1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990, 1993, 1994
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Mike Olson.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)bt_split.c 8.10 (Berkeley) 1/9/95";
37 #endif /* LIBC_SCCS and not lint */
38 #include <sys/cdefs.h>
39 __FBSDID("$FreeBSD$");
40
41 #include <sys/param.h>
42
43 #include <limits.h>
44 #include <stdio.h>
45 #include <stdlib.h>
46 #include <string.h>
47
48 #include <db.h>
49 #include "btree.h"
50
51 static int bt_broot(BTREE *, PAGE *, PAGE *, PAGE *);
52 static PAGE *bt_page(BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t);
53 static int bt_preserve(BTREE *, pgno_t);
54 static PAGE *bt_psplit(BTREE *, PAGE *, PAGE *, PAGE *, indx_t *, size_t);
55 static PAGE *bt_root(BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t);
56 static int bt_rroot(BTREE *, PAGE *, PAGE *, PAGE *);
57 static recno_t rec_total(PAGE *);
58
59 #ifdef STATISTICS
60 u_long bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved;
61 #endif
62
63 /*
64 * __BT_SPLIT -- Split the tree.
65 *
66 * Parameters:
67 * t: tree
68 * sp: page to split
69 * key: key to insert
70 * data: data to insert
71 * flags: BIGKEY/BIGDATA flags
72 * ilen: insert length
73 * skip: index to leave open
74 *
75 * Returns:
76 * RET_ERROR, RET_SUCCESS
77 */
78 int
__bt_split(BTREE * t,PAGE * sp,const DBT * key,const DBT * data,int flags,size_t ilen,u_int32_t argskip)79 __bt_split(BTREE *t, PAGE *sp, const DBT *key, const DBT *data, int flags,
80 size_t ilen, u_int32_t argskip)
81 {
82 BINTERNAL *bi;
83 BLEAF *bl, *tbl;
84 DBT a, b;
85 EPGNO *parent;
86 PAGE *h, *l, *r, *lchild, *rchild;
87 indx_t nxtindex;
88 u_int16_t skip;
89 u_int32_t n, nbytes, nksize;
90 int parentsplit;
91 char *dest;
92
93 /*
94 * Split the page into two pages, l and r. The split routines return
95 * a pointer to the page into which the key should be inserted and with
96 * skip set to the offset which should be used. Additionally, l and r
97 * are pinned.
98 */
99 skip = argskip;
100 h = sp->pgno == P_ROOT ?
101 bt_root(t, sp, &l, &r, &skip, ilen) :
102 bt_page(t, sp, &l, &r, &skip, ilen);
103 if (h == NULL)
104 return (RET_ERROR);
105
106 /*
107 * Insert the new key/data pair into the leaf page. (Key inserts
108 * always cause a leaf page to split first.)
109 */
110 h->linp[skip] = h->upper -= ilen;
111 dest = (char *)h + h->upper;
112 if (F_ISSET(t, R_RECNO))
113 WR_RLEAF(dest, data, flags)
114 else
115 WR_BLEAF(dest, key, data, flags)
116
117 /* If the root page was split, make it look right. */
118 if (sp->pgno == P_ROOT &&
119 (F_ISSET(t, R_RECNO) ?
120 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR)
121 goto err2;
122
123 /*
124 * Now we walk the parent page stack -- a LIFO stack of the pages that
125 * were traversed when we searched for the page that split. Each stack
126 * entry is a page number and a page index offset. The offset is for
127 * the page traversed on the search. We've just split a page, so we
128 * have to insert a new key into the parent page.
129 *
130 * If the insert into the parent page causes it to split, may have to
131 * continue splitting all the way up the tree. We stop if the root
132 * splits or the page inserted into didn't have to split to hold the
133 * new key. Some algorithms replace the key for the old page as well
134 * as the new page. We don't, as there's no reason to believe that the
135 * first key on the old page is any better than the key we have, and,
136 * in the case of a key being placed at index 0 causing the split, the
137 * key is unavailable.
