1 /* $NetBSD: bt_split.c,v 1.9 1997/10/10 21:08:55 is 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 #include <sys/cdefs.h> 40 #if defined(LIBC_SCCS) && !defined(lint) 41 #if 0 42 static char sccsid[] = "@(#)bt_split.c 8.9 (Berkeley) 7/26/94"; 43 #else 44 __RCSID("$NetBSD: bt_split.c,v 1.9 1997/10/10 21:08:55 is Exp $"); 45 #endif 46 #endif /* LIBC_SCCS and not lint */ 47 48 #include "namespace.h" 49 #include <sys/types.h> 50 51 #include <limits.h> 52 #include <stdio.h> 53 #include <stdlib.h> 54 #include <string.h> 55 56 #include <db.h> 57 #include "btree.h" 58 59 static int bt_broot __P((BTREE *, PAGE *, PAGE *, PAGE *)); 60 static PAGE *bt_page 61 __P((BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t)); 62 static int bt_preserve __P((BTREE *, pgno_t)); 63 static PAGE *bt_psplit 64 __P((BTREE *, PAGE *, PAGE *, PAGE *, indx_t *, size_t)); 65 static PAGE *bt_root 66 __P((BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t)); 67 static int bt_rroot __P((BTREE *, PAGE *, PAGE *, PAGE *)); 68 static recno_t rec_total __P((PAGE *)); 69 70 #ifdef STATISTICS 71 u_long bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved; 72 #endif 73 74 /* 75 * __BT_SPLIT -- Split the tree. 76 * 77 * Parameters: 78 * t: tree 79 * sp: page to split 80 * key: key to insert 81 * data: data to insert 82 * flags: BIGKEY/BIGDATA flags 83 * ilen: insert length 84 * skip: index to leave open 85 * 86 * Returns: 87 * RET_ERROR, RET_SUCCESS 88 */ 89 int 90 __bt_split(t, sp, key, data, flags, ilen, argskip) 91 BTREE *t; 92 PAGE *sp; 93 const DBT *key, *data; 94 int flags; 95 size_t ilen; 96 u_int32_t argskip; 97 { 98 BINTERNAL *bi = NULL; /* pacify gcc */ 99 BLEAF *bl = NULL, *tbl; /* pacify gcc */ 100 DBT a, b; 101 EPGNO *parent; 102 PAGE *h, *l, *r, *lchild, *rchild; 103 indx_t nxtindex; 104 u_int16_t skip; 105 u_int32_t n, nbytes, nksize = 0; /* pacify gcc */ 106 int parentsplit; 107 char *dest; 108 109 /* 110 * Split the page into two pages, l and r. The split routines return 111 * a pointer to the page into which the key should be inserted and with 112 * skip set to the offset which should be used. Additionally, l and r 113 * are pinned. 114 */ 115 skip = argskip; 116 h = sp->pgno == P_ROOT ? 117 bt_root(t, sp, &l, &r, &skip, ilen) : 118 bt_page(t, sp, &l, &r, &skip, ilen); 119 if (h == NULL) 120 return (RET_ERROR); 121 122 /* 123 * Insert the new key/data pair into the leaf page. (Key inserts 124 * always cause a leaf page to split first.) 125 */ 126 h->linp[skip] = h->upper -= ilen; 127 dest = (char *)h + h->upper; 128 if (F_ISSET(t, R_RECNO)) 129 WR_RLEAF(dest, data, flags) 130 else 131 WR_BLEAF(dest, key, data, flags) 132 133 /* If the root page was split, make it look right. */ 134 if (sp->pgno == P_ROOT && 135 (F_ISSET(t, R_RECNO) ? 136 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 137 goto err2; 138 139 /* 140 * Now we walk the parent page stack -- a LIFO stack of the pages that 141 * were traversed when we searched for the page that split. Each stack 142 * entry is a page number and a page index offset. The offset is for 143 * the page traversed on the search. We've just split a page, so we 144 * have to insert a new key into the parent page. 145 * 146 * If the insert into the parent page causes it to split, may have to 147 * continue splitting all the way up the tree. We stop if the root 148 * splits or the page inserted into didn't have to split to hold the 149 * new key. Some algorithms replace the key for the old page as well 150 * as the new page. We don't, as there's no reason to believe that the 151 * first key on the old page is any better than the key we have, and, 152 * in the case of a key being placed at index 0 causing the split, the 153 * key is unavailable. 