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. 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 * @(#)bt_split.c 8.9 (Berkeley) 7/26/94 33 * $DragonFly: src/lib/libc/db/btree/bt_split.c,v 1.8 2005/11/19 20:46:32 swildner Exp $ 34 */ 35 36 #include <sys/types.h> 37 38 #include <limits.h> 39 #include <stdio.h> 40 #include <stdlib.h> 41 #include <string.h> 42 43 #include <db.h> 44 #include "btree.h" 45 46 static int bt_broot(BTREE *, PAGE *, PAGE *, PAGE *); 47 static PAGE *bt_page(BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t); 48 static int bt_preserve(BTREE *, pgno_t); 49 static PAGE *bt_psplit(BTREE *, PAGE *, PAGE *, PAGE *, indx_t *, size_t); 50 static PAGE *bt_root(BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t); 51 static int bt_rroot(BTREE *, PAGE *, PAGE *, PAGE *); 52 static recno_t rec_total(PAGE *); 53 54 #ifdef STATISTICS 55 u_long bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved; 56 #endif 57 58 /* 59 * __BT_SPLIT -- Split the tree. 60 * 61 * Parameters: 62 * t: tree 63 * sp: page to split 64 * key: key to insert 65 * data: data to insert 66 * flags: BIGKEY/BIGDATA flags 67 * ilen: insert length 68 * skip: index to leave open 69 * 70 * Returns: 71 * RET_ERROR, RET_SUCCESS 72 */ 73 int 74 __bt_split(BTREE *t, PAGE *sp, const DBT *key, const DBT *data, int flags, 75 size_t ilen, u_int32_t argskip) 76 { 77 BINTERNAL *bi; 78 BLEAF *bl, *tbl; 79 DBT a, b; 80 EPGNO *parent; 81 PAGE *h, *l, *r, *lchild, *rchild; 82 indx_t nxtindex; 83 u_int16_t skip; 84 u_int32_t n, nbytes, nksize; 85 int parentsplit; 86 char *dest; 87 88 bi = NULL; 89 bl = NULL; 90 nksize = 0; 91 /* 92 * Split the page into two pages, l and r. The split routines return 93 * a pointer to the page into which the key should be inserted and with 94 * skip set to the offset which should be used. Additionally, l and r 95 * are pinned. 96 */ 97 skip = argskip; 98 h = sp->pgno == P_ROOT ? 99 bt_root(t, sp, &l, &r, &skip, ilen) : 100 bt_page(t, sp, &l, &r, &skip, ilen); 101 if (h == NULL) 102 return (RET_ERROR); 103 104 /* 105 * Insert the new key/data pair into the leaf page. (Key inserts 106 * always cause a leaf page to split first.) 107 */ 108 h->linp[skip] = h->upper -= ilen; 109 dest = (char *)h + h->upper; 110 if (F_ISSET(t, R_RECNO)) 111 WR_RLEAF(dest, data, flags) 112 else 113 WR_BLEAF(dest, key, data, flags) 114 115 /* If the root page was split, make it look right. */ 116 if (sp->pgno == P_ROOT && 117 (F_ISSET(t, R_RECNO) ? 118 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 119 goto err2; 120 121 /* 122 * Now we walk the parent page stack -- a LIFO stack of the pages that 123 * were traversed when we searched for the page that split. Each stack 124 * entry is a page number and a page index offset. The offset is for 125 * the page traversed on the search. We've just split a page, so we 126 * have to insert a new key into the parent page. 127 * 128 * If the insert into the parent page causes it to split, may have to 129 * continue splitting all the way up the tree. We stop if the root 130 * splits or the page inserted into didn't have to split to hold the 131 * new key. Some algorithms replace the key for the old page as well 132 * as the new page. We don't, as there's no reason to believe that the 133 * first key on the old page is any better than the key we have, and, 134 * in the case of a key being placed at index 0 causing the split, the 135 * key is unavailable. 136 * 137 * There are a maximum of 5 pages pinned at any time. We keep the left 138 * and right pages pinned while working on the parent. The 5 are the 139 * two children, left parent and right parent (when the parent splits) 140 * and the root page or the overflow key page when calling bt_preserve. 