138 *
139 * There are a maximum of 5 pages pinned at any time. We keep the left
140 * and right pages pinned while working on the parent. The 5 are the
141 * two children, left parent and right parent (when the parent splits)
142 * and the root page or the overflow key page when calling bt_preserve.
143 * This code must make sure that all pins are released other than the
144 * root page or overflow page which is unlocked elsewhere.
145 */
146 while ((parent = BT_POP(t)) != NULL) {
147 lchild = l;
148 rchild = r;
149
150 /* Get the parent page. */
151 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
152 goto err2;
153
154 /*
155 * The new key goes ONE AFTER the index, because the split
156 * was to the right.
157 */
158 skip = parent->index + 1;
159
160 /*
161 * Calculate the space needed on the parent page.
162 *
163 * Prefix trees: space hack when inserting into BINTERNAL
164 * pages. Retain only what's needed to distinguish between
165 * the new entry and the LAST entry on the page to its left.
166 * If the keys compare equal, retain the entire key. Note,
167 * we don't touch overflow keys, and the entire key must be
168 * retained for the next-to-left most key on the leftmost
169 * page of each level, or the search will fail. Applicable
170 * ONLY to internal pages that have leaf pages as children.
171 * Further reduction of the key between pairs of internal
172 * pages loses too much information.
173 */
174 switch (rchild->flags & P_TYPE) {
175 case P_BINTERNAL:
176 bi = GETBINTERNAL(rchild, 0);
177 nbytes = NBINTERNAL(bi->ksize);
178 break;
179 case P_BLEAF:
180 bl = GETBLEAF(rchild, 0);
181 nbytes = NBINTERNAL(bl->ksize);
182 if (t->bt_pfx && !(bl->flags & P_BIGKEY) &&
183 (h->prevpg != P_INVALID || skip > 1)) {
184 tbl = GETBLEAF(lchild, NEXTINDEX(lchild) - 1);
185 a.size = tbl->ksize;
186 a.data = tbl->bytes;
187 b.size = bl->ksize;
188 b.data = bl->bytes;
189 nksize = t->bt_pfx(&a, &b);
190 n = NBINTERNAL(nksize);
191 if (n < nbytes) {
192 #ifdef STATISTICS
193 bt_pfxsaved += nbytes - n;
194 #endif
195 nbytes = n;
196 } else
197 nksize = 0;
198 } else
199 nksize = 0;
200 break;
201 case P_RINTERNAL:
202 case P_RLEAF:
203 nbytes = NRINTERNAL;
204 break;
205 default:
206 abort();
207 }
208
209 /* Split the parent page if necessary or shift the indices. */
210 if ((u_int32_t)(h->upper - h->lower) < nbytes + sizeof(indx_t)) {
211 sp = h;
212 h = h->pgno == P_ROOT ?
213 bt_root(t, h, &l, &r, &skip, nbytes) :
214 bt_page(t, h, &l, &r, &skip, nbytes);
215 if (h == NULL)
216 goto err1;
217 parentsplit = 1;
218 } else {
219 if (skip < (nxtindex = NEXTINDEX(h)))
220 memmove(h->linp + skip + 1, h->linp + skip,
221 (nxtindex - skip) * sizeof(indx_t));
222 h->lower += sizeof(indx_t);
223 parentsplit = 0;
224 }
225
226 /* Insert the key into the parent page. */
227 switch (rchild->flags & P_TYPE) {
228 case P_BINTERNAL:
229 h->linp[skip] = h->upper -= nbytes;
230 dest = (char *)h + h->linp[skip];
231 memmove(dest, bi, nbytes);
232 ((BINTERNAL *)dest)->pgno = rchild->pgno;
233 break;
234 case P_BLEAF:
235 h->linp[skip] = h->upper -= nbytes;
236 dest = (char *)h + h->linp[skip];
237 WR_BINTERNAL(dest, nksize ? nksize : bl->ksize,
238 rchild->pgno, bl->flags & P_BIGKEY);
239 memmove(dest, bl->bytes, nksize ? nksize : bl->ksize);
240 if (bl->flags & P_BIGKEY) {
241 pgno_t pgno;
242 memcpy(&pgno, bl->bytes, sizeof(pgno));
243 if (bt_preserve(t, pgno) == RET_ERROR)
244 goto err1;
245 }
246 break;
247 case P_RINTERNAL:
248 /*
249 * Update the left page count. If split
250 * added at index 0, fix the correct page.
