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 * 3. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed by the University of
19 * California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37 #if defined(LIBC_SCCS) && !defined(lint)
38 static char sccsid[] = "@(#)bt_split.c 8.10 (Berkeley) 1/9/95";
39 #endif /* LIBC_SCCS and not lint */
40
41 #include <sys/types.h>
42
43 #include <limits.h>
44 #include <stdio.h>
45 #include <stdlib.h>
46 #include <string.h>
47
48 #include "db-int.h"
49 #include "btree.h"
50
51 static int bt_broot __P((BTREE *, PAGE *, PAGE *, PAGE *));
52 static PAGE *bt_page
53 __P((BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t));
54 static int bt_preserve __P((BTREE *, db_pgno_t));
55 static PAGE *bt_psplit
56 __P((BTREE *, PAGE *, PAGE *, PAGE *, indx_t *, size_t));
57 static PAGE *bt_root
58 __P((BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t));
59 static int bt_rroot __P((BTREE *, PAGE *, PAGE *, PAGE *));
60 static recno_t rec_total __P((PAGE *));
61
62 #ifdef STATISTICS
63 u_long bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved;
64 #endif
65
66 /*
67 * __BT_SPLIT -- Split the tree.
68 *
69 * Parameters:
70 * t: tree
71 * sp: page to split
72 * key: key to insert
73 * data: data to insert
74 * flags: BIGKEY/BIGDATA flags
75 * ilen: insert length
76 * skip: index to leave open
77 *
78 * Returns:
79 * RET_ERROR, RET_SUCCESS
80 */
81 int
__bt_split(t,sp,key,data,flags,ilen,argskip)82 __bt_split(t, sp, key, data, flags, ilen, argskip)
83 BTREE *t;
84 PAGE *sp;
85 const DBT *key, *data;
86 int flags;
87 size_t ilen;
88 u_int32_t argskip;
89 {
90 BINTERNAL *bi;
91 BLEAF *bl, *tbl;
92 DBT a, b;
93 EPGNO *parent;
94 PAGE *h, *l, *r, *lchild, *rchild;
95 indx_t nxtindex;
96 u_int16_t skip;
97 u_int32_t n, nbytes, nksize;
98 int parentsplit;
99 char *dest;
100
101 /*
102 * Split the page into two pages, l and r. The split routines return
103 * a pointer to the page into which the key should be inserted and with
104 * skip set to the offset which should be used. Additionally, l and r
105 * are pinned.
106 */
107 skip = argskip;
108 h = sp->pgno == P_ROOT ?
109 bt_root(t, sp, &l, &r, &skip, ilen) :
110 bt_page(t, sp, &l, &r, &skip, ilen);
111 if (h == NULL)
112 return (RET_ERROR);
113
114 /*
115 * Insert the new key/data pair into the leaf page. (Key inserts
116 * always cause a leaf page to split first.)
117 */
118 h->linp[skip] = h->upper -= ilen;
119 dest = (char *)h + h->upper;
120 if (F_ISSET(t, R_RECNO))
121 WR_RLEAF(dest, data, flags)
122 else
123 WR_BLEAF(dest, key, data, flags)
124
125 /* If the root page was split, make it look right. */
126 if (sp->pgno == P_ROOT &&
127 (F_ISSET(t, R_RECNO) ?
128 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR)
129 goto err2;
130
131 /*
132 * Now we walk the parent page stack -- a LIFO stack of the pages that
133 * were traversed when we searched for the page that split. Each stack
134 * entry is a page number and a page index offset. The offset is for
135 * the page traversed on the search. We've just split a page, so we
136 * have to insert a new key into the parent page.
137 *
138 * If the insert into the parent page causes it to split, may have to
139 * continue splitting all the way up the tree. We stop if the root
140 * splits or the page inserted into didn't have to split to hold the
141 * new key. Some algorithms replace the key for the old page as well
142 * as the new page. We don't, as there's no reason to believe that the
143 * first key on the old page is any better than the key we have, and,
144 * in the case of a key being placed at index 0 causing the split, the
145 * key is unavailable.
