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[glibc.git] / db / btree / bt_split.c
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1 /*-
2 * Copyright (c) 1990, 1993, 1994
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
6 * Mike Olson.
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.
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.
37 #if defined(LIBC_SCCS) && !defined(lint)
38 static char sccsid[] = "@(#)bt_split.c 8.9 (Berkeley) 7/26/94";
39 #endif /* LIBC_SCCS and not lint */
41 #include <sys/types.h>
43 #include <limits.h>
44 #include <stdio.h>
45 #include <stdlib.h>
46 #include <string.h>
48 #include <db.h>
49 #include "btree.h"
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 *, 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 *));
62 #ifdef STATISTICS
63 u_long bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved;
64 #endif
67 * __BT_SPLIT -- Split the tree.
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
78 * Returns:
79 * RET_ERROR, RET_SUCCESS
81 int
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;
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;
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.
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);
115 * Insert the new key/data pair into the leaf page. (Key inserts
116 * always cause a leaf page to split first.)
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)
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;
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.
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.
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.
154 while ((parent = BT_POP(t)) != NULL) {
155 lchild = l;
156 rchild = r;
158 /* Get the parent page. */
159 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
160 goto err2;
163 * The new key goes ONE AFTER the index, because the split
164 * was to the right.
166 skip = parent->index + 1;
169 * Calculate the space needed on the parent page.
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.
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();
217 /* Split the parent page if necessary or shift the indices. */
218 if ((u_int32_t) (h->upper - h->lower)
219 < nbytes + sizeof(indx_t)) {
220 sp = h;
221 h = h->pgno == P_ROOT ?
222 bt_root(t, h, &l, &r, &skip, nbytes) :
223 bt_page(t, h, &l, &r, &skip, nbytes);
224 if (h == NULL)
225 goto err1;
226 parentsplit = 1;
227 } else {
228 if (skip < (nxtindex = NEXTINDEX(h)))
229 memmove(h->linp + skip + 1, h->linp + skip,
230 (nxtindex - skip) * sizeof(indx_t));
231 h->lower += sizeof(indx_t);
232 parentsplit = 0;
235 /* Insert the key into the parent page. */
236 switch (rchild->flags & P_TYPE) {
237 case P_BINTERNAL:
238 h->linp[skip] = h->upper -= nbytes;
239 dest = (char *)h + h->linp[skip];
240 memmove(dest, bi, nbytes);
241 ((BINTERNAL *)dest)->pgno = rchild->pgno;
242 break;
243 case P_BLEAF:
244 h->linp[skip] = h->upper -= nbytes;
245 dest = (char *)h + h->linp[skip];
246 WR_BINTERNAL(dest, nksize ? nksize : bl->ksize,
247 rchild->pgno, bl->flags & P_BIGKEY);
248 memmove(dest, bl->bytes, nksize ? nksize : bl->ksize);
249 if (bl->flags & P_BIGKEY &&
250 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR)
251 goto err1;
252 break;
253 case P_RINTERNAL:
255 * Update the left page count. If split
256 * added at index 0, fix the correct page.
258 if (skip > 0)
259 dest = (char *)h + h->linp[skip - 1];
260 else
261 dest = (char *)l + l->linp[NEXTINDEX(l) - 1];
262 ((RINTERNAL *)dest)->nrecs = rec_total(lchild);
263 ((RINTERNAL *)dest)->pgno = lchild->pgno;
265 /* Update the right page count. */
266 h->linp[skip] = h->upper -= nbytes;
267 dest = (char *)h + h->linp[skip];
268 ((RINTERNAL *)dest)->nrecs = rec_total(rchild);
269 ((RINTERNAL *)dest)->pgno = rchild->pgno;
270 break;
271 case P_RLEAF:
273 * Update the left page count. If split
274 * added at index 0, fix the correct page.