251 */
252 if (skip > 0)
253 dest = (char *)h + h->linp[skip - 1];
254 else
255 dest = (char *)l + l->linp[NEXTINDEX(l) - 1];
256 ((RINTERNAL *)dest)->nrecs = rec_total(lchild);
257 ((RINTERNAL *)dest)->pgno = lchild->pgno;
258
259 /* Update the right page count. */
260 h->linp[skip] = h->upper -= nbytes;
261 dest = (char *)h + h->linp[skip];
262 ((RINTERNAL *)dest)->nrecs = rec_total(rchild);
263 ((RINTERNAL *)dest)->pgno = rchild->pgno;
264 break;
265 case P_RLEAF:
266 /*
267 * Update the left page count. If split
268 * added at index 0, fix the correct page.
269 */
270 if (skip > 0)
271 dest = (char *)h + h->linp[skip - 1];
272 else
273 dest = (char *)l + l->linp[NEXTINDEX(l) - 1];
274 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(lchild);
275 ((RINTERNAL *)dest)->pgno = lchild->pgno;
276
277 /* Update the right page count. */
278 h->linp[skip] = h->upper -= nbytes;
279 dest = (char *)h + h->linp[skip];
280 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(rchild);
281 ((RINTERNAL *)dest)->pgno = rchild->pgno;
282 break;
283 default:
284 abort();
285 }
286
287 /* Unpin the held pages. */
288 if (!parentsplit) {
289 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
290 break;
291 }
292
293 /* If the root page was split, make it look right. */
294 if (sp->pgno == P_ROOT &&
295 (F_ISSET(t, R_RECNO) ?
296 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR)
297 goto err1;
298
299 mpool_put(t->bt_mp, lchild, MPOOL_DIRTY);
300 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY);
301 }
302
303 /* Unpin the held pages. */
304 mpool_put(t->bt_mp, l, MPOOL_DIRTY);
305 mpool_put(t->bt_mp, r, MPOOL_DIRTY);
306
307 /* Clear any pages left on the stack. */
308 return (RET_SUCCESS);
309
310 /*
311 * If something fails in the above loop we were already walking back
312 * up the tree and the tree is now inconsistent. Nothing much we can
313 * do about it but release any memory we're holding.
314 */
315 err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY);
316 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY);
317
318 err2: mpool_put(t->bt_mp, l, 0);
319 mpool_put(t->bt_mp, r, 0);
320 __dbpanic(t->bt_dbp);
321 return (RET_ERROR);
322 }
323
324 /*
325 * BT_PAGE -- Split a non-root page of a btree.
326 *
327 * Parameters:
328 * t: tree
329 * h: root page
330 * lp: pointer to left page pointer
331 * rp: pointer to right page pointer
332 * skip: pointer to index to leave open
333 * ilen: insert length
334 *
335 * Returns:
336 * Pointer to page in which to insert or NULL on error.
