1 /*- 2 * Copyright (c) 1990, 1993, 1994 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Mike Olson. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#)bt_split.c 8.9 (Berkeley) 7/26/94 37 * $DragonFly: src/lib/libc/db/btree/bt_split.c,v 1.5 2004/09/19 18:08:21 asmodai Exp $ 38 */ 39 40 #include <sys/types.h> 41 42 #include <limits.h> 43 #include <stdio.h> 44 #include <stdlib.h> 45 #include <string.h> 46 47 #include <db.h> 48 #include "btree.h" 49 50 static int bt_broot (BTREE *, PAGE *, PAGE *, PAGE *); 51 static PAGE *bt_page 52 (BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t); 53 static int bt_preserve (BTREE *, pgno_t); 54 static PAGE *bt_psplit 55 (BTREE *, PAGE *, PAGE *, PAGE *, indx_t *, size_t); 56 static PAGE *bt_root 57 (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 #ifdef PURIFY 393 memset(l, 0xff, t->bt_psize); 394 #endif 395 l->pgno = h->pgno; 396 l->nextpg = r->pgno; 397 l->prevpg = h->prevpg; 398 l->lower = BTDATAOFF; 399 l->upper = t->bt_psize; 400 l->flags = h->flags & P_TYPE; 401 402 /* Fix up the previous pointer of the page after the split page. */ 403 if (h->nextpg != P_INVALID) { 404 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) { 405 free(l); 406 /* XXX mpool_free(t->bt_mp, r->pgno); */ 407 return (NULL); 408 } 409 tp->prevpg = r->pgno; 410 mpool_put(t->bt_mp, tp, MPOOL_DIRTY); 411 } 412 413 /* 414 * Split right. The key/data pairs aren't sorted in the btree page so 415 * it's simpler to copy the data from the split page onto two new pages 416 * instead of copying half the data to the right page and compacting 417 * the left page in place. Since the left page can't change, we have 418 * to swap the original and the allocated left page after the split. 419 */ 420 tp = bt_psplit(t, h, l, r, skip, ilen); 421 422 /* Move the new left page onto the old left page. */ 423 memmove(h, l, t->bt_psize); 424 if (tp == l) 425 tp = h; 426 free(l); 427 428 *lp = h; 429 *rp = r; 430 return (tp); 431 } 432 433 /* 434 * BT_ROOT -- Split the root page of a btree. 435 * 436 * Parameters: 437 * t: tree 438 * h: root page 439 * lp: pointer to left page pointer 440 * rp: pointer to right page pointer 441 * skip: pointer to index to leave open 442 * ilen: insert length 443 * 444 * Returns: 445 * Pointer to page in which to insert or NULL on error. 446 */ 447 static PAGE * 448 bt_root(t, h, lp, rp, skip, ilen) 449 BTREE *t; 450 PAGE *h, **lp, **rp; 451 indx_t *skip; 452 size_t ilen; 453 { 454 PAGE *l, *r, *tp; 455 pgno_t lnpg, rnpg; 456 457 #ifdef STATISTICS 458 ++bt_split; 459 ++bt_rootsplit; 460 #endif 461 /* Put the new left and right pages for the split into place. */ 462 if ((l = __bt_new(t, &lnpg)) == NULL || 463 (r = __bt_new(t, &rnpg)) == NULL) 464 return (NULL); 465 l->pgno = lnpg; 466 r->pgno = rnpg; 467 l->nextpg = r->pgno; 468 r->prevpg = l->pgno; 469 l->prevpg = r->nextpg = P_INVALID; 470 l->lower = r->lower = BTDATAOFF; 471 l->upper = r->upper = t->bt_psize; 472 l->flags = r->flags = h->flags & P_TYPE; 473 474 /* Split the root page. */ 475 tp = bt_psplit(t, h, l, r, skip, ilen); 476 477 *lp = l; 478 *rp = r; 479 return (tp); 480 } 481 482 /* 483 * BT_RROOT -- Fix up the recno root page after it has been split. 484 * 485 * Parameters: 486 * t: tree 487 * h: root page 488 * l: left page 489 * r: right page 490 * 491 * Returns: 492 * RET_ERROR, RET_SUCCESS 493 */ 494 static int 495 bt_rroot(t, h, l, r) 496 BTREE *t; 497 PAGE *h, *l, *r; 498 { 499 char *dest; 500 501 /* Insert the left and right keys, set the header information. */ 502 h->linp[0] = h->upper = t->bt_psize - NRINTERNAL; 503 dest = (char *)h + h->upper; 504 WR_RINTERNAL(dest, 505 l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno); 506 507 h->linp[1] = h->upper -= NRINTERNAL; 508 dest = (char *)h + h->upper; 509 WR_RINTERNAL(dest, 510 r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno); 511 512 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 513 514 /* Unpin the root page, set to recno internal page. */ 515 h->flags &= ~P_TYPE; 516 h->flags |= P_RINTERNAL; 517 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 518 519 return (RET_SUCCESS); 520 } 521 522 /* 523 * BT_BROOT -- Fix up the btree root page after it has been split. 