1 /* $OpenBSD: bt_split.c,v 1.10 2003/05/01 20:23:40 avsm 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. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #if defined(LIBC_SCCS) && !defined(lint) 40 #if 0 41 static char sccsid[] = "@(#)bt_split.c 8.10 (Berkeley) 1/9/95"; 42 #else 43 static const char rcsid[] = "$OpenBSD: bt_split.c,v 1.10 2003/05/01 20:23:40 avsm Exp $"; 44 #endif 45 #endif /* LIBC_SCCS and not lint */ 46 47 #include <sys/types.h> 48 49 #include <limits.h> 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include <string.h> 53 54 #include <db.h> 55 #include "btree.h" 56 57 static int bt_broot(BTREE *, PAGE *, PAGE *, PAGE *); 58 static PAGE *bt_page(BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t); 59 static int bt_preserve(BTREE *, pgno_t); 60 static PAGE *bt_psplit(BTREE *, PAGE *, PAGE *, PAGE *, indx_t *, size_t); 61 static PAGE *bt_root(BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t); 62 static int bt_rroot(BTREE *, PAGE *, PAGE *, PAGE *); 63 static recno_t rec_total(PAGE *); 64 65 #ifdef STATISTICS 66 u_long bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved; 67 #endif 68 69 /* 70 * __BT_SPLIT -- Split the tree. 71 * 72 * Parameters: 73 * t: tree 74 * sp: page to split 75 * key: key to insert 76 * data: data to insert 77 * flags: BIGKEY/BIGDATA flags 78 * ilen: insert length 79 * skip: index to leave open 80 * 81 * Returns: 82 * RET_ERROR, RET_SUCCESS 83 */ 84 int 85 __bt_split(t, sp, key, data, flags, ilen, argskip) 86 BTREE *t; 87 PAGE *sp; 88 const DBT *key, *data; 89 int flags; 90 size_t ilen; 91 u_int32_t argskip; 92 { 93 BINTERNAL *bi; 94 BLEAF *bl, *tbl; 95 DBT a, b; 96 EPGNO *parent; 97 PAGE *h, *l, *r, *lchild, *rchild; 98 indx_t nxtindex; 99 u_int16_t skip; 100 u_int32_t n, nbytes, nksize; 101 int parentsplit; 102 char *dest; 103 104 /* 105 * Split the page into two pages, l and r. The split routines return 106 * a pointer to the page into which the key should be inserted and with 107 * skip set to the offset which should be used. Additionally, l and r 108 * are pinned. 109 */ 110 skip = argskip; 111 h = sp->pgno == P_ROOT ? 112 bt_root(t, sp, &l, &r, &skip, ilen) : 113 bt_page(t, sp, &l, &r, &skip, ilen); 114 if (h == NULL) 115 return (RET_ERROR); 116 117 /* 118 * Insert the new key/data pair into the leaf page. (Key inserts 119 * always cause a leaf page to split first.) 120 */ 121 h->linp[skip] = h->upper -= ilen; 122 dest = (char *)h + h->upper; 123 if (F_ISSET(t, R_RECNO)) 124 WR_RLEAF(dest, data, flags) 125 else 126 WR_BLEAF(dest, key, data, flags) 127 128 /* If the root page was split, make it look right. */ 129 if (sp->pgno == P_ROOT && 130 (F_ISSET(t, R_RECNO) ? 131 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 132 goto err2; 133 134 /* 135 * Now we walk the parent page stack -- a LIFO stack of the pages that 136 * were traversed when we searched for the page that split. Each stack 137 * entry is a page number and a page index offset. The offset is for 138 * the page traversed on the search. We've just split a page, so we 139 * have to insert a new key into the parent page. 140 * 141 * If the insert into the parent page causes it to split, may have to 142 * continue splitting all the way up the tree. We stop if the root 143 * splits or the page inserted into didn't have to split to hold the 144 * new key. Some algorithms replace the key for the old page as well 145 * as the new page. We don't, as there's no reason to believe that the 146 * first key on the old page is any better than the key we have, and, 147 * in the case of a key being placed at index 0 causing the split, the 148 * key is unavailable. 