276 if (skip > 0)
277 dest = (char *)h + h->linp[skip - 1];
278 else
279 dest = (char *)l + l->linp[NEXTINDEX(l) - 1];
280 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(lchild);
281 ((RINTERNAL *)dest)->pgno = lchild->pgno;
283 /* Update the right page count. */
284 h->linp[skip] = h->upper -= nbytes;
285 dest = (char *)h + h->linp[skip];
286 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(rchild);
287 ((RINTERNAL *)dest)->pgno = rchild->pgno;
288 break;
289 default:
290 abort();
293 /* Unpin the held pages. */
294 if (!parentsplit) {
295 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
296 break;
299 /* If the root page was split, make it look right. */
300 if (sp->pgno == P_ROOT &&
301 (F_ISSET(t, R_RECNO) ?
302 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR)
303 goto err1;
305 mpool_put(t->bt_mp, lchild, MPOOL_DIRTY);
306 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY);
309 /* Unpin the held pages. */
310 mpool_put(t->bt_mp, l, MPOOL_DIRTY);
311 mpool_put(t->bt_mp, r, MPOOL_DIRTY);
313 /* Clear any pages left on the stack. */
314 return (RET_SUCCESS);
317 * If something fails in the above loop we were already walking back
318 * up the tree and the tree is now inconsistent. Nothing much we can
319 * do about it but release any memory we're holding.
321 err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY);
322 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY);
324 err2: mpool_put(t->bt_mp, l, 0);
325 mpool_put(t->bt_mp, r, 0);
326 __dbpanic(t->bt_dbp);
327 return (RET_ERROR);
331 * BT_PAGE -- Split a non-root page of a btree.
333 * Parameters:
334 * t: tree
335 * h: root page
336 * lp: pointer to left page pointer
337 * rp: pointer to right page pointer
338 * skip: pointer to index to leave open
339 * ilen: insert length
341 * Returns:
342 * Pointer to page in which to insert or NULL on error.
344 static PAGE *
345 bt_page(t, h, lp, rp, skip, ilen)
346 BTREE *t;
347 PAGE *h, **lp, **rp;
348 indx_t *skip;
349 size_t ilen;
351 PAGE *l, *r, *tp;
352 pgno_t npg;
354 #ifdef STATISTICS
355 ++bt_split;
356 #endif
357 /* Put the new right page for the split into place. */
358 if ((r = __bt_new(t, &npg)) == NULL)
359 return (NULL);
360 r->pgno = npg;
361 r->lower = BTDATAOFF;
362 r->upper = t->bt_psize;
363 r->nextpg = h->nextpg;
364 r->prevpg = h->pgno;
365 r->flags = h->flags & P_TYPE;
368 * If we're splitting the last page on a level because we're appending
369 * a key to it (skip is NEXTINDEX()), it's likely that the data is
370 * sorted. Adding an empty page on the side of the level is less work
371 * and can push the fill factor much higher than normal. If we're
372 * wrong it's no big deal, we'll just do the split the right way next
373 * time. It may look like it's equally easy to do a similar hack for
374 * reverse sorted data, that is, split the tree left, but it's not.
375 * Don't even try.
377 if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) {
378 #ifdef STATISTICS
379 ++bt_sortsplit;
380 #endif
381 h->nextpg = r->pgno;
382 r->lower = BTDATAOFF + sizeof(indx_t);
383 *skip = 0;
384 *lp = h;
385 *rp = r;
386 return (r);
389 /* Put the new left page for the split into place. */
390 if ((l = (PAGE *)malloc(t->bt_psize)) == NULL) {
391 mpool_put(t->bt_mp, r, 0);
392 return (NULL);
394 #ifdef PURIFY
395 memset(l, 0xff, t->bt_psize);
396 #endif
397 l->pgno = h->pgno;
398 l->nextpg = r->pgno;
399 l->prevpg = h->prevpg;
400 l->lower = BTDATAOFF;
401 l->upper = t->bt_psize;
402 l->flags = h->flags & P_TYPE;
404 /* Fix up the previous pointer of the page after the split page. */
405 if (h->nextpg != P_INVALID) {
406 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) {
407 free(l);
408 /* XXX mpool_free(t->bt_mp, r->pgno); */
409 return (NULL);
411 tp->prevpg = r->pgno;
412 mpool_put(t->bt_mp, tp, MPOOL_DIRTY);
416 * Split right. The key/data pairs aren't sorted in the btree page so
417 * it's simpler to copy the data from the split page onto two new pages
418 * instead of copying half the data to the right page and compacting
419 * the left page in place. Since the left page can't change, we have
420 * to swap the original and the allocated left page after the split.