337 */
338 static PAGE *
bt_page(BTREE * t,PAGE * h,PAGE ** lp,PAGE ** rp,indx_t * skip,size_t ilen)339 bt_page(BTREE *t, PAGE *h, PAGE **lp, PAGE **rp, indx_t *skip, size_t ilen)
340 {
341 PAGE *l, *r, *tp;
342 pgno_t npg;
343
344 #ifdef STATISTICS
345 ++bt_split;
346 #endif
347 /* Put the new right page for the split into place. */
348 if ((r = __bt_new(t, &npg)) == NULL)
349 return (NULL);
350 r->pgno = npg;
351 r->lower = BTDATAOFF;
352 r->upper = t->bt_psize;
353 r->nextpg = h->nextpg;
354 r->prevpg = h->pgno;
355 r->flags = h->flags & P_TYPE;
356
357 /*
358 * If we're splitting the last page on a level because we're appending
359 * a key to it (skip is NEXTINDEX()), it's likely that the data is
360 * sorted. Adding an empty page on the side of the level is less work
361 * and can push the fill factor much higher than normal. If we're
362 * wrong it's no big deal, we'll just do the split the right way next
363 * time. It may look like it's equally easy to do a similar hack for
364 * reverse sorted data, that is, split the tree left, but it's not.
365 * Don't even try.
366 */
367 if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) {
368 #ifdef STATISTICS
369 ++bt_sortsplit;
370 #endif
371 h->nextpg = r->pgno;
372 r->lower = BTDATAOFF + sizeof(indx_t);
373 *skip = 0;
374 *lp = h;
375 *rp = r;
376 return (r);
377 }
378
379 /* Put the new left page for the split into place. */
380 if ((l = (PAGE *)calloc(1, t->bt_psize)) == NULL) {
381 mpool_put(t->bt_mp, r, 0);
382 return (NULL);
383 }
384 l->pgno = h->pgno;
385 l->nextpg = r->pgno;
386 l->prevpg = h->prevpg;
387 l->lower = BTDATAOFF;
388 l->upper = t->bt_psize;
389 l->flags = h->flags & P_TYPE;
390
391 /* Fix up the previous pointer of the page after the split page. */
392 if (h->nextpg != P_INVALID) {
393 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) {
394 free(l);
395 /* XXX mpool_free(t->bt_mp, r->pgno); */
396 return (NULL);
397 }
398 tp->prevpg = r->pgno;
399 mpool_put(t->bt_mp, tp, MPOOL_DIRTY);
400 }
401
402 /*
403 * Split right. The key/data pairs aren't sorted in the btree page so
404 * it's simpler to copy the data from the split page onto two new pages
405 * instead of copying half the data to the right page and compacting
406 * the left page in place. Since the left page can't change, we have
407 * to swap the original and the allocated left page after the split.
408 */
409 tp = bt_psplit(t, h, l, r, skip, ilen);
410
411 /* Move the new left page onto the old left page. */
412 memmove(h, l, t->bt_psize);
413 if (tp == l)
414 tp = h;
415 free(l);
416
417 *lp = h;
418 *rp = r;
419 return (tp);
420 }
421
422 /*
423 * BT_ROOT -- Split the root page of a btree.
424 *
425 * Parameters:
426 * t: tree
427 * h: root page
428 * lp: pointer to left page pointer
429 * rp: pointer to right page pointer
430 * skip: pointer to index to leave open
431 * ilen: insert length
432 *
433 * Returns:
434 * Pointer to page in which to insert or NULL on error.
435 */
436 static PAGE *
bt_root(BTREE * t,PAGE * h,PAGE ** lp,PAGE ** rp,indx_t * skip,size_t ilen)437 bt_root(BTREE *t, PAGE *h, PAGE **lp, PAGE **rp, indx_t *skip, size_t ilen)
438 {
439 PAGE *l, *r, *tp;
440 pgno_t lnpg, rnpg;
441
442 #ifdef STATISTICS
443 ++bt_split;
444 ++bt_rootsplit;
445 #endif
446 /* Put the new left and right pages for the split into place. */
447 if ((l = __bt_new(t, &lnpg)) == NULL ||
448 (r = __bt_new(t, &rnpg)) == NULL)
449 return (NULL);
450 l->pgno = lnpg;
451 r->pgno = rnpg;
452 l->nextpg = r->pgno;
453 r->prevpg = l->pgno;
454 l->prevpg = r->nextpg = P_INVALID;
455 l->lower = r->lower = BTDATAOFF;
456 l->upper = r->upper = t->bt_psize;
457 l->flags = r->flags = h->flags & P_TYPE;
458
459 /* Split the root page. */
460 tp = bt_psplit(t, h, l, r, skip, ilen);
461
462 *lp = l;
463 *rp = r;
464 return (tp);
465 }
466
467 /*
468 * BT_RROOT -- Fix up the recno root page after it has been split.