149 * 150 * There are a maximum of 5 pages pinned at any time. We keep the left 151 * and right pages pinned while working on the parent. The 5 are the 152 * two children, left parent and right parent (when the parent splits) 153 * and the root page or the overflow key page when calling bt_preserve. 154 * This code must make sure that all pins are released other than the 155 * root page or overflow page which is unlocked elsewhere. 156 */ 157 while ((parent = BT_POP(t)) != NULL) { 158 lchild = l; 159 rchild = r; 160 161 /* Get the parent page. */ 162 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) 163 goto err2; 164 165 /* 166 * The new key goes ONE AFTER the index, because the split 167 * was to the right. 168 */ 169 skip = parent->index + 1; 170 171 /* 172 * Calculate the space needed on the parent page. 173 * 174 * Prefix trees: space hack when inserting into BINTERNAL 175 * pages. Retain only what's needed to distinguish between 176 * the new entry and the LAST entry on the page to its left. 177 * If the keys compare equal, retain the entire key. Note, 178 * we don't touch overflow keys, and the entire key must be 179 * retained for the next-to-left most key on the leftmost 180 * page of each level, or the search will fail. Applicable 181 * ONLY to internal pages that have leaf pages as children. 182 * Further reduction of the key between pairs of internal 183 * pages loses too much information. 184 */ 185 switch (rchild->flags & P_TYPE) { 186 case P_BINTERNAL: 187 bi = GETBINTERNAL(rchild, 0); 188 nbytes = NBINTERNAL(bi->ksize); 189 break; 190 case P_BLEAF: 191 bl = GETBLEAF(rchild, 0); 192 nbytes = NBINTERNAL(bl->ksize); 193 if (t->bt_pfx && !(bl->flags & P_BIGKEY) && 194 (h->prevpg != P_INVALID || skip > 1)) { 195 tbl = GETBLEAF(lchild, NEXTINDEX(lchild) - 1); 196 a.size = tbl->ksize; 197 a.data = tbl->bytes; 198 b.size = bl->ksize; 199 b.data = bl->bytes; 200 nksize = t->bt_pfx(&a, &b); 201 n = NBINTERNAL(nksize); 202 if (n < nbytes) { 203 #ifdef STATISTICS 204 bt_pfxsaved += nbytes - n; 205 #endif 206 nbytes = n; 207 } else 208 nksize = 0; 209 } else 210 nksize = 0; 211 break; 212 case P_RINTERNAL: 213 case P_RLEAF: 214 nbytes = NRINTERNAL; 215 break; 216 default: 217 abort(); 218 } 219 220 /* Split the parent page if necessary or shift the indices. */ 221 if (h->upper - h->lower < nbytes + sizeof(indx_t)) { 222 sp = h; 223 h = h->pgno == P_ROOT ? 224 bt_root(t, h, &l, &r, &skip, nbytes) : 225 bt_page(t, h, &l, &r, &skip, nbytes); 226 if (h == NULL) 227 goto err1; 228 parentsplit = 1; 229 } else { 230 if (skip < (nxtindex = NEXTINDEX(h))) 231 memmove(h->linp + skip + 1, h->linp + skip, 232 (nxtindex - skip) * sizeof(indx_t)); 233 h->lower += sizeof(indx_t); 234 parentsplit = 0; 235 } 236 237 /* Insert the key into the parent page. */ 238 switch (rchild->flags & P_TYPE) { 239 case P_BINTERNAL: 240 h->linp[skip] = h->upper -= nbytes; 241 dest = (char *)h + h->linp[skip]; 242 memmove(dest, bi, nbytes); 243 ((BINTERNAL *)dest)->pgno = rchild->pgno; 244 break; 245 case P_BLEAF: 246 h->linp[skip] = h->upper -= nbytes; 247 dest = (char *)h + h->linp[skip]; 248 WR_BINTERNAL(dest, nksize ? nksize : bl->ksize, 249 rchild->pgno, bl->flags & P_BIGKEY); 250 memmove(dest, bl->bytes, nksize ? nksize : bl->ksize); 251 if (bl->flags & P_BIGKEY && 252 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 253 goto err1; 254 break; 255 case P_RINTERNAL: 256 /* 257 * Update the left page count. If split 258 * added at index 0, fix the correct page. 259 */ 260 if (skip > 0) 261 dest = (char *)h + h->linp[skip - 1]; 262 else 263 dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; 264 ((RINTERNAL *)dest)->nrecs = rec_total(lchild); 265 ((RINTERNAL *)dest)->pgno = lchild->pgno; 266 267 /* Update the right page count. */ 268 h->linp[skip] = h->upper -= nbytes; 269 dest = (char *)h + h->linp[skip]; 270 ((RINTERNAL *)dest)->nrecs = rec_total(rchild); 271 ((RINTERNAL *)dest)->pgno = rchild->pgno; 272 break; 273 case P_RLEAF: 274 /* 275 * Update the left page count. If split 276 * added at index 0, fix the correct page. 277 */ 278 if (skip > 0) 279 dest = (char *)h + h->linp[skip - 1]; 280 else 281 dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; 282 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(lchild); 283 ((RINTERNAL *)dest)->pgno = lchild->pgno; 284 285 /* Update the right page count. */ 286 h->linp[skip] = h->upper -= nbytes; 287 dest = (char *)h + h->linp[skip]; 288 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(rchild); 289 ((RINTERNAL *)dest)->pgno = rchild->pgno; 290 break; 291 default: 292 abort(); 293 } 294 295 /* Unpin the held pages. */ 296 if (!parentsplit) { 297 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 298 break; 299 } 300 301 /* If the root page was split, make it look right. */ 302 if (sp->pgno == P_ROOT && 303 (F_ISSET(t, R_RECNO) ? 304 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 305 goto err1; 306 307 mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 308 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 309 } 310 311 /* Unpin the held pages. */ 312 mpool_put(t->bt_mp, l, MPOOL_DIRTY); 313 mpool_put(t->bt_mp, r, MPOOL_DIRTY); 314 315 /* Clear any pages left on the stack. */ 316 return (RET_SUCCESS); 317 318 /* 319 * If something fails in the above loop we were already walking back 320 * up the tree and the tree is now inconsistent. Nothing much we can 321 * do about it but release any memory we're holding. 322 */ 323 err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 324 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 325 326 err2: mpool_put(t->bt_mp, l, 0); 327 mpool_put(t->bt_mp, r, 0); 328 __dbpanic(t->bt_dbp); 329 return (RET_ERROR); 330 } 331 332 /* 333 * BT_PAGE -- Split a non-root page of a btree. 334 * 335 * Parameters: 336 * t: tree 337 * h: root page 338 * lp: pointer to left page pointer 339 * rp: pointer to right page pointer 340 * skip: pointer to index to leave open 341 * ilen: insert length 342 * 343 * Returns: 344 * Pointer to page in which to insert or NULL on error. 345 */ 346 static PAGE * 347 bt_page(t, h, lp, rp, skip, ilen) 348 BTREE *t; 349 PAGE *h, **lp, **rp; 350 indx_t *skip; 351 size_t ilen; 352 { 353 PAGE *l, *r, *tp; 354 pgno_t npg; 355 356 #ifdef STATISTICS 357 ++bt_split; 358 #endif 359 /* Put the new right page for the split into place. */ 360 if ((r = __bt_new(t, &npg)) == NULL) 361 return (NULL); 362 r->pgno = npg; 363 r->lower = BTDATAOFF; 364 r->upper = t->bt_psize; 365 r->nextpg = h->nextpg; 366 r->prevpg = h->pgno; 367 r->flags = h->flags & P_TYPE; 368 369 /* 370 * If we're splitting the last page on a level because we're appending 371 * a key to it (skip is NEXTINDEX()), it's likely that the data is 372 * sorted. Adding an empty page on the side of the level is less work 373 * and can push the fill factor much higher than normal. If we're 374 * wrong it's no big deal, we'll just do the split the right way next 375 * time. It may look like it's equally easy to do a similar hack for 376 * reverse sorted data, that is, split the tree left, but it's not. 377 * Don't even try. 378 */ 379 if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) { 380 #ifdef STATISTICS 381 ++bt_sortsplit; 382 #endif 383 h->nextpg = r->pgno; 384 r->lower = BTDATAOFF + sizeof(indx_t); 385 *skip = 0; 386 *lp = h; 387 *rp = r; 388 return (r); 389 } 390 391 /* Put the new left page for the split into place. */ 392 if ((l = (PAGE *)malloc(t->bt_psize)) == NULL) { 393 mpool_put(t->bt_mp, r, 0); 394 return (NULL); 395 } 396 memset(l, 0xff, t->bt_psize); 397 l->pgno = h->pgno; 398 l->nextpg = r->pgno; 399 l->prevpg = h->prevpg; 400 l->lower = BTDATAOFF; 401 l->upper = t->bt_psize; 402 l->flags = h->flags & P_TYPE; 403 404 /* Fix up the previous pointer of the page after the split page. */ 405 if (h->nextpg != P_INVALID) { 406 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) { 407 free(l); 408 /* XXX mpool_free(t->bt_mp, r->pgno); */ 409 return (NULL); 410 } 411 tp->prevpg = r->pgno; 412 mpool_put(t->bt_mp, tp, MPOOL_DIRTY); 413 } 414 415 /* 416 * Split right. The key/data pairs aren't sorted in the btree page so 417 * it's simpler to copy the data from the split page onto two new pages 418 * instead of copying half the data to the right page and compacting 419 * the left page in place. Since the left page can't change, we have 420 * to swap the original and the allocated left page after the split. 421 */ 422 tp = bt_psplit(t, h, l, r, skip, ilen); 423 424 /* Move the new left page onto the old left page. */ 425 memmove(h, l, t->bt_psize); 426 if (tp == l) 427 tp = h; 428 free(l); 429 430 *lp = h; 431 *rp = r; 432 return (tp); 433 } 434 435 /* 436 * BT_ROOT -- Split the root page of a btree. 437 * 438 * Parameters: 439 * t: tree 440 * h: root page 441 * lp: pointer to left page pointer 442 * rp: pointer to right page pointer 443 * skip: pointer to index to leave open 444 * ilen: insert length 445 * 446 * Returns: 447 * Pointer to page in which to insert or NULL on error. 448 */ 449 static PAGE * 450 bt_root(t, h, lp, rp, skip, ilen) 451 BTREE *t; 452 PAGE *h, **lp, **rp; 453 indx_t *skip; 454 size_t ilen; 455 { 456 PAGE *l, *r, *tp; 457 pgno_t lnpg, rnpg; 458 459 #ifdef STATISTICS 460 ++bt_split; 461 ++bt_rootsplit; 462 #endif 463 /* Put the new left and right pages for the split into place. */ 464 if ((l = __bt_new(t, &lnpg)) == NULL || 465 (r = __bt_new(t, &rnpg)) == NULL) 466 return (NULL); 467 l->pgno = lnpg; 468 r->pgno = rnpg; 469 l->nextpg = r->pgno; 470 r->prevpg = l->pgno; 471 l->prevpg = r->nextpg = P_INVALID; 472 l->lower = r->lower = BTDATAOFF; 473 l->upper = r->upper = t->bt_psize; 474 l->flags = r->flags = h->flags & P_TYPE; 475 476 /* Split the root page. */ 477 tp = bt_psplit(t, h, l, r, skip, ilen); 478 479 *lp = l; 480 *rp = r; 481 return (tp); 482 } 483 484 /* 485 * BT_RROOT -- Fix up the recno root page after it has been split. 486 * 487 * Parameters: 488 * t: tree 489 * h: root page 490 * l: left page 491 * r: right page 492 * 493 * Returns: 494 * RET_ERROR, RET_SUCCESS 495 */ 496 static int 497 bt_rroot(t, h, l, r) 498 BTREE *t; 499 PAGE *h, *l, *r; 500 { 501 char *dest; 502 503 /* Insert the left and right keys, set the header information. */ 504 h->linp[0] = h->upper = t->bt_psize - NRINTERNAL; 505 dest = (char *)h + h->upper; 506 WR_RINTERNAL(dest, 507 l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno); 508 509 h->linp[1] = h->upper -= NRINTERNAL; 510 dest = (char *)h + h->upper; 511 WR_RINTERNAL(dest, 512 r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno); 513 514 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 515 516 /* Unpin the root page, set to recno internal page. */ 517 h->flags &= ~P_TYPE; 518 h->flags |= P_RINTERNAL; 519 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 520 521 return (RET_SUCCESS); 522 } 523 524 /* 525 * BT_BROOT -- Fix up the btree root page after it has been split. 