1 #pragma ident "%Z%%M% %I% %E% SMI"
2
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. All advertising materials mentioning features or use of this software
19 * must display the following acknowledgement:
20 * This product includes software developed by the University of
21 * California, Berkeley and its contributors.
22 * 4. Neither the name of the University nor the names of its contributors
23 * may be used to endorse or promote products derived from this software
24 * without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 */
38
39 #if defined(LIBC_SCCS) && !defined(lint)
40 static char sccsid[] = "@(#)bt_split.c 8.10 (Berkeley) 1/9/95";
41 #endif /* LIBC_SCCS and not lint */
42
43 #include <sys/types.h>
44
45 #include <limits.h>
46 #include <stdio.h>
47 #include <stdlib.h>
48 #include <string.h>
49
50 #include "db-int.h"
51 #include "btree.h"
52
53 static int bt_broot __P((BTREE *, PAGE *, PAGE *, PAGE *));
54 static PAGE *bt_page
55 __P((BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t));
56 static int bt_preserve __P((BTREE *, db_pgno_t));
57 static PAGE *bt_psplit
58 __P((BTREE *, PAGE *, PAGE *, PAGE *, indx_t *, size_t));
59 static PAGE *bt_root
60 __P((BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t));
61 static int bt_rroot __P((BTREE *, PAGE *, PAGE *, PAGE *));
62 static recno_t rec_total __P((PAGE *));
63
64 #ifdef STATISTICS
65 u_long bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved;
66 #endif
67
68 /*
69 * __BT_SPLIT -- Split the tree.
70 *
71 * Parameters:
72 * t: tree
73 * sp: page to split
74 * key: key to insert
75 * data: data to insert
76 * flags: BIGKEY/BIGDATA flags
77 * ilen: insert length
78 * skip: index to leave open
79 *
80 * Returns:
81 * RET_ERROR, RET_SUCCESS
82 */
83 int
__bt_split(t,sp,key,data,flags,ilen,argskip)84 __bt_split(t, sp, key, data, flags, ilen, argskip)
85 BTREE *t;
86 PAGE *sp;
87 const DBT *key, *data;
88 int flags;
89 size_t ilen;
90 u_int32_t argskip;
91 {
92 BINTERNAL *bi;
93 BLEAF *bl, *tbl;
94 DBT a, b;
95 EPGNO *parent;
96 PAGE *h, *l, *r, *lchild, *rchild;
97 indx_t nxtindex;
98 u_int16_t skip;
99 u_int32_t n, nbytes, nksize;
100 int parentsplit;
101 char *dest;
102
103 /*
104 * Split the page into two pages, l and r. The split routines return
105 * a pointer to the page into which the key should be inserted and with
106 * skip set to the offset which should be used. Additionally, l and r
107 * are pinned.
108 */
109 skip = argskip;
110 h = sp->pgno == P_ROOT ?
111 bt_root(t, sp, &l, &r, &skip, ilen) :
112 bt_page(t, sp, &l, &r, &skip, ilen);
113 if (h == NULL)
114 return (RET_ERROR);
115
116 /*
117 * Insert the new key/data pair into the leaf page. (Key inserts
118 * always cause a leaf page to split first.)
119 */
120 h->linp[skip] = h->upper -= ilen;
121 dest = (char *)h + h->upper;
122 if (F_ISSET(t, R_RECNO))
123 WR_RLEAF(dest, data, flags)
124 else
125 WR_BLEAF(dest, key, data, flags)
126
127 /* If the root page was split, make it look right. */
128 if (sp->pgno == P_ROOT &&
129 (F_ISSET(t, R_RECNO) ?
130 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR)
131 goto err2;
132
133 /*
134 * Now we walk the parent page stack -- a LIFO stack of the pages that
135 * were traversed when we searched for the page that split. Each stack
136 * entry is a page number and a page index offset. The offset is for
137 * the page traversed on the search. We've just split a page, so we
138 * have to insert a new key into the parent page.
