1 /* $NetBSD: bt_split.c,v 1.5 1995/02/27 13:20:55 cgd 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 8.6 (Berkeley) 6/16/94"; 42 #else 43 static char rcsid[] = "$NetBSD: bt_split.c,v 1.5 1995/02/27 13:20:55 cgd 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 __P((BTREE *, PAGE *, PAGE *, PAGE *)); 58 static PAGE *bt_page 59 __P((BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t)); 60 static int bt_preserve __P((BTREE *, pgno_t)); 61 static PAGE *bt_psplit 62 __P((BTREE *, PAGE *, PAGE *, PAGE *, indx_t *, size_t)); 63 static PAGE *bt_root 64 __P((BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t)); 65 static int bt_rroot __P((BTREE *, PAGE *, PAGE *, PAGE *)); 66 static recno_t rec_total __P((PAGE *)); 67 68 #ifdef STATISTICS 69 u_long bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved; 70 #endif 71 72 /* 73 * __BT_SPLIT -- Split the tree. 74 * 75 * Parameters: 76 * t: tree 77 * sp: page to split 78 * key: key to insert 79 * data: data to insert 80 * flags: BIGKEY/BIGDATA flags 81 * ilen: insert length 82 * skip: index to leave open 83 * 84 * Returns: 85 * RET_ERROR, RET_SUCCESS 86 */ 87 int 88 __bt_split(t, sp, key, data, flags, ilen, argskip) 89 BTREE *t; 90 PAGE *sp; 91 const DBT *key, *data; 92 int flags; 93 size_t ilen; 94 u_int32_t argskip; 95 { 96 BINTERNAL *bi; 97 BLEAF *bl, *tbl; 98 DBT a, b; 99 EPGNO *parent; 100 PAGE *h, *l, *r, *lchild, *rchild; 101 indx_t nxtindex; 102 u_int16_t skip; 103 u_int32_t n, nbytes, nksize; 104 int parentsplit; 105 char *dest; 106 107 /* 108 * Split the page into two pages, l and r. The split routines return 109 * a pointer to the page into which the key should be inserted and with 110 * skip set to the offset which should be used. Additionally, l and r 111 * are pinned. 112 */ 113 skip = argskip; 114 h = sp->pgno == P_ROOT ? 115 bt_root(t, sp, &l, &r, &skip, ilen) : 116 bt_page(t, sp, &l, &r, &skip, ilen); 117 if (h == NULL) 118 return (RET_ERROR); 119 120 /* 121 * Insert the new key/data pair into the leaf page. (Key inserts 122 * always cause a leaf page to split first.) 123 */ 124 h->linp[skip] = h->upper -= ilen; 125 dest = (char *)h + h->upper; 126 if (ISSET(t, R_RECNO)) 127 WR_RLEAF(dest, data, flags) 128 else 129 WR_BLEAF(dest, key, data, flags) 130 131 /* If the root page was split, make it look right. */ 132 if (sp->pgno == P_ROOT && 133 (ISSET(t, R_RECNO) ? 134 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 135 goto err2; 136 137 /* 138 * Now we walk the parent page stack -- a LIFO stack of the pages that 139 * were traversed when we searched for the page that split. Each stack 140 * entry is a page number and a page index offset. The offset is for 141 * the page traversed on the search. We've just split a page, so we 142 * have to insert a new key into the parent page. 143 * 144 * If the insert into the parent page causes it to split, may have to 145 * continue splitting all the way up the tree. We stop if the root 146 * splits or the page inserted into didn't have to split to hold the 147 * new key. Some algorithms replace the key for the old page as well 148 * as the new page. We don't, as there's no reason to believe that the 149 * first key on the old page is any better than the key we have, and, 150 * in the case of a key being placed at index 0 causing the split, the 151 * key is unavailable. 152 * 153 * There are a maximum of 5 pages pinned at any time. We keep the left 154 * and right pages pinned while working on the parent. The 5 are the 155 * two children, left parent and right parent (when the parent splits) 156 * and the root page or the overflow key page when calling bt_preserve. 