526 * 527 * Parameters: 528 * t: tree 529 * h: root page 530 * l: left page 531 * r: right page 532 * 533 * Returns: 534 * RET_ERROR, RET_SUCCESS 535 */ 536 static int 537 bt_broot(t, h, l, r) 538 BTREE *t; 539 PAGE *h, *l, *r; 540 { 541 BINTERNAL *bi; 542 BLEAF *bl; 543 u_int32_t nbytes; 544 char *dest; 545 546 /* 547 * If the root page was a leaf page, change it into an internal page. 548 * We copy the key we split on (but not the key's data, in the case of 549 * a leaf page) to the new root page. 550 * 551 * The btree comparison code guarantees that the left-most key on any 552 * level of the tree is never used, so it doesn't need to be filled in. 553 */ 554 nbytes = NBINTERNAL(0); 555 h->linp[0] = h->upper = t->bt_psize - nbytes; 556 dest = (char *)h + h->upper; 557 WR_BINTERNAL(dest, 0, l->pgno, 0); 558 559 switch (h->flags & P_TYPE) { 560 case P_BLEAF: 561 bl = GETBLEAF(r, 0); 562 nbytes = NBINTERNAL(bl->ksize); 563 h->linp[1] = h->upper -= nbytes; 564 dest = (char *)h + h->upper; 565 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0); 566 memmove(dest, bl->bytes, bl->ksize); 567 568 /* 569 * If the key is on an overflow page, mark the overflow chain 570 * so it isn't deleted when the leaf copy of the key is deleted. 571 */ 572 if (bl->flags & P_BIGKEY && 573 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 574 return (RET_ERROR); 575 break; 576 case P_BINTERNAL: 577 bi = GETBINTERNAL(r, 0); 578 nbytes = NBINTERNAL(bi->ksize); 579 h->linp[1] = h->upper -= nbytes; 580 dest = (char *)h + h->upper; 581 memmove(dest, bi, nbytes); 582 ((BINTERNAL *)dest)->pgno = r->pgno; 583 break; 584 default: 585 abort(); 586 } 587 588 /* There are two keys on the page. */ 589 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 590 591 /* Unpin the root page, set to btree internal page. */ 592 h->flags &= ~P_TYPE; 593 h->flags |= P_BINTERNAL; 594 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 595 596 return (RET_SUCCESS); 597 } 598 599 /* 600 * BT_PSPLIT -- Do the real work of splitting the page. 601 * 602 * Parameters: 603 * t: tree 604 * h: page to be split 605 * l: page to put lower half of data 606 * r: page to put upper half of data 607 * pskip: pointer to index to leave open 608 * ilen: insert length 609 * 610 * Returns: 611 * Pointer to page in which to insert. 612 */ 613 static PAGE * 614 bt_psplit(t, h, l, r, pskip, ilen) 615 BTREE *t; 616 PAGE *h, *l, *r; 617 indx_t *pskip; 618 size_t ilen; 619 { 620 BINTERNAL *bi; 621 BLEAF *bl; 622 CURSOR *c; 623 RLEAF *rl; 624 PAGE *rval; 625 void *src; 626 indx_t full, half, nxt, off, skip, top, used; 627 u_int32_t nbytes; 628 int bigkeycnt, isbigkey; 629 630 /* 631 * Split the data to the left and right pages. Leave the skip index 632 * open. Additionally, make some effort not to split on an overflow 633 * key. This makes internal page processing faster and can save 634 * space as overflow keys used by internal pages are never deleted. 635 */ 636 bigkeycnt = 0; 637 skip = *pskip; 638 full = t->bt_psize - BTDATAOFF; 639 half = full / 2; 640 used = 0; 641 for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) { 642 if (skip == off) { 643 nbytes = ilen; 644 isbigkey = 0; /* XXX: not really known. */ 645 } else 646 switch (h->flags & P_TYPE) { 647 case P_BINTERNAL: 648 src = bi = GETBINTERNAL(h, nxt); 649 nbytes = NBINTERNAL(bi->ksize); 650 isbigkey = bi->flags & P_BIGKEY; 651 break; 652 case P_BLEAF: 653 src = bl = GETBLEAF(h, nxt); 654 nbytes = NBLEAF(bl); 655 isbigkey = bl->flags & P_BIGKEY; 656 break; 657 case P_RINTERNAL: 658 src = GETRINTERNAL(h, nxt); 659 nbytes = NRINTERNAL; 660 isbigkey = 0; 661 break; 662 case P_RLEAF: 663 src = rl = GETRLEAF(h, nxt); 664 nbytes = NRLEAF(rl); 665 isbigkey = 0; 666 break; 667 default: 668 abort(); 669 } 670 671 /* 672 * If the key/data pairs are substantial fractions of the max 673 * possible size for the page, it's possible to get situations 674 * where we decide to try and copy too much onto the left page. 675 * Make sure that doesn't happen. 