146 *
147 * There are a maximum of 5 pages pinned at any time. We keep the left
148 * and right pages pinned while working on the parent. The 5 are the
149 * two children, left parent and right parent (when the parent splits)
150 * and the root page or the overflow key page when calling bt_preserve.
151 * This code must make sure that all pins are released other than the
152 * root page or overflow page which is unlocked elsewhere.
153 */
154 while ((parent = BT_POP(t)) != NULL) {
155 lchild = l;
156 rchild = r;
157
158 /* Get the parent page. */
159 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
160 goto err2;
161
162 /*
163 * The new key goes ONE AFTER the index, because the split
164 * was to the right.
165 */
166 skip = parent->index + 1;
167
168 /*
169 * Calculate the space needed on the parent page.
170 *
171 * Prefix trees: space hack when inserting into BINTERNAL
172 * pages. Retain only what's needed to distinguish between
173 * the new entry and the LAST entry on the page to its left.
174 * If the keys compare equal, retain the entire key. Note,
175 * we don't touch overflow keys, and the entire key must be
176 * retained for the next-to-left most key on the leftmost
177 * page of each level, or the search will fail. Applicable
178 * ONLY to internal pages that have leaf pages as children.
179 * Further reduction of the key between pairs of internal
180 * pages loses too much information.
181 */
182 switch (rchild->flags & P_TYPE) {
183 case P_BINTERNAL:
184 bi = GETBINTERNAL(rchild, 0);
185 nbytes = NBINTERNAL(bi->ksize);
186 break;
187 case P_BLEAF:
188 bl = GETBLEAF(rchild, 0);
189 nbytes = NBINTERNAL(bl->ksize);
190 if (t->bt_pfx && !(bl->flags & P_BIGKEY) &&
191 (h->prevpg != P_INVALID || skip > 1)) {
192 tbl = GETBLEAF(lchild, NEXTINDEX(lchild) - 1);
193 a.size = tbl->ksize;
194 a.data = tbl->bytes;
195 b.size = bl->ksize;
196 b.data = bl->bytes;
197 nksize = t->bt_pfx(&a, &b);
198 n = NBINTERNAL(nksize);
199 if (n < nbytes) {
200 #ifdef STATISTICS
201 bt_pfxsaved += nbytes - n;
202 #endif
203 nbytes = n;
204 } else
205 nksize = 0;
206 } else
207 nksize = 0;
208 break;
209 case P_RINTERNAL:
210 case P_RLEAF:
211 nbytes = NRINTERNAL;
212 break;
213 default:
214 abort();
215 }
216
217 /* Split the parent page if necessary or shift the indices. */
218 if (h->upper - h->lower < nbytes + sizeof(indx_t)) {
219 sp = h;
220 h = h->pgno == P_ROOT ?
221 bt_root(t, h, &l, &r, &skip, nbytes) :
222 bt_page(t, h, &l, &r, &skip, nbytes);
223 if (h == NULL)
224 goto err1;
225 parentsplit = 1;
226 } else {
227 if (skip < (nxtindex = NEXTINDEX(h)))
228 memmove(h->linp + skip + 1, h->linp + skip,
229 (nxtindex - skip) * sizeof(indx_t));
230 h->lower += sizeof(indx_t);
231 parentsplit = 0;
232 }
233
234 /* Insert the key into the parent page. */
235 switch (rchild->flags & P_TYPE) {
236 case P_BINTERNAL:
237 h->linp[skip] = h->upper -= nbytes;
238 dest = (char *)h + h->linp[skip];
239 memmove(dest, bi, nbytes);
240 ((BINTERNAL *)dest)->pgno = rchild->pgno;
241 break;
242 case P_BLEAF:
243 h->linp[skip] = h->upper -= nbytes;
244 dest = (char *)h + h->linp[skip];
245 WR_BINTERNAL(dest, nksize ? nksize : bl->ksize,
246 rchild->pgno, bl->flags & P_BIGKEY);
247 memmove(dest, bl->bytes, nksize ? nksize : bl->ksize);
248 if (bl->flags & P_BIGKEY &&
249 bt_preserve(t, *(db_pgno_t *)bl->bytes) == RET_ERROR)
250 goto err1;
251 break;
252 case P_RINTERNAL:
253 /*
254 * Update the left page count. If split
255 * added at index 0, fix the correct page.
