1 /* $OpenBSD: bt_split.c,v 1.13 2005/08/05 13:03:00 espie 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 #include <sys/types.h> 36 37 #include <limits.h> 38 #include <stdio.h> 39 #include <stdlib.h> 40 #include <string.h> 41 42 #include <db.h> 43 #include "btree.h" 44 45 static int bt_broot(BTREE *, PAGE *, PAGE *, PAGE *); 46 static PAGE *bt_page(BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t); 47 static int bt_preserve(BTREE *, pgno_t); 48 static PAGE *bt_psplit(BTREE *, PAGE *, PAGE *, PAGE *, indx_t *, size_t); 49 static PAGE *bt_root(BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t); 50 static int bt_rroot(BTREE *, PAGE *, PAGE *, PAGE *); 51 static recno_t rec_total(PAGE *); 52 53 #ifdef STATISTICS 54 u_long bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved; 55 #endif 56 57 /* 58 * __BT_SPLIT -- Split the tree. 59 * 60 * Parameters: 61 * t: tree 62 * sp: page to split 63 * key: key to insert 64 * data: data to insert 65 * flags: BIGKEY/BIGDATA flags 66 * ilen: insert length 67 * skip: index to leave open 68 * 69 * Returns: 70 * RET_ERROR, RET_SUCCESS 71 */ 72 int 73 __bt_split(BTREE *t, PAGE *sp, const DBT *key, const DBT *data, int flags, 74 size_t ilen, u_int32_t argskip) 75 { 76 BINTERNAL *bi; 77 BLEAF *bl, *tbl; 78 DBT a, b; 79 EPGNO *parent; 80 PAGE *h, *l, *r, *lchild, *rchild; 81 indx_t nxtindex; 82 u_int16_t skip; 83 u_int32_t n, nbytes, nksize; 84 int parentsplit; 85 char *dest; 86 87 /* 88 * Split the page into two pages, l and r. The split routines return 89 * a pointer to the page into which the key should be inserted and with 90 * skip set to the offset which should be used. Additionally, l and r 91 * are pinned. 92 */ 93 skip = argskip; 94 h = sp->pgno == P_ROOT ? 95 bt_root(t, sp, &l, &r, &skip, ilen) : 96 bt_page(t, sp, &l, &r, &skip, ilen); 97 if (h == NULL) 98 return (RET_ERROR); 99 100 /* 101 * Insert the new key/data pair into the leaf page. (Key inserts 102 * always cause a leaf page to split first.) 103 */ 104 h->linp[skip] = h->upper -= ilen; 105 dest = (char *)h + h->upper; 106 if (F_ISSET(t, R_RECNO)) 107 WR_RLEAF(dest, data, flags) 108 else 109 WR_BLEAF(dest, key, data, flags) 110 111 /* If the root page was split, make it look right. */ 112 if (sp->pgno == P_ROOT && 113 (F_ISSET(t, R_RECNO) ? 114 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 115 goto err2; 116 117 /* 118 * Now we walk the parent page stack -- a LIFO stack of the pages that 119 * were traversed when we searched for the page that split. Each stack 120 * entry is a page number and a page index offset. The offset is for 121 * the page traversed on the search. We've just split a page, so we 122 * have to insert a new key into the parent page. 123 * 124 * If the insert into the parent page causes it to split, may have to 125 * continue splitting all the way up the tree. We stop if the root 126 * splits or the page inserted into didn't have to split to hold the 127 * new key. Some algorithms replace the key for the old page as well 128 * as the new page. We don't, as there's no reason to believe that the 129 * first key on the old page is any better than the key we have, and, 130 * in the case of a key being placed at index 0 causing the split, the 131 * key is unavailable. 132 * 133 * There are a maximum of 5 pages pinned at any time. We keep the left 134 * and right pages pinned while working on the parent. The 5 are the 135 * two children, left parent and right parent (when the parent splits) 136 * and the root page or the overflow key page when calling bt_preserve. 137 * This code must make sure that all pins are released other than the 138 * root page or overflow page which is unlocked elsewhere. 