676 */ 677 if ((skip <= off && used + nbytes + sizeof(indx_t) >= full) || 678 nxt == top - 1) { 679 --off; 680 break; 681 } 682 683 /* Copy the key/data pair, if not the skipped index. */ 684 if (skip != off) { 685 ++nxt; 686 687 l->linp[off] = l->upper -= nbytes; 688 memmove((char *)l + l->upper, src, nbytes); 689 } 690 691 used += nbytes + sizeof(indx_t); 692 if (used >= half) { 693 if (!isbigkey || bigkeycnt == 3) 694 break; 695 else 696 ++bigkeycnt; 697 } 698 } 699 700 /* 701 * Off is the last offset that's valid for the left page. 702 * Nxt is the first offset to be placed on the right page. 703 */ 704 l->lower += (off + 1) * sizeof(indx_t); 705 706 /* 707 * If splitting the page that the cursor was on, the cursor has to be 708 * adjusted to point to the same record as before the split. If the 709 * cursor is at or past the skipped slot, the cursor is incremented by 710 * one. If the cursor is on the right page, it is decremented by the 711 * number of records split to the left page. 712 */ 713 c = &t->bt_cursor; 714 if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) { 715 if (c->pg.index >= skip) 716 ++c->pg.index; 717 if (c->pg.index < nxt) /* Left page. */ 718 c->pg.pgno = l->pgno; 719 else { /* Right page. */ 720 c->pg.pgno = r->pgno; 721 c->pg.index -= nxt; 722 } 723 } 724 725 /* 726 * If the skipped index was on the left page, just return that page. 727 * Otherwise, adjust the skip index to reflect the new position on 728 * the right page. 729 */ 730 if (skip <= off) { 731 skip = MAX_PAGE_OFFSET; 732 rval = l; 733 } else { 734 rval = r; 735 *pskip -= nxt; 736 } 737 738 for (off = 0; nxt < top; ++off) { 739 if (skip == nxt) { 740 ++off; 741 skip = MAX_PAGE_OFFSET; 742 } 743 switch (h->flags & P_TYPE) { 744 case P_BINTERNAL: 745 src = bi = GETBINTERNAL(h, nxt); 746 nbytes = NBINTERNAL(bi->ksize); 747 break; 748 case P_BLEAF: 749 src = bl = GETBLEAF(h, nxt); 750 nbytes = NBLEAF(bl); 751 break; 752 case P_RINTERNAL: 753 src = GETRINTERNAL(h, nxt); 754 nbytes = NRINTERNAL; 755 break; 756 case P_RLEAF: 757 src = rl = GETRLEAF(h, nxt); 758 nbytes = NRLEAF(rl); 759 break; 760 default: 761 abort(); 762 } 763 ++nxt; 764 r->linp[off] = r->upper -= nbytes; 765 memmove((char *)r + r->upper, src, nbytes); 766 } 767 r->lower += off * sizeof(indx_t); 768 769 /* If the key is being appended to the page, adjust the index. */ 770 if (skip == top) 771 r->lower += sizeof(indx_t); 772 773 return (rval); 774 } 775 776 /* 777 * BT_PRESERVE -- Mark a chain of pages as used by an internal node. 778 * 779 * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the 780 * record that references them gets deleted. Chains pointed to by internal 781 * pages never get deleted. This routine marks a chain as pointed to by an 782 * internal page. 783 * 784 * Parameters: 785 * t: tree 786 * pg: page number of first page in the chain. 787 * 788 * Returns: 789 * RET_SUCCESS, RET_ERROR. 790 */ 791 static int 792 bt_preserve(t, pg) 793 BTREE *t; 794 pgno_t pg; 795 { 796 PAGE *h; 797 798 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 799 return (RET_ERROR); 800 h->flags |= P_PRESERVE; 801 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 802 return (RET_SUCCESS); 803 } 804 805 /* 806 * REC_TOTAL -- Return the number of recno entries below a page. 807 * 808 * Parameters: 809 * h: page 810 * 811 * Returns: 812 * The number of recno entries below a page. 813 * 814 * XXX 815 * These values could be set by the bt_psplit routine. The problem is that the 816 * entry has to be popped off of the stack etc. or the values have to be passed 817 * all the way back to bt_split/bt_rroot and it's not very clean. 818 */ 819 static recno_t 820 rec_total(h) 821 PAGE *h; 822 { 823 recno_t recs; 824 indx_t nxt, top; 825 826 for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt) 827 recs += GETRINTERNAL(h, nxt)->nrecs; 828 return (recs); 829 } 830