256 */
257 if (skip > 0)
258 dest = (char *)h + h->linp[skip - 1];
259 else
260 dest = (char *)l + l->linp[NEXTINDEX(l) - 1];
261 ((RINTERNAL *)dest)->nrecs = rec_total(lchild);
262 ((RINTERNAL *)dest)->pgno = lchild->pgno;
263
264 /* Update the right page count. */
265 h->linp[skip] = h->upper -= nbytes;
266 dest = (char *)h + h->linp[skip];
267 ((RINTERNAL *)dest)->nrecs = rec_total(rchild);
268 ((RINTERNAL *)dest)->pgno = rchild->pgno;
269 break;
270 case P_RLEAF:
271 /*
272 * Update the left page count. If split
273 * added at index 0, fix the correct page.
274 */
275 if (skip > 0)
276 dest = (char *)h + h->linp[skip - 1];
277 else
278 dest = (char *)l + l->linp[NEXTINDEX(l) - 1];
279 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(lchild);
280 ((RINTERNAL *)dest)->pgno = lchild->pgno;
281
282 /* Update the right page count. */
283 h->linp[skip] = h->upper -= nbytes;
284 dest = (char *)h + h->linp[skip];
285 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(rchild);
286 ((RINTERNAL *)dest)->pgno = rchild->pgno;
287 break;
288 default:
289 abort();
290 }
291
292 /* Unpin the held pages. */
293 if (!parentsplit) {
294 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
295 break;
296 }
297
298 /* If the root page was split, make it look right. */
299 if (sp->pgno == P_ROOT &&
300 (F_ISSET(t, R_RECNO) ?
301 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR)
302 goto err1;
303
304 mpool_put(t->bt_mp, lchild, MPOOL_DIRTY);
305 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY);
306 }
307
308 /* Unpin the held pages. */
309 mpool_put(t->bt_mp, l, MPOOL_DIRTY);
310 mpool_put(t->bt_mp, r, MPOOL_DIRTY);
311
312 /* Clear any pages left on the stack. */
313 return (RET_SUCCESS);
314
315 /*
316 * If something fails in the above loop we were already walking back
317 * up the tree and the tree is now inconsistent. Nothing much we can
318 * do about it but release any memory we're holding.
319 */
320 err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY);
321 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY);
322
323 err2: mpool_put(t->bt_mp, l, 0);
324 mpool_put(t->bt_mp, r, 0);
325 __dbpanic(t->bt_dbp);
326 return (RET_ERROR);
327 }
328
329 /*
330 * BT_PAGE -- Split a non-root page of a btree.
331 *
332 * Parameters:
333 * t: tree
334 * h: root page
335 * lp: pointer to left page pointer
336 * rp: pointer to right page pointer
337 * skip: pointer to index to leave open
338 * ilen: insert length
339 *
340 * Returns:
341 * Pointer to page in which to insert or NULL on error.
