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 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 */ 40 41 #include <sys/types.h> 42 43 #include <limits.h> 44 #include <stdio.h> 45 #include <stdlib.h> 46 #include <string.h> 47 48 #include <db.h> 49 #include "btree.h" 50 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 *)); 61 62 #ifdef STATISTICS 63 u_long bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved; 64 #endif 65 66 /* 67 * __BT_SPLIT -- Split the tree. 68 * 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 77 * 78 * Returns: 79 * RET_ERROR, RET_SUCCESS 80 */ 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; 89 { 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; 100 101 /* 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. 106 */ 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); 113 114 /* 115 * Insert the new key/data pair into the leaf page. (Key inserts 116 * always cause a leaf page to split first.) 117 */ 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) 124 125 /* 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; 130 131 /* 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. 137 * 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. 146 * 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. 153 */ 154 while ((parent = BT_POP(t)) != NULL) { 155 lchild = l; 156 rchild = r; 157 158 /* Get the parent page. */ 159 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) 160 goto err2; 161 162 /* 163 * The new key goes ONE AFTER the index, because the split 164 * was to the right. 165 */ 166 skip = parent->index + 1; 167 168 /* 169 * Calculate the space needed on the parent page. 170 * 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. 181 */ 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(); 215 } 216 217 /* Split the parent page if necessary or shift the indices. */ 218 if (h->upper - h->lower < nbytes + sizeof(indx_t)) { 219 sp = h; 220 h = h->pgno == P_ROOT ? 221 bt_root(t, h, &l, &r, &skip, nbytes) : 222 bt_page(t, h, &l, &r, &skip, nbytes); 223 if (h == NULL) 224 goto err1; 225 parentsplit = 1; 226 } else { 227 if (skip < (nxtindex = NEXTINDEX(h))) 228 memmove(h->linp + skip + 1, h->linp + skip, 229 (nxtindex - skip) * sizeof(indx_t)); 230 h->lower += sizeof(indx_t); 231 parentsplit = 0; 232 } 233 234 /* Insert the key into the parent page. */ 235 switch (rchild->flags & P_TYPE) { 236 case P_BINTERNAL: 237 h->linp[skip] = h->upper -= nbytes; 238 dest = (char *)h + h->linp[skip]; 239 memmove(dest, bi, nbytes); 240 ((BINTERNAL *)dest)->pgno = rchild->pgno; 241 break; 242 case P_BLEAF: 243 h->linp[skip] = h->upper -= nbytes; 244 dest = (char *)h + h->linp[skip]; 245 WR_BINTERNAL(dest, nksize ? nksize : bl->ksize, 246 rchild->pgno, bl->flags & P_BIGKEY); 247 memmove(dest, bl->bytes, nksize ? nksize : bl->ksize); 248 if (bl->flags & P_BIGKEY && 249 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 250 goto err1; 251 break; 252 case P_RINTERNAL: 253 /* 254 * Update the left page count. If split 255 * added at index 0, fix the correct page. 256 */ 257 if (skip > 0) 258 dest = (char *)h + h->linp[skip - 1]; 259 else 260 dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; 261 ((RINTERNAL *)dest)->nrecs = rec_total(lchild); 262 ((RINTERNAL *)dest)->pgno = lchild->pgno; 263 264 /* Update the right page count. */ 265 h->linp[skip] = h->upper -= nbytes; 266 dest = (char *)h + h->linp[skip]; 267 ((RINTERNAL *)dest)->nrecs = rec_total(rchild); 268 ((RINTERNAL *)dest)->pgno = rchild->pgno; 269 break; 270 case P_RLEAF: 271 /* 272 * Update the left page count. If split 273 * added at index 0, fix the correct page. 274 */ 275 if (skip > 0) 