154 * 155 * There are a maximum of 5 pages pinned at any time. We keep the left 156 * and right pages pinned while working on the parent. The 5 are the 157 * two children, left parent and right parent (when the parent splits) 158 * and the root page or the overflow key page when calling bt_preserve. 159 * This code must make sure that all pins are released other than the 160 * root page or overflow page which is unlocked elsewhere. 161 */ 162 while ((parent = BT_POP(t)) != NULL) { 163 lchild = l; 164 rchild = r; 165 166 /* Get the parent page. */ 167 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) 168 goto err2; 169 170 /* 171 * The new key goes ONE AFTER the index, because the split 172 * was to the right. 173 */ 174 skip = parent->index + 1; 175 176 /* 177 * Calculate the space needed on the parent page. 178 * 179 * Prefix trees: space hack when inserting into BINTERNAL 180 * pages. Retain only what's needed to distinguish between 181 * the new entry and the LAST entry on the page to its left. 182 * If the keys compare equal, retain the entire key. Note, 183 * we don't touch overflow keys, and the entire key must be 184 * retained for the next-to-left most key on the leftmost 185 * page of each level, or the search will fail. Applicable 186 * ONLY to internal pages that have leaf pages as children. 187 * Further reduction of the key between pairs of internal 188 * pages loses too much information. 189 */ 190 switch (rchild->flags & P_TYPE) { 191 case P_BINTERNAL: 192 bi = GETBINTERNAL(rchild, 0); 193 nbytes = NBINTERNAL(bi->ksize); 194 break; 195 case P_BLEAF: 196 bl = GETBLEAF(rchild, 0); 197 nbytes = NBINTERNAL(bl->ksize); 198 if (t->bt_pfx && !(bl->flags & P_BIGKEY) && 199 (h->prevpg != P_INVALID || skip > 1)) { 200 tbl = GETBLEAF(lchild, NEXTINDEX(lchild) - 1); 201 a.size = tbl->ksize; 202 a.data = tbl->bytes; 203 b.size = bl->ksize; 204 b.data = bl->bytes; 205 nksize = t->bt_pfx(&a, &b); 206 n = NBINTERNAL(nksize); 207 if (n < nbytes) { 208 #ifdef STATISTICS 209 bt_pfxsaved += nbytes - n; 210 #endif 211 nbytes = n; 212 } else 213 nksize = 0; 214 } else 215 nksize = 0; 216 break; 217 case P_RINTERNAL: 218 case P_RLEAF: 219 nbytes = NRINTERNAL; 220 break; 221 default: 222 abort(); 223 } 224 225 /* Split the parent page if necessary or shift the indices. */ 226 if (h->upper - h->lower < nbytes + sizeof(indx_t)) { 227 sp = h; 228 h = h->pgno == P_ROOT ? 229 bt_root(t, h, &l, &r, &skip, nbytes) : 230 bt_page(t, h, &l, &r, &skip, nbytes); 231 if (h == NULL) 232 goto err1; 233 parentsplit = 1; 234 } else { 235 if (skip < (nxtindex = NEXTINDEX(h))) 236 memmove(h->linp + skip + 1, h->linp + skip, 237 (nxtindex - skip) * sizeof(indx_t)); 238 h->lower += sizeof(indx_t); 239 parentsplit = 0; 240 } 241 242 /* Insert the key into the parent page. */ 243 switch (rchild->flags & P_TYPE) { 244 case P_BINTERNAL: 245 h->linp[skip] = h->upper -= nbytes; 246 dest = (char *)h + h->linp[skip]; 247 memmove(dest, bi, nbytes); 248 ((BINTERNAL *)dest)->pgno = rchild->pgno; 249 break; 250 case P_BLEAF: 251 h->linp[skip] = h->upper -= nbytes; 252 dest = (char *)h + h->linp[skip]; 253 WR_BINTERNAL(dest, nksize ? nksize : bl->ksize, 254 rchild->pgno, bl->flags & P_BIGKEY); 255 memmove(dest, bl->bytes, nksize ? nksize : bl->ksize); 256 if (bl->flags & P_BIGKEY && 257 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 258 goto err1; 259 break; 260 case P_RINTERNAL: 261 /* 262 * Update the left page count. If split 263 * added at index 0, fix the correct page. 264 */ 265 if (skip > 0) 266 dest = (char *)h + h->linp[skip - 1]; 267 else 268 dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; 269 ((RINTERNAL *)dest)->nrecs = rec_total(lchild); 270 ((RINTERNAL *)dest)->pgno = lchild->pgno; 271 272 /* Update the right page count. */ 273 