422 tp = bt_psplit(t, h, l, r, skip, ilen);
424 /* Move the new left page onto the old left page. */
425 memmove(h, l, t->bt_psize);
426 if (tp == l)
427 tp = h;
428 free(l);
430 *lp = h;
431 *rp = r;
432 return (tp);
436 * BT_ROOT -- Split the root page of a btree.
438 * Parameters:
439 * t: tree
440 * h: root page
441 * lp: pointer to left page pointer
442 * rp: pointer to right page pointer
443 * skip: pointer to index to leave open
444 * ilen: insert length
446 * Returns:
447 * Pointer to page in which to insert or NULL on error.
449 static PAGE *
450 bt_root(t, h, lp, rp, skip, ilen)
451 BTREE *t;
452 PAGE *h, **lp, **rp;
453 indx_t *skip;
454 size_t ilen;
456 PAGE *l, *r, *tp;
457 pgno_t lnpg, rnpg;
459 #ifdef STATISTICS
460 ++bt_split;
461 ++bt_rootsplit;
462 #endif
463 /* Put the new left and right pages for the split into place. */
464 if ((l = __bt_new(t, &lnpg)) == NULL ||
465 (r = __bt_new(t, &rnpg)) == NULL)
466 return (NULL);
467 l->pgno = lnpg;
468 r->pgno = rnpg;
469 l->nextpg = r->pgno;
470 r->prevpg = l->pgno;
471 l->prevpg = r->nextpg = P_INVALID;
472 l->lower = r->lower = BTDATAOFF;
473 l->upper = r->upper = t->bt_psize;
474 l->flags = r->flags = h->flags & P_TYPE;
476 /* Split the root page. */
477 tp = bt_psplit(t, h, l, r, skip, ilen);
479 *lp = l;
480 *rp = r;
481 return (tp);
485 * BT_RROOT -- Fix up the recno root page after it has been split.
487 * Parameters:
488 * t: tree
489 * h: root page
490 * l: left page
491 * r: right page
493 * Returns:
494 * RET_ERROR, RET_SUCCESS
496 static int
497 bt_rroot(t, h, l, r)
498 BTREE *t;
499 PAGE *h, *l, *r;
501 char *dest;
503 /* Insert the left and right keys, set the header information. */
504 h->linp[0] = h->upper = t->bt_psize - NRINTERNAL;
505 dest = (char *)h + h->upper;
506 WR_RINTERNAL(dest,
507 l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno);
509 h->linp[1] = h->upper -= NRINTERNAL;
510 dest = (char *)h + h->upper;
511 WR_RINTERNAL(dest,
512 r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno);
514 h->lower = BTDATAOFF + 2 * sizeof(indx_t);
516 /* Unpin the root page, set to recno internal page. */
517 h->flags &= ~P_TYPE;
518 h->flags |= P_RINTERNAL;
519 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
521 return (RET_SUCCESS);
525 * BT_BROOT -- Fix up the btree root page after it has been split.
527 * Parameters:
528 * t: tree
529 * h: root page
530 * l: left page
531 * r: right page
533 * Returns:
534 * RET_ERROR, RET_SUCCESS
536 static int
537 bt_broot(t, h, l, r)
538 BTREE *t;
539 PAGE *h, *l, *r;
541 BINTERNAL *bi;
542 BLEAF *bl;
543 u_int32_t nbytes;
544 char *dest;
547 * If the root page was a leaf page, change it into an internal page.
548 * We copy the key we split on (but not the key's data, in the case of
549 * a leaf page) to the new root page.
551 * The btree comparison code guarantees that the left-most key on any
552 * level of the tree is never used, so it doesn't need to be filled in.