276 dest = (char *)h + h->linp[skip - 1]; 277 else 278 dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; 279 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(lchild); 280 ((RINTERNAL *)dest)->pgno = lchild->pgno; 281 282 /* Update the right page count. */ 283 h->linp[skip] = h->upper -= nbytes; 284 dest = (char *)h + h->linp[skip]; 285 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(rchild); 286 ((RINTERNAL *)dest)->pgno = rchild->pgno; 287 break; 288 default: 289 abort(); 290 } 291 292 /* Unpin the held pages. */ 293 if (!parentsplit) { 294 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 295 break; 296 } 297 298 /* If the root page was split, make it look right. */ 299 if (sp->pgno == P_ROOT && 300 (F_ISSET(t, R_RECNO) ? 301 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 302 goto err1; 303 304 mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 305 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 306 } 307 308 /* Unpin the held pages. */ 309 mpool_put(t->bt_mp, l, MPOOL_DIRTY); 310 mpool_put(t->bt_mp, r, MPOOL_DIRTY); 311 312 /* Clear any pages left on the stack. */ 313 return (RET_SUCCESS); 314 315 /* 316 * If something fails in the above loop we were already walking back 317 * up the tree and the tree is now inconsistent. Nothing much we can 318 * do about it but release any memory we're holding. 319 */ 320 err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 321 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 322 323 err2: mpool_put(t->bt_mp, l, 0); 324 mpool_put(t->bt_mp, r, 0); 325 __dbpanic(t->bt_dbp); 326 return (RET_ERROR); 327 } 328 329 /* 330 * BT_PAGE -- Split a non-root page of a btree. 331 * 332 * Parameters: 333 * t: tree 334 * h: root page 335 * lp: pointer to left page pointer 336 * rp: pointer to right page pointer 337 * skip: pointer to index to leave open 338 * ilen: insert length 339 * 340 * Returns: 341 * Pointer to page in which to insert or NULL on error. 342 */ 343 static PAGE * 344 bt_page(t, h, lp, rp, skip, ilen) 345 BTREE *t; 346 PAGE *h, **lp, **rp; 347 indx_t *skip; 348 size_t ilen; 349 { 350 PAGE *l, *r, *tp; 351 pgno_t npg; 352 353 #ifdef STATISTICS 354 ++bt_split; 355 #endif 356 /* Put the new right page for the split into place. */ 357 if ((r = __bt_new(t, &npg)) == NULL) 358 return (NULL); 359 r->pgno = npg; 360 r->lower = BTDATAOFF; 361 r->upper = t->bt_psize; 362 r->nextpg = h->nextpg; 363 r->prevpg = h->pgno; 364 r->flags = h->flags & P_TYPE; 365 366 /* 367 * If we're splitting the last page on a level because we're appending 368 * a key to it (skip is NEXTINDEX()), it's likely that the data is 369 * sorted. Adding an empty page on the side of the level is less work 370 * and can push the fill factor much higher than normal. If we're 371 * wrong it's no big deal, we'll just do the split the right way next 372 * time. It may look like it's equally easy to do a similar hack for 373 * reverse sorted data, that is, split the tree left, but it's not. 374 * Don't even try. 375 */ 376 if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) { 377 #ifdef STATISTICS 378 ++bt_sortsplit; 379 #endif 380 h->nextpg = r->pgno; 381 r->lower = BTDATAOFF + sizeof(indx_t); 382 *skip = 0; 383 *lp = h; 384 *rp = r; 385 return (r); 386 } 387 388 /* Put the new left page for the split into place. */ 389 if ((l = (PAGE *)malloc(t->bt_psize)) == NULL) { 390 mpool_put(t->bt_mp, r, 0); 391 return (NULL); 392 } 393 #ifdef PURIFY 394 memset(l, 0xff, t->bt_psize); 395 #endif 396 l->pgno = h->pgno; 397 l->nextpg = r->pgno; 398 l->prevpg = h->prevpg; 399 l->lower = BTDATAOFF; 400 l->upper = t->bt_psize; 401 l->flags = h->flags & P_TYPE; 402 403 /* Fix up the