141 * This code must make sure that all pins are released other than the 142 * root page or overflow page which is unlocked elsewhere. 143 */ 144 while ((parent = BT_POP(t)) != NULL) { 145 lchild = l; 146 rchild = r; 147 148 /* Get the parent page. */ 149 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) 150 goto err2; 151 152 /* 153 * The new key goes ONE AFTER the index, because the split 154 * was to the right. 155 */ 156 skip = parent->index + 1; 157 158 /* 159 * Calculate the space needed on the parent page. 160 * 161 * Prefix trees: space hack when inserting into BINTERNAL 162 * pages. Retain only what's needed to distinguish between 163 * the new entry and the LAST entry on the page to its left. 164 * If the keys compare equal, retain the entire key. Note, 165 * we don't touch overflow keys, and the entire key must be 166 * retained for the next-to-left most key on the leftmost 167 * page of each level, or the search will fail. Applicable 168 * ONLY to internal pages that have leaf pages as children. 169 * Further reduction of the key between pairs of internal 170 * pages loses too much information. 171 */ 172 switch (rchild->flags & P_TYPE) { 173 case P_BINTERNAL: 174 bi = GETBINTERNAL(rchild, 0); 175 nbytes = NBINTERNAL(bi->ksize); 176 break; 177 case P_BLEAF: 178 bl = GETBLEAF(rchild, 0); 179 nbytes = NBINTERNAL(bl->ksize); 180 if (t->bt_pfx && !(bl->flags & P_BIGKEY) && 181 (h->prevpg != P_INVALID || skip > 1)) { 182 tbl = GETBLEAF(lchild, NEXTINDEX(lchild) - 1); 183 a.size = tbl->ksize; 184 a.data = tbl->bytes; 185 b.size = bl->ksize; 186 b.data = bl->bytes; 187 nksize = t->bt_pfx(&a, &b); 188 n = NBINTERNAL(nksize); 189 if (n < nbytes) { 190 #ifdef STATISTICS 191 bt_pfxsaved += nbytes - n; 192 #endif 193 nbytes = n; 194 } else 195 nksize = 0; 196 } else 197 nksize = 0; 198 break; 199 case P_RINTERNAL: 200 case P_RLEAF: 201 nbytes = NRINTERNAL; 202 break; 203 default: 204 abort(); 205 } 206 207 /* Split the parent page if necessary or shift the indices. */ 208 if (h->upper - h->lower < nbytes + sizeof(indx_t)) { 209 sp = h; 210 h = h->pgno == P_ROOT ? 211 bt_root(t, h, &l, &r, &skip, nbytes) : 212 bt_page(t, h, &l, &r, &skip, nbytes); 213 if (h == NULL) 214 goto err1; 215 parentsplit = 1; 216 } else { 217 if (skip < (nxtindex = NEXTINDEX(h))) 218 memmove(h->linp + skip + 1, h->linp + skip, 219 (nxtindex - skip) * sizeof(indx_t)); 220 h->lower += sizeof(indx_t); 221 parentsplit = 0; 222 } 223 224 /* Insert the key into the parent page. */ 225 switch (rchild->flags & P_TYPE) { 226 case P_BINTERNAL: 227 h->linp[skip] = h->upper -= nbytes; 228 dest = (char *)h + h->linp[skip]; 229 memmove(dest, bi, nbytes); 230 ((BINTERNAL *)dest)->pgno = rchild->pgno; 231 break; 232 case P_BLEAF: 233 h->linp[skip] = h->upper -= nbytes; 234 dest = (char *)h + h->linp[skip]; 235 WR_BINTERNAL(dest, nksize ? nksize : bl->ksize, 236 rchild->pgno, bl->flags & P_BIGKEY); 237 memmove(dest, bl->bytes, nksize ? nksize : bl->ksize); 238 if (bl->flags & P_BIGKEY && 239 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 240 goto err1; 241 break; 242 case P_RINTERNAL: 243 /* 244 * Update the left page count. If split 245 * added at index 0, fix the correct page. 246 */ 247 if (skip > 0) 248 dest = (char *)h + h->linp[skip - 1]; 249 else 250 dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; 251 ((RINTERNAL *)dest)->nrecs = rec_total(lchild); 252 ((RINTERNAL *)dest)->pgno = lchild->pgno; 253 254 /* Update the right page count. */ 255 h->linp[skip] = h->upper -= nbytes; 256 dest = (char *)h + h->linp[skip]; 257 ((RINTERNAL *)dest)->nrecs = rec_total(rchild); 258 ((RINTERNAL *)dest)->pgno = rchild->pgno; 259 break; 260 case P_RLEAF: 261 /* 262 * Update the left page count. If split 263 * added at index 0, fix the correct page. 264 */ 265 if (skip > 0) 266 dest = (char *)h + h->linp[skip - 1]; 267 else 268 dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; 269 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(lchild); 270 ((RINTERNAL *)dest)->pgno = lchild->pgno; 271 272 /* Update the right page count. */ 273 h->linp[skip] = h->upper -= nbytes; 274 dest = (char *)h + h->linp[skip]; 275 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(rchild); 276 ((RINTERNAL *)dest)->pgno = rchild->pgno; 277 break; 278 default: 279 abort(); 280 } 281 282 /* Unpin the held pages. */ 283 if (!parentsplit) { 284 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 285 break; 286 } 287 288 /* If the root page was split, make it look right. */ 289 if (sp->pgno == P_ROOT && 290 (F_ISSET(t, R_RECNO) ? 291 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 292 goto err1; 293 294 mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 295 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 296 } 297 298 /* Unpin the held pages. */ 299 mpool_put(t->bt_mp, l, MPOOL_DIRTY); 300 mpool_put(t->bt_mp, r, MPOOL_DIRTY); 301 302 /* Clear any pages left on the stack. */ 303 return (RET_SUCCESS); 304 305 /* 306 * If something fails in the above loop we were already walking back 307 * up the tree and the tree is now inconsistent. Nothing much we can 308 * do about it but release any memory we're holding. 309 */ 310 err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 311 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 312 313 err2: mpool_put(t->bt_mp, l, 0); 314 mpool_put(t->bt_mp, r, 0); 315 __dbpanic(t->bt_dbp); 316 return (RET_ERROR); 317 } 318 319 /* 320 * BT_PAGE -- Split a non-root page of a btree. 321 * 322 * Parameters: 323 * t: tree 324 * h: root page 325 * lp: pointer to left page pointer 326 * rp: pointer to right page pointer 327 * skip: pointer to index to leave open 328 * ilen: insert length 329 * 330 * Returns: 331 * Pointer to page in which to insert or NULL on error. 332 */ 333 static PAGE * 334 bt_page(BTREE *t, PAGE *h, PAGE **lp, PAGE **rp, indx_t *skip, size_t ilen) 335 { 336 PAGE *l, *r, *tp; 337 pgno_t npg; 338 339 #ifdef STATISTICS 340 ++bt_split; 341 #endif 342 /* Put the new right page for the split into place. */ 343 if ((r = __bt_new(t, &npg)) == NULL) 344 return (NULL); 345 r->pgno = npg; 346 r->lower = BTDATAOFF; 347 r->upper = t->bt_psize; 348 r->nextpg = h->nextpg; 349 r->prevpg = h->pgno; 350 r->flags = h->flags & P_TYPE; 351 352 /* 353 * If we're splitting the last page on a level because we're appending 354 * a key to it (skip is NEXTINDEX()), it's likely that the data is 355 * sorted. Adding an empty page on the side of the level is less work 356 * and can push the fill factor much higher than normal. If we're 357 * wrong it's no big deal, we'll just do the split the right way next 358 * time. It may look like it's equally easy to do a similar hack for 359 * reverse sorted data, that is, split the tree left, but it's not. 360 * Don't even try. 361 */ 362 if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) { 363 #ifdef STATISTICS 364 ++bt_sortsplit; 365 #endif 366 h->nextpg = r->pgno; 367 r->lower = BTDATAOFF + sizeof(indx_t); 368 *skip = 0; 369 *lp = h; 370 *rp = r; 371 return (r); 372 } 373 374 /* Put the new left page for the split into place. */ 375 if ((l = (PAGE *)malloc(t->bt_psize)) == NULL) { 376 mpool_put(t->bt_mp, r, 0); 377 return (NULL); 378 } 379 #ifdef PURIFY 380 memset(l, 0xff, t->bt_psize); 381 #endif 382 l->pgno = h->pgno; 383 l->nextpg = r->pgno; 384 l->prevpg = h->prevpg; 