139 *
140 * If the insert into the parent page causes it to split, may have to
141 * continue splitting all the way up the tree. We stop if the root
142 * splits or the page inserted into didn't have to split to hold the
143 * new key. Some algorithms replace the key for the old page as well
144 * as the new page. We don't, as there's no reason to believe that the
145 * first key on the old page is any better than the key we have, and,
146 * in the case of a key being placed at index 0 causing the split, the
147 * key is unavailable.
148 *
149 * There are a maximum of 5 pages pinned at any time. We keep the left
150 * and right pages pinned while working on the parent. The 5 are the
151 * two children, left parent and right parent (when the parent splits)
152 * and the root page or the overflow key page when calling bt_preserve.
153 * This code must make sure that all pins are released other than the
154 * root page or overflow page which is unlocked elsewhere.
155 */
156 while ((parent = BT_POP(t)) != NULL) {
157 lchild = l;
158 rchild = r;
159
160 /* Get the parent page. */
161 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
162 goto err2;
163
164 /*
165 * The new key goes ONE AFTER the index, because the split
166 * was to the right.
167 */
168 skip = parent->index + 1;
169
170 /*
171 * Calculate the space needed on the parent page.
172 *
173 * Prefix trees: space hack when inserting into BINTERNAL
174 * pages. Retain only what's needed to distinguish between
175 * the new entry and the LAST entry on the page to its left.
176 * If the keys compare equal, retain the entire key. Note,
177 * we don't touch overflow keys, and the entire key must be
178 * retained for the next-to-left most key on the leftmost
179 * page of each level, or the search will fail. Applicable
180 * ONLY to internal pages that have leaf pages as children.
181 * Further reduction of the key between pairs of internal
182 * pages loses too much information.
183 */
184 switch (rchild->flags & P_TYPE) {
185 case P_BINTERNAL:
186 bi = GETBINTERNAL(rchild, 0);
187 nbytes = NBINTERNAL(bi->ksize);
188 break;
189 case P_BLEAF:
190 bl = GETBLEAF(rchild, 0);
191 nbytes = NBINTERNAL(bl->ksize);
192 if (t->bt_pfx && !(bl->flags & P_BIGKEY) &&
193 (h->prevpg != P_INVALID || skip > 1)) {
194 tbl = GETBLEAF(lchild, NEXTINDEX(lchild) - 1);
195 a.size = tbl->ksize;
196 a.data = tbl->bytes;
197 b.size = bl->ksize;
198 b.data = bl->bytes;
199 nksize = t->bt_pfx(&a, &b);
200 n = NBINTERNAL(nksize);
201 if (n < nbytes) {
202 #ifdef STATISTICS
203 bt_pfxsaved += nbytes - n;
204 #endif
205 nbytes = n;
206 } else
207 nksize = 0;
208 } else
209 nksize = 0;
210 break;
211 case P_RINTERNAL:
212 case P_RLEAF:
213 nbytes = NRINTERNAL;
214 break;
215 default:
216 abort();
217 }
218
219 /* Split the parent page if necessary or shift the indices. */
220 if (h->upper - h->lower < nbytes + sizeof(indx_t)) {
221 sp = h;
222 h = h->pgno == P_ROOT ?
