1 /* $OpenBSD: bt_split.c,v 1.11 2003/06/02 20:18:33 millert Exp $ */ 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. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #if defined(LIBC_SCCS) && !defined(lint) 36 #if 0 37 static char sccsid[] = "@(#)bt_split.c 8.10 (Berkeley) 1/9/95"; 38 #else 39 static const char rcsid[] = "$OpenBSD: bt_split.c,v 1.11 2003/06/02 20:18:33 millert Exp $"; 40 #endif 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.h> 51 #include "btree.h" 52 53 static int bt_broot(BTREE *, PAGE *, PAGE *, PAGE *); 54 static PAGE *bt_page(BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t); 55 static int bt_preserve(BTREE *, pgno_t); 56 static PAGE *bt_psplit(BTREE *, PAGE *, PAGE *, PAGE *, indx_t *, size_t); 57 static PAGE *bt_root(BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t); 58 static int bt_rroot(BTREE *, PAGE *, PAGE *, PAGE *); 59 static recno_t rec_total(PAGE *); 60 61 #ifdef STATISTICS 62 u_long bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved; 63 #endif 64 65 /* 66 * __BT_SPLIT -- Split the tree. 67 * 68 * Parameters: 69 * t: tree 70 * sp: page to split 71 * key: key to insert 72 * data: data to insert 73 * flags: BIGKEY/BIGDATA flags 74 * ilen: insert length 75 * skip: index to leave open 76 * 77 * Returns: 78 * RET_ERROR, RET_SUCCESS 79 */ 80 int 81 __bt_split(t, sp, key, data, flags, ilen, argskip) 82 BTREE *t; 83 PAGE *sp; 84 const DBT *key, *data; 85 int flags; 86 size_t ilen; 87 u_int32_t argskip; 88 { 89 BINTERNAL *bi; 90 BLEAF *bl, *tbl; 91 DBT a, b; 92 EPGNO *parent; 93 PAGE *h, *l, *r, *lchild, *rchild; 94 indx_t nxtindex; 95 u_int16_t skip; 96 u_int32_t n, nbytes, nksize; 97 int parentsplit; 98 char *dest; 99 100 /* 101 * Split the page into two pages, l and r. The split routines return 102 * a pointer to the page into which the key should be inserted and with 103 * skip set to the offset which should be used. Additionally, l and r 104 * are pinned. 105 */ 106 skip = argskip; 107 h = sp->pgno == P_ROOT ? 108 bt_root(t, sp, &l, &r, &skip, ilen) : 109 bt_page(t, sp, &l, &r, &skip, ilen); 110 if (h == NULL) 111 return (RET_ERROR); 112 113 /* 114 * Insert the new key/data pair into the leaf page. (Key inserts 115 * always cause a leaf page to split first.) 116 */ 117 h->linp[skip] = h->upper -= ilen; 118 dest = (char *)h + h->upper; 119 if (F_ISSET(t, R_RECNO)) 120 WR_RLEAF(dest, data, flags) 121 else 122 WR_BLEAF(dest, key, data, flags) 123 124 /* If the root page was split, make it look right. */ 125 if (sp->pgno == P_ROOT && 126 (F_ISSET(t, R_RECNO) ? 127 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 128 goto err2; 129 130 /* 131 * Now we walk the parent page stack -- a LIFO stack of the pages that 132 * were traversed when we searched for the page that split. Each stack 133 * entry is a page number and a page index offset. The offset is for 134 * the page traversed on the search. We've just split a page, so we 135 * have to insert a new key into the parent page. 136 * 137 * If the insert into the parent page causes it to split, may have to 138 * continue splitting all the way up the tree. We stop if the root 139 * splits or the page inserted into didn't have to split to hold the 140 * new key. Some algorithms replace the key for the old page as well 141 * as the new page. We don't, as there's no reason to believe that the 142 * first key on the old page is any better than the key we have, and, 143 * in the case of a key being placed at index 0 causing the split, the 144 * key is unavailable. 145 * 146 * There are a maximum of 5 pages pinned at any time. We keep the left 147 * and right pages pinned while working on the parent. The 5 are the 148 * two children, left parent and right parent (when the parent splits) 149 * and the root page or the overflow key page when calling bt_preserve. 