157 * This code must make sure that all pins are released other than the 158 * root page or overflow page which is unlocked elsewhere. 159 */ 160 while ((parent = BT_POP(t)) != NULL) { 161 lchild = l; 162 rchild = r; 163 164 /* Get the parent page. */ 165 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) 166 goto err2; 167 168 /* 169 * The new key goes ONE AFTER the index, because the split 170 * was to the right. 171 */ 172 skip = parent->index + 1; 173 174 /* 175 * Calculate the space needed on the parent page. 176 * 177 * Prefix trees: space hack when inserting into BINTERNAL 178 * pages. Retain only what's needed to distinguish between 179 * the new entry and the LAST entry on the page to its left. 180 * If the keys compare equal, retain the entire key. Note, 181 * we don't touch overflow keys, and the entire key must be 182 * retained for the next-to-left most key on the leftmost 183 * page of each level, or the search will fail. Applicable 184 * ONLY to internal pages that have leaf pages as children. 185 * Further reduction of the key between pairs of internal 186 * pages loses too much information. 187 */ 188 switch (rchild->flags & P_TYPE) { 189 case P_BINTERNAL: 190 bi = GETBINTERNAL(rchild, 0); 191 nbytes = NBINTERNAL(bi->ksize); 192 break; 193 case P_BLEAF: 194 bl = GETBLEAF(rchild, 0); 195 nbytes = NBINTERNAL(bl->ksize); 196 if (t->bt_pfx && !(bl->flags & P_BIGKEY) && 197 (h->prevpg != P_INVALID || skip > 1)) { 198 tbl = GETBLEAF(lchild, NEXTINDEX(lchild) - 1); 199 a.size = tbl->ksize; 200 a.data = tbl->bytes; 201 b.size = bl->ksize; 202 b.data = bl->bytes; 203 nksize = t->bt_pfx(&a, &b); 204 n = NBINTERNAL(nksize); 205 if (n < nbytes) { 206 #ifdef STATISTICS 207 bt_pfxsaved += nbytes - n; 208 #endif 209 nbytes = n; 210 } else 211 nksize = 0; 212 } else 213 nksize = 0; 214 break; 215 case P_RINTERNAL: 216 case P_RLEAF: 217 nbytes = NRINTERNAL; 218 break; 219 default: 220 abort(); 221 } 222 223 /* Split the parent page if necessary or shift the indices. */ 224 if (h->upper - h->lower < nbytes + sizeof(indx_t)) { 225 sp = h; 226 h = h->pgno == P_ROOT ? 227 bt_root(t, h, &l, &r, &skip, nbytes) : 228 bt_page(t, h, &l, &r, &skip, nbytes); 229 if (h == NULL) 230 goto err1; 231 parentsplit = 1; 232 } else { 233 if (skip < (nxtindex = NEXTINDEX(h))) 234 memmove(h->linp + skip + 1, h->linp + skip, 235 (nxtindex - skip) * sizeof(indx_t)); 236 h->lower += sizeof(indx_t); 237 parentsplit = 0; 238 } 239 240 /* Insert the key into the parent page. */ 241 switch(rchild->flags & P_TYPE) { 242 case P_BINTERNAL: 243 h->linp[skip] = h->upper -= nbytes; 244 dest = (char *)h + h->linp[skip]; 245 memmove(dest, bi, nbytes); 246 ((BINTERNAL *)dest)->pgno = rchild->pgno; 247 break; 248 case P_BLEAF: 249 h->linp[skip] = h->upper -= nbytes; 250 dest = (char *)h + h->linp[skip]; 251 WR_BINTERNAL(dest, nksize ? nksize : bl->ksize, 252 rchild->pgno, bl->flags & P_BIGKEY); 253 memmove(dest, bl->bytes, nksize ? nksize : bl->ksize); 254 if (bl->flags & P_BIGKEY && 255 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 256 goto err1; 257 break; 258 case P_RINTERNAL: 259 /* 260 * Update the left page count. If split 261 * added at index 0, fix the correct page. 262 */ 263 if (skip > 0) 264 dest = (char *)h + h->linp[skip - 1]; 265 else 266 dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; 267 ((RINTERNAL *)dest)->nrecs = rec_total(lchild); 268 ((RINTERNAL *)dest)->pgno = lchild->pgno; 269 270 /* Update the right page count. */ 271 h->linp[skip] = h->upper -= nbytes; 272 dest = (char *)h + h->linp[skip]; 273 ((RINTERNAL *)dest)->nrecs = rec_total(rchild); 274 ((RINTERNAL *)dest)->pgno = rchild->pgno; 275 break; 276 case P_RLEAF: 277 /* 278 * Update the left