previous pointer of the page after the split page. */ 404 if (h->nextpg != P_INVALID) { 405 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) { 406 free(l); 407 /* XXX mpool_free(t->bt_mp, r->pgno); */ 408 return (NULL); 409 } 410 tp->prevpg = r->pgno; 411 mpool_put(t->bt_mp, tp, MPOOL_DIRTY); 412 } 413 414 /* 415 * Split right. The key/data pairs aren't sorted in the btree page so 416 * it's simpler to copy the data from the split page onto two new pages 417 * instead of copying half the data to the right page and compacting 418 * the left page in place. Since the left page can't change, we have 419 * to swap the original and the allocated left page after the split. 420 */ 421 tp = bt_psplit(t, h, l, r, skip, ilen); 422 423 /* Move the new left page onto the old left page. */ 424 memmove(h, l, t->bt_psize); 425 if (tp == l) 426 tp = h; 427 free(l); 428 429 *lp = h; 430 *rp = r; 431 return (tp); 432 } 433 434 /* 435 * BT_ROOT -- Split the root page of a btree. 436 * 437 * Parameters: 438 * t: tree 439 * h: root page 440 * lp: pointer to left page pointer 441 * rp: pointer to right page pointer 442 * skip: pointer to index to leave open 443 * ilen: insert length 444 * 445 * Returns: 446 * Pointer to page in which to insert or NULL on error. 447 */ 448 static PAGE * 449 bt_root(t, h, lp, rp, skip, ilen) 450 BTREE *t; 451 PAGE *h, **lp, **rp; 452 indx_t *skip; 453 size_t ilen; 454 { 455 PAGE *l, *r, *tp; 456 pgno_t lnpg, rnpg; 457 458 #ifdef STATISTICS 459 ++bt_split; 460 ++bt_rootsplit; 461 #endif 462 /* Put the new left and right pages for the split into place. */ 463 if ((l = __bt_new(t, &lnpg)) == NULL || 464 (r = __bt_new(t, &rnpg)) == NULL) 465 return (NULL); 466 l->pgno = lnpg; 467 r->pgno = rnpg; 468 l->nextpg = r->pgno; 469 r->prevpg = l->pgno; 470 l->prevpg = r->nextpg = P_INVALID; 471 l->lower = r->lower = BTDATAOFF; 472 l->upper = r->upper = t->bt_psize; 473 l->flags = r->flags = h->flags & P_TYPE; 474 475 /* Split the root page. */ 476 tp = bt_psplit(t, h, l, r, skip, ilen); 477 478 *lp = l; 479 *rp = r; 480 return (tp); 481 } 482 483 /* 484 * BT_RROOT -- Fix up the recno root page after it has been split. 485 * 486 * Parameters: 487 * t: tree 488 * h: root page 489 * l: left page 490 * r: right page 491 * 492 * Returns: 493 * RET_ERROR, RET_SUCCESS 494 */ 495 static int 496 bt_rroot(t, h, l, r) 497 BTREE *t; 498 PAGE *h, *l, *r; 499 { 500 char *dest; 501 502 /* Insert the left and right keys, set the header information. */ 503 h->linp[0] = h->upper = t->bt_psize - NRINTERNAL; 504 dest = (char *)h + h->upper; 505 WR_RINTERNAL(dest, 506 l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno); 507 508 h->linp[1] = h->upper -= NRINTERNAL; 509 dest = (char *)h + h->upper; 510 WR_RINTERNAL(dest, 511 r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno); 512 513 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 514 515 /* Unpin the root page, set to recno internal page. */ 516 h->flags &= ~P_TYPE; 517 h->flags |= P_RINTERNAL; 518 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 519 520 return (RET_SUCCESS); 521 } 522 523 /* 524 * BT_BROOT -- Fix up the btree root page after it has been split. 