1 /* $NetBSD: bt_split.c,v 1.13 2003/08/07 16:42:41 agc 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/cdefs.h> 36 #if defined(LIBC_SCCS) && !defined(lint) 37 #if 0 38 static char sccsid[] = "@(#)bt_split.c 8.9 (Berkeley) 7/26/94"; 39 #else 40 __RCSID("$NetBSD: bt_split.c,v 1.13 2003/08/07 16:42:41 agc Exp $"); 41 #endif 42 #endif /* LIBC_SCCS and not lint */ 43 44 #include "namespace.h" 45 #include <sys/types.h> 46 47 #include <limits.h> 48 #include <stdio.h> 49 #include <stdlib.h> 50 #include <string.h> 51 52 #include <db.h> 53 #include "btree.h" 54 55 static int bt_broot __P((BTREE *, PAGE *, PAGE *, PAGE *)); 56 static PAGE *bt_page 57 __P((BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t)); 58 static int bt_preserve __P((BTREE *, pgno_t)); 59 static PAGE *bt_psplit 60 __P((BTREE *, PAGE *, PAGE *, PAGE *, indx_t *, size_t)); 61 static PAGE *bt_root 62 __P((BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t)); 63 static int bt_rroot __P((BTREE *, PAGE *, PAGE *, PAGE *)); 64 static recno_t rec_total __P((PAGE *)); 65 66 #ifdef STATISTICS 67 u_long bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved; 68 #endif 69 70 /* 71 * __BT_SPLIT -- Split the tree. 72 * 73 * Parameters: 74 * t: tree 75 * sp: page to split 76 * key: key to insert 77 * data: data to insert 78 * flags: BIGKEY/BIGDATA flags 79 * ilen: insert length 80 * skip: index to leave open 81 * 82 * Returns: 83 * RET_ERROR, RET_SUCCESS 84 */ 85 int 86 __bt_split(t, sp, key, data, flags, ilen, argskip) 87 BTREE *t; 88 PAGE *sp; 89 const DBT *key, *data; 90 int flags; 91 size_t ilen; 92 u_int32_t argskip; 93 { 94 BINTERNAL *bi = NULL; /* pacify gcc */ 95 BLEAF *bl = NULL, *tbl; /* pacify gcc */ 96 DBT a, b; 97 EPGNO *parent; 98 PAGE *h, *l, *r, *lchild, *rchild; 99 indx_t nxtindex; 100 u_int16_t skip; 101 u_int32_t n, nbytes, nksize = 0; /* pacify gcc */ 102 int parentsplit; 103 char *dest; 104 105 /* 106 * Split the page into two pages, l and r. The split routines return 107 * a pointer to the page into which the key should be inserted and with 108 * skip set to the offset which should be used. Additionally, l and r 109 * are pinned. 110 */ 111 skip = argskip; 112 h = sp->pgno == P_ROOT ? 113 bt_root(t, sp, &l, &r, &skip, ilen) : 114 bt_page(t, sp, &l, &r, &skip, ilen); 115 if (h == NULL) 116 return (RET_ERROR); 117 118 /* 119 * Insert the new key/data pair into the leaf page. (Key inserts 120 * always cause a leaf page to split first.) 121 */ 122 h->linp[skip] = h->upper -= ilen; 123 dest = (char *)(void *)h + h->upper; 124 if (F_ISSET(t, R_RECNO)) 125 WR_RLEAF(dest, data, flags) 126 else 127 WR_BLEAF(dest, key, data, flags) 128 129 /* If the root page was split, make it look right. */ 130 if (sp->pgno == P_ROOT && 131 (F_ISSET(t, R_RECNO) ? 132 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 133 goto err2; 134 135 /* 136 * Now we walk the parent page stack -- a LIFO stack of the pages that 137 * were traversed when we searched for the page that split. Each stack 138 * entry is a page number and a page index offset. The offset is for 139 * the page traversed on the search. We've just split a page, so we 140 * have to insert a new key into the parent page. 141 * 142 * If the insert into the parent page causes it to split, may have to 143 * continue splitting all the way up the tree. We stop if the root 144 * splits or the page inserted into didn't have to split to hold the 145 * new key. Some algorithms replace the key for the old page as well 146 * as the new page. We don't, as there's no reason to believe that the 147 * first key on the old page is any better than the key we have, and, 148 * in the case of a key being placed at index 0 causing the split, the 149 * key is unavailable. 