139 */ 140 while ((parent = BT_POP(t)) != NULL) { 141 lchild = l; 142 rchild = r; 143 144 /* Get the parent page. */ 145 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) 146 goto err2; 147 148 /* 149 * The new key goes ONE AFTER the index, because the split 150 * was to the right. 151 */ 152 skip = parent->index + 1; 153 154 /* 155 * Calculate the space needed on the parent page. 156 * 157 * Prefix trees: space hack when inserting into BINTERNAL 158 * pages. Retain only what's needed to distinguish between 159 * the new entry and the LAST entry on the page to its left. 160 * If the keys compare equal, retain the entire key. Note, 161 * we don't touch overflow keys, and the entire key must be 162 * retained for the next-to-left most key on the leftmost 163 * page of each level, or the search will fail. Applicable 164 * ONLY to internal pages that have leaf pages as children. 165 * Further reduction of the key between pairs of internal 166 * pages loses too much information. 167 */ 168 switch (rchild->flags & P_TYPE) { 169 case P_BINTERNAL: 170 bi = GETBINTERNAL(rchild, 0); 171 nbytes = NBINTERNAL(bi->ksize); 172 break; 173 case P_BLEAF: 174 bl = GETBLEAF(rchild, 0); 175 nbytes = NBINTERNAL(bl->ksize); 176 if (t->bt_pfx && !(bl->flags & P_BIGKEY) && 177 (h->prevpg != P_INVALID || skip > 1)) { 178 tbl = GETBLEAF(lchild, NEXTINDEX(lchild) - 1); 179 a.size = tbl->ksize; 180 a.data = tbl->bytes; 181 b.size = bl->ksize; 182 b.data = bl->bytes; 183 nksize = t->bt_pfx(&a, &b); 184 n = NBINTERNAL(nksize); 185 if (n < nbytes) { 186 #ifdef STATISTICS 187 bt_pfxsaved += nbytes - n; 188 #endif 189 nbytes = n; 190 } else 191 nksize = 0; 192 } else 193 nksize = 0; 194 break; 195 case P_RINTERNAL: 196 case P_RLEAF: 197 nbytes = NRINTERNAL; 198 break; 199 default: 200 abort(); 201 } 202 203 /* Split the parent page if necessary or shift the indices. */ 204 if (h->upper - h->lower < nbytes + sizeof(indx_t)) { 205 sp = h; 206 h = h->pgno == P_ROOT ? 207 bt_root(t, h, &l, &r, &skip, nbytes) : 208 bt_page(t, h, &l, &r, &skip, nbytes); 209 if (h == NULL) 210 goto err1; 211 parentsplit = 1; 212 } else { 213 if (skip < (nxtindex = NEXTINDEX(h))) 214 memmove(h->linp + skip + 1, h->linp + skip, 215 (nxtindex - skip) * sizeof(indx_t)); 216 h->lower += sizeof(indx_t); 217 parentsplit = 0; 218 } 219 220 /* Insert the key into the parent page. */ 221 switch (rchild->flags & P_TYPE) { 222 case P_BINTERNAL: 223 h->linp[skip] = h->upper -= nbytes; 224 dest = (char *)h + h->linp[skip]; 225 memmove(dest, bi, nbytes); 226 ((BINTERNAL *)dest)->pgno = rchild->pgno; 227 break; 228 case P_BLEAF: 229 h->linp[skip] = h->upper -= nbytes; 230 dest = (char *)h + h->linp[skip]; 231 WR_BINTERNAL(dest, nksize ? nksize : bl->ksize, 232 rchild->pgno, bl->flags & P_BIGKEY); 233 memmove(dest, bl->bytes, nksize ? nksize : bl->ksize); 234 if (bl->flags & P_BIGKEY && 235 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 236 goto err1; 237 break; 238 case P_RINTERNAL: 239 /* 240 * Update the left page count. If split 241 * added at index 0, fix the correct page. 242 */ 243 if (skip > 0) 244 dest = (char *)h + h->linp[skip - 1]; 245 else 246 dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; 247 ((RINTERNAL *)dest)->nrecs = rec_total(lchild); 248 ((RINTERNAL *)dest)->pgno = lchild->pgno; 249 250 /* Update the right page count. */ 251 h->linp[skip] = h->upper -= nbytes; 252 dest = (char *)h + h->linp[skip]; 253 ((RINTERNAL *)dest)->nrecs = rec_total(rchild); 254 ((RINTERNAL *)dest)->pgno = rchild->pgno; 255 break; 256 case P_RLEAF: 257 /* 258 * Update the left page count. If split 259 * added at