525 * 526 * Parameters: 527 * t: tree 528 * h: root page 529 * l: left page 530 * r: right page 531 * 532 * Returns: 533 * RET_ERROR, RET_SUCCESS 534 */ 535 static int 536 bt_broot(t, h, l, r) 537 BTREE *t; 538 PAGE *h, *l, *r; 539 { 540 BINTERNAL *bi; 541 BLEAF *bl; 542 u_int32_t nbytes; 543 char *dest; 544 545 /* 546 * If the root page was a leaf page, change it into an internal page. 547 * We copy the key we split on (but not the key's data, in the case of 548 * a leaf page) to the new root page. 549 * 550 * The btree comparison code guarantees that the left-most key on any 551 * level of the tree is never used, so it doesn't need to be filled in. 552 */ 553 nbytes = NBINTERNAL(0); 554 h->linp[0] = h->upper = t->bt_psize - nbytes; 555 dest = (char *)h + h->upper; 556 WR_BINTERNAL(dest, 0, l->pgno, 0); 557 558 switch (h->flags & P_TYPE) { 559 case P_BLEAF: 560 bl = GETBLEAF(r, 0); 561 nbytes = NBINTERNAL(bl->ksize); 562 h->linp[1] = h->upper -= nbytes; 563 dest = (char *)h + h->upper; 564 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0); 565 memmove(dest, bl->bytes, bl->ksize); 566 567 /* 568 * If the key is on an overflow page, mark the overflow chain 569 * so it isn't deleted when the leaf copy of the key is deleted. 570 */ 571 if (bl->flags & P_BIGKEY && 572 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 573 return (RET_ERROR); 574 break; 575 case P_BINTERNAL: 576 bi = GETBINTERNAL(r, 0); 577 nbytes = NBINTERNAL(bi->ksize); 578 h->linp[1] = h->upper -= nbytes; 579 dest = (char *)h + h->upper; 580 memmove(dest, bi, nbytes); 581 ((BINTERNAL *)dest)->pgno = r->pgno; 582 break; 583 default: 584 abort(); 585 } 586 587 /* There are two keys on the page. */ 588 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 589 590 /* Unpin the root page, set to btree internal page. */ 591 h->flags &= ~P_TYPE; 592 h->flags |= P_BINTERNAL; 593 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 594 595 return (RET_SUCCESS); 596 } 597 598 /* 599 * BT_PSPLIT -- Do the real work of splitting the page. 600 * 601 * Parameters: 602 * t: tree 603 * h: page to be split 604 * l: page to put lower half of data 605 * r: page to put upper half of data 606 * pskip: pointer to index to leave open 607 * ilen: insert length 608 * 609 * Returns: 610 * Pointer to page in which to insert. 611 */ 612 static PAGE * 613 bt_psplit(t, h, l, r, pskip, ilen) 614 BTREE *t; 615 PAGE *h, *l, *r; 616 indx_t *pskip; 617 size_t ilen; 618 { 619 BINTERNAL *bi; 620 BLEAF *bl; 621 CURSOR *c; 622 RLEAF *rl; 623 PAGE *rval; 624 void *src; 625 indx_t full, half, nxt, off, skip, top, used; 626 u_int32_t nbytes; 627 int bigkeycnt, isbigkey; 628 629 /* 630 * Split the data to the left and right pages. Leave the skip index 631 * open. Additionally, make some effort not to split on an overflow 632 * key. This makes internal page processing faster and can save 633 * space as overflow keys used by internal pages are never deleted. 634 */ 635 bigkeycnt = 0; 636 skip = *pskip; 637 full = t->bt_psize - BTDATAOFF; 638 half = full / 2; 639 used = 0; 640 for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) { 641 if (skip == off) { 642 nbytes = ilen; 643 isbigkey = 0; /* XXX: not really known. */ 644 } else 645 switch (h->flags & P_TYPE) { 646 case P_BINTERNAL: 647 src = bi = GETBINTERNAL(h, nxt); 648 nbytes = NBINTERNAL(bi->ksize); 649 isbigkey = bi->flags & P_BIGKEY; 650 break; 651 case P_BLEAF: 652 src = bl = GETBLEAF(h, nxt); 653 nbytes = NBLEAF(bl); 654 isbigkey = bl->flags & P_BIGKEY; 655 break; 656 case P_RINTERNAL: 657 src = GETRINTERNAL(h, nxt); 658 nbytes = NRINTERNAL; 659 isbigkey = 0; 660 break; 661 case P_RLEAF: 662 src = rl = GETRLEAF(h, nxt); 663 nbytes = NRLEAF(rl); 664 isbigkey = 0; 665 break; 666 default: 667 abort(); 668 } 669 670 /* 671 * If the key/data pairs are substantial fractions of the max 672 * possible size for the page, it's possible to get situations 673 * where we decide to try and copy too much onto the left page. 674 * Make sure that doesn't happen. 