342 */
343 static PAGE *
bt_page(t,h,lp,rp,skip,ilen)344 bt_page(t, h, lp, rp, skip, ilen)
345 BTREE *t;
346 PAGE *h, **lp, **rp;
347 indx_t *skip;
348 size_t ilen;
349 {
350 PAGE *l, *r, *tp;
351 db_pgno_t npg;
352
353 #ifdef STATISTICS
354 ++bt_split;
355 #endif
356 /* Put the new right page for the split into place. */
357 if ((r = __bt_new(t, &npg)) == NULL)
358 return (NULL);
359 r->pgno = npg;
360 r->lower = BTDATAOFF;
361 r->upper = t->bt_psize;
362 r->nextpg = h->nextpg;
363 r->prevpg = h->pgno;
364 r->flags = h->flags & P_TYPE;
365
366 /*
367 * If we're splitting the last page on a level because we're appending
368 * a key to it (skip is NEXTINDEX()), it's likely that the data is
369 * sorted. Adding an empty page on the side of the level is less work
370 * and can push the fill factor much higher than normal. If we're
371 * wrong it's no big deal, we'll just do the split the right way next
372 * time. It may look like it's equally easy to do a similar hack for
373 * reverse sorted data, that is, split the tree left, but it's not.
374 * Don't even try.
375 */
376 if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) {
377 #ifdef STATISTICS
378 ++bt_sortsplit;
379 #endif
380 h->nextpg = r->pgno;
381 r->lower = BTDATAOFF + sizeof(indx_t);
382 *skip = 0;
383 *lp = h;
384 *rp = r;
385 return (r);
386 }
387
388 /* Put the new left page for the split into place. */
389 if ((l = (PAGE *)malloc(t->bt_psize)) == NULL) {
390 mpool_put(t->bt_mp, r, 0);
391 return (NULL);
392 }
393 #ifdef PURIFY
394 memset(l, 0xff, t->bt_psize);
395 #endif
396 l->pgno = h->pgno;
397 l->nextpg = r->pgno;
398 l->prevpg = h->prevpg;
399 l->lower = BTDATAOFF;
400 l->upper = t->bt_psize;
401 l->flags = h->flags & P_TYPE;
402
403 /* Fix up the previous pointer of the page after the split page. */
404 if (h->nextpg != P_INVALID) {
405 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) {
406 free(l);
407 /* XXX mpool_free(t->bt_mp, r->pgno); */
408 return (NULL);
409 }
410 tp->prevpg = r->pgno;
411 mpool_put(t->bt_mp, tp, MPOOL_DIRTY);
412 }
413
414 /*
415 * Split right. The key/data pairs aren't sorted in the btree page so
416 * it's simpler to copy the data from the split page onto two new pages
417 * instead of copying half the data to the right page and compacting
418 * the left page in place. Since the left page can't change, we have
419 * to swap the original and the allocated left page after the split.
420 */
421 tp = bt_psplit(t, h, l, r, skip, ilen);
422
423 /* Move the new left page onto the old left page. */
424 memmove(h, l, t->bt_psize);
425 if (tp == l)
426 tp = h;
427 free(l);
428
429 *lp = h;
430 *rp = r;
431 return (tp);
432 }
433
434 /*
435 * BT_ROOT -- Split the root page of a btree.
436 *
437 * Parameters:
438 * t: tree
439 * h: root page
440 * lp: pointer to left page pointer
441 * rp: pointer to right page pointer
442 * skip: pointer to index to leave open
443 * ilen: insert length
444 *
445 * Returns:
446 * Pointer to page in which to insert or NULL on error.
447 */
448 static PAGE *
bt_root(t,h,lp,rp,skip,ilen)449 bt_root(t, h, lp, rp, skip, ilen)
450 BTREE *t;
451 PAGE *h, **lp, **rp;
452 indx_t *skip;
453 size_t ilen;
454 {
455 PAGE *l, *r, *tp;
456 db_pgno_t lnpg, rnpg;
457
458 #ifdef STATISTICS
459 ++bt_split;
460 ++bt_rootsplit;
461 #endif
462 /* Put the new left and right pages for the split into place. */
463 if ((l = __bt_new(t, &lnpg)) == NULL ||
464 (r = __bt_new(t, &rnpg)) == NULL)
465 return (NULL);
466 l->pgno = lnpg;
467 r->pgno = rnpg;
468 l->nextpg = r->pgno;
469 r->prevpg = l->pgno;
470 l->prevpg = r->nextpg = P_INVALID;
471 l->lower = r->lower = BTDATAOFF;
472 l->upper = r->upper = t->bt_psize;
473 l->flags = r->flags = h->flags & P_TYPE;
474
475 /* Split the root page. */
476 tp = bt_psplit(t, h, l, r, skip, ilen);
477
478 *lp = l;
479 *rp = r;
480 return (tp);
481 }
482
483 /*
484 * BT_RROOT -- Fix up the recno root page after it has been split.