h->linp[skip] = h->upper -= nbytes; 274 dest = (char *)h + h->linp[skip]; 275 ((RINTERNAL *)dest)->nrecs = rec_total(rchild); 276 ((RINTERNAL *)dest)->pgno = rchild->pgno; 277 break; 278 case P_RLEAF: 279 /* 280 * Update the left page count. If split 281 * added at index 0, fix the correct page. 282 */ 283 if (skip > 0) 284 dest = (char *)h + h->linp[skip - 1]; 285 else 286 dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; 287 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(lchild); 288 ((RINTERNAL *)dest)->pgno = lchild->pgno; 289 290 /* Update the right page count. */ 291 h->linp[skip] = h->upper -= nbytes; 292 dest = (char *)h + h->linp[skip]; 293 ((RINTERNAL *)dest)->nrecs = NEXTINDEX(rchild); 294 ((RINTERNAL *)dest)->pgno = rchild->pgno; 295 break; 296 default: 297 abort(); 298 } 299 300 /* Unpin the held pages. */ 301 if (!parentsplit) { 302 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 303 break; 304 } 305 306 /* If the root page was split, make it look right. */ 307 if (sp->pgno == P_ROOT && 308 (F_ISSET(t, R_RECNO) ? 309 bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) 310 goto err1; 311 312 mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 313 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 314 } 315 316 /* Unpin the held pages. */ 317 mpool_put(t->bt_mp, l, MPOOL_DIRTY); 318 mpool_put(t->bt_mp, r, MPOOL_DIRTY); 319 320 /* Clear any pages left on the stack. */ 321 return (RET_SUCCESS); 322 323 /* 324 * If something fails in the above loop we were already walking back 325 * up the tree and the tree is now inconsistent. Nothing much we can 326 * do about it but release any memory we're holding. 327 */ 328 err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); 329 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); 330 331 err2: mpool_put(t->bt_mp, l, 0); 332 mpool_put(t->bt_mp, r, 0); 333 __dbpanic(t->bt_dbp); 334 return (RET_ERROR); 335 } 336 337 /* 338 * BT_PAGE -- Split a non-root page of a btree. 339 * 340 * Parameters: 341 * t: tree 342 * h: root page 343 * lp: pointer to left page pointer 344 * rp: pointer to right page pointer 345 * skip: pointer to index to leave open 346 * ilen: insert length 347 * 348 * Returns: 349 * Pointer to page in which to insert or NULL on error. 350 */ 351 static PAGE * 352 bt_page(t, h, lp, rp, skip, ilen) 353 BTREE *t; 354 PAGE *h, **lp, **rp; 355 indx_t *skip; 356 size_t ilen; 357 { 358 PAGE *l, *r, *tp; 359 pgno_t npg; 360 361 #ifdef STATISTICS 362 ++bt_split; 363 #endif 364 /* Put the new right page for the split into place. */ 365 if ((r = __bt_new(t, &npg)) == NULL) 366 return (NULL); 367 r->pgno = npg; 368 r->lower = BTDATAOFF; 369 r->upper = t->bt_psize; 370 r->nextpg = h->nextpg; 371 r->prevpg = h->pgno; 372 r->flags = h->flags & P_TYPE; 373 374 /* 375 * If we're splitting the last page on a level because we're appending 376 * a key to it (skip is NEXTINDEX()), it's likely that the data is 377 * sorted. Adding an empty page on the side of the level is less work 378 * and can push the fill factor much higher than normal. If we're 379 * wrong it's no big deal, we'll just do the split the right way next 380 * time. It may look like it's equally easy to do a similar hack for 381 * reverse sorted data, that is, split the tree left, but it's not. 382 * Don't even try. 383 */ 384 if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) { 385 #ifdef STATISTICS 386 ++bt_sortsplit; 387 #endif 388 h->nextpg = r->pgno; 389 r->lower = BTDATAOFF + sizeof(indx_t); 390 *skip = 0; 391 *lp = h; 392 *rp = r; 393 return (r); 394 } 395 396 /* Put the new left page for the split into place. */ 397 if ((l = (PAGE *)malloc(t->bt_psize)) == NULL) { 398 mpool_put(t->bt_mp, r, 0); 399 return (NULL); 400 } 401 #ifdef PURIFY 402 memset(l, 