675 */ 676 if (skip <= off && 677 used + nbytes + sizeof(indx_t) >= full || nxt == top - 1) { 678 --off; 679 break; 680 } 681 682 /* Copy the key/data pair, if not the skipped index. */ 683 if (skip != off) { 684 ++nxt; 685 686 l->linp[off] = l->upper -= nbytes; 687 memmove((char *)l + l->upper, src, nbytes); 688 } 689 690 used += nbytes + sizeof(indx_t); 691 if (used >= half) { 692 if (!isbigkey || bigkeycnt == 3) 693 break; 694 else 695 ++bigkeycnt; 696 } 697 } 698 699 /* 700 * Off is the last offset that's valid for the left page. 701 * Nxt is the first offset to be placed on the right page. 702 */ 703 l->lower += (off + 1) * sizeof(indx_t); 704 705 /* 706 * If splitting the page that the cursor was on, the cursor has to be 707 * adjusted to point to the same record as before the split. If the 708 * cursor is at or past the skipped slot, the cursor is incremented by 709 * one. If the cursor is on the right page, it is decremented by the 710 * number of records split to the left page. 711 */ 712 c = &t->bt_cursor; 713 if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) { 714 if (c->pg.index >= skip) 715 ++c->pg.index; 716 if (c->pg.index < nxt) /* Left page. */ 717 c->pg.pgno = l->pgno; 718 else { /* Right page. */ 719 c->pg.pgno = r->pgno; 720 c->pg.index -= nxt; 721 } 722 } 723 724 /* 725 * If the skipped index was on the left page, just return that page. 726 * Otherwise, adjust the skip index to reflect the new position on 727 * the right page. 728 */ 729 if (skip <= off) { 730 skip = 0; 731 rval = l; 732 } else { 733 rval = r; 734 *pskip -= nxt; 735 } 736 737 for (off = 0; nxt < top; ++off) { 738 if (skip == nxt) { 739 ++off; 740 skip = 0; 741 } 742 switch (h->flags & P_TYPE) { 743 case P_BINTERNAL: 744 src = bi = GETBINTERNAL(h, nxt); 745 nbytes = NBINTERNAL(bi->ksize); 746 break; 747 case P_BLEAF: 748 src = bl = GETBLEAF(h, nxt); 749 nbytes = NBLEAF(bl); 750 break; 751 case P_RINTERNAL: 752 src = GETRINTERNAL(h, nxt); 753 nbytes = NRINTERNAL; 754 break; 755 case P_RLEAF: 756 src = rl = GETRLEAF(h, nxt); 757 nbytes = NRLEAF(rl); 758 break; 759 default: 760 abort(); 761 } 762 ++nxt; 763 r->linp[off] = r->upper -= nbytes; 764 memmove((char *)r + r->upper, src, nbytes); 765 } 766 r->lower += off * sizeof(indx_t); 767 768 /* If the key is being appended to the page, adjust the index. */ 769 if (skip == top) 770 r->lower += sizeof(indx_t); 771 772 return (rval); 773 } 774 775 /* 776 * BT_PRESERVE -- Mark a chain of pages as used by an internal node. 777 * 778 * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the 779 * record that references them gets deleted. Chains pointed to by internal 780 * pages never get deleted. This routine marks a chain as pointed to by an 781 * internal page. 782 * 783 * Parameters: 784 * t: tree 785 * pg: page number of first page in the chain. 786 * 787 * Returns: 788 * RET_SUCCESS, RET_ERROR. 789 */ 790 static int 791 bt_preserve(t, pg) 792 BTREE *t; 793 pgno_t pg; 794 { 795 PAGE *h; 796 797 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 798 return (RET_ERROR); 799 h->flags |= P_PRESERVE; 800 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 801 return (RET_SUCCESS); 802 } 803 804 /* 805 * REC_TOTAL -- Return the number of recno entries below a page. 806 * 807 * Parameters: 808 * h: page 809 * 810 * Returns: 811 * The number of recno entries below a page. 812 * 813 * XXX 814 * These values could be set by the bt_psplit routine. The problem is that the 815 * entry has to be popped off of the stack etc. or the values have to be passed 816 * all the way back to bt_split/bt_rroot and it's not very clean. 817 */ 818 static recno_t 819 rec_total(h) 820 PAGE *h; 821 { 822 recno_t recs; 823 indx_t nxt, top; 824 825 for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt) 826 recs += GETRINTERNAL(h, nxt)->nrecs; 827 return (recs); 828 } 829