150 * This code must make sure that all pins are released other than the 151 * root page or overflow page which is unlocked elsewhere. 152 */ 153 while ((parent = BT_POP(t)) != NULL) { 154 lchild = l; 155 rchild = r; 156 157 /* Get the parent page. */ 158 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) 159 goto err2; 160 161 /* 162 * The new key goes ONE AFTER the index, because the split 163 * was to the right. 164 */ 165 skip = parent->index + 1; 166 167 /* 168 * Calculate the space needed on the parent page. 169 * 170 * Prefix trees: space hack when inserting into BINTERNAL 171 * pages. Retain only what's needed to distinguish between 172 * the new entry and the LAST entry on the page to its left. 173 * If the keys compare equal, retain the entire key. Note, 174 * we don't touch overflow keys, and the entire key must be 175 * retained for the next-to-left most key on the leftmost 176 * page of each level, or the search will fail. Applicable 177 * ONLY to internal pages that have leaf pages as children. 178 * Further reduction of the key between pairs of internal 179 * pages loses too much information. 180 */ 181 switch (rchild->flags & P_TYPE) { 182 case P_BINTERNAL: 183 bi = GETBINTERNAL(rchild, 0); 184 nbytes = NBINTERNAL(bi->ksize); 185 break; 186 case P_BLEAF: 187 bl = GETBLEAF(rchild, 0); 188 nbytes = NBINTERNAL(bl->ksize); 189 if (t->bt_pfx && !(bl->flags & P_BIGKEY) && 190 (h->prevpg != P_INVALID || skip > 1)) { 191 tbl = GETBLEAF(lchild, NEXTINDEX(lchild) - 1); 192 a.size = tbl->ksize; 193 a.data = tbl->bytes; 194 b.size = bl->ksize; 195 b.data = bl->bytes; 196 nksize = t->bt_pfx(&a, &b); 197 n = NBINTERNAL(nksize); 198 if (n < nbytes) { 199 #ifdef STATISTICS 200 bt_pfxsaved += nbytes - n; 201 #endif 202 nbytes = n; 203 } else 204 nksize = 0; 205 } else 206 nksize = 0; 207 break; 208 case P_RINTERNAL: 209 case P_RLEAF: 210 nbytes = NRINTERNAL; 211 break; 212 default: 213 abort(); 214 } 215 216 /* Split the parent page if necessary or shift the indices. */ 217 if (h->upper - h->lower < nbytes + sizeof(indx_t)) { 218 sp = h; 219 h = h->pgno == P_ROOT ? 220 bt_root(t, h, &l, &r, &skip, nbytes) : 221 bt_page(t, h, &l, &r, &skip, nbytes); 222 if (h == NULL) 223 goto err1; 224 parentsplit = 1; 225 } else { 226 if (skip < (nxtindex = NEXTINDEX(h))) 227 memmove(h->linp + skip + 1, h->linp + skip, 228 (nxtindex - skip) * sizeof(indx_t)); 229 h->lower += sizeof(indx_t); 230 parentsplit = 0; 231 } 232 233 /* Insert the key into the parent page. */ 234 switch (rchild->flags & P_TYPE) { 235 case P_BINTERNAL: 236 h->linp[skip] = h->upper -= nbytes; 237 dest = (char *)h + h->linp[skip]; 238 memmove(dest, bi, nbytes); 239 ((BINTERNAL *)dest)->pgno = rchild->pgno; 240 break; 241 case P_BLEAF: 242 h->linp[skip] = h->upper -= nbytes; 243 dest = (char *)h + h->linp[skip]; 244 WR_BINTERNAL(dest, nksize ? nksize : bl->ksize, 245 rchild->pgno, bl->flags & P_BIGKEY); 246 memmove(dest, bl->bytes, nksize ? nksize : bl->ksize); 247 if (bl->flags & P_BIGKEY && 248 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 249 goto err1; 250 break; 251 case P_RINTERNAL: 252 /* 253 * Update the left page count. If split 254 * added at index 0, fix the correct page. 255 */ 256 if (skip > 0) 257 dest = (char *)h + h->linp[skip - 1]; 258 else 259 dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; 260 ((RINTERNAL *)dest)->nrecs = rec_total(lchild); 261 ((RINTERNAL *)dest)->pgno = lchild->pgno; 262 263 /* Update the right page count. */ 264 h->linp[skip] = h->upper -= nbytes; 265 dest = (char *)h + h->linp[skip]; 266 ((RINTERNAL *)dest)->nrecs = rec_total(rchild); 267 ((RINTERNAL *)dest)->pgno = rchild->pgno; 268 break; 269 case P_RLEAF: 270 /* 271 * Update the left page count. If split 272 * added at index 0, fix the correct page. 273 */ 274 if (skip > 0) 275 dest = (char *)h + h->linp[skip - 1]; 276 else 277 dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; 278 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(lchild); 279 ((RINTERNAL *)dest)->pgno = lchild->pgno; 280 281 /* Update the right page count. */ 282 h->linp[skip] = h->upper -= nbytes; 283 dest = (char *)h + h->linp[skip]; 284 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(rchild); 285 ((RINTERNAL *)dest)->pgno = rchild->pgno; 286 break; 287 default: 288 abort(); 289 } 290 291 /* Unpin the held pages. */ 292 if (!parentsplit) { 293 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 294 break; 295 } 296 297 /* If the root page was split, make it look right. */ 298 if (sp->pgno == P_ROOT && 299 (F_ISSET(t, R_RECNO) ? 300 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 301 goto err1; 302 303 mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 304 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 305 } 306 307 /* Unpin the held pages. */ 308 mpool_put(t->bt_mp, l, MPOOL_DIRTY); 309 mpool_put(t->bt_mp, r, MPOOL_DIRTY); 310 311 /* Clear any pages left on the stack. */ 312 return (RET_SUCCESS); 313 314 /* 315 * If something fails in the above loop we were already walking back 316 * up the tree and the tree is now inconsistent. Nothing much we can 317 * do about it but release any memory we're holding. 318 */ 319 err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 320 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 321 322 err2: mpool_put(t->bt_mp, l, 0); 323 mpool_put(t->bt_mp, r, 0); 324 __dbpanic(t->bt_dbp); 325 return (RET_ERROR); 326 } 327 328 /* 329 * BT_PAGE -- Split a non-root page of a btree. 330 * 331 * Parameters: 332 * t: tree 333 * h: root page 334 * lp: pointer to left page pointer 335 * rp: pointer to right page pointer 336 * skip: pointer to index to leave open 337 * ilen: insert length 338 * 339 * Returns: 340 * Pointer to page in which to insert or NULL on error. 341 */ 342 static PAGE * 343 bt_page(t, h, lp, rp, skip, ilen) 344 BTREE *t; 345 PAGE *h, **lp, **rp; 346 indx_t *skip; 347 size_t ilen; 348 { 349 PAGE *l, *r, *tp; 350 pgno_t npg; 351 352 #ifdef STATISTICS 353 ++bt_split; 354 #endif 355 /* Put the new right page for the split into place. */ 356 if ((r = __bt_new(t, &npg)) == NULL) 357 return (NULL); 358 r->pgno = npg; 359 r->lower = BTDATAOFF; 360 r->upper = t->bt_psize; 361 r->nextpg = h->nextpg; 362 r->prevpg = h->pgno; 363 r->flags = h->flags & P_TYPE; 364 365 /* 366 * If we're splitting the last page on a level because we're appending 367 * a key to it (skip is NEXTINDEX()), it's likely that the data is 368 * sorted. Adding an empty page on the side of the level is less work 369 * and can push the fill factor much higher than normal. If we're 370 * wrong it's no big deal, we'll just do the split the right way next 371 * time. It may look like it's equally easy to do a similar hack for 372 * reverse sorted data, that is, split the tree left, but it's not. 373 * Don't even try. 374 */ 375 if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) { 376 #ifdef STATISTICS 377 ++bt_sortsplit; 378 #endif 379 h->nextpg = r->pgno; 380 r->lower = BTDATAOFF + sizeof(indx_t); 381 *skip = 0; 382 *lp = h; 383 *rp = r; 384 return (r); 385 } 386 387 /* Put the new left page for the split into place. */ 388 if ((l = (PAGE *)malloc(t->bt_psize)) == NULL) { 389 mpool_put(t->bt_mp, r, 0); 390 return (NULL); 391 } 392 memset(l, 0xff, t->bt_psize); 393 l->pgno = h->pgno; 394 l->nextpg = r->pgno; 395 l->prevpg = h->prevpg; 