index 0, fix the correct page. 260 */ 261 if (skip > 0) 262 dest = (char *)h + h->linp[skip - 1]; 263 else 264 dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; 265 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(lchild); 266 ((RINTERNAL *)dest)->pgno = lchild->pgno; 267 268 /* Update the right page count. */ 269 h->linp[skip] = h->upper -= nbytes; 270 dest = (char *)h + h->linp[skip]; 271 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(rchild); 272 ((RINTERNAL *)dest)->pgno = rchild->pgno; 273 break; 274 default: 275 abort(); 276 } 277 278 /* Unpin the held pages. */ 279 if (!parentsplit) { 280 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 281 break; 282 } 283 284 /* If the root page was split, make it look right. */ 285 if (sp->pgno == P_ROOT && 286 (F_ISSET(t, R_RECNO) ? 287 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 288 goto err1; 289 290 mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 291 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 292 } 293 294 /* Unpin the held pages. */ 295 mpool_put(t->bt_mp, l, MPOOL_DIRTY); 296 mpool_put(t->bt_mp, r, MPOOL_DIRTY); 297 298 /* Clear any pages left on the stack. */ 299 return (RET_SUCCESS); 300 301 /* 302 * If something fails in the above loop we were already walking back 303 * up the tree and the tree is now inconsistent. Nothing much we can 304 * do about it but release any memory we're holding. 305 */ 306 err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 307 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 308 309 err2: mpool_put(t->bt_mp, l, 0); 310 mpool_put(t->bt_mp, r, 0); 311 __dbpanic(t->bt_dbp); 312 return (RET_ERROR); 313 } 314 315 /* 316 * BT_PAGE -- Split a non-root page of a btree. 317 * 318 * Parameters: 319 * t: tree 320 * h: root page 321 * lp: pointer to left page pointer 322 * rp: pointer to right page pointer 323 * skip: pointer to index to leave open 324 * ilen: insert length 325 * 326 * Returns: 327 * Pointer to page in which to insert or NULL on error. 328 */ 329 static PAGE * 330 bt_page(BTREE *t, PAGE *h, PAGE **lp, PAGE **rp, indx_t *skip, size_t ilen) 331 { 332 PAGE *l, *r, *tp; 333 pgno_t npg; 334 335 #ifdef STATISTICS 336 ++bt_split; 337 #endif 338 /* Put the new right page for the split into place. */ 339 if ((r = __bt_new(t, &npg)) == NULL) 340 return (NULL); 341 r->pgno = npg; 342 r->lower = BTDATAOFF; 343 r->upper = t->bt_psize; 344 r->nextpg = h->nextpg; 345 r->prevpg = h->pgno; 346 r->flags = h->flags & P_TYPE; 347 348 /* 349 * If we're splitting the last page on a level because we're appending 350 * a key to it (skip is NEXTINDEX()), it's likely that the data is 351 * sorted. Adding an empty page on the side of the level is less work 352 * and can push the fill factor much higher than normal. If we're 353 * wrong it's no big deal, we'll just do the split the right way next 354 * time. It may look like it's equally easy to do a similar hack for 355 * reverse sorted data, that is, split the tree left, but it's not. 356 * Don't even try. 357 */ 358 if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) { 359 #ifdef STATISTICS 360 ++bt_sortsplit; 361 #endif 362 h->nextpg = r->pgno; 363 r->lower = BTDATAOFF + sizeof(indx_t); 364 *skip = 0; 365 *lp = h; 366 *rp = r; 367 return (r); 368 } 369 370 /* Put the new left page for the split into place. */ 371 if ((l = (PAGE *)malloc(t->bt_psize)) == NULL) { 372 mpool_put(t->bt_mp, r, 0); 373 return (NULL); 374 } 375 memset(l, 0xff, t->bt_psize); 376 l->pgno = h->pgno; 377 l->nextpg = r->pgno; 378 l->prevpg = h->prevpg; 379 l->lower = BTDATAOFF; 380 l->upper = t->bt_psize; 381 l->flags = h->flags & P_TYPE; 382 383 /* Fix up the previous pointer of the page after the split page. */ 384 if (h->nextpg != P_INVALID) { 385 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) { 386 free(l); 387 /* XXX mpool_free(t->bt_mp, r->pgno); */ 388 return (NULL); 389 } 390 tp->prevpg = r->pgno; 391 mpool_put(t->bt_mp, tp, MPOOL_DIRTY); 392 } 393 394 /* 395 * Split right. The key/data pairs aren't sorted in the btree page so 396 * it's simpler to copy the data from the split page onto two new pages 397 * instead of copying half the data to the right page and compacting 398 * the left page in place. Since the left page can't change, we have 399 * to swap the original and the allocated left page after the split. 400 */ 401 tp = bt_psplit(t, h, l, r, skip, ilen); 402 403 /* Move the new left page onto the old left page. */ 404 memmove(h, l, t->bt_psize); 405 if (tp == l) 406 tp = h; 407 free(l); 408 409 *lp = h; 410 *rp = r; 411 return (tp); 412 } 413 414 /* 415 * BT_ROOT -- Split the root page of a btree. 416 * 417 * Parameters: 418 * t: tree 419 * h: root page 420 * lp: pointer to left page pointer 421 * rp: pointer to right page pointer 422 * skip: pointer to index to leave open 423 * ilen: insert length 424 * 425 * Returns: 426 * Pointer to page in which to insert or NULL on error. 427 */ 428 static PAGE * 429 bt_root(BTREE *t, PAGE *h, PAGE **lp, PAGE **rp, indx_t *skip, size_t ilen) 430 { 431 PAGE *l, *r, *tp; 432 pgno_t lnpg, rnpg; 433 434 #ifdef STATISTICS 435 ++bt_split; 436 ++bt_rootsplit; 437 #endif 438 /* Put the new left and right pages for the split into place. */ 439 if ((l = __bt_new(t, &lnpg)) == NULL || 440 (r = __bt_new(t, &rnpg)) == NULL) 441 return (NULL); 442 l->pgno = lnpg; 443 r->pgno = rnpg; 444 l->nextpg = r->pgno; 445 r->prevpg = l->pgno; 446 l->prevpg = r->nextpg = P_INVALID; 447 l->lower = r->lower = BTDATAOFF; 448 l->upper = r->upper = t->bt_psize; 449 l->flags = r->flags = h->flags & P_TYPE; 450 451 /* Split the root page. */ 452 tp = bt_psplit(t, h, l, r, skip, ilen); 453 454 *lp = l; 455 *rp = r; 456 return (tp); 457 } 458 459 /* 460 * BT_RROOT -- Fix up the recno root page after it has been split. 461 * 462 * Parameters: 463 * t: tree 464 * h: root page 465 * l: left page 466 * r: right page 467 * 468 * Returns: 469 * RET_ERROR, RET_SUCCESS 470 */ 471 static int 472 bt_rroot(BTREE *t, PAGE *h, PAGE *l, PAGE *r) 473 { 474 char *dest; 475 476 /* Insert the left and right keys, set the header information. */ 477 h->linp[0] = h->upper = t->bt_psize - NRINTERNAL; 478 dest = (char *)h + h->upper; 479 WR_RINTERNAL(dest, 480 l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno); 481 482 h->linp[1] = h->upper -= NRINTERNAL; 483 dest = (char *)h + h->upper; 484 WR_RINTERNAL(dest, 485 r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno); 486 487 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 488 489 /* Unpin the root page, set to recno internal page. */ 490 h->flags &= ~P_TYPE; 491 h->flags |= P_RINTERNAL; 492 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 493 494 return (RET_SUCCESS); 495 } 496 497 /* 498 * BT_BROOT -- Fix up the btree root page after it has been split. 