page count. If split 279 * added at index 0, fix the correct page. 280 */ 281 if (skip > 0) 282 dest = (char *)h + h->linp[skip - 1]; 283 else 284 dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; 285 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(lchild); 286 ((RINTERNAL *)dest)->pgno = lchild->pgno; 287 288 /* Update the right page count. */ 289 h->linp[skip] = h->upper -= nbytes; 290 dest = (char *)h + h->linp[skip]; 291 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(rchild); 292 ((RINTERNAL *)dest)->pgno = rchild->pgno; 293 break; 294 default: 295 abort(); 296 } 297 298 /* Unpin the held pages. */ 299 if (!parentsplit) { 300 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 301 break; 302 } 303 304 /* If the root page was split, make it look right. */ 305 if (sp->pgno == P_ROOT && 306 (ISSET(t, R_RECNO) ? 307 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 308 goto err1; 309 310 mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 311 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 312 } 313 314 /* Unpin the held pages. */ 315 mpool_put(t->bt_mp, l, MPOOL_DIRTY); 316 mpool_put(t->bt_mp, r, MPOOL_DIRTY); 317 318 /* Clear any pages left on the stack. */ 319 return (RET_SUCCESS); 320 321 /* 322 * If something fails in the above loop we were already walking back 323 * up the tree and the tree is now inconsistent. Nothing much we can 324 * do about it but release any memory we're holding. 325 */ 326 err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 327 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 328 329 err2: mpool_put(t->bt_mp, l, 0); 330 mpool_put(t->bt_mp, r, 0); 331 __dbpanic(t->bt_dbp); 332 return (RET_ERROR); 333 } 334 335 /* 336 * BT_PAGE -- Split a non-root page of a btree. 337 * 338 * Parameters: 339 * t: tree 340 * h: root page 341 * lp: pointer to left page pointer 342 * rp: pointer to right page pointer 343 * skip: pointer to index to leave open 344 * ilen: insert length 345 * 346 * Returns: 347 * Pointer to page in which to insert or NULL on error. 348 */ 349 static PAGE * 350 bt_page(t, h, lp, rp, skip, ilen) 351 BTREE *t; 352 PAGE *h, **lp, **rp; 353 indx_t *skip; 354 size_t ilen; 355 { 356 PAGE *l, *r, *tp; 357 pgno_t npg; 358 359 #ifdef STATISTICS 360 ++bt_split; 361 #endif 362 /* Put the new right page for the split into place. */ 363 if ((r = __bt_new(t, &npg)) == NULL) 364 return (NULL); 365 r->pgno = npg; 366 r->lower = BTDATAOFF; 367 r->upper = t->bt_psize; 368 r->nextpg = h->nextpg; 369 r->prevpg = h->pgno; 370 r->flags = h->flags & P_TYPE; 371 372 /* 373 * If we're splitting the last page on a level because we're appending 374 * a key to it (skip is NEXTINDEX()), it's likely that the data is 375 * sorted. Adding an empty page on the side of the level is less work 376 * and can push the fill factor much higher than normal. If we're 377 * wrong it's no big deal, we'll just do the split the right way next 378 * time. It may look like it's equally easy to do a similar hack for 379 * reverse sorted data, that is, split the tree left, but it's not. 380 * Don't even try. 381 */ 382 if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) { 383 #ifdef STATISTICS 384 ++bt_sortsplit; 385 #endif 386 h->nextpg = r->pgno; 387 r->lower = BTDATAOFF + sizeof(indx_t); 388 *skip = 0; 389 *lp = h; 390 *rp = r; 391 return (r); 392 } 393 394 /* Put the new left page for the split into place. */ 395 if ((l = (PAGE *)malloc(t->bt_psize)) == NULL) { 396 mpool_put(t->bt_mp, r, 0); 397 return (NULL); 398 } 399 l->pgno = h->pgno; 400 l->nextpg = r->pgno; 401 l->prevpg = h->prevpg; 402 l->lower = BTDATAOFF; 403 l->upper = t->bt_psize; 404 l->flags = h->flags & P_TYPE; 