469 *
470 * Parameters:
471 * t: tree
472 * h: root page
473 * l: left page
474 * r: right page
475 *
476 * Returns:
477 * RET_ERROR, RET_SUCCESS
478 */
479 static int
bt_rroot(BTREE * t,PAGE * h,PAGE * l,PAGE * r)480 bt_rroot(BTREE *t, PAGE *h, PAGE *l, PAGE *r)
481 {
482 char *dest;
483
484 /* Insert the left and right keys, set the header information. */
485 h->linp[0] = h->upper = t->bt_psize - NRINTERNAL;
486 dest = (char *)h + h->upper;
487 WR_RINTERNAL(dest,
488 l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno);
489
490 __PAST_END(h->linp, 1) = h->upper -= NRINTERNAL;
491 dest = (char *)h + h->upper;
492 WR_RINTERNAL(dest,
493 r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno);
494
495 h->lower = BTDATAOFF + 2 * sizeof(indx_t);
496
497 /* Unpin the root page, set to recno internal page. */
498 h->flags &= ~P_TYPE;
499 h->flags |= P_RINTERNAL;
500 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
501
502 return (RET_SUCCESS);
503 }
504
505 /*
506 * BT_BROOT -- Fix up the btree root page after it has been split.
507 *
508 * Parameters:
509 * t: tree
510 * h: root page
511 * l: left page
512 * r: right page
513 *
514 * Returns:
515 * RET_ERROR, RET_SUCCESS
516 */
517 static int
bt_broot(BTREE * t,PAGE * h,PAGE * l,PAGE * r)518 bt_broot(BTREE *t, PAGE *h, PAGE *l, PAGE *r)
519 {
520 BINTERNAL *bi;
521 BLEAF *bl;
522 u_int32_t nbytes;
523 char *dest;
524
525 /*
526 * If the root page was a leaf page, change it into an internal page.
527 * We copy the key we split on (but not the key's data, in the case of
528 * a leaf page) to the new root page.
529 *
530 * The btree comparison code guarantees that the left-most key on any
531 * level of the tree is never used, so it doesn't need to be filled in.
532 */
533 nbytes = NBINTERNAL(0);
534 h->linp[0] = h->upper = t->bt_psize - nbytes;
535 dest = (char *)h + h->upper;
536 WR_BINTERNAL(dest, 0, l->pgno, 0);
537
538 switch (h->flags & P_TYPE) {
539 case P_BLEAF:
540 bl = GETBLEAF(r, 0);
541 nbytes = NBINTERNAL(bl->ksize);
542 __PAST_END(h->linp, 1) = h->upper -= nbytes;
543 dest = (char *)h + h->upper;
544 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0);
545 memmove(dest, bl->bytes, bl->ksize);
546
547 /*
548 * If the key is on an overflow page, mark the overflow chain
549 * so it isn't deleted when the leaf copy of the key is deleted.