485 *
486 * Parameters:
487 * t: tree
488 * h: root page
489 * l: left page
490 * r: right page
491 *
492 * Returns:
493 * RET_ERROR, RET_SUCCESS
494 */
495 static int
bt_rroot(t,h,l,r)496 bt_rroot(t, h, l, r)
497 BTREE *t;
498 PAGE *h, *l, *r;
499 {
500 char *dest;
501
502 /* Insert the left and right keys, set the header information. */
503 h->linp[0] = h->upper = t->bt_psize - NRINTERNAL;
504 dest = (char *)h + h->upper;
505 WR_RINTERNAL(dest,
506 l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno);
507
508 h->linp[1] = h->upper -= NRINTERNAL;
509 dest = (char *)h + h->upper;
510 WR_RINTERNAL(dest,
511 r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno);
512
513 h->lower = BTDATAOFF + 2 * sizeof(indx_t);
514
515 /* Unpin the root page, set to recno internal page. */
516 h->flags &= ~P_TYPE;
517 h->flags |= P_RINTERNAL;
518 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
519
520 return (RET_SUCCESS);
521 }
522
523 /*
524 * BT_BROOT -- Fix up the btree root page after it has been split.
525 *
526 * Parameters:
527 * t: tree
528 * h: root page
529 * l: left page
530 * r: right page
531 *
532 * Returns:
533 * RET_ERROR, RET_SUCCESS
534 */
535 static int
bt_broot(t,h,l,r)536 bt_broot(t, h, l, r)
537 BTREE *t;
538 PAGE *h, *l, *r;
539 {
540 BINTERNAL *bi;
541 BLEAF *bl;
542 u_int32_t nbytes;
543 char *dest;
544
545 /*
546 * If the root page was a leaf page, change it into an internal page.
547 * We copy the key we split on (but not the key's data, in the case of
548 * a leaf page) to the new root page.
549 *
550 * The btree comparison code guarantees that the left-most key on any
551 * level of the tree is never used, so it doesn't need to be filled in.
552 */
553 nbytes = NBINTERNAL(0);
554 h->linp[0] = h->upper = t->bt_psize - nbytes;
555 dest = (char *)h + h->upper;
556 WR_BINTERNAL(dest, 0, l->pgno, 0);
557
558 switch (h->flags & P_TYPE) {
559 case P_BLEAF:
560 bl = GETBLEAF(r, 0);
561 nbytes = NBINTERNAL(bl->ksize);
562 h->linp[1] = h->upper -= nbytes;
563 dest = (char *)h + h->upper;
564 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0);
565 memmove(dest, bl->bytes, bl->ksize);
566
567 /*
568 * If the key is on an overflow page, mark the overflow chain
569 * so it isn't deleted when the leaf copy of the key is deleted.
570 */
571 if (bl->flags & P_BIGKEY &&
572 bt_preserve(t, *(db_pgno_t *)bl->bytes) == RET_ERROR)
573 return (RET_ERROR);
574 break;
575 case P_BINTERNAL:
576 bi = GETBINTERNAL(r, 0);
577 nbytes = NBINTERNAL(bi->ksize);
578 h->linp[1] = h->upper -= nbytes;
579 dest = (char *)h + h->upper;
580 memmove(dest, bi, nbytes);
581 ((BINTERNAL *)dest)->pgno = r->pgno;
582 break;
583 default:
584 abort();
585 }
586
587 /* There are two keys on the page. */
588 h->lower = BTDATAOFF + 2 * sizeof(indx_t);
589
590 /* Unpin the root page, set to btree internal page. */
591 h->flags &= ~P_TYPE;
592 h->flags |= P_BINTERNAL;
593 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
594
595 return (RET_SUCCESS);
596 }
597
598 /*
599 * BT_PSPLIT -- Do the real work of splitting the page.