405 406 /* Fix up the previous pointer of the page after the split page. */ 407 if (h->nextpg != P_INVALID) { 408 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) { 409 free(l); 410 /* XXX mpool_free(t->bt_mp, r->pgno); */ 411 return (NULL); 412 } 413 tp->prevpg = r->pgno; 414 mpool_put(t->bt_mp, tp, 0); 415 } 416 417 /* 418 * Split right. The key/data pairs aren't sorted in the btree page so 419 * it's simpler to copy the data from the split page onto two new pages 420 * instead of copying half the data to the right page and compacting 421 * the left page in place. Since the left page can't change, we have 422 * to swap the original and the allocated left page after the split. 423 */ 424 tp = bt_psplit(t, h, l, r, skip, ilen); 425 426 /* Move the new left page onto the old left page. */ 427 memmove(h, l, t->bt_psize); 428 if (tp == l) 429 tp = h; 430 free(l); 431 432 *lp = h; 433 *rp = r; 434 return (tp); 435 } 436 437 /* 438 * BT_ROOT -- Split the root page of a btree. 439 * 440 * Parameters: 441 * t: tree 442 * h: root page 443 * lp: pointer to left page pointer 444 * rp: pointer to right page pointer 445 * skip: pointer to index to leave open 446 * ilen: insert length 447 * 448 * Returns: 449 * Pointer to page in which to insert or NULL on error. 450 */ 451 static PAGE * 452 bt_root(t, h, lp, rp, skip, ilen) 453 BTREE *t; 454 PAGE *h, **lp, **rp; 455 indx_t *skip; 456 size_t ilen; 457 { 458 PAGE *l, *r, *tp; 459 pgno_t lnpg, rnpg; 460 461 #ifdef STATISTICS 462 ++bt_split; 463 ++bt_rootsplit; 464 #endif 465 /* Put the new left and right pages for the split into place. */ 466 if ((l = __bt_new(t, &lnpg)) == NULL || 467 (r = __bt_new(t, &rnpg)) == NULL) 468 return (NULL); 469 l->pgno = lnpg; 470 r->pgno = rnpg; 471 l->nextpg = r->pgno; 472 r->prevpg = l->pgno; 473 l->prevpg = r->nextpg = P_INVALID; 474 l->lower = r->lower = BTDATAOFF; 475 l->upper = r->upper = t->bt_psize; 476 l->flags = r->flags = h->flags & P_TYPE; 477 478 /* Split the root page. */ 479 tp = bt_psplit(t, h, l, r, skip, ilen); 480 481 *lp = l; 482 *rp = r; 483 return (tp); 484 } 485 486 /* 487 * BT_RROOT -- Fix up the recno root page after it has been split. 488 * 489 * Parameters: 490 * t: tree 491 * h: root page 492 * l: left page 493 * r: right page 494 * 495 * Returns: 496 * RET_ERROR, RET_SUCCESS 497 */ 498 static int 499 bt_rroot(t, h, l, r) 500 BTREE *t; 501 PAGE *h, *l, *r; 502 { 503 char *dest; 504 505 /* Insert the left and right keys, set the header information. */ 506 h->linp[0] = h->upper = t->bt_psize - NRINTERNAL; 507 dest = (char *)h + h->upper; 508 WR_RINTERNAL(dest, 509 l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno); 510 511 h->linp[1] = h->upper -= NRINTERNAL; 512 dest = (char *)h + h->upper; 513 WR_RINTERNAL(dest, 514 r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno); 515 516 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 517 518 /* Unpin the root page, set to recno internal page. */ 519 h->flags &= ~P_TYPE; 520 h->flags |= P_RINTERNAL; 521 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 522 523 return (RET_SUCCESS); 524 } 525 526 /* 527 * BT_BROOT -- Fix up the btree root page after it has been split. 