
672
           * This will force us to adopt this page's penalty values
673
           * as the best for all the remaining columns during
674
           * subsequent loop iterations.
675
           */
676
0
          which = i;
677
0
          best_penalty[j] = usize;
678
679
0
          if (j < IndexRelationGetNumberOfKeyAttributes(r) - 1)
680
0
            best_penalty[j + 1] = -1;
681
0
        }
682
0
        else if (best_penalty[j] == usize)
683
0
        {
684
          /*
685
           * The current page is exactly as good for this column as
686
           * the best page seen so far.  The next iteration of this
687
           * loop will compare the next column.
688
           */
689
0
        }
690
0
        else
691
0
        {
692
          /*
693
           * The current page is worse for this column than the best
694
           * page seen so far.  Skip the remaining columns and move
695
           * on to the next page, if any.
696
           */
697
0
          zero_penalty = false;  /* so outer loop won't exit */
698
0
          break;
699
0
        }
700
0
      }
701
702
      /*
703
       * If we find a page with zero penalty for all columns, there's no
704
       * need to examine remaining pages; just break out of the loop and
705
       * return it.
706
       */
707
0
      if (zero_penalty)
708
0
        break;
709
0
    }
710
711
    /* OK, "which" is the page index to push the tuple to */
712
0
    targetBufferInfo = &relocationBuffersInfos[which];
713
714
    /* Push item to selected node buffer */
715
0
    gistPushItupToNodeBuffer(gfbb, targetBufferInfo->nodeBuffer, itup);
716
717
    /* Adjust the downlink for this page, if needed. */
718
0
    newtup = gistgetadjusted(r, targetBufferInfo->splitinfo->downlink,
719
0
                 itup, giststate);
720
0
    if (newtup)
721
0
    {
722
0
      gistDeCompressAtt(giststate, r,
723
0
                newtup, NULL, (OffsetNumber) 0,
724
0
                targetBufferInfo->entry,
725
0
                targetBufferInfo->isnull);
726
727
0
      targetBufferInfo->splitinfo->downlink = newtup;
728
0
    }
729
0
  }
730
731
0
  pfree(relocationBuffersInfos);
732
0
}
733
734
735
/*
736
 * Wrappers around BufFile operations. The main difference is that these
737
 * wrappers report errors with ereport(), so that the callers don't need
738
 * to check the return code.
739
 */
740
741
static void
742
ReadTempFileBlock(BufFile *file, long blknum, void *ptr)
743
0
{
744
0
  if (BufFileSeekBlock(file, blknum) != 0)
745
0
    elog(ERROR, "could not seek to block %ld in temporary file", blknum);
746
0
  BufFileReadExact(file, ptr, BLCKSZ);
747
0
}
748
749
static void
750
WriteTempFileBlock(BufFile *file, long blknum, const void *ptr)
751
0
{
752
0
  if (BufFileSeekBlock(file, blknum) != 0)
753
0
    elog(ERROR, "could not seek to block %ld in temporary file", blknum);
754
0
  BufFileWrite(file, ptr, BLCKSZ);
755
0
}