150 * 151 * There are a maximum of 5 pages pinned at any time. We keep the left 152 * and right pages pinned while working on the parent. The 5 are the 153 * two children, left parent and right parent (when the parent splits) 154 * and the root page or the overflow key page when calling bt_preserve. 155 * This code must make sure that all pins are released other than the 156 * root page or overflow page which is unlocked elsewhere. 157 */ 158 while ((parent = BT_POP(t)) != NULL) { 159 lchild = l; 160 rchild = r; 161 162 /* Get the parent page. */ 163 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) 164 goto err2; 165 166 /* 167 * The new key goes ONE AFTER the index, because the split 168 * was to the right. 169 */ 170 skip = parent->index + 1; 171 172 /* 173 * Calculate the space needed on the parent page. 174 * 175 * Prefix trees: space hack when inserting into BINTERNAL 176 * pages. Retain only what's needed to distinguish between 177 * the new entry and the LAST entry on the page to its left. 178 * If the keys compare equal, retain the entire key. Note, 179 * we don't touch overflow keys, and the entire key must be 180 * retained for the next-to-left most key on the leftmost 181 * page of each level, or the search will fail. Applicable 182 * ONLY to internal pages that have leaf pages as children. 183 * Further reduction of the key between pairs of internal 184 * pages loses too much information. 185 */ 186 switch (rchild->flags & P_TYPE) { 187 case P_BINTERNAL: 188 bi = GETBINTERNAL(rchild, 0); 189 nbytes = NBINTERNAL(bi->ksize); 190 break; 191 case P_BLEAF: 192 bl = GETBLEAF(rchild, 0); 193 nbytes = NBINTERNAL(bl->ksize); 194 if (t->bt_pfx && !(bl->flags & P_BIGKEY) && 195 (h->prevpg != P_INVALID || skip > 1)) { 196 tbl = GETBLEAF(lchild, NEXTINDEX(lchild) - 1); 197 a.size = tbl->ksize; 198 a.data = tbl->bytes; 199 b.size = bl->ksize; 200 b.data = bl->bytes; 201 nksize = t->bt_pfx(&a, &b); 202 n = NBINTERNAL(nksize); 203 if (n < nbytes) { 204 #ifdef STATISTICS 205 bt_pfxsaved += nbytes - n; 206 #endif 207 nbytes = n; 208 } else 209 nksize = 0; 210 } else 211 nksize = 0; 212 break; 213 case P_RINTERNAL: 214 case P_RLEAF: 215 nbytes = NRINTERNAL; 216 break; 217 default: 218 abort(); 219 } 220 221 /* Split the parent page if necessary or shift the indices. */ 222 if (h->upper - h->lower < nbytes + sizeof(indx_t)) { 223 sp = h; 224 h = h->pgno == P_ROOT ? 225 bt_root(t, h, &l, &r, &skip, nbytes) : 226 bt_page(t, h, &l, &r, &skip, nbytes); 227 if (h == NULL) 228 goto err1; 229 parentsplit = 1; 230 } else { 231 if (skip < (nxtindex = NEXTINDEX(h))) 232 memmove(h->linp + skip + 1, h->linp + skip, 233 (nxtindex - skip) * sizeof(indx_t)); 234 h->lower += sizeof(indx_t); 235 parentsplit = 0; 236 } 237 238 /* Insert the key into the parent page. */ 239 switch (rchild->flags & P_TYPE) { 240 case P_BINTERNAL: 241 h->linp[skip] = h->upper -= nbytes; 242 dest = (char *)(void *)h + h->linp[skip]; 243 memmove(dest, bi, nbytes); 244 ((BINTERNAL *)(void *)dest)->pgno = rchild->pgno; 245 break; 246 case P_BLEAF: 247 h->linp[skip] = h->upper -= nbytes; 248 dest = (char *)(void *)h + h->linp[skip]; 249 WR_BINTERNAL(dest, nksize ? nksize : bl->ksize, 250 rchild->pgno, bl->flags & P_BIGKEY); 251 memmove(dest, bl->bytes, nksize ? nksize : bl->ksize); 252 if (bl->flags & P_BIGKEY && 253 bt_preserve(t, *(pgno_t *)(void *)bl->bytes) == 254 RET_ERROR) 255 goto err1; 256 break; 257 case P_RINTERNAL: 258 /* 259 * Update the left page count. If split 260 * added at index 0, fix the correct page. 261 */ 262 if (skip > 0) 263 dest = (char *)(void *)h + h->linp[skip - 1]; 264 else 265 dest = (char *)(void *)l + l->linp[NEXTINDEX(l) - 1]; 266 ((RINTERNAL *)(void *)dest)->nrecs = rec_total(lchild); 267 ((RINTERNAL *)(void *)dest)->pgno = lchild->pgno; 268 269 /* Update the right page count. */ 270 h->linp[skip] = h->upper -= nbytes; 271 dest = (char *)(void *)h + h->linp[skip]; 272 ((RINTERNAL *)(void *)dest)->nrecs = rec_total(rchild); 273 ((RINTERNAL *)(void *)dest)->pgno = rchild->pgno; 274 break; 275 case P_RLEAF: 276 /* 277 * Update the left page count. If split 278 * added at index 0, fix the correct page. 279 */ 280 if (skip > 0) 281 dest = (char *)(void *)h + h->linp[skip - 1]; 282 else 283 dest = (char *)(void *)l + l->linp[NEXTINDEX(l) - 1]; 284 ((RINTERNAL *)(void *)dest)->nrecs = NEXTINDEX(lchild); 285 ((RINTERNAL *)(void *)dest)->pgno = lchild->pgno; 286 287 /* Update the right page count. */ 288 h->linp[skip] = h->upper -= nbytes; 289 dest = (char *)(void *)h + h->linp[skip]; 290 ((RINTERNAL *)(void *)dest)->nrecs = NEXTINDEX(rchild); 291 ((RINTERNAL *)(void *)dest)->pgno = rchild->pgno; 292 break; 293 default: 294 abort(); 295 } 296 297 /* Unpin the held pages. */ 298 if (!parentsplit) { 299 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 300 break; 301 } 302 303 /* If the root page was split, make it look right. */ 304 if (sp->pgno == P_ROOT && 305 (F_ISSET(t, R_RECNO) ? 306 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 307 goto err1; 308 309 mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 310 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 311 } 312 313 /* Unpin the held pages. */ 314 mpool_put(t->bt_mp, l, MPOOL_DIRTY); 315 mpool_put(t->bt_mp, r, MPOOL_DIRTY); 316 317 /* Clear any pages left on the stack. */ 318 return (RET_SUCCESS); 319 320 /* 321 * If something fails in the above loop we were already walking back 322 * up the tree and the tree is now inconsistent. Nothing much we can 323 * do about it but release any memory we're holding. 324 */ 325 err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 326 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 327 328 err2: mpool_put(t->bt_mp, l, 0); 329 mpool_put(t->bt_mp, r, 0); 330 __dbpanic(t->bt_dbp); 331 return (RET_ERROR); 332 } 333 334 /* 335 * BT_PAGE -- Split a non-root page of a btree. 336 * 337 * Parameters: 338 * t: tree 339 * h: root page 340 * lp: pointer to left page pointer 341 * rp: pointer to right page pointer 342 * skip: pointer to index to leave open 343 * ilen: insert length 344 * 345 * Returns: 346 * Pointer to page in which to insert or NULL on error. 