223 bt_root(t, h, &l, &r, &skip, nbytes) :
224 bt_page(t, h, &l, &r, &skip, nbytes);
225 if (h == NULL)
226 goto err1;
227 parentsplit = 1;
228 } else {
229 if (skip < (nxtindex = NEXTINDEX(h)))
230 memmove(h->linp + skip + 1, h->linp + skip,
231 (nxtindex - skip) * sizeof(indx_t));
232 h->lower += sizeof(indx_t);
233 parentsplit = 0;
234 }
235
236 /* Insert the key into the parent page. */
237 switch (rchild->flags & P_TYPE) {
238 case P_BINTERNAL:
239 h->linp[skip] = h->upper -= nbytes;
240 dest = (char *)h + h->linp[skip];
241 memmove(dest, bi, nbytes);
242 ((BINTERNAL *)dest)->pgno = rchild->pgno;
243 break;
244 case P_BLEAF:
245 h->linp[skip] = h->upper -= nbytes;
246 dest = (char *)h + h->linp[skip];
247 WR_BINTERNAL(dest, nksize ? nksize : bl->ksize,
248 rchild->pgno, bl->flags & P_BIGKEY);
249 memmove(dest, bl->bytes, nksize ? nksize : bl->ksize);
250 if (bl->flags & P_BIGKEY &&
251 bt_preserve(t, *(db_pgno_t *)bl->bytes) == RET_ERROR)
252 goto err1;
253 break;
254 case P_RINTERNAL:
255 /*
256 * Update the left page count. If split
257 * added at index 0, fix the correct page.
258 */
259 if (skip > 0)
260 dest = (char *)h + h->linp[skip - 1];
261 else
262 dest = (char *)l + l->linp[NEXTINDEX(l) - 1];
263 ((RINTERNAL *)dest)->nrecs = rec_total(lchild);
264 ((RINTERNAL *)dest)->pgno = lchild->pgno;
265
266 /* Update the right page count. */
267 h->linp[skip] = h->upper -= nbytes;
268 dest = (char *)h + h->linp[skip];
269 ((RINTERNAL *)dest)->nrecs = rec_total(rchild);
270 ((RINTERNAL *)dest)->pgno = rchild->pgno;
271 break;
272 case P_RLEAF:
273 /*
274 * Update the left page count. If split
275 * added at index 0, fix the correct page.
276 */
277 if (skip > 0)
278 dest = (char *)h + h->linp[skip - 1];
279 else
280 dest = (char *)l + l->linp[NEXTINDEX(l) - 1];
281 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(lchild);
282 ((RINTERNAL *)dest)->pgno = lchild->pgno;
283
284 /* Update the right page count. */
285 h->linp[skip] = h->upper -= nbytes;
286 dest = (char *)h + h->linp[skip];
287 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(rchild);
288 ((RINTERNAL *)dest)->pgno = rchild->pgno;
289 break;
290 default:
291 abort();
292 }
293
294 /* Unpin the held pages. */
295 if (!parentsplit) {
296 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
297 break;
298 }
299
300 /* If the root page was split, make it look right. */
301 if (sp->pgno == P_ROOT &&
302 (F_ISSET(t, R_RECNO) ?
303 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR)
304 goto err1;
305
306 mpool_put(t->bt_mp, lchild, MPOOL_DIRTY);
307 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY);
308 }
309
310 /* Unpin the held pages. */
311 mpool_put(t->bt_mp, l, MPOOL_DIRTY);
312 mpool_put(t->bt_mp, r, MPOOL_DIRTY);
313
314 /* Clear any pages left on the stack. */
315 return (RET_SUCCESS);
316
317 /*
318 * If something fails in the above loop we were already walking back
319 * up the tree and the tree is now inconsistent. Nothing much we can
320 * do about it but release any memory we're holding.
321 */
322 err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY);
323 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY);
324
325 err2: mpool_put(t->bt_mp, l, 0);
326 mpool_put(t->bt_mp, r, 0);
327 __dbpanic(t->bt_dbp);
328 return (RET_ERROR);
329 }
330
331 /*
332 * BT_PAGE -- Split a non-root page of a btree.
333 *
334 * Parameters:
335 * t: tree
336 * h: root page
337 * lp: pointer to left page pointer
338 * rp: pointer to right page pointer
339 * skip: pointer to index to leave open
340 * ilen: insert length
341 *
342 * Returns:
343 * Pointer to page in which to insert or NULL on error.