528 * 529 * Parameters: 530 * t: tree 531 * h: root page 532 * l: left page 533 * r: right page 534 * 535 * Returns: 536 * RET_ERROR, RET_SUCCESS 537 */ 538 static int 539 bt_broot(t, h, l, r) 540 BTREE *t; 541 PAGE *h, *l, *r; 542 { 543 BINTERNAL *bi; 544 BLEAF *bl; 545 u_int32_t nbytes; 546 char *dest; 547 548 /* 549 * If the root page was a leaf page, change it into an internal page. 550 * We copy the key we split on (but not the key's data, in the case of 551 * a leaf page) to the new root page. 552 * 553 * The btree comparison code guarantees that the left-most key on any 554 * level of the tree is never used, so it doesn't need to be filled in. 555 */ 556 nbytes = NBINTERNAL(0); 557 h->linp[0] = h->upper = t->bt_psize - nbytes; 558 dest = (char *)h + h->upper; 559 WR_BINTERNAL(dest, 0, l->pgno, 0); 560 561 switch(h->flags & P_TYPE) { 562 case P_BLEAF: 563 bl = GETBLEAF(r, 0); 564 nbytes = NBINTERNAL(bl->ksize); 565 h->linp[1] = h->upper -= nbytes; 566 dest = (char *)h + h->upper; 567 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0); 568 memmove(dest, bl->bytes, bl->ksize); 569 570 /* 571 * If the key is on an overflow page, mark the overflow chain 572 * so it isn't deleted when the leaf copy of the key is deleted. 573 */ 574 if (bl->flags & P_BIGKEY && 575 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 576 return (RET_ERROR); 577 break; 578 case P_BINTERNAL: 579 bi = GETBINTERNAL(r, 0); 580 nbytes = NBINTERNAL(bi->ksize); 581 h->linp[1] = h->upper -= nbytes; 582 dest = (char *)h + h->upper; 583 memmove(dest, bi, nbytes); 584 ((BINTERNAL *)dest)->pgno = r->pgno; 585 break; 586 default: 587 abort(); 588 } 589 590 /* There are two keys on the page. */ 591 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 592 593 /* Unpin the root page, set to btree internal page. */ 594 h->flags &= ~P_TYPE; 595 h->flags |= P_BINTERNAL; 596 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 597 598 return (RET_SUCCESS); 599 } 600 601 /* 602 * BT_PSPLIT -- Do the real work of splitting the page. 603 * 604 * Parameters: 605 * t: tree 606 * h: page to be split 607 * l: page to put lower half of data 608 * r: page to put upper half of data 609 * pskip: pointer to index to leave open 610 * ilen: insert length 611 * 612 * Returns: 613 * Pointer to page in which to insert. 614 */ 615 static PAGE * 616 bt_psplit(t, h, l, r, pskip, ilen) 617 BTREE *t; 618 PAGE *h, *l, *r; 619 indx_t *pskip; 620 size_t ilen; 621 { 622 BINTERNAL *bi; 623 BLEAF *bl; 624 RLEAF *rl; 625 EPGNO *c; 626 PAGE *rval; 627 void *src; 628 indx_t full, half, nxt, off, skip, top, used; 629 u_int32_t nbytes; 630 int bigkeycnt, isbigkey; 631 632 /* 633 * Split the data to the left and right pages. Leave the skip index 634 * open. Additionally, make some effort not to split on an overflow 635 * key. This makes internal page processing faster and can save 636 * space as overflow keys used by internal pages are never deleted. 637 */ 638 bigkeycnt = 0; 639 skip = *pskip; 640 full = t->bt_psize - BTDATAOFF; 641 half = full / 2; 642 used = 0; 643 for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) { 644 if (skip == off) { 645 nbytes = ilen; 646 isbigkey = 0; /* XXX: not really known. */ 647 } else 648 switch (h->flags & P_TYPE) { 649 case P_BINTERNAL: 650 src = bi = GETBINTERNAL(h, nxt); 651 nbytes = NBINTERNAL(bi->ksize); 652 isbigkey = bi->flags & P_BIGKEY; 653 break; 654 case P_BLEAF: 655 src = bl = GETBLEAF(h, nxt); 656 nbytes = NBLEAF(bl); 657 isbigkey = bl->flags & P_BIGKEY; 658 break; 659 case P_RINTERNAL: 660 src = GETRINTERNAL(h, nxt); 661 nbytes = NRINTERNAL; 662 isbigkey = 0; 663 break; 664 case P_RLEAF: 665 src = rl = GETRLEAF(h, nxt); 666 nbytes = NRLEAF(rl); 667 isbigkey = 0; 668 break; 669 default: 670 abort(); 671 } 672 673 /* 674 * If the key/data pairs are substantial fractions of the max 675 * possible size for the page, it's possible to get situations 676 * where we decide to try and copy too much onto the left page. 677 * Make sure that doesn't happen. 