396 l->lower = BTDATAOFF; 397 l->upper = t->bt_psize; 398 l->flags = h->flags & P_TYPE; 399 400 /* Fix up the previous pointer of the page after the split page. */ 401 if (h->nextpg != P_INVALID) { 402 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) { 403 free(l); 404 /* XXX mpool_free(t->bt_mp, r->pgno); */ 405 return (NULL); 406 } 407 tp->prevpg = r->pgno; 408 mpool_put(t->bt_mp, tp, MPOOL_DIRTY); 409 } 410 411 /* 412 * Split right. The key/data pairs aren't sorted in the btree page so 413 * it's simpler to copy the data from the split page onto two new pages 414 * instead of copying half the data to the right page and compacting 415 * the left page in place. Since the left page can't change, we have 416 * to swap the original and the allocated left page after the split. 417 */ 418 tp = bt_psplit(t, h, l, r, skip, ilen); 419 420 /* Move the new left page onto the old left page. */ 421 memmove(h, l, t->bt_psize); 422 if (tp == l) 423 tp = h; 424 free(l); 425 426 *lp = h; 427 *rp = r; 428 return (tp); 429 } 430 431 /* 432 * BT_ROOT -- Split the root page of a btree. 433 * 434 * Parameters: 435 * t: tree 436 * h: root page 437 * lp: pointer to left page pointer 438 * rp: pointer to right page pointer 439 * skip: pointer to index to leave open 440 * ilen: insert length 441 * 442 * Returns: 443 * Pointer to page in which to insert or NULL on error. 444 */ 445 static PAGE * 446 bt_root(t, h, lp, rp, skip, ilen) 447 BTREE *t; 448 PAGE *h, **lp, **rp; 449 indx_t *skip; 450 size_t ilen; 451 { 452 PAGE *l, *r, *tp; 453 pgno_t lnpg, rnpg; 454 455 #ifdef STATISTICS 456 ++bt_split; 457 ++bt_rootsplit; 458 #endif 459 /* Put the new left and right pages for the split into place. */ 460 if ((l = __bt_new(t, &lnpg)) == NULL || 461 (r = __bt_new(t, &rnpg)) == NULL) 462 return (NULL); 463 l->pgno = lnpg; 464 r->pgno = rnpg; 465 l->nextpg = r->pgno; 466 r->prevpg = l->pgno; 467 l->prevpg = r->nextpg = P_INVALID; 468 l->lower = r->lower = BTDATAOFF; 469 l->upper = r->upper = t->bt_psize; 470 l->flags = r->flags = h->flags & P_TYPE; 471 472 /* Split the root page. */ 473 tp = bt_psplit(t, h, l, r, skip, ilen); 474 475 *lp = l; 476 *rp = r; 477 return (tp); 478 } 479 480 /* 481 * BT_RROOT -- Fix up the recno root page after it has been split. 482 * 483 * Parameters: 484 * t: tree 485 * h: root page 486 * l: left page 487 * r: right page 488 * 489 * Returns: 490 * RET_ERROR, RET_SUCCESS 491 */ 492 static int 493 bt_rroot(t, h, l, r) 494 BTREE *t; 495 PAGE *h, *l, *r; 496 { 497 char *dest; 498 499 /* Insert the left and right keys, set the header information. */ 500 h->linp[0] = h->upper = t->bt_psize - NRINTERNAL; 501 dest = (char *)h + h->upper; 502 WR_RINTERNAL(dest, 503 l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno); 504 505 h->linp[1] = h->upper -= NRINTERNAL; 506 dest = (char *)h + h->upper; 507 WR_RINTERNAL(dest, 508 r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno); 509 510 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 511 512 /* Unpin the root page, set to recno internal page. */ 513 h->flags &= ~P_TYPE; 514 h->flags |= P_RINTERNAL; 515 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 516 517 return (RET_SUCCESS); 518 } 519 520 /* 521 * BT_BROOT -- Fix up the btree root page after it has been split. 