524 * 525 * Parameters: 526 * t: tree 527 * h: root page 528 * l: left page 529 * r: right page 530 * 531 * Returns: 532 * RET_ERROR, RET_SUCCESS 533 */ 534 static int 535 bt_broot(t, h, l, r) 536 BTREE *t; 537 PAGE *h, *l, *r; 538 { 539 BINTERNAL *bi; 540 BLEAF *bl; 541 u_int32_t nbytes; 542 char *dest; 543 544 /* 545 * If the root page was a leaf page, change it into an internal page. 546 * We copy the key we split on (but not the key's data, in the case of 547 * a leaf page) to the new root page. 548 * 549 * The btree comparison code guarantees that the left-most key on any 550 * level of the tree is never used, so it doesn't need to be filled in. 551 */ 552 nbytes = NBINTERNAL(0); 553 h->linp[0] = h->upper = t->bt_psize - nbytes; 554 dest = (char *)h + h->upper; 555 WR_BINTERNAL(dest, 0, l->pgno, 0); 556 557 switch (h->flags & P_TYPE) { 558 case P_BLEAF: 559 bl = GETBLEAF(r, 0); 560 nbytes = NBINTERNAL(bl->ksize); 561 h->linp[1] = h->upper -= nbytes; 562 dest = (char *)h + h->upper; 563 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0); 564 memmove(dest, bl->bytes, bl->ksize); 565 566 /* 567 * If the key is on an overflow page, mark the overflow chain 568 * so it isn't deleted when the leaf copy of the key is deleted. 569 */ 570 if (bl->flags & P_BIGKEY && 571 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 572 return (RET_ERROR); 573 break; 574 case P_BINTERNAL: 575 bi = GETBINTERNAL(r, 0); 576 nbytes = NBINTERNAL(bi->ksize); 577 h->linp[1] = h->upper -= nbytes; 578 dest = (char *)h + h->upper; 579 memmove(dest, bi, nbytes); 580 ((BINTERNAL *)dest)->pgno = r->pgno; 581 break; 582 default: 583 abort(); 584 } 585 586 /* There are two keys on the page. */ 587 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 588 589 /* Unpin the root page, set to btree internal page. */ 590 h->flags &= ~P_TYPE; 591 h->flags |= P_BINTERNAL; 592 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 593 594 return (RET_SUCCESS); 595 } 596 597 /* 598 * BT_PSPLIT -- Do the real work of splitting the page. 599 * 600 * Parameters: 601 * t: tree 602 * h: page to be split 603 * l: page to put lower half of data 604 * r: page to put upper half of data 605 * pskip: pointer to index to leave open 606 * ilen: insert length 607 * 608 * Returns: 609 * Pointer to page in which to insert. 610 */ 611 static PAGE * 612 bt_psplit(t, h, l, r, pskip, ilen) 613 BTREE *t; 614 PAGE *h, *l, *r; 615 indx_t *pskip; 616 size_t ilen; 617 { 618 BINTERNAL *bi; 619 BLEAF *bl; 620 CURSOR *c; 621 RLEAF *rl; 622 PAGE *rval; 623 void *src; 624 indx_t full, half, nxt, off, skip, top, used; 625 u_int32_t nbytes; 626 int bigkeycnt, isbigkey; 627 628 /* 629 * Split the data to the left and right pages. Leave the skip index 630 * open. Additionally, make some effort not to split on an overflow 631 * key. This makes internal page processing faster and can save 632 * space as overflow keys used by internal pages are never deleted. 633 */ 634 bigkeycnt = 0; 635 skip = *pskip; 636 full = t->bt_psize - BTDATAOFF; 637 half = full / 2; 638 used = 0; 639 for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) { 640 if (skip == off) { 641 nbytes = ilen; 642 isbigkey = 0; /* XXX: not really known. */ 643 } else 644 switch (h->flags & P_TYPE) { 645 case P_BINTERNAL: 646 src = bi = GETBINTERNAL(h, nxt); 647 nbytes = NBINTERNAL(bi->ksize); 648 isbigkey = bi->flags & P_BIGKEY; 649 break; 650 case P_BLEAF: 651 src = bl = GETBLEAF(h, nxt); 652 nbytes = NBLEAF(bl); 653 isbigkey = bl->flags & P_BIGKEY; 654 break; 655 case P_RINTERNAL: 656 src = GETRINTERNAL(h, nxt); 657 nbytes = NRINTERNAL; 658 isbigkey = 0; 659 break; 660 case P_RLEAF: 661 src = rl = GETRLEAF(h, nxt); 662 nbytes = NRLEAF(rl); 663 isbigkey = 0; 664 break; 665 default: 666 abort(); 667 } 668 669 /* 670 * If the key/data pairs are substantial fractions of the max 671 * possible size for the page, it's possible to get situations 672 * where we decide to try and copy too much onto the left page. 673 * Make sure that doesn't happen. 