600 *
601 * Parameters:
602 * t: tree
603 * h: page to be split
604 * l: page to put lower half of data
605 * r: page to put upper half of data
606 * pskip: pointer to index to leave open
607 * ilen: insert length
608 *
609 * Returns:
610 * Pointer to page in which to insert.
611 */
612 static PAGE *
bt_psplit(t,h,l,r,pskip,ilen)613 bt_psplit(t, h, l, r, pskip, ilen)
614 BTREE *t;
615 PAGE *h, *l, *r;
616 indx_t *pskip;
617 size_t ilen;
618 {
619 BINTERNAL *bi;
620 BLEAF *bl;
621 CURSOR *c;
622 RLEAF *rl;
623 PAGE *rval;
624 void *src;
625 indx_t full, half, nxt, off, skip, top, used;
626 u_int32_t nbytes;
627 int bigkeycnt, isbigkey;
628
629 /*
630 * Split the data to the left and right pages. Leave the skip index
631 * open. Additionally, make some effort not to split on an overflow
632 * key. This makes internal page processing faster and can save
633 * space as overflow keys used by internal pages are never deleted.
634 */
635 bigkeycnt = 0;
636 skip = *pskip;
637 full = t->bt_psize - BTDATAOFF;
638 half = full / 2;
639 used = 0;
640 for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) {
641 if (skip == off) {
642 nbytes = ilen;
643 isbigkey = 0; /* XXX: not really known. */
644 } else
645 switch (h->flags & P_TYPE) {
646 case P_BINTERNAL:
647 src = bi = GETBINTERNAL(h, nxt);
648 nbytes = NBINTERNAL(bi->ksize);
649 isbigkey = bi->flags & P_BIGKEY;
650 break;
651 case P_BLEAF:
652 src = bl = GETBLEAF(h, nxt);
653 nbytes = NBLEAF(bl);
654 isbigkey = bl->flags & P_BIGKEY;
655 break;
656 case P_RINTERNAL:
657 src = GETRINTERNAL(h, nxt);
658 nbytes = NRINTERNAL;
659 isbigkey = 0;
660 break;
661 case P_RLEAF:
662 src = rl = GETRLEAF(h, nxt);
663 nbytes = NRLEAF(rl);
664 isbigkey = 0;
665 break;
666 default:
667 abort();
668 }
669
670 /*
671 * If the key/data pairs are substantial fractions of the max
672 * possible size for the page, it's possible to get situations
673 * where we decide to try and copy too much onto the left page.
674 * Make sure that doesn't happen.
675 */
676 if ((skip <= off && used + nbytes + sizeof(indx_t) >= full)
677 || nxt == top - 1) {
678 --off;
679 break;
680 }
681
682 /* Copy the key/data pair, if not the skipped index. */
683 if (skip != off) {
684 ++nxt;
685
686 l->linp[off] = l->upper -= nbytes;
687 memmove((char *)l + l->upper, src, nbytes);
688 }
689
690 used += nbytes + sizeof(indx_t);
691 if (used >= half) {
692 if (!isbigkey || bigkeycnt == 3)
693 break;
694 else
695 ++bigkeycnt;
696 }
697 }
698
699 /*
700 * Off is the last offset that's valid for the left page.
701 * Nxt is the first offset to be placed on the right page.