499 * 500 * Parameters: 501 * t: tree 502 * h: root page 503 * l: left page 504 * r: right page 505 * 506 * Returns: 507 * RET_ERROR, RET_SUCCESS 508 */ 509 static int 510 bt_broot(BTREE *t, PAGE *h, PAGE *l, PAGE *r) 511 { 512 BINTERNAL *bi; 513 BLEAF *bl; 514 u_int32_t nbytes; 515 char *dest; 516 517 /* 518 * If the root page was a leaf page, change it into an internal page. 519 * We copy the key we split on (but not the key's data, in the case of 520 * a leaf page) to the new root page. 521 * 522 * The btree comparison code guarantees that the left-most key on any 523 * level of the tree is never used, so it doesn't need to be filled in. 524 */ 525 nbytes = NBINTERNAL(0); 526 h->linp[0] = h->upper = t->bt_psize - nbytes; 527 dest = (char *)h + h->upper; 528 WR_BINTERNAL(dest, 0, l->pgno, 0); 529 530 switch (h->flags & P_TYPE) { 531 case P_BLEAF: 532 bl = GETBLEAF(r, 0); 533 nbytes = NBINTERNAL(bl->ksize); 534 h->linp[1] = h->upper -= nbytes; 535 dest = (char *)h + h->upper; 536 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0); 537 memmove(dest, bl->bytes, bl->ksize); 538 539 /* 540 * If the key is on an overflow page, mark the overflow chain 541 * so it isn't deleted when the leaf copy of the key is deleted. 542 */ 543 if (bl->flags & P_BIGKEY && 544 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 545 return (RET_ERROR); 546 break; 547 case P_BINTERNAL: 548 bi = GETBINTERNAL(r, 0); 549 nbytes = NBINTERNAL(bi->ksize); 550 h->linp[1] = h->upper -= nbytes; 551 dest = (char *)h + h->upper; 552 memmove(dest, bi, nbytes); 553 ((BINTERNAL *)dest)->pgno = r->pgno; 554 break; 555 default: 556 abort(); 557 } 558 559 /* There are two keys on the page. */ 560 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 561 562 /* Unpin the root page, set to btree internal page. */ 563 h->flags &= ~P_TYPE; 564 h->flags |= P_BINTERNAL; 565 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 566 567 return (RET_SUCCESS); 568 } 569 570 /* 571 * BT_PSPLIT -- Do the real work of splitting the page. 572 * 573 * Parameters: 574 * t: tree 575 * h: page to be split 576 * l: page to put lower half of data 577 * r: page to put upper half of data 578 * pskip: pointer to index to leave open 579 * ilen: insert length 580 * 581 * Returns: 582 * Pointer to page in which to insert. 583 */ 584 static PAGE * 585 bt_psplit(BTREE *t, PAGE *h, PAGE *l, PAGE *r, indx_t *pskip, size_t ilen) 586 { 587 BINTERNAL *bi; 588 BLEAF *bl; 589 CURSOR *c; 590 RLEAF *rl; 591 PAGE *rval; 592 void *src; 593 indx_t full, half, nxt, off, skip, top, used; 594 u_int32_t nbytes; 595 int bigkeycnt, isbigkey; 596 597 /* 598 * Split the data to the left and right pages. Leave the skip index 599 * open. Additionally, make some effort not to split on an overflow 600 * key. This makes internal page processing faster and can save 601 * space as overflow keys used by internal pages are never deleted. 602 */ 603 bigkeycnt = 0; 604 skip = *pskip; 605 full = t->bt_psize - BTDATAOFF; 606 half = full / 2; 607 used = 0; 608 for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) { 609 if (skip == off) { 610 nbytes = ilen; 611 isbigkey = 0; /* XXX: not really known. */ 612 } else 613 switch (h->flags & P_TYPE) { 614 case P_BINTERNAL: 615 src = bi = GETBINTERNAL(h, nxt); 616 nbytes = NBINTERNAL(bi->ksize); 617 isbigkey = bi->flags & P_BIGKEY; 618 break; 619 case P_BLEAF: 620 src = bl = GETBLEAF(h, nxt); 621 nbytes = NBLEAF(bl); 622 isbigkey = bl->flags & P_BIGKEY; 623 break; 624 case P_RINTERNAL: 625 src = GETRINTERNAL(h, nxt); 626 nbytes = NRINTERNAL; 627 isbigkey = 0; 628 break; 629 case P_RLEAF: 630 src = rl = GETRLEAF(h, nxt); 631 nbytes = NRLEAF(rl); 632 isbigkey = 0; 633 break; 634 default: 635 abort(); 636 } 637 638 /* 639 * If the key/data pairs are substantial fractions of the max 640 * possible size for the page, it's possible to get situations 641 * where we decide to try and copy too much onto the left page. 642 * Make sure that doesn't happen. 