554 nbytes = NBINTERNAL(0);
555 h->linp[0] = h->upper = t->bt_psize - nbytes;
556 dest = (char *)h + h->upper;
557 WR_BINTERNAL(dest, 0, l->pgno, 0);
559 switch (h->flags & P_TYPE) {
560 case P_BLEAF:
561 bl = GETBLEAF(r, 0);
562 nbytes = NBINTERNAL(bl->ksize);
563 h->linp[1] = h->upper -= nbytes;
564 dest = (char *)h + h->upper;
565 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0);
566 memmove(dest, bl->bytes, bl->ksize);
569 * If the key is on an overflow page, mark the overflow chain
570 * so it isn't deleted when the leaf copy of the key is deleted.
572 if (bl->flags & P_BIGKEY &&
573 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR)
574 return (RET_ERROR);
575 break;
576 case P_BINTERNAL:
577 bi = GETBINTERNAL(r, 0);
578 nbytes = NBINTERNAL(bi->ksize);
579 h->linp[1] = h->upper -= nbytes;
580 dest = (char *)h + h->upper;
581 memmove(dest, bi, nbytes);
582 ((BINTERNAL *)dest)->pgno = r->pgno;
583 break;
584 default:
585 abort();
588 /* There are two keys on the page. */
589 h->lower = BTDATAOFF + 2 * sizeof(indx_t);
591 /* Unpin the root page, set to btree internal page. */
592 h->flags &= ~P_TYPE;
593 h->flags |= P_BINTERNAL;
594 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
596 return (RET_SUCCESS);
600 * BT_PSPLIT -- Do the real work of splitting the page.
602 * Parameters:
603 * t: tree
604 * h: page to be split
605 * l: page to put lower half of data
606 * r: page to put upper half of data
607 * pskip: pointer to index to leave open
608 * ilen: insert length
610 * Returns:
611 * Pointer to page in which to insert.
613 static PAGE *
614 bt_psplit(t, h, l, r, pskip, ilen)
615 BTREE *t;
616 PAGE *h, *l, *r;
617 indx_t *pskip;
618 size_t ilen;
620 BINTERNAL *bi;
621 BLEAF *bl;
622 CURSOR *c;
623 RLEAF *rl;
624 PAGE *rval;
625 void *src;
626 indx_t full, half, nxt, off, skip, top, used;
627 u_int32_t nbytes;
628 int bigkeycnt, isbigkey;
631 * Split the data to the left and right pages. Leave the skip index
632 * open. Additionally, make some effort not to split on an overflow
633 * key. This makes internal page processing faster and can save
634 * space as overflow keys used by internal pages are never deleted.
636 bigkeycnt = 0;
637 skip = *pskip;
638 full = t->bt_psize - BTDATAOFF;
639 half = full / 2;
640 used = 0;
641 for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) {
642 if (skip == off) {
643 nbytes = ilen;
644 isbigkey = 0; /* XXX: not really known. */
645 } else
646 switch (h->flags & P_TYPE) {
647 case P_BINTERNAL:
648 src = bi = GETBINTERNAL(h, nxt);
649 nbytes = NBINTERNAL(bi->ksize);
650 isbigkey = bi->flags & P_BIGKEY;
651 break;
652 case P_BLEAF:
653 src = bl = GETBLEAF(h, nxt);
654 nbytes = NBLEAF(bl);
655 isbigkey = bl->flags & P_BIGKEY;
656 break;
657 case P_RINTERNAL:
658 src = GETRINTERNAL(h, nxt);
659 nbytes = NRINTERNAL;
660 isbigkey = 0;
661 break;
662 case P_RLEAF:
663 src = rl = GETRLEAF(h, nxt);
664 nbytes = NRLEAF(rl);
665 isbigkey = 0;
666 break;
667 default:
668 abort();
672 * If the key/data pairs are substantial fractions of the max
673 * possible size for the page, it's possible to get situations
674 * where we decide to try and copy too much onto the left page.
675 * Make sure that doesn't happen.