702 */
703 l->lower += (off + 1) * sizeof(indx_t);
704
705 /*
706 * If splitting the page that the cursor was on, the cursor has to be
707 * adjusted to point to the same record as before the split. If the
708 * cursor is at or past the skipped slot, the cursor is incremented by
709 * one. If the cursor is on the right page, it is decremented by the
710 * number of records split to the left page.
711 */
712 c = &t->bt_cursor;
713 if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) {
714 if (c->pg.index >= skip)
715 ++c->pg.index;
716 if (c->pg.index < nxt) /* Left page. */
717 c->pg.pgno = l->pgno;
718 else { /* Right page. */
719 c->pg.pgno = r->pgno;
720 c->pg.index -= nxt;
721 }
722 }
723
724 /*
725 * If the skipped index was on the left page, just return that page.
726 * Otherwise, adjust the skip index to reflect the new position on
727 * the right page.
728 */
729 if (skip <= off) {
730 /*
731 * If we get here then 'skip' is in the left page. We do
732 * not want to mix this with the right page, so we assign
733 * an unrealistic value (-1).
734 */
735 skip = (indx_t)-1;
736 rval = l;
737 } else {
738 rval = r;
739 *pskip -= nxt;
740 }
741
742 for (off = 0; nxt < top; ++off) {
743 if (skip == nxt) {
744 ++off;
745 /*
746 * Assign 'skip' an unrealistic value (-1) to ensure
747 * it is not matched again.
748 */
749 skip = (indx_t)-1;
750 }
751 switch (h->flags & P_TYPE) {
752 case P_BINTERNAL:
753 src = bi = GETBINTERNAL(h, nxt);
754 nbytes = NBINTERNAL(bi->ksize);
755 break;
756 case P_BLEAF:
757 src = bl = GETBLEAF(h, nxt);
758 nbytes = NBLEAF(bl);
759 break;
760 case P_RINTERNAL:
761 src = GETRINTERNAL(h, nxt);
762 nbytes = NRINTERNAL;
763 break;
764 case P_RLEAF:
765 src = rl = GETRLEAF(h, nxt);
766 nbytes = NRLEAF(rl);
767 break;
768 default:
769 abort();
770 }
771 ++nxt;
772 r->linp[off] = r->upper -= nbytes;
773 memmove((char *)r + r->upper, src, nbytes);
774 }
775 r->lower += off * sizeof(indx_t);
776
777 /* If the key is being appended to the page, adjust the index. */
778 if (skip == top)
779 r->lower += sizeof(indx_t);
780
781 return (rval);
782 }
783
784 /*
785 * BT_PRESERVE -- Mark a chain of pages as used by an internal node.
786 *
787 * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the
788 * record that references them gets deleted. Chains pointed to by internal
789 * pages never get deleted. This routine marks a chain as pointed to by an
790 * internal page.
791 *
792 * Parameters:
793 * t: tree
794 * pg: page number of first page in the chain.
795 *
796 * Returns:
797 * RET_SUCCESS, RET_ERROR.
798 */
799 static int
bt_preserve(t,pg)800 bt_preserve(t, pg)
801 BTREE *t;
802 db_pgno_t pg;
803 {
804 PAGE *h;
805
806 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
807 return (RET_ERROR);
808 h->flags |= P_PRESERVE;
809 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
810 return (RET_SUCCESS);
811 }
812
813 /*
814 * REC_TOTAL -- Return the number of recno entries below a page.
815 *
816 * Parameters:
817 * h: page
818 *
819 * Returns:
820 * The number of recno entries below a page.
821 *
822 * XXX
823 * These values could be set by the bt_psplit routine. The problem is that the
824 * entry has to be popped off of the stack etc. or the values have to be passed
825 * all the way back to bt_split/bt_rroot and it's not very clean.
826 */
827 static recno_t
rec_total(h)828 rec_total(h)
829 PAGE *h;
830 {
831 recno_t recs;
832 indx_t nxt, top;
833
834 for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt)
835 recs += GETRINTERNAL(h, nxt)->nrecs;
836 return (recs);
837 }
838