347 */ 348 static PAGE * 349 bt_page(t, h, lp, rp, skip, ilen) 350 BTREE *t; 351 PAGE *h, **lp, **rp; 352 indx_t *skip; 353 size_t ilen; 354 { 355 PAGE *l, *r, *tp; 356 pgno_t npg; 357 358 #ifdef STATISTICS 359 ++bt_split; 360 #endif 361 /* Put the new right page for the split into place. */ 362 if ((r = __bt_new(t, &npg)) == NULL) 363 return (NULL); 364 r->pgno = npg; 365 r->lower = BTDATAOFF; 366 r->upper = t->bt_psize; 367 r->nextpg = h->nextpg; 368 r->prevpg = h->pgno; 369 r->flags = h->flags & P_TYPE; 370 371 /* 372 * If we're splitting the last page on a level because we're appending 373 * a key to it (skip is NEXTINDEX()), it's likely that the data is 374 * sorted. Adding an empty page on the side of the level is less work 375 * and can push the fill factor much higher than normal. If we're 376 * wrong it's no big deal, we'll just do the split the right way next 377 * time. It may look like it's equally easy to do a similar hack for 378 * reverse sorted data, that is, split the tree left, but it's not. 379 * Don't even try. 380 */ 381 if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) { 382 #ifdef STATISTICS 383 ++bt_sortsplit; 384 #endif 385 h->nextpg = r->pgno; 386 r->lower = BTDATAOFF + sizeof(indx_t); 387 *skip = 0; 388 *lp = h; 389 *rp = r; 390 return (r); 391 } 392 393 /* Put the new left page for the split into place. */ 394 if ((l = (PAGE *)malloc(t->bt_psize)) == NULL) { 395 mpool_put(t->bt_mp, r, 0); 396 return (NULL); 397 } 398 #ifdef PURIFY 399 memset(l, 0xff, t->bt_psize); 400 #endif 401 l->pgno = h->pgno; 402 l->nextpg = r->pgno; 403 l->prevpg = h->prevpg; 404 l->lower = BTDATAOFF; 405 l->upper = t->bt_psize; 406 l->flags = h->flags & P_TYPE; 407 408 /* Fix up the previous pointer of the page after the split page. */ 409 if (h->nextpg != P_INVALID) { 410 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) { 411 free(l); 412 /* XXX mpool_free(t->bt_mp, r->pgno); */ 413 return (NULL); 414 } 415 tp->prevpg = r->pgno; 416 mpool_put(t->bt_mp, tp, MPOOL_DIRTY); 417 } 418 419 /* 420 * Split right. The key/data pairs aren't sorted in the btree page so 421 * it's simpler to copy the data from the split page onto two new pages 422 * instead of copying half the data to the right page and compacting 423 * the left page in place. Since the left page can't change, we have 424 * to swap the original and the allocated left page after the split. 425 */ 426 tp = bt_psplit(t, h, l, r, skip, ilen); 427 428 /* Move the new left page onto the old left page. */ 429 memmove(h, l, t->bt_psize); 430 if (tp == l) 431 tp = h; 432 free(l); 433 434 *lp = h; 435 *rp = r; 436 return (tp); 437 } 438 439 /* 440 * BT_ROOT -- Split the root page of a btree. 441 * 442 * Parameters: 443 * t: tree 444 * h: root page 445 * lp: pointer to left page pointer 446 * rp: pointer to right page pointer 447 * skip: pointer to index to leave open 448 * ilen: insert length 449 * 450 * Returns: 451 * Pointer to page in which to insert or NULL on error. 452 */ 453 static PAGE * 454 bt_root(t, h, lp, rp, skip, ilen) 455 BTREE *t; 456 PAGE *h, **lp, **rp; 457 indx_t *skip; 458 size_t ilen; 459 { 460 PAGE *l, *r, *tp; 461 pgno_t lnpg, rnpg; 462 463 #ifdef STATISTICS 464 ++bt_split; 465 ++bt_rootsplit; 466 #endif 467 /* Put the new left and right pages for the split into place. */ 468 if ((l = __bt_new(t, &lnpg)) == NULL || 469 (r = __bt_new(t, &rnpg)) == NULL) 470 return (NULL); 471 l->pgno = lnpg; 472 r->pgno = rnpg; 473 l->nextpg = r->pgno; 474 r->prevpg = l->pgno; 475 l->prevpg = r->nextpg = P_INVALID; 476 l->lower = r->lower = BTDATAOFF; 477 l->upper = r->upper = t->bt_psize; 478 l->flags = r->flags = h->flags & P_TYPE; 479 480 /* Split the root page. */ 481 tp = bt_psplit(t, h, l, r, skip, ilen); 482 483 *lp = l; 484 *rp = r; 485 return (tp); 486 } 487 488 /* 489 * BT_RROOT -- Fix up the recno root page after it has been split. 