522 * 523 * Parameters: 524 * t: tree 525 * h: root page 526 * l: left page 527 * r: right page 528 * 529 * Returns: 530 * RET_ERROR, RET_SUCCESS 531 */ 532 static int 533 bt_broot(t, h, l, r) 534 BTREE *t; 535 PAGE *h, *l, *r; 536 { 537 BINTERNAL *bi; 538 BLEAF *bl; 539 u_int32_t nbytes; 540 char *dest; 541 542 /* 543 * If the root page was a leaf page, change it into an internal page. 544 * We copy the key we split on (but not the key's data, in the case of 545 * a leaf page) to the new root page. 546 * 547 * The btree comparison code guarantees that the left-most key on any 548 * level of the tree is never used, so it doesn't need to be filled in. 549 */ 550 nbytes = NBINTERNAL(0); 551 h->linp[0] = h->upper = t->bt_psize - nbytes; 552 dest = (char *)h + h->upper; 553 WR_BINTERNAL(dest, 0, l->pgno, 0); 554 555 switch (h->flags & P_TYPE) { 556 case P_BLEAF: 557 bl = GETBLEAF(r, 0); 558 nbytes = NBINTERNAL(bl->ksize); 559 h->linp[1] = h->upper -= nbytes; 560 dest = (char *)h + h->upper; 561 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0); 562 memmove(dest, bl->bytes, bl->ksize); 563 564 /* 565 * If the key is on an overflow page, mark the overflow chain 566 * so it isn't deleted when the leaf copy of the key is deleted. 567 */ 568 if (bl->flags & P_BIGKEY && 569 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 570 return (RET_ERROR); 571 break; 572 case P_BINTERNAL: 573 bi = GETBINTERNAL(r, 0); 574 nbytes = NBINTERNAL(bi->ksize); 575 h->linp[1] = h->upper -= nbytes; 576 dest = (char *)h + h->upper; 577 memmove(dest, bi, nbytes); 578 ((BINTERNAL *)dest)->pgno = r->pgno; 579 break; 580 default: 581 abort(); 582 } 583 584 /* There are two keys on the page. */ 585 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 586 587 /* Unpin the root page, set to btree internal page. */ 588 h->flags &= ~P_TYPE; 589 h->flags |= P_BINTERNAL; 590 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 591 592 return (RET_SUCCESS); 593 } 594 595 /* 596 * BT_PSPLIT -- Do the real work of splitting the page. 597 * 598 * Parameters: 599 * t: tree 600 * h: page to be split 601 * l: page to put lower half of data 602 * r: page to put upper half of data 603 * pskip: pointer to index to leave open 604 * ilen: insert length 605 * 606 * Returns: 607 * Pointer to page in which to insert. 608 */ 609 static PAGE * 610 bt_psplit(t, h, l, r, pskip, ilen) 611 BTREE *t; 612 PAGE *h, *l, *r; 613 indx_t *pskip; 614 size_t ilen; 615 { 616 BINTERNAL *bi; 617 BLEAF *bl; 618 CURSOR *c; 619 RLEAF *rl; 620 PAGE *rval; 621 void *src; 622 indx_t full, half, nxt, off, skip, top, used; 623 u_int32_t nbytes; 624 int bigkeycnt, isbigkey; 625 626 /* 627 * Split the data to the left and right pages. Leave the skip index 628 * open. Additionally, make some effort not to split on an overflow 629 * key. This makes internal page processing faster and can save 630 * space as overflow keys used by internal pages are never deleted. 631 */ 632 bigkeycnt = 0; 633 skip = *pskip; 634 full = t->bt_psize - BTDATAOFF; 635 half = full / 2; 636 used = 0; 637 for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) { 638 if (skip == off) { 639 nbytes = ilen; 640 isbigkey = 0; /* XXX: not really known. */ 641 } else 642 switch (h->flags & P_TYPE) { 643 case P_BINTERNAL: 644 src = bi = GETBINTERNAL(h, nxt); 645 nbytes = NBINTERNAL(bi->ksize); 646 isbigkey = bi->flags & P_BIGKEY; 647 break; 648 case P_BLEAF: 649 src = bl = GETBLEAF(h, nxt); 650 nbytes = NBLEAF(bl); 651 isbigkey = bl->flags & P_BIGKEY; 652 break; 653 case P_RINTERNAL: 654 src = GETRINTERNAL(h, nxt); 655 nbytes = NRINTERNAL; 656 isbigkey = 0; 657 break; 658 case P_RLEAF: 659 src = rl = GETRLEAF(h, nxt); 660 nbytes = NRLEAF(rl); 661 isbigkey = 0; 662 break; 663 default: 664 abort(); 665 } 666 667 /* 668 * If the key/data pairs are substantial fractions of the max 669 * possible size for the page, it's possible to get situations 670 * where we decide to try and copy too much onto the left page. 671 * Make sure that doesn't happen. 