344 */
345 static PAGE *
bt_page(t,h,lp,rp,skip,ilen)346 bt_page(t, h, lp, rp, skip, ilen)
347 BTREE *t;
348 PAGE *h, **lp, **rp;
349 indx_t *skip;
350 size_t ilen;
351 {
352 PAGE *l, *r, *tp;
353 db_pgno_t npg;
354
355 #ifdef STATISTICS
356 ++bt_split;
357 #endif
358 /* Put the new right page for the split into place. */
359 if ((r = __bt_new(t, &npg)) == NULL)
360 return (NULL);
361 r->pgno = npg;
362 r->lower = BTDATAOFF;
363 r->upper = t->bt_psize;
364 r->nextpg = h->nextpg;
365 r->prevpg = h->pgno;
366 r->flags = h->flags & P_TYPE;
367
368 /*
369 * If we're splitting the last page on a level because we're appending
370 * a key to it (skip is NEXTINDEX()), it's likely that the data is
371 * sorted. Adding an empty page on the side of the level is less work
372 * and can push the fill factor much higher than normal. If we're
373 * wrong it's no big deal, we'll just do the split the right way next
374 * time. It may look like it's equally easy to do a similar hack for
375 * reverse sorted data, that is, split the tree left, but it's not.
376 * Don't even try.
377 */
378 if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) {
379 #ifdef STATISTICS
380 ++bt_sortsplit;
381 #endif
382 h->nextpg = r->pgno;
383 r->lower = BTDATAOFF + sizeof(indx_t);
384 *skip = 0;
385 *lp = h;
386 *rp = r;
387 return (r);
388 }
389
390 /* Put the new left page for the split into place. */
391 if ((l = (PAGE *)malloc(t->bt_psize)) == NULL) {
392 mpool_put(t->bt_mp, r, 0);
393 return (NULL);
394 }
395 #ifdef PURIFY
396 memset(l, 0xff, t->bt_psize);
397 #endif
398 l->pgno = h->pgno;
399 l->nextpg = r->pgno;
400 l->prevpg = h->prevpg;
401 l->lower = BTDATAOFF;
402 l->upper = t->bt_psize;
403 l->flags = h->flags & P_TYPE;
404
405 /* Fix up the previous pointer of the page after the split page. */
406 if (h->nextpg != P_INVALID) {
407 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) {
408 free(l);
409 /* XXX mpool_free(t->bt_mp, r->pgno); */
410 return (NULL);
411 }
412 tp->prevpg = r->pgno;
413 mpool_put(t->bt_mp, tp, MPOOL_DIRTY);
414 }
415
416 /*
417 * Split right. The key/data pairs aren't sorted in the btree page so
418 * it's simpler to copy the data from the split page onto two new pages
419 * instead of copying half the data to the right page and compacting
420 * the left page in place. Since the left page can't change, we have
421 * to swap the original and the allocated left page after the split.
422 */
423 tp = bt_psplit(t, h, l, r, skip, ilen);
424
425 /* Move the new left page onto the old left page. */
426 memmove(h, l, t->bt_psize);
427 if (tp == l)
428 tp = h;
429 free(l);
430
431 *lp = h;
432 *rp = r;
433 return (tp);
434 }
435
436 /*
437 * BT_ROOT -- Split the root page of a btree.
438 *
439 * Parameters:
440 * t: tree
441 * h: root page
442 * lp: pointer to left page pointer
443 * rp: pointer to right page pointer
444 * skip: pointer to index to leave open
445 * ilen: insert length
446 *
447 * Returns:
448 * Pointer to page in which to insert or NULL on error.