0xff, t->bt_psize); 403 #endif 404 l->pgno = h->pgno; 405 l->nextpg = r->pgno; 406 l->prevpg = h->prevpg; 407 l->lower = BTDATAOFF; 408 l->upper = t->bt_psize; 409 l->flags = h->flags & P_TYPE; 410 411 /* Fix up the previous pointer of the page after the split page. */ 412 if (h->nextpg != P_INVALID) { 413 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) { 414 free(l); 415 /* XXX mpool_free(t->bt_mp, r->pgno); */ 416 return (NULL); 417 } 418 tp->prevpg = r->pgno; 419 mpool_put(t->bt_mp, tp, MPOOL_DIRTY); 420 } 421 422 /* 423 * Split right. The key/data pairs aren't sorted in the btree page so 424 * it's simpler to copy the data from the split page onto two new pages 425 * instead of copying half the data to the right page and compacting 426 * the left page in place. Since the left page can't change, we have 427 * to swap the original and the allocated left page after the split. 428 */ 429 tp = bt_psplit(t, h, l, r, skip, ilen); 430 431 /* Move the new left page onto the old left page. */ 432 memmove(h, l, t->bt_psize); 433 if (tp == l) 434 tp = h; 435 free(l); 436 437 *lp = h; 438 *rp = r; 439 return (tp); 440 } 441 442 /* 443 * BT_ROOT -- Split the root page of a btree. 444 * 445 * Parameters: 446 * t: tree 447 * h: root page 448 * lp: pointer to left page pointer 449 * rp: pointer to right page pointer 450 * skip: pointer to index to leave open 451 * ilen: insert length 452 * 453 * Returns: 454 * Pointer to page in which to insert or NULL on error. 455 */ 456 static PAGE * 457 bt_root(t, h, lp, rp, skip, ilen) 458 BTREE *t; 459 PAGE *h, **lp, **rp; 460 indx_t *skip; 461 size_t ilen; 462 { 463 PAGE *l, *r, *tp; 464 pgno_t lnpg, rnpg; 465 466 #ifdef STATISTICS 467 ++bt_split; 468 ++bt_rootsplit; 469 #endif 470 /* Put the new left and right pages for the split into place. */ 471 if ((l = __bt_new(t, &lnpg)) == NULL || 472 (r = __bt_new(t, &rnpg)) == NULL) 473 return (NULL); 474 l->pgno = lnpg; 475 r->pgno = rnpg; 476 l->nextpg = r->pgno; 477 r->prevpg = l->pgno; 478 l->prevpg = r->nextpg = P_INVALID; 479 l->lower = r->lower = BTDATAOFF; 480 l->upper = r->upper = t->bt_psize; 481 l->flags = r->flags = h->flags & P_TYPE; 482 483 /* Split the root page. */ 484 tp = bt_psplit(t, h, l, r, skip, ilen); 485 486 *lp = l; 487 *rp = r; 488 return (tp); 489 } 490 491 /* 492 * BT_RROOT -- Fix up the recno root page after it has been split. 493 * 494 * Parameters: 495 * t: tree 496 * h: root page 497 * l: left page 498 * r: right page 499 * 500 * Returns: 501 * RET_ERROR, RET_SUCCESS 502 */ 503 static int 504 bt_rroot(t, h, l, r) 505 BTREE *t; 506 PAGE *h, *l, *r; 507 { 508 char *dest; 509 510 /* Insert the left and right keys, set the header information. */ 511 h->linp[0] = h->upper = t->bt_psize - NRINTERNAL; 512 dest = (char *)h + h->upper; 513 WR_RINTERNAL(dest, 514 l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno); 515 516 h->linp[1] = h->upper -= NRINTERNAL; 517 dest = (char *)h + h->upper; 518 WR_RINTERNAL(dest, 519 r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno); 520 521 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 522 523 /* Unpin the root page, set to recno internal page. */ 524 h->flags &= ~P_TYPE; 525 h->flags |= P_RINTERNAL; 526 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 527 528 return (RET_SUCCESS); 529 } 530 531 /* 532 * BT_BROOT -- Fix up the btree root page after it has been split. 