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