449 */
450 static PAGE *
bt_root(t,h,lp,rp,skip,ilen)451 bt_root(t, h, lp, rp, skip, ilen)
452 BTREE *t;
453 PAGE *h, **lp, **rp;
454 indx_t *skip;
455 size_t ilen;
456 {
457 PAGE *l, *r, *tp;
458 db_pgno_t lnpg, rnpg;
459
460 #ifdef STATISTICS
461 ++bt_split;
462 ++bt_rootsplit;
463 #endif
464 /* Put the new left and right pages for the split into place. */
465 if ((l = __bt_new(t, &lnpg)) == NULL ||
466 (r = __bt_new(t, &rnpg)) == NULL)
467 return (NULL);
468 l->pgno = lnpg;
469 r->pgno = rnpg;
470 l->nextpg = r->pgno;
471 r->prevpg = l->pgno;
472 l->prevpg = r->nextpg = P_INVALID;
473 l->lower = r->lower = BTDATAOFF;
474 l->upper = r->upper = t->bt_psize;
475 l->flags = r->flags = h->flags & P_TYPE;
476
477 /* Split the root page. */
478 tp = bt_psplit(t, h, l, r, skip, ilen);
479
480 *lp = l;
481 *rp = r;
482 return (tp);
483 }
484
485 /*
486 * BT_RROOT -- Fix up the recno root page after it has been split.
487 *
488 * Parameters:
489 * t: tree
490 * h: root page
491 * l: left page
492 * r: right page
493 *
494 * Returns:
495 * RET_ERROR, RET_SUCCESS
496 */
497 static int
bt_rroot(t,h,l,r)498 bt_rroot(t, h, l, r)
499 BTREE *t;
500 PAGE *h, *l, *r;
501 {
502 char *dest;
503
504 /* Insert the left and right keys, set the header information. */
505 h->linp[0] = h->upper = t->bt_psize - NRINTERNAL;
506 dest = (char *)h + h->upper;
507 WR_RINTERNAL(dest,
508 l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno);
509
510 h->linp[1] = h->upper -= NRINTERNAL;
511 dest = (char *)h + h->upper;
512 WR_RINTERNAL(dest,
513 r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno);
514
515 h->lower = BTDATAOFF + 2 * sizeof(indx_t);
516
517 /* Unpin the root page, set to recno internal page. */
518 h->flags &= ~P_TYPE;
519 h->flags |= P_RINTERNAL;
520 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
521
522 return (RET_SUCCESS);
523 }
524
525 /*
526 * BT_BROOT -- Fix up the btree root page after it has been split.
527 *
528 * Parameters:
529 * t: tree
530 * h: root page
531 * l: left page
532 * r: right page
533 *
534 * Returns:
535 * RET_ERROR, RET_SUCCESS
536 */
537 static int
bt_broot(t,h,l,r)538 bt_broot(t, h, l, r)
539 BTREE *t;
540 PAGE *h, *l, *r;
541 {
542 BINTERNAL *bi;
543 BLEAF *bl;
544 u_int32_t nbytes;
545 char *dest;
546
547 /*
548 * If the root page was a leaf page, change it into an internal page.
549 * We copy the key we split on (but not the key's data, in the case of
550 * a leaf page) to the new root page.
551 *
552 * The btree comparison code guarantees that the left-most key on any
553 * level of the tree is never used, so it doesn't need to be filled in.
554 */
555 nbytes = NBINTERNAL(0);
556 h->linp[0] = h->upper = t->bt_psize - nbytes;
557 dest = (char *)h + h->upper;
558 WR_BINTERNAL(dest, 0, l->pgno, 0);
559
560 switch (h->flags & P_TYPE) {
561 case P_BLEAF:
562 bl = GETBLEAF(r, 0);
563 nbytes = NBINTERNAL(bl->ksize);
564 h->linp[1] = h->upper -= nbytes;
565 dest = (char *)h + h->upper;
566 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0);
567 memmove(dest, bl->bytes, bl->ksize);
568
569 /*
570 * If the key is on an overflow page, mark the overflow chain
571 * so it isn't deleted when the leaf copy of the key is deleted.