533 * 534 * Parameters: 535 * t: tree 536 * h: root page 537 * l: left page 538 * r: right page 539 * 540 * Returns: 541 * RET_ERROR, RET_SUCCESS 542 */ 543 static int 544 bt_broot(t, h, l, r) 545 BTREE *t; 546 PAGE *h, *l, *r; 547 { 548 BINTERNAL *bi = NULL; /* pacify gcc */ 549 BLEAF *bl; 550 u_int32_t nbytes; 551 char *dest; 552 553 /* 554 * If the root page was a leaf page, change it into an internal page. 555 * We copy the key we split on (but not the key's data, in the case of 556 * a leaf page) to the new root page. 557 * 558 * The btree comparison code guarantees that the left-most key on any 559 * level of the tree is never used, so it doesn't need to be filled in. 560 */ 561 nbytes = NBINTERNAL(0); 562 h->linp[0] = h->upper = t->bt_psize - nbytes; 563 dest = (char *)h + h->upper; 564 WR_BINTERNAL(dest, 0, l->pgno, 0); 565 566 switch (h->flags & P_TYPE) { 567 case P_BLEAF: 568 bl = GETBLEAF(r, 0); 569 nbytes = NBINTERNAL(bl->ksize); 570 h->linp[1] = h->upper -= nbytes; 571 dest = (char *)h + h->upper; 572 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0); 573 memmove(dest, bl->bytes, bl->ksize); 574 575 /* 576 * If the key is on an overflow page, mark the overflow chain 577 * so it isn't deleted when the leaf copy of the key is deleted. 578 */ 579 if (bl->flags & P_BIGKEY && 580 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 581 return (RET_ERROR); 582 break; 583 case P_BINTERNAL: 584 bi = GETBINTERNAL(r, 0); 585 nbytes = NBINTERNAL(bi->ksize); 586 h->linp[1] = h->upper -= nbytes; 587 dest = (char *)h + h->upper; 588 memmove(dest, bi, nbytes); 589 ((BINTERNAL *)dest)->pgno = r->pgno; 590 break; 591 default: 592 abort(); 593 } 594 595 /* There are two keys on the page. */ 596 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 597 598 /* Unpin the root page, set to btree internal page. */ 599 h->flags &= ~P_TYPE; 600 h->flags |= P_BINTERNAL; 601 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 602 603 return (RET_SUCCESS); 604 } 605 606 /* 607 * BT_PSPLIT -- Do the real work of splitting the page. 608 * 609 * Parameters: 610 * t: tree 611 * h: page to be split 612 * l: page to put lower half of data 613 * r: page to put upper half of data 614 * pskip: pointer to index to leave open 615 * ilen: insert length 616 * 617 * Returns: 618 * Pointer to page in which to insert. 619 */ 620 static PAGE * 621 bt_psplit(t, h, l, r, pskip, ilen) 622 BTREE *t; 623 PAGE *h, *l, *r; 624 indx_t *pskip; 625 size_t ilen; 626 { 627 BINTERNAL *bi; 628 BLEAF *bl; 629 CURSOR *c; 630 RLEAF *rl; 631 PAGE *rval; 632 void *src = NULL; /* pacify gcc */ 633 indx_t full, half, nxt, off, skip, top, used; 634 u_int32_t nbytes; 635 int bigkeycnt, isbigkey; 636 637 /* 638 * Split the data to the left and right pages. Leave the skip index 639 * open. Additionally, make some effort not to split on an overflow 640 * key. This makes internal page processing faster and can save 641 * space as overflow keys used by internal pages are never deleted. 642 */ 643 bigkeycnt = 0; 644 skip = *pskip; 645 full = t->bt_psize - BTDATAOFF; 646 half = full / 2; 647 used = 0; 648 for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) { 649 if (skip == off) { 650 nbytes = ilen; 651 isbigkey = 0; /* XXX: not really known. */ 652 } else 653 switch (h->flags & P_TYPE) { 654 case P_BINTERNAL: 655 src = bi = GETBINTERNAL(h, nxt); 656 nbytes = NBINTERNAL(bi->ksize); 657 isbigkey = bi->flags & P_BIGKEY; 658 break; 659 case P_BLEAF: 660 src = bl = GETBLEAF(h, nxt); 661 nbytes = NBLEAF(bl); 662 isbigkey = bl->flags & P_BIGKEY; 663 break; 664 case P_RINTERNAL: 665 src = GETRINTERNAL(h, nxt); 666 nbytes = NRINTERNAL; 667 isbigkey = 0; 668 break; 669 case P_RLEAF: 670 src = rl = GETRLEAF(h, nxt); 671 nbytes = NRLEAF(rl); 672 isbigkey = 0; 673 break; 674 default: 675 abort(); 676 } 677 678 /* 679 * If the key/data pairs are substantial fractions of the max 680 * possible size for the page, it's possible to get situations 681 * where we decide to try and copy too much onto the left page. 682 * Make sure that doesn't happen. 