490 * 491 * Parameters: 492 * t: tree 493 * h: root page 494 * l: left page 495 * r: right page 496 * 497 * Returns: 498 * RET_ERROR, RET_SUCCESS 499 */ 500 static int 501 bt_rroot(t, h, l, r) 502 BTREE *t; 503 PAGE *h, *l, *r; 504 { 505 char *dest; 506 507 /* Insert the left and right keys, set the header information. */ 508 h->linp[0] = h->upper = t->bt_psize - NRINTERNAL; 509 dest = (char *)(void *)h + h->upper; 510 WR_RINTERNAL(dest, 511 l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno); 512 513 h->linp[1] = h->upper -= NRINTERNAL; 514 dest = (char *)(void *)h + h->upper; 515 WR_RINTERNAL(dest, 516 r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno); 517 518 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 519 520 /* Unpin the root page, set to recno internal page. */ 521 h->flags &= ~P_TYPE; 522 h->flags |= P_RINTERNAL; 523 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 524 525 return (RET_SUCCESS); 526 } 527 528 /* 529 * BT_BROOT -- Fix up the btree root page after it has been split. 530 * 531 * Parameters: 532 * t: tree 533 * h: root page 534 * l: left page 535 * r: right page 536 * 537 * Returns: 538 * RET_ERROR, RET_SUCCESS 539 */ 540 static int 541 bt_broot(t, h, l, r) 542 BTREE *t; 543 PAGE *h, *l, *r; 544 { 545 BINTERNAL *bi = NULL; /* pacify gcc */ 546 BLEAF *bl; 547 u_int32_t nbytes; 548 char *dest; 549 550 /* 551 * If the root page was a leaf page, change it into an internal page. 552 * We copy the key we split on (but not the key's data, in the case of 553 * a leaf page) to the new root page. 554 * 555 * The btree comparison code guarantees that the left-most key on any 556 * level of the tree is never used, so it doesn't need to be filled in. 557 */ 558 nbytes = NBINTERNAL(0); 559 h->linp[0] = h->upper = t->bt_psize - nbytes; 560 dest = (char *)(void *)h + h->upper; 561 WR_BINTERNAL(dest, 0, l->pgno, 0); 562 563 switch (h->flags & P_TYPE) { 564 case P_BLEAF: 565 bl = GETBLEAF(r, 0); 566 nbytes = NBINTERNAL(bl->ksize); 567 h->linp[1] = h->upper -= nbytes; 568 dest = (char *)(void *)h + h->upper; 569 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0); 570 memmove(dest, bl->bytes, bl->ksize); 571 572 /* 573 * If the key is on an overflow page, mark the overflow chain 574 * so it isn't deleted when the leaf copy of the key is deleted. 575 */ 576 if (bl->flags & P_BIGKEY && 577 bt_preserve(t, *(pgno_t *)(void *)bl->bytes) == RET_ERROR) 578 return (RET_ERROR); 579 break; 580 case P_BINTERNAL: 581 bi = GETBINTERNAL(r, 0); 582 nbytes = NBINTERNAL(bi->ksize); 583 h->linp[1] = h->upper -= nbytes; 584 dest = (char *)(void *)h + h->upper; 585 memmove(dest, bi, nbytes); 586 ((BINTERNAL *)(void *)dest)->pgno = r->pgno; 587 break; 588 default: 589 abort(); 590 } 591 592 /* There are two keys on the page. */ 593 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 594 595 /* Unpin the root page, set to btree internal page. */ 596 h->flags &= ~P_TYPE; 597 h->flags |= P_BINTERNAL; 598 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 599 600 return (RET_SUCCESS); 601 } 602 603 /* 604 * BT_PSPLIT -- Do the real work of splitting the page. 605 * 606 * Parameters: 607 * t: tree 608 * h: page to be split 609 * l: page to put lower half of data 610 * r: page to put upper half of data 611 * pskip: pointer to index to leave open 612 * ilen: insert length 613 * 614 * Returns: 615 * Pointer to page in which to insert. 