385 l->lower = BTDATAOFF; 386 l->upper = t->bt_psize; 387 l->flags = h->flags & P_TYPE; 388 389 /* Fix up the previous pointer of the page after the split page. */ 390 if (h->nextpg != P_INVALID) { 391 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) { 392 free(l); 393 /* XXX mpool_free(t->bt_mp, r->pgno); */ 394 return (NULL); 395 } 396 tp->prevpg = r->pgno; 397 mpool_put(t->bt_mp, tp, MPOOL_DIRTY); 398 } 399 400 /* 401 * Split right. The key/data pairs aren't sorted in the btree page so 402 * it's simpler to copy the data from the split page onto two new pages 403 * instead of copying half the data to the right page and compacting 404 * the left page in place. Since the left page can't change, we have 405 * to swap the original and the allocated left page after the split. 406 */ 407 tp = bt_psplit(t, h, l, r, skip, ilen); 408 409 /* Move the new left page onto the old left page. */ 410 memmove(h, l, t->bt_psize); 411 if (tp == l) 412 tp = h; 413 free(l); 414 415 *lp = h; 416 *rp = r; 417 return (tp); 418 } 419 420 /* 421 * BT_ROOT -- Split the root page of a btree. 422 * 423 * Parameters: 424 * t: tree 425 * h: root page 426 * lp: pointer to left page pointer 427 * rp: pointer to right page pointer 428 * skip: pointer to index to leave open 429 * ilen: insert length 430 * 431 * Returns: 432 * Pointer to page in which to insert or NULL on error. 433 */ 434 static PAGE * 435 bt_root(BTREE *t, PAGE *h, PAGE **lp, PAGE **rp, indx_t *skip, size_t ilen) 436 { 437 PAGE *l, *r, *tp; 438 pgno_t lnpg, rnpg; 439 440 #ifdef STATISTICS 441 ++bt_split; 442 ++bt_rootsplit; 443 #endif 444 /* Put the new left and right pages for the split into place. */ 445 if ((l = __bt_new(t, &lnpg)) == NULL || 446 (r = __bt_new(t, &rnpg)) == NULL) 447 return (NULL); 448 l->pgno = lnpg; 449 r->pgno = rnpg; 450 l->nextpg = r->pgno; 451 r->prevpg = l->pgno; 452 l->prevpg = r->nextpg = P_INVALID; 453 l->lower = r->lower = BTDATAOFF; 454 l->upper = r->upper = t->bt_psize; 455 l->flags = r->flags = h->flags & P_TYPE; 456 457 /* Split the root page. */ 458 tp = bt_psplit(t, h, l, r, skip, ilen); 459 460 *lp = l; 461 *rp = r; 462 return (tp); 463 } 464 465 /* 466 * BT_RROOT -- Fix up the recno root page after it has been split. 467 * 468 * Parameters: 469 * t: tree 470 * h: root page 471 * l: left page 472 * r: right page 473 * 474 * Returns: 475 * RET_ERROR, RET_SUCCESS 476 */ 477 static int 478 bt_rroot(BTREE *t, PAGE *h, PAGE *l, PAGE *r) 479 { 480 char *dest; 481 482 /* Insert the left and right keys, set the header information. */ 483 h->linp[0] = h->upper = t->bt_psize - NRINTERNAL; 484 dest = (char *)h + h->upper; 485 WR_RINTERNAL(dest, 486 l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno); 487 488 h->linp[1] = h->upper -= NRINTERNAL; 489 dest = (char *)h + h->upper; 490 WR_RINTERNAL(dest, 491 r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno); 492 493 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 494 495 /* Unpin the root page, set to recno internal page. */ 496 h->flags &= ~P_TYPE; 497 h->flags |= P_RINTERNAL; 498 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 499 500 return (RET_SUCCESS); 501 } 502 503 /* 504 * BT_BROOT -- Fix up the btree root page after it has been split. 