674 */ 675 if (skip <= off && 676 used + nbytes + sizeof(indx_t) >= full || nxt == top - 1) { 677 --off; 678 break; 679 } 680 681 /* Copy the key/data pair, if not the skipped index. */ 682 if (skip != off) { 683 ++nxt; 684 685 l->linp[off] = l->upper -= nbytes; 686 memmove((char *)l + l->upper, src, nbytes); 687 } 688 689 used += nbytes + sizeof(indx_t); 690 if (used >= half) { 691 if (!isbigkey || bigkeycnt == 3) 692 break; 693 else 694 ++bigkeycnt; 695 } 696 } 697 698 /* 699 * Off is the last offset that's valid for the left page. 700 * Nxt is the first offset to be placed on the right page. 701 */ 702 l->lower += (off + 1) * sizeof(indx_t); 703 704 /* 705 * If splitting the page that the cursor was on, the cursor has to be 706 * adjusted to point to the same record as before the split. If the 707 * cursor is at or past the skipped slot, the cursor is incremented by 708 * one. If the cursor is on the right page, it is decremented by the 709 * number of records split to the left page. 710 */ 711 c = &t->bt_cursor; 712 if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) { 713 if (c->pg.index >= skip) 714 ++c->pg.index; 715 if (c->pg.index < nxt) /* Left page. */ 716 c->pg.pgno = l->pgno; 717 else { /* Right page. */ 718 c->pg.pgno = r->pgno; 719 c->pg.index -= nxt; 720 } 721 } 722 723 /* 724 * If the skipped index was on the left page, just return that page. 725 * Otherwise, adjust the skip index to reflect the new position on 726 * the right page. 727 */ 728 if (skip <= off) { 729 skip = MAX_PAGE_OFFSET; 730 rval = l; 731 } else { 732 rval = r; 733 *pskip -= nxt; 734 } 735 736 for (off = 0; nxt < top; ++off) { 737 if (skip == nxt) { 738 ++off; 739 skip = MAX_PAGE_OFFSET; 740 } 741 switch (h->flags & P_TYPE) { 742 case P_BINTERNAL: 743 src = bi = GETBINTERNAL(h, nxt); 744 nbytes = NBINTERNAL(bi->ksize); 745 break; 746 case P_BLEAF: 747 src = bl = GETBLEAF(h, nxt); 748 nbytes = NBLEAF(bl); 749 break; 750 case P_RINTERNAL: 751 src = GETRINTERNAL(h, nxt); 752 nbytes = NRINTERNAL; 753 break; 754 case P_RLEAF: 755 src = rl = GETRLEAF(h, nxt); 756 nbytes = NRLEAF(rl); 757 break; 758 default: 759 abort(); 760 } 761 ++nxt; 762 r->linp[off] = r->upper -= nbytes; 763 memmove((char *)r + r->upper, src, nbytes); 764 } 765 r->lower += off * sizeof(indx_t); 766 767 /* If the key is being appended to the page, adjust the index. */ 768 if (skip == top) 769 r->lower += sizeof(indx_t); 770 771 return (rval); 772 } 773 774 /* 775 * BT_PRESERVE -- Mark a chain of pages as used by an internal node. 776 * 777 * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the 778 * record that references them gets deleted. Chains pointed to by internal 779 * pages never get deleted. This routine marks a chain as pointed to by an 780 * internal page. 781 * 782 * Parameters: 783 * t: tree 784 * pg: page number of first page in the chain. 785 * 786 * Returns: 787 * RET_SUCCESS, RET_ERROR. 788 */ 789 static int 790 bt_preserve(t, pg) 791 BTREE *t; 792 pgno_t pg; 793 { 794 PAGE *h; 795 796 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 797 return (RET_ERROR); 798 h->flags |= P_PRESERVE; 799 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 800 return (RET_SUCCESS); 801 } 802 803 /* 804 * REC_TOTAL -- Return the number of recno entries below a page. 805 * 806 * Parameters: 807 * h: page 808 * 809 * Returns: 810 * The number of recno entries below a page. 811 * 812 * XXX 813 * These values could be set by the bt_psplit routine. The problem is that the 814 * entry has to be popped off of the stack etc. or the values have to be passed 815 * all the way back to bt_split/bt_rroot and it's not very clean. 816 */ 817 static recno_t 818 rec_total(h) 819 PAGE *h; 820 { 821 recno_t recs; 822 indx_t nxt, top; 823 824 for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt) 825 recs += GETRINTERNAL(h, nxt)->nrecs; 826 return (recs); 827 } 828