677 if ((skip <= off && used + nbytes + sizeof(indx_t) >= full)
678 || nxt == top - 1) {
679 --off;
680 break;
683 /* Copy the key/data pair, if not the skipped index. */
684 if (skip != off) {
685 ++nxt;
687 l->linp[off] = l->upper -= nbytes;
688 memmove((char *)l + l->upper, src, nbytes);
691 used += nbytes + sizeof(indx_t);
692 if (used >= half) {
693 if (!isbigkey || bigkeycnt == 3)
694 break;
695 else
696 ++bigkeycnt;
701 * Off is the last offset that's valid for the left page.
702 * Nxt is the first offset to be placed on the right page.
704 l->lower += (off + 1) * sizeof(indx_t);
707 * If splitting the page that the cursor was on, the cursor has to be
708 * adjusted to point to the same record as before the split. If the
709 * cursor is at or past the skipped slot, the cursor is incremented by
710 * one. If the cursor is on the right page, it is decremented by the
711 * number of records split to the left page.
713 c = &t->bt_cursor;
714 if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) {
715 if (c->pg.index >= skip)
716 ++c->pg.index;
717 if (c->pg.index < nxt) /* Left page. */
718 c->pg.pgno = l->pgno;
719 else { /* Right page. */
720 c->pg.pgno = r->pgno;
721 c->pg.index -= nxt;
726 * If the skipped index was on the left page, just return that page.
727 * Otherwise, adjust the skip index to reflect the new position on
728 * the right page.
730 if (skip <= off) {
731 skip = 0;
732 rval = l;
733 } else {
734 rval = r;
735 *pskip -= nxt;
738 for (off = 0; nxt < top; ++off) {
739 if (skip == nxt) {
740 ++off;
741 skip = 0;
743 switch (h->flags & P_TYPE) {
744 case P_BINTERNAL:
745 src = bi = GETBINTERNAL(h, nxt);
746 nbytes = NBINTERNAL(bi->ksize);
747 break;
748 case P_BLEAF:
749 src = bl = GETBLEAF(h, nxt);
750 nbytes = NBLEAF(bl);
751 break;
752 case P_RINTERNAL:
753 src = GETRINTERNAL(h, nxt);
754 nbytes = NRINTERNAL;
755 break;
756 case P_RLEAF:
757 src = rl = GETRLEAF(h, nxt);
758 nbytes = NRLEAF(rl);
759 break;
760 default:
761 abort();
763 ++nxt;
764 r->linp[off] = r->upper -= nbytes;
765 memmove((char *)r + r->upper, src, nbytes);
767 r->lower += off * sizeof(indx_t);
769 /* If the key is being appended to the page, adjust the index. */
770 if (skip == top)
771 r->lower += sizeof(indx_t);
773 return (rval);
777 * BT_PRESERVE -- Mark a chain of pages as used by an internal node.
779 * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the
780 * record that references them gets deleted. Chains pointed to by internal
781 * pages never get deleted. This routine marks a chain as pointed to by an
782 * internal page.
784 * Parameters:
785 * t: tree
786 * pg: page number of first page in the chain.
788 * Returns:
789 * RET_SUCCESS, RET_ERROR.
791 static int
792 bt_preserve(t, pg)
793 BTREE *t;
794 pgno_t pg;
796 PAGE *h;
798 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
799 return (RET_ERROR);
800 h->flags |= P_PRESERVE;
801 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
802 return (RET_SUCCESS);
806 * REC_TOTAL -- Return the number of recno entries below a page.
808 * Parameters:
809 * h: page
811 * Returns:
812 * The number of recno entries below a page.
814 * XXX
815 * These values could be set by the bt_psplit routine. The problem is that the
816 * entry has to be popped off of the stack etc. or the values have to be passed
817 * all the way back to bt_split/bt_rroot and it's not very clean.
819 static recno_t
820 rec_total(h)
821 PAGE *h;
823 recno_t recs;
824 indx_t nxt, top;
826 for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt)
827 recs += GETRINTERNAL(h, nxt)->nrecs;
828 return (recs);