616 */ 617 static PAGE * 618 bt_psplit(t, h, l, r, pskip, ilen) 619 BTREE *t; 620 PAGE *h, *l, *r; 621 indx_t *pskip; 622 size_t ilen; 623 { 624 BINTERNAL *bi; 625 BLEAF *bl; 626 CURSOR *c; 627 RLEAF *rl; 628 PAGE *rval; 629 void *src = NULL; /* pacify gcc */ 630 indx_t full, half, nxt, off, skip, top, used; 631 u_int32_t nbytes; 632 int bigkeycnt, isbigkey; 633 634 /* 635 * Split the data to the left and right pages. Leave the skip index 636 * open. Additionally, make some effort not to split on an overflow 637 * key. This makes internal page processing faster and can save 638 * space as overflow keys used by internal pages are never deleted. 639 */ 640 bigkeycnt = 0; 641 skip = *pskip; 642 full = t->bt_psize - BTDATAOFF; 643 half = full / 2; 644 used = 0; 645 for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) { 646 if (skip == off) { 647 nbytes = ilen; 648 isbigkey = 0; /* XXX: not really known. */ 649 } else 650 switch (h->flags & P_TYPE) { 651 case P_BINTERNAL: 652 src = bi = GETBINTERNAL(h, nxt); 653 nbytes = NBINTERNAL(bi->ksize); 654 isbigkey = bi->flags & P_BIGKEY; 655 break; 656 case P_BLEAF: 657 src = bl = GETBLEAF(h, nxt); 658 nbytes = NBLEAF(bl); 659 isbigkey = bl->flags & P_BIGKEY; 660 break; 661 case P_RINTERNAL: 662 src = GETRINTERNAL(h, nxt); 663 nbytes = NRINTERNAL; 664 isbigkey = 0; 665 break; 666 case P_RLEAF: 667 src = rl = GETRLEAF(h, nxt); 668 nbytes = NRLEAF(rl); 669 isbigkey = 0; 670 break; 671 default: 672 abort(); 673 } 674 675 /* 676 * If the key/data pairs are substantial fractions of the max 677 * possible size for the page, it's possible to get situations 678 * where we decide to try and copy too much onto the left page. 679 * Make sure that doesn't happen. 680 */ 681 if ((skip <= off && used + nbytes + sizeof(indx_t) >= full) || 682 nxt == top - 1) { 683 --off; 684 break; 685 } 686 687 /* Copy the key/data pair, if not the skipped index. */ 688 if (skip != off) { 689 ++nxt; 690 691 l->linp[off] = l->upper -= nbytes; 692 memmove((char *)(void *)l + l->upper, src, nbytes); 693 } 694 695 used += nbytes + sizeof(indx_t); 696 if (used >= half) { 697 if (!isbigkey || bigkeycnt == 3) 698 break; 699 else 700 ++bigkeycnt; 701 } 702 } 703 704 /* 705 * Off is the last offset that's valid for the left page. 706 * Nxt is the first offset to be placed on the right page. 707 */ 708 l->lower += (off + 1) * sizeof(indx_t); 709 710 /* 711 * If splitting the page that the cursor was on, the cursor has to be 712 * adjusted to point to the same record as before the split. If the 713 * cursor is at or past the skipped slot, the cursor is incremented by 714 * one. If the cursor is on the right page, it is decremented by the 715 * number of records split to the left page. 716 */ 717 c = &t->bt_cursor; 718 if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) { 719 if (c->pg.index >= skip) 720 ++c->pg.index; 721 if (c->pg.index < nxt) /* Left page. */ 722 c->pg.pgno = l->pgno; 723 else { /* Right page. */ 724 c->pg.pgno = r->pgno; 725 c->pg.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 = MAX_PAGE_OFFSET; 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 = MAX_PAGE_OFFSET; 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 *)(void *)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