550 */
551 if (bl->flags & P_BIGKEY) {
552 pgno_t pgno;
553 memcpy(&pgno, bl->bytes, sizeof(pgno));
554 if (bt_preserve(t, pgno) == RET_ERROR)
555 return (RET_ERROR);
556 }
557 break;
558 case P_BINTERNAL:
559 bi = GETBINTERNAL(r, 0);
560 nbytes = NBINTERNAL(bi->ksize);
561 __PAST_END(h->linp, 1) = h->upper -= nbytes;
562 dest = (char *)h + h->upper;
563 memmove(dest, bi, nbytes);
564 ((BINTERNAL *)dest)->pgno = r->pgno;
565 break;
566 default:
567 abort();
568 }
569
570 /* There are two keys on the page. */
571 h->lower = BTDATAOFF + 2 * sizeof(indx_t);
572
573 /* Unpin the root page, set to btree internal page. */
574 h->flags &= ~P_TYPE;
575 h->flags |= P_BINTERNAL;
576 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
577
578 return (RET_SUCCESS);
579 }
580
581 /*
582 * BT_PSPLIT -- Do the real work of splitting the page.
583 *
584 * Parameters:
585 * t: tree
586 * h: page to be split
587 * l: page to put lower half of data
588 * r: page to put upper half of data
589 * pskip: pointer to index to leave open
590 * ilen: insert length
591 *
592 * Returns:
593 * Pointer to page in which to insert.
594 */
595 static PAGE *
bt_psplit(BTREE * t,PAGE * h,PAGE * l,PAGE * r,indx_t * pskip,size_t ilen)596 bt_psplit(BTREE *t, PAGE *h, PAGE *l, PAGE *r, indx_t *pskip, size_t ilen)
597 {
598 BINTERNAL *bi;
599 BLEAF *bl;
600 CURSOR *c;
601 RLEAF *rl;
602 PAGE *rval;
603 void *src;
604 indx_t full, half, nxt, off, skip, top, used;
605 u_int32_t nbytes;
606 int bigkeycnt, isbigkey;
607
608 /*
609 * Split the data to the left and right pages. Leave the skip index
610 * open. Additionally, make some effort not to split on an overflow
611 * key. This makes internal page processing faster and can save
612 * space as overflow keys used by internal pages are never deleted.
613 */
614 bigkeycnt = 0;
615 skip = *pskip;
616 full = t->bt_psize - BTDATAOFF;
617 half = full / 2;
618 used = 0;
619 for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) {
620 if (skip == off) {
621 nbytes = ilen;
622 isbigkey = 0; /* XXX: not really known. */
623 } else
624 switch (h->flags & P_TYPE) {
625 case P_BINTERNAL:
626 src = bi = GETBINTERNAL(h, nxt);
627 nbytes = NBINTERNAL(bi->ksize);
628 isbigkey = bi->flags & P_BIGKEY;
629 break;
630 case P_BLEAF:
631 src = bl = GETBLEAF(h, nxt);
632 nbytes = NBLEAF(bl);
633 isbigkey = bl->flags & P_BIGKEY;
634 break;
635 case P_RINTERNAL:
636 src = GETRINTERNAL(h, nxt);
637 nbytes = NRINTERNAL;
638 isbigkey = 0;
639 break;
640 case P_RLEAF:
641 src = rl = GETRLEAF(h, nxt);
642 nbytes = NRLEAF(rl);
643 isbigkey = 0;
644 break;
645 default:
646 abort();
647 }
648
649 /*
650 * If the key/data pairs are substantial fractions of the max
651 * possible size for the page, it's possible to get situations
652 * where we decide to try and copy too much onto the left page.
653 * Make sure that doesn't happen.
654 */
655 if ((skip <= off && used + nbytes + sizeof(indx_t) >= full) ||
656 nxt == top - 1) {
657 --off;
658 break;
659 }
660
661 /* Copy the key/data pair, if not the skipped index. */
662 if (skip != off) {
663 ++nxt;
664
665 l->linp[off] = l->upper -= nbytes;
666 memmove((char *)l + l->upper, src, nbytes);
667 }
668
669 used += nbytes + sizeof(indx_t);
670 if (used >= half) {
671 if (!isbigkey || bigkeycnt == 3)
672 break;
673 else
674 ++bigkeycnt;
675 }
676 }
677
678 /*
679 * Off is the last offset that's valid for the left page.