572 */
573 if (bl->flags & P_BIGKEY &&
574 bt_preserve(t, *(db_pgno_t *)bl->bytes) == RET_ERROR)
575 return (RET_ERROR);
576 break;
577 case P_BINTERNAL:
578 bi = GETBINTERNAL(r, 0);
579 nbytes = NBINTERNAL(bi->ksize);
580 h->linp[1] = h->upper -= nbytes;
581 dest = (char *)h + h->upper;
582 memmove(dest, bi, nbytes);
583 ((BINTERNAL *)dest)->pgno = r->pgno;
584 break;
585 default:
586 abort();
587 }
588
589 /* There are two keys on the page. */
590 h->lower = BTDATAOFF + 2 * sizeof(indx_t);
591
592 /* Unpin the root page, set to btree internal page. */
593 h->flags &= ~P_TYPE;
594 h->flags |= P_BINTERNAL;
595 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
596
597 return (RET_SUCCESS);
598 }
599
600 /*
601 * BT_PSPLIT -- Do the real work of splitting the page.
602 *
603 * Parameters:
604 * t: tree
605 * h: page to be split
606 * l: page to put lower half of data
607 * r: page to put upper half of data
608 * pskip: pointer to index to leave open
609 * ilen: insert length
610 *
611 * Returns:
612 * Pointer to page in which to insert.
613 */
614 static PAGE *
bt_psplit(t,h,l,r,pskip,ilen)615 bt_psplit(t, h, l, r, pskip, ilen)
616 BTREE *t;
617 PAGE *h, *l, *r;
618 indx_t *pskip;
619 size_t ilen;
620 {
621 BINTERNAL *bi;
622 BLEAF *bl;
623 CURSOR *c;
624 RLEAF *rl;
625 PAGE *rval;
626 void *src;
627 indx_t full, half, nxt, off, skip, top, used;
628 u_int32_t nbytes;
629 int bigkeycnt, isbigkey;
630
631 /*
632 * Split the data to the left and right pages. Leave the skip index
633 * open. Additionally, make some effort not to split on an overflow
634 * key. This makes internal page processing faster and can save
635 * space as overflow keys used by internal pages are never deleted.
636 */
637 bigkeycnt = 0;
638 skip = *pskip;
639 full = t->bt_psize - BTDATAOFF;
640 half = full / 2;
641 used = 0;
642 for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) {
643 if (skip == off) {
644 nbytes = ilen;
645 isbigkey = 0; /* XXX: not really known. */
646 } else
647 switch (h->flags & P_TYPE) {
648 case P_BINTERNAL:
649 src = bi = GETBINTERNAL(h, nxt);
650 nbytes = NBINTERNAL(bi->ksize);
651 isbigkey = bi->flags & P_BIGKEY;
652 break;
653 case P_BLEAF:
654 src = bl = GETBLEAF(h, nxt);
655 nbytes = NBLEAF(bl);
656 isbigkey = bl->flags & P_BIGKEY;
657 break;
658 case P_RINTERNAL:
659 src = GETRINTERNAL(h, nxt);
660 nbytes = NRINTERNAL;
661 isbigkey = 0;
662 break;
663 case P_RLEAF:
664 src = rl = GETRLEAF(h, nxt);
665 nbytes = NRLEAF(rl);
666 isbigkey = 0;
667 break;
668 default:
669 abort();
670 }
671
672 /*
673 * If the key/data pairs are substantial fractions of the max
674 * possible size for the page, it's possible to get situations
675 * where we decide to try and copy too much onto the left page.
676 * Make sure that doesn't happen.
677 */
678 if ((skip <= off && used + nbytes + sizeof(indx_t) >= full)
679 || nxt == top - 1) {
680 --off;
681 break;
682 }
683
684 /* Copy the key/data pair, if not the skipped index. */
685 if (skip != off) {
686 ++nxt;
687
688 l->linp[off] = l->upper -= nbytes;
689 memmove((char *)l + l->upper, src, nbytes);
690 }
691
692 used += nbytes + sizeof(indx_t);
693 if (used >= half) {
694 if (!isbigkey || bigkeycnt == 3)
695 break;
696 else
697 ++bigkeycnt;
698 }
699 }
700
701 /*
702 * Off is the last offset that's valid for the left page.
703 * Nxt is the first offset to be placed on the right page.