683 */ 684 if ((skip <= off && used + nbytes + sizeof(indx_t) >= full) || 685 nxt == top - 1) { 686 --off; 687 break; 688 } 689 690 /* Copy the key/data pair, if not the skipped index. */ 691 if (skip != off) { 692 ++nxt; 693 694 l->linp[off] = l->upper -= nbytes; 695 memmove((char *)l + l->upper, src, nbytes); 696 } 697 698 used += nbytes + sizeof(indx_t); 699 if (used >= half) { 700 if (!isbigkey || bigkeycnt == 3) 701 break; 702 else 703 ++bigkeycnt; 704 } 705 } 706 707 /* 708 * Off is the last offset that's valid for the left page. 709 * Nxt is the first offset to be placed on the right page. 710 */ 711 l->lower += (off + 1) * sizeof(indx_t); 712 713 /* 714 * If splitting the page that the cursor was on, the cursor has to be 715 * adjusted to point to the same record as before the split. If the 716 * cursor is at or past the skipped slot, the cursor is incremented by 717 * one. If the cursor is on the right page, it is decremented by the 718 * number of records split to the left page. 719 */ 720 c = &t->bt_cursor; 721 if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) { 722 if (c->pg.index >= skip) 723 ++c->pg.index; 724 if (c->pg.index < nxt) /* Left page. */ 725 c->pg.pgno = l->pgno; 726 else { /* Right page. */ 727 c->pg.pgno = r->pgno; 728 c->pg.index -= nxt; 729 } 730 } 731 732 /* 733 * If the skipped index was on the left page, just return that page. 734 * Otherwise, adjust the skip index to reflect the new position on 735 * the right page. 736 */ 737 if (skip <= off) { 738 skip = 0; 739 rval = l; 740 } else { 741 rval = r; 742 *pskip -= nxt; 743 } 744 745 for (off = 0; nxt < top; ++off) { 746 if (skip == nxt) { 747 ++off; 748 skip = 0; 749 } 750 switch (h->flags & P_TYPE) { 751 case P_BINTERNAL: 752 src = bi = GETBINTERNAL(h, nxt); 753 nbytes = NBINTERNAL(bi->ksize); 754 break; 755 case P_BLEAF: 756 src = bl = GETBLEAF(h, nxt); 757 nbytes = NBLEAF(bl); 758 break; 759 case P_RINTERNAL: 760 src = GETRINTERNAL(h, nxt); 761 nbytes = NRINTERNAL; 762 break; 763 case P_RLEAF: 764 src = rl = GETRLEAF(h, nxt); 765 nbytes = NRLEAF(rl); 766 break; 767 default: 768 abort(); 769 } 770 ++nxt; 771 r->linp[off] = r->upper -= nbytes; 772 memmove((char *)r + r->upper, src, nbytes); 773 } 774 r->lower += off * sizeof(indx_t); 775 776 /* If the key is being appended to the page, adjust the index. */ 777 if (skip == top) 778 r->lower += sizeof(indx_t); 779 780 return (rval); 781 } 782 783 /* 784 * BT_PRESERVE -- Mark a chain of pages as used by an internal node. 785 * 786 * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the 787 * record that references them gets deleted. Chains pointed to by internal 788 * pages never get deleted. This routine marks a chain as pointed to by an 789 * internal page. 790 * 791 * Parameters: 792 * t: tree 793 * pg: page number of first page in the chain. 794 * 795 * Returns: 796 * RET_SUCCESS, RET_ERROR. 797 */ 798 static int 799 bt_preserve(t, pg) 800 BTREE *t; 801 pgno_t pg; 802 { 803 PAGE *h; 804 805 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 806 return (RET_ERROR); 807 h->flags |= P_PRESERVE; 808 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 809 return (RET_SUCCESS); 810 } 811 812 /* 813 * REC_TOTAL -- Return the number of recno entries below a page. 814 * 815 * Parameters: 816 * h: page 817 * 818 * Returns: 819 * The number of recno entries below a page. 820 * 821 * XXX 822 * These values could be set by the bt_psplit routine. The problem is that the 823 * entry has to be popped off of the stack etc. or the values have to be passed 824 * all the way back to bt_split/bt_rroot and it's not very clean. 825 */ 826 static recno_t 827 rec_total(h) 828 PAGE *h; 829 { 830 recno_t recs; 831 indx_t nxt, top; 832 833 for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt) 834 recs += GETRINTERNAL(h, nxt)->nrecs; 835 return (recs); 836 } 837