680 * Nxt is the first offset to be placed on the right page.
681 */
682 l->lower += (off + 1) * sizeof(indx_t);
683
684 /*
685 * If splitting the page that the cursor was on, the cursor has to be
686 * adjusted to point to the same record as before the split. If the
687 * cursor is at or past the skipped slot, the cursor is incremented by
688 * one. If the cursor is on the right page, it is decremented by the
689 * number of records split to the left page.
690 */
691 c = &t->bt_cursor;
692 if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) {
693 if (c->pg.index >= skip)
694 ++c->pg.index;
695 if (c->pg.index < nxt) /* Left page. */
696 c->pg.pgno = l->pgno;
697 else { /* Right page. */
698 c->pg.pgno = r->pgno;
699 c->pg.index -= nxt;
700 }
701 }
702
703 /*
704 * If the skipped index was on the left page, just return that page.
705 * Otherwise, adjust the skip index to reflect the new position on
706 * the right page.
707 */
708 if (skip <= off) {
709 skip = MAX_PAGE_OFFSET;
710 rval = l;
711 } else {
712 rval = r;
713 *pskip -= nxt;
714 }
715
716 for (off = 0; nxt < top; ++off) {
717 if (skip == nxt) {
718 ++off;
719 skip = MAX_PAGE_OFFSET;
720 }
721 switch (h->flags & P_TYPE) {
722 case P_BINTERNAL:
723 src = bi = GETBINTERNAL(h, nxt);
724 nbytes = NBINTERNAL(bi->ksize);
725 break;
726 case P_BLEAF:
727 src = bl = GETBLEAF(h, nxt);
728 nbytes = NBLEAF(bl);
729 break;
730 case P_RINTERNAL:
731 src = GETRINTERNAL(h, nxt);
732 nbytes = NRINTERNAL;
733 break;
734 case P_RLEAF:
735 src = rl = GETRLEAF(h, nxt);
736 nbytes = NRLEAF(rl);
737 break;
738 default:
739 abort();
740 }
741 ++nxt;
742 r->linp[off] = r->upper -= nbytes;
743 memmove((char *)r + r->upper, src, nbytes);
744 }
745 r->lower += off * sizeof(indx_t);
746
747 /* If the key is being appended to the page, adjust the index. */
748 if (skip == top)
749 r->lower += sizeof(indx_t);
750
751 return (rval);
752 }
753
754 /*
755 * BT_PRESERVE -- Mark a chain of pages as used by an internal node.
756 *
757 * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the
758 * record that references them gets deleted. Chains pointed to by internal
759 * pages never get deleted. This routine marks a chain as pointed to by an
760 * internal page.
761 *
762 * Parameters:
763 * t: tree
764 * pg: page number of first page in the chain.
765 *
766 * Returns:
767 * RET_SUCCESS, RET_ERROR.
768 */
769 static int
bt_preserve(BTREE * t,pgno_t pg)770 bt_preserve(BTREE *t, pgno_t pg)
771 {
772 PAGE *h;
773
774 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
775 return (RET_ERROR);
776 h->flags |= P_PRESERVE;
777 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
778 return (RET_SUCCESS);
779 }
780
781 /*
782 * REC_TOTAL -- Return the number of recno entries below a page.
783 *
784 * Parameters:
785 * h: page
786 *
787 * Returns:
788 * The number of recno entries below a page.
789 *
790 * XXX
791 * These values could be set by the bt_psplit routine. The problem is that the
792 * entry has to be popped off of the stack etc. or the values have to be passed
793 * all the way back to bt_split/bt_rroot and it's not very clean.
794 */
795 static recno_t
rec_total(PAGE * h)796 rec_total(PAGE *h)
797 {
798 recno_t recs;
799 indx_t nxt, top;
800
801 for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt)
802 recs += GETRINTERNAL(h, nxt)->nrecs;
803 return (recs);
804 }
805