643 */ 644 if ((skip <= off && used + nbytes + sizeof(indx_t) >= full) || 645 nxt == top - 1) { 646 --off; 647 break; 648 } 649 650 /* Copy the key/data pair, if not the skipped index. */ 651 if (skip != off) { 652 ++nxt; 653 654 l->linp[off] = l->upper -= nbytes; 655 memmove((char *)l + l->upper, src, nbytes); 656 } 657 658 used += nbytes + sizeof(indx_t); 659 if (used >= half) { 660 if (!isbigkey || bigkeycnt == 3) 661 break; 662 else 663 ++bigkeycnt; 664 } 665 } 666 667 /* 668 * Off is the last offset that's valid for the left page. 669 * Nxt is the first offset to be placed on the right page. 670 */ 671 l->lower += (off + 1) * sizeof(indx_t); 672 673 /* 674 * If splitting the page that the cursor was on, the cursor has to be 675 * adjusted to point to the same record as before the split. If the 676 * cursor is at or past the skipped slot, the cursor is incremented by 677 * one. If the cursor is on the right page, it is decremented by the 678 * number of records split to the left page. 679 */ 680 c = &t->bt_cursor; 681 if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) { 682 if (c->pg.index >= skip) 683 ++c->pg.index; 684 if (c->pg.index < nxt) /* Left page. */ 685 c->pg.pgno = l->pgno; 686 else { /* Right page. */ 687 c->pg.pgno = r->pgno; 688 c->pg.index -= nxt; 689 } 690 } 691 692 /* 693 * If the skipped index was on the left page, just return that page. 694 * Otherwise, adjust the skip index to reflect the new position on 695 * the right page. 696 */ 697 if (skip <= off) { 698 skip = MAX_PAGE_OFFSET; 699 rval = l; 700 } else { 701 rval = r; 702 *pskip -= nxt; 703 } 704 705 for (off = 0; nxt < top; ++off) { 706 if (skip == nxt) { 707 ++off; 708 skip = MAX_PAGE_OFFSET; 709 } 710 switch (h->flags & P_TYPE) { 711 case P_BINTERNAL: 712 src = bi = GETBINTERNAL(h, nxt); 713 nbytes = NBINTERNAL(bi->ksize); 714 break; 715 case P_BLEAF: 716 src = bl = GETBLEAF(h, nxt); 717 nbytes = NBLEAF(bl); 718 break; 719 case P_RINTERNAL: 720 src = GETRINTERNAL(h, nxt); 721 nbytes = NRINTERNAL; 722 break; 723 case P_RLEAF: 724 src = rl = GETRLEAF(h, nxt); 725 nbytes = NRLEAF(rl); 726 break; 727 default: 728 abort(); 729 } 730 ++nxt; 731 r->linp[off] = r->upper -= nbytes; 732 memmove((char *)r + r->upper, src, nbytes); 733 } 734 r->lower += off * sizeof(indx_t); 735 736 /* If the key is being appended to the page, adjust the index. */ 737 if (skip == top) 738 r->lower += sizeof(indx_t); 739 740 return (rval); 741 } 742 743 /* 744 * BT_PRESERVE -- Mark a chain of pages as used by an internal node. 745 * 746 * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the 747 * record that references them gets deleted. Chains pointed to by internal 748 * pages never get deleted. This routine marks a chain as pointed to by an 749 * internal page. 750 * 751 * Parameters: 752 * t: tree 753 * pg: page number of first page in the chain. 754 * 755 * Returns: 756 * RET_SUCCESS, RET_ERROR. 757 */ 758 static int 759 bt_preserve(BTREE *t, pgno_t pg) 760 { 761 PAGE *h; 762 763 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 764 return (RET_ERROR); 765 h->flags |= P_PRESERVE; 766 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 767 return (RET_SUCCESS); 768 } 769 770 /* 771 * REC_TOTAL -- Return the number of recno entries below a page. 772 * 773 * Parameters: 774 * h: page 775 * 776 * Returns: 777 * The number of recno entries below a page. 778 * 779 * XXX 780 * These values could be set by the bt_psplit routine. The problem is that the 781 * entry has to be popped off of the stack etc. or the values have to be passed 782 * all the way back to bt_split/bt_rroot and it's not very clean. 783 */ 784 static recno_t 785 rec_total(PAGE *h) 786 { 787 recno_t recs; 788 indx_t nxt, top; 789 790 for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt) 791 recs += GETRINTERNAL(h, nxt)->nrecs; 792 return (recs); 793 } 794