672 */ 673 if ((skip <= off && used + nbytes + sizeof(indx_t) >= full) || 674 nxt == top - 1) { 675 --off; 676 break; 677 } 678 679 /* Copy the key/data pair, if not the skipped index. */ 680 if (skip != off) { 681 ++nxt; 682 683 l->linp[off] = l->upper -= nbytes; 684 memmove((char *)l + l->upper, src, nbytes); 685 } 686 687 used += nbytes + sizeof(indx_t); 688 if (used >= half) { 689 if (!isbigkey || bigkeycnt == 3) 690 break; 691 else 692 ++bigkeycnt; 693 } 694 } 695 696 /* 697 * Off is the last offset that's valid for the left page. 698 * Nxt is the first offset to be placed on the right page. 699 */ 700 l->lower += (off + 1) * sizeof(indx_t); 701 702 /* 703 * If splitting the page that the cursor was on, the cursor has to be 704 * adjusted to point to the same record as before the split. If the 705 * cursor is at or past the skipped slot, the cursor is incremented by 706 * one. If the cursor is on the right page, it is decremented by the 707 * number of records split to the left page. 708 */ 709 c = &t->bt_cursor; 710 if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) { 711 if (c->pg.index >= skip) 712 ++c->pg.index; 713 if (c->pg.index < nxt) /* Left page. */ 714 c->pg.pgno = l->pgno; 715 else { /* Right page. */ 716 c->pg.pgno = r->pgno; 717 c->pg.index -= nxt; 718 } 719 } 720 721 /* 722 * If the skipped index was on the left page, just return that page. 723 * Otherwise, adjust the skip index to reflect the new position on 724 * the right page. 725 */ 726 if (skip <= off) { 727 skip = MAX_PAGE_OFFSET; 728 rval = l; 729 } else { 730 rval = r; 731 *pskip -= nxt; 732 } 733 734 for (off = 0; nxt < top; ++off) { 735 if (skip == nxt) { 736 ++off; 737 skip = MAX_PAGE_OFFSET; 738 } 739 switch (h->flags & P_TYPE) { 740 case P_BINTERNAL: 741 src = bi = GETBINTERNAL(h, nxt); 742 nbytes = NBINTERNAL(bi->ksize); 743 break; 744 case P_BLEAF: 745 src = bl = GETBLEAF(h, nxt); 746 nbytes = NBLEAF(bl); 747 break; 748 case P_RINTERNAL: 749 src = GETRINTERNAL(h, nxt); 750 nbytes = NRINTERNAL; 751 break; 752 case P_RLEAF: 753 src = rl = GETRLEAF(h, nxt); 754 nbytes = NRLEAF(rl); 755 break; 756 default: 757 abort(); 758 } 759 ++nxt; 760 r->linp[off] = r->upper -= nbytes; 761 memmove((char *)r + r->upper, src, nbytes); 762 } 763 r->lower += off * sizeof(indx_t); 764 765 /* If the key is being appended to the page, adjust the index. */ 766 if (skip == top) 767 r->lower += sizeof(indx_t); 768 769 return (rval); 770 } 771 772 /* 773 * BT_PRESERVE -- Mark a chain of pages as used by an internal node. 774 * 775 * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the 776 * record that references them gets deleted. Chains pointed to by internal 777 * pages never get deleted. This routine marks a chain as pointed to by an 778 * internal page. 779 * 780 * Parameters: 781 * t: tree 782 * pg: page number of first page in the chain. 783 * 784 * Returns: 785 * RET_SUCCESS, RET_ERROR. 786 */ 787 static int 788 bt_preserve(t, pg) 789 BTREE *t; 790 pgno_t pg; 791 { 792 PAGE *h; 793 794 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 795 return (RET_ERROR); 796 h->flags |= P_PRESERVE; 797 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 798 return (RET_SUCCESS); 799 } 800 801 /* 802 * REC_TOTAL -- Return the number of recno entries below a page. 803 * 804 * Parameters: 805 * h: page 806 * 807 * Returns: 808 * The number of recno entries below a page. 809 * 810 * XXX 811 * These values could be set by the bt_psplit routine. The problem is that the 812 * entry has to be popped off of the stack etc. or the values have to be passed 813 * all the way back to bt_split/bt_rroot and it's not very clean. 814 */ 815 static recno_t 816 rec_total(h) 817 PAGE *h; 818 { 819 recno_t recs; 820 indx_t nxt, top; 821 822 for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt) 823 recs += GETRINTERNAL(h, nxt)->nrecs; 824 return (recs); 825 } 826