704 */
705 l->lower += (off + 1) * sizeof(indx_t);
706
707 /*
708 * If splitting the page that the cursor was on, the cursor has to be
709 * adjusted to point to the same record as before the split. If the
710 * cursor is at or past the skipped slot, the cursor is incremented by
711 * one. If the cursor is on the right page, it is decremented by the
712 * number of records split to the left page.
713 */
714 c = &t->bt_cursor;
715 if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) {
716 if (c->pg.index >= skip)
717 ++c->pg.index;
718 if (c->pg.index < nxt) /* Left page. */
719 c->pg.pgno = l->pgno;
720 else { /* Right page. */
721 c->pg.pgno = r->pgno;
722 c->pg.index -= nxt;
723 }
724 }
725
726 /*
727 * If the skipped index was on the left page, just return that page.
728 * Otherwise, adjust the skip index to reflect the new position on
729 * the right page.
730 */
731 if (skip <= off) {
732 /*
733 * If we get here then 'skip' is in the left page. We do
734 * not want to mix this with the right page, so we assign
735 * an unrealistic value (-1).
736 */
737 skip = (indx_t)-1;
738 rval = l;
739 } else {
740 rval = r;
741 *pskip -= nxt;
742 }
743
744 for (off = 0; nxt < top; ++off) {
745 if (skip == nxt) {
746 ++off;
747 /*
748 * Assign 'skip' an unrealistic value (-1) to ensure
749 * it is not matched again.
750 */
751 skip = (indx_t)-1;
752 }
753 switch (h->flags & P_TYPE) {
754 case P_BINTERNAL:
755 src = bi = GETBINTERNAL(h, nxt);
756 nbytes = NBINTERNAL(bi->ksize);
757 break;
758 case P_BLEAF:
759 src = bl = GETBLEAF(h, nxt);
760 nbytes = NBLEAF(bl);
761 break;
762 case P_RINTERNAL:
763 src = GETRINTERNAL(h, nxt);
764 nbytes = NRINTERNAL;
765 break;
766 case P_RLEAF:
767 src = rl = GETRLEAF(h, nxt);
768 nbytes = NRLEAF(rl);
769 break;
770 default:
771 abort();
772 }
773 ++nxt;
774 r->linp[off] = r->upper -= nbytes;
775 memmove((char *)r + r->upper, src, nbytes);
776 }
777 r->lower += off * sizeof(indx_t);
778
779 /* If the key is being appended to the page, adjust the index. */
780 if (skip == top)
781 r->lower += sizeof(indx_t);
782
783 return (rval);
784 }
785
786 /*
787 * BT_PRESERVE -- Mark a chain of pages as used by an internal node.
788 *
789 * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the
790 * record that references them gets deleted. Chains pointed to by internal
791 * pages never get deleted. This routine marks a chain as pointed to by an
792 * internal page.
793 *
794 * Parameters:
795 * t: tree
796 * pg: page number of first page in the chain.
797 *
798 * Returns:
799 * RET_SUCCESS, RET_ERROR.
800 */
801 static int
bt_preserve(t,pg)802 bt_preserve(t, pg)
803 BTREE *t;
804 db_pgno_t pg;
805 {
806 PAGE *h;
807
808 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
809 return (RET_ERROR);
810 h->flags |= P_PRESERVE;
811 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
812 return (RET_SUCCESS);
813 }
814
815 /*
816 * REC_TOTAL -- Return the number of recno entries below a page.
817 *
818 * Parameters:
819 * h: page
820 *
821 * Returns:
822 * The number of recno entries below a page.
823 *
824 * XXX
825 * These values could be set by the bt_psplit routine. The problem is that the
826 * entry has to be popped off of the stack etc. or the values have to be passed
827 * all the way back to bt_split/bt_rroot and it's not very clean.
828 */
829 static recno_t
rec_total(h)830 rec_total(h)
831 PAGE *h;
832 {
833 recno_t recs;
834 indx_t nxt, top;
835
836 for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt)
837 recs += GETRINTERNAL(h, nxt)->nrecs;
838 return (recs);
839 }
840