678 */ 679 if (skip <= off && used + nbytes >= full) { 680 --off; 681 break; 682 } 683 684 /* Copy the key/data pair, if not the skipped index. */ 685 if (skip != off) { 686 ++nxt; 687 688 l->linp[off] = l->upper -= nbytes; 689 memmove((char *)l + l->upper, src, nbytes); 690 } 691 692 used += nbytes; 693 if (used >= half) { 694 if (!isbigkey || bigkeycnt == 3) 695 break; 696 else 697 ++bigkeycnt; 698 } 699 } 700 701 /* 702 * Off is the last offset that's valid for the left page. 703 * Nxt is the first offset to be placed on the right page. 704 */ 705 l->lower += (off + 1) * sizeof(indx_t); 706 707 /* 708 * If splitting the page that the cursor was on, the cursor has to be 709 * adjusted to point to the same record as before the split. If the 710 * cursor is at or past the skipped slot, the cursor is incremented by 711 * one. If the cursor is on the right page, it is decremented by the 712 * number of records split to the left page. 713 * 714 * Don't bother checking for the B_SEQINIT flag, the page number will 715 * be P_INVALID. 716 */ 717 c = &t->bt_bcursor; 718 if (c->pgno == h->pgno) { 719 if (c->index >= skip) 720 ++c->index; 721 if (c->index < nxt) /* Left page. */ 722 c->pgno = l->pgno; 723 else { /* Right page. */ 724 c->pgno = r->pgno; 725 c->index -= nxt; 726 } 727 } 728 729 /* 730 * If the skipped index was on the left page, just return that page. 731 * Otherwise, adjust the skip index to reflect the new position on 732 * the right page. 733 */ 734 if (skip <= off) { 735 skip = 0; 736 rval = l; 737 } else { 738 rval = r; 739 *pskip -= nxt; 740 } 741 742 for (off = 0; nxt < top; ++off) { 743 if (skip == nxt) { 744 ++off; 745 skip = 0; 746 } 747 switch (h->flags & P_TYPE) { 748 case P_BINTERNAL: 749 src = bi = GETBINTERNAL(h, nxt); 750 nbytes = NBINTERNAL(bi->ksize); 751 break; 752 case P_BLEAF: 753 src = bl = GETBLEAF(h, nxt); 754 nbytes = NBLEAF(bl); 755 break; 756 case P_RINTERNAL: 757 src = GETRINTERNAL(h, nxt); 758 nbytes = NRINTERNAL; 759 break; 760 case P_RLEAF: 761 src = rl = GETRLEAF(h, nxt); 762 nbytes = NRLEAF(rl); 763 break; 764 default: 765 abort(); 766 } 767 ++nxt; 768 r->linp[off] = r->upper -= nbytes; 769 memmove((char *)r + r->upper, src, nbytes); 770 } 771 r->lower += off * sizeof(indx_t); 772 773 /* If the key is being appended to the page, adjust the index. */ 774 if (skip == top) 775 r->lower += sizeof(indx_t); 776 777 return (rval); 778 } 779 780 /* 781 * BT_PRESERVE -- Mark a chain of pages as used by an internal node. 782 * 783 * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the 784 * record that references them gets deleted. Chains pointed to by internal 785 * pages never get deleted. This routine marks a chain as pointed to by an 786 * internal page. 787 * 788 * Parameters: 789 * t: tree 790 * pg: page number of first page in the chain. 791 * 792 * Returns: 793 * RET_SUCCESS, RET_ERROR. 794 */ 795 static int 796 bt_preserve(t, pg) 797 BTREE *t; 798 pgno_t pg; 799 { 800 PAGE *h; 801 802 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 803 return (RET_ERROR); 804 h->flags |= P_PRESERVE; 805 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 806 return (RET_SUCCESS); 807 } 808 809 /* 810 * REC_TOTAL -- Return the number of recno entries below a page. 811 * 812 * Parameters: 813 * h: page 814 * 815 * Returns: 816 * The number of recno entries below a page. 817 * 818 * XXX 819 * These values could be set by the bt_psplit routine. The problem is that the 820 * entry has to be popped off of the stack etc. or the values have to be passed 821 * all the way back to bt_split/bt_rroot and it's not very clean. 822 */ 823 static recno_t 824 rec_total(h) 825 PAGE *h; 826 { 827 recno_t recs; 828 indx_t nxt, top; 829 830 for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt) 831 recs += GETRINTERNAL(h, nxt)->nrecs; 832 return (recs); 833 } 834