505 * 506 * Parameters: 507 * t: tree 508 * h: root page 509 * l: left page 510 * r: right page 511 * 512 * Returns: 513 * RET_ERROR, RET_SUCCESS 514 */ 515 static int 516 bt_broot(BTREE *t, PAGE *h, PAGE *l, PAGE *r) 517 { 518 BINTERNAL *bi; 519 BLEAF *bl; 520 u_int32_t nbytes; 521 char *dest; 522 523 /* 524 * If the root page was a leaf page, change it into an internal page. 525 * We copy the key we split on (but not the key's data, in the case of 526 * a leaf page) to the new root page. 527 * 528 * The btree comparison code guarantees that the left-most key on any 529 * level of the tree is never used, so it doesn't need to be filled in. 530 */ 531 nbytes = NBINTERNAL(0); 532 h->linp[0] = h->upper = t->bt_psize - nbytes; 533 dest = (char *)h + h->upper; 534 WR_BINTERNAL(dest, 0, l->pgno, 0); 535 536 switch (h->flags & P_TYPE) { 537 case P_BLEAF: 538 bl = GETBLEAF(r, 0); 539 nbytes = NBINTERNAL(bl->ksize); 540 h->linp[1] = h->upper -= nbytes; 541 dest = (char *)h + h->upper; 542 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0); 543 memmove(dest, bl->bytes, bl->ksize); 544 545 /* 546 * If the key is on an overflow page, mark the overflow chain 547 * so it isn't deleted when the leaf copy of the key is deleted. 548 */ 549 if (bl->flags & P_BIGKEY && 550 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 551 return (RET_ERROR); 552 break; 553 case P_BINTERNAL: 554 bi = GETBINTERNAL(r, 0); 555 nbytes = NBINTERNAL(bi->ksize); 556 h->linp[1] = h->upper -= nbytes; 557 dest = (char *)h + h->upper; 558 memmove(dest, bi, nbytes); 559 ((BINTERNAL *)dest)->pgno = r->pgno; 560 break; 561 default: 562 abort(); 563 } 564 565 /* There are two keys on the page. */ 566 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 567 568 /* Unpin the root page, set to btree internal page. */ 569 h->flags &= ~P_TYPE; 570 h->flags |= P_BINTERNAL; 571 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 572 573 return (RET_SUCCESS); 574 } 575 576 /* 577 * BT_PSPLIT -- Do the real work of splitting the page. 578 * 579 * Parameters: 580 * t: tree 581 * h: page to be split 582 * l: page to put lower half of data 583 * r: page to put upper half of data 584 * pskip: pointer to index to leave open 585 * ilen: insert length 586 * 587 * Returns: 588 * Pointer to page in which to insert. 589 */ 590 static PAGE * 591 bt_psplit(BTREE *t, PAGE *h, PAGE *l, PAGE *r, indx_t *pskip, size_t ilen) 592 { 593 BINTERNAL *bi; 594 BLEAF *bl; 595 CURSOR *c; 596 RLEAF *rl; 597 PAGE *rval; 598 void *src; 599 indx_t full, half, nxt, off, skip, top, used; 600 u_int32_t nbytes; 601 int bigkeycnt, isbigkey; 602 603 src = NULL; 604 /* 605 * Split the data to the left and right pages. Leave the skip index 606 * open. Additionally, make some effort not to split on an overflow 607 * key. This makes internal page processing faster and can save 608 * space as overflow keys used by internal pages are never deleted. 609 */ 610 bigkeycnt = 0; 611 skip = *pskip; 612 full = t->bt_psize - BTDATAOFF; 613 half = full / 2; 614 used = 0; 615 for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) { 616 if (skip == off) { 617 nbytes = ilen; 618 isbigkey = 0; /* XXX: not really known. */ 619 } else 620 switch (h->flags & P_TYPE) { 621 case P_BINTERNAL: 622 src = bi = GETBINTERNAL(h, nxt); 623 nbytes = NBINTERNAL(bi->ksize); 624 isbigkey = bi->flags & P_BIGKEY; 625 break; 626 case P_BLEAF: 627 src = bl = GETBLEAF(h, nxt); 628 nbytes = NBLEAF(bl); 629 isbigkey = bl->flags & P_BIGKEY; 630 break; 631 case P_RINTERNAL: 632 src = GETRINTERNAL(h, nxt); 633 nbytes = NRINTERNAL; 634 isbigkey = 0; 635 break; 636 case P_RLEAF: 637 src = rl = GETRLEAF(h, nxt); 638 nbytes = NRLEAF(rl); 639 isbigkey = 0; 640 break; 641 default: 642 abort(); 643 } 644 645 /* 646 * If the key/data pairs are substantial fractions of the max 647 * possible size for the page, it's possible to get situations 648 * where we decide to try and copy too much onto the left page. 649 * Make sure that doesn't happen. 650 */ 651 if ((skip <= off && 652 used + nbytes + sizeof(indx_t) >= full) || nxt == top - 1) { 653 --off; 654 break; 655 } 656 657 /* Copy the key/data pair, if not the skipped index. */ 658 if (skip != off) { 659 ++nxt; 660 661 l->linp[off] = l->upper -= nbytes; 662 memmove((char *)l + l->upper, src, nbytes); 663 } 664 665 used += nbytes + sizeof(indx_t); 666 if (used >= half) { 667 if (!isbigkey || bigkeycnt == 3) 668 break; 669 else 670 ++bigkeycnt; 671 } 672 } 673 674 /* 675 * Off is the last offset that's valid for the left page. 676 * Nxt is the first offset to be placed on the right page. 677 */ 678 l->lower += (off + 1) * sizeof(indx_t); 679 680 /* 681 * If splitting the page that the cursor was on, the cursor has to be 682 * adjusted to point to the same record as before the split. If the 683 * cursor is at or past the skipped slot, the cursor is incremented by 684 * one. If the cursor is on the right page, it is decremented by the 685 * number of records split to the left page. 686 */ 687 c = &t->bt_cursor; 688 if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) { 689 if (c->pg.index >= skip) 690 ++c->pg.index; 691 if (c->pg.index < nxt) /* Left page. */ 692 c->pg.pgno = l->pgno; 693 else { /* Right page. */ 694 c->pg.pgno = r->pgno; 695 c->pg.index -= nxt; 696 } 697 } 698 699 /* 700 * If the skipped index was on the left page, just return that page. 701 * Otherwise, adjust the skip index to reflect the new position on 702 * the right page. 703 */ 704 if (skip <= off) { 705 skip = MAX_PAGE_OFFSET; 706 rval = l; 707 } else { 708 rval = r; 709 *pskip -= nxt; 710 } 711 712 for (off = 0; nxt < top; ++off) { 713 if (skip == nxt) { 714 ++off; 715 skip = MAX_PAGE_OFFSET; 716 } 717 switch (h->flags & P_TYPE) { 718 case P_BINTERNAL: 719 src = bi = GETBINTERNAL(h, nxt); 720 nbytes = NBINTERNAL(bi->ksize); 721 break; 722 case P_BLEAF: 723 src = bl = GETBLEAF(h, nxt); 724 nbytes = NBLEAF(bl); 725 break; 726 case P_RINTERNAL: 727 src = GETRINTERNAL(h, nxt); 728 nbytes = NRINTERNAL; 729 break; 730 case P_RLEAF: 731 src = rl = GETRLEAF(h, nxt); 732 nbytes = NRLEAF(rl); 733 break; 734 default: 735 abort(); 736 } 737 ++nxt; 738 r->linp[off] = r->upper -= nbytes; 739 memmove((char *)r + r->upper, src, nbytes); 740 } 741 r->lower += off * sizeof(indx_t); 742 743 /* If the key is being appended to the page, adjust the index. */ 744 if (skip == top) 745 r->lower += sizeof(indx_t); 746 747 return (rval); 748 } 749 750 /* 751 * BT_PRESERVE -- Mark a chain of pages as used by an internal node. 752 * 753 * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the 754 * record that references them gets deleted. Chains pointed to by internal 755 * pages never get deleted. This routine marks a chain as pointed to by an 756 * internal page. 757 * 758 * Parameters: 759 * t: tree 760 * pg: page number of first page in the chain. 761 * 762 * Returns: 763 * RET_SUCCESS, RET_ERROR. 764 */ 765 static int 766 bt_preserve(BTREE *t, pgno_t pg) 767 { 768 PAGE *h; 769 770 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 771 return (RET_ERROR); 772 h->flags |= P_PRESERVE; 773 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 774 return (RET_SUCCESS); 775 } 776 777 /* 778 * REC_TOTAL -- Return the number of recno entries below a page. 779 * 780 * Parameters: 781 * h: page 782 * 783 * Returns: 784 * The number of recno entries below a page. 785 * 786 * XXX 787 * These values could be set by the bt_psplit routine. The problem is that the 788 * entry has to be popped off of the stack etc. or the values have to be passed 789 * all the way back to bt_split/bt_rroot and it's not very clean. 790 */ 791 static recno_t 792 rec_total(PAGE *h) 793 { 794 recno_t recs; 795 indx_t nxt, top; 796 797 for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt) 798 recs += GETRINTERNAL(h, nxt)->nrecs; 799 return (recs); 800 } 801