bt_split.c revision 1.6
1 /* $NetBSD: bt_split.c,v 1.6 1996/05/03 21:50:56 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 8.9 (Berkeley) 7/26/94"; 42 #else 43 static char rcsid[] = "$NetBSD: bt_split.c,v 1.6 1996/05/03 21:50:56 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 (F_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 (F_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 (F_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 #ifdef PURIFY 400 memset(l, 0xff, t->bt_psize); 401 #endif 402 l->pgno = h->pgno; 403 l->nextpg = r->pgno; 404 l->prevpg = h->prevpg; 405 l->lower = BTDATAOFF; 406 l->upper = t->bt_psize; 407 l->flags = h->flags & P_TYPE; 408 409 /* Fix up the previous pointer of the page after the split page. */ 410 if (h->nextpg != P_INVALID) { 411 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) { 412 free(l); 413 /* XXX mpool_free(t->bt_mp, r->pgno); */ 414 return (NULL); 415 } 416 tp->prevpg = r->pgno; 417 mpool_put(t->bt_mp, tp, MPOOL_DIRTY); 418 } 419 420 /* 421 * Split right. The key/data pairs aren't sorted in the btree page so 422 * it's simpler to copy the data from the split page onto two new pages 423 * instead of copying half the data to the right page and compacting 424 * the left page in place. Since the left page can't change, we have 425 * to swap the original and the allocated left page after the split. 426 */ 427 tp = bt_psplit(t, h, l, r, skip, ilen); 428 429 /* Move the new left page onto the old left page. */ 430 memmove(h, l, t->bt_psize); 431 if (tp == l) 432 tp = h; 433 free(l); 434 435 *lp = h; 436 *rp = r; 437 return (tp); 438 } 439 440 /* 441 * BT_ROOT -- Split the root page of a btree. 442 * 443 * Parameters: 444 * t: tree 445 * h: root page 446 * lp: pointer to left page pointer 447 * rp: pointer to right page pointer 448 * skip: pointer to index to leave open 449 * ilen: insert length 450 * 451 * Returns: 452 * Pointer to page in which to insert or NULL on error. 453 */ 454 static PAGE * 455 bt_root(t, h, lp, rp, skip, ilen) 456 BTREE *t; 457 PAGE *h, **lp, **rp; 458 indx_t *skip; 459 size_t ilen; 460 { 461 PAGE *l, *r, *tp; 462 pgno_t lnpg, rnpg; 463 464 #ifdef STATISTICS 465 ++bt_split; 466 ++bt_rootsplit; 467 #endif 468 /* Put the new left and right pages for the split into place. */ 469 if ((l = __bt_new(t, &lnpg)) == NULL || 470 (r = __bt_new(t, &rnpg)) == NULL) 471 return (NULL); 472 l->pgno = lnpg; 473 r->pgno = rnpg; 474 l->nextpg = r->pgno; 475 r->prevpg = l->pgno; 476 l->prevpg = r->nextpg = P_INVALID; 477 l->lower = r->lower = BTDATAOFF; 478 l->upper = r->upper = t->bt_psize; 479 l->flags = r->flags = h->flags & P_TYPE; 480 481 /* Split the root page. */ 482 tp = bt_psplit(t, h, l, r, skip, ilen); 483 484 *lp = l; 485 *rp = r; 486 return (tp); 487 } 488 489 /* 490 * BT_RROOT -- Fix up the recno root page after it has been split. 491 * 492 * Parameters: 493 * t: tree 494 * h: root page 495 * l: left page 496 * r: right page 497 * 498 * Returns: 499 * RET_ERROR, RET_SUCCESS 500 */ 501 static int 502 bt_rroot(t, h, l, r) 503 BTREE *t; 504 PAGE *h, *l, *r; 505 { 506 char *dest; 507 508 /* Insert the left and right keys, set the header information. */ 509 h->linp[0] = h->upper = t->bt_psize - NRINTERNAL; 510 dest = (char *)h + h->upper; 511 WR_RINTERNAL(dest, 512 l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno); 513 514 h->linp[1] = h->upper -= NRINTERNAL; 515 dest = (char *)h + h->upper; 516 WR_RINTERNAL(dest, 517 r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno); 518 519 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 520 521 /* Unpin the root page, set to recno internal page. */ 522 h->flags &= ~P_TYPE; 523 h->flags |= P_RINTERNAL; 524 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 525 526 return (RET_SUCCESS); 527 } 528 529 /* 530 * BT_BROOT -- Fix up the btree root page after it has been split. 531 * 532 * Parameters: 533 * t: tree 534 * h: root page 535 * l: left page 536 * r: right page 537 * 538 * Returns: 539 * RET_ERROR, RET_SUCCESS 540 */ 541 static int 542 bt_broot(t, h, l, r) 543 BTREE *t; 544 PAGE *h, *l, *r; 545 { 546 BINTERNAL *bi; 547 BLEAF *bl; 548 u_int32_t nbytes; 549 char *dest; 550 551 /* 552 * If the root page was a leaf page, change it into an internal page. 553 * We copy the key we split on (but not the key's data, in the case of 554 * a leaf page) to the new root page. 555 * 556 * The btree comparison code guarantees that the left-most key on any 557 * level of the tree is never used, so it doesn't need to be filled in. 558 */ 559 nbytes = NBINTERNAL(0); 560 h->linp[0] = h->upper = t->bt_psize - nbytes; 561 dest = (char *)h + h->upper; 562 WR_BINTERNAL(dest, 0, l->pgno, 0); 563 564 switch (h->flags & P_TYPE) { 565 case P_BLEAF: 566 bl = GETBLEAF(r, 0); 567 nbytes = NBINTERNAL(bl->ksize); 568 h->linp[1] = h->upper -= nbytes; 569 dest = (char *)h + h->upper; 570 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0); 571 memmove(dest, bl->bytes, bl->ksize); 572 573 /* 574 * If the key is on an overflow page, mark the overflow chain 575 * so it isn't deleted when the leaf copy of the key is deleted. 576 */ 577 if (bl->flags & P_BIGKEY && 578 bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) 579 return (RET_ERROR); 580 break; 581 case P_BINTERNAL: 582 bi = GETBINTERNAL(r, 0); 583 nbytes = NBINTERNAL(bi->ksize); 584 h->linp[1] = h->upper -= nbytes; 585 dest = (char *)h + h->upper; 586 memmove(dest, bi, nbytes); 587 ((BINTERNAL *)dest)->pgno = r->pgno; 588 break; 589 default: 590 abort(); 591 } 592 593 /* There are two keys on the page. */ 594 h->lower = BTDATAOFF + 2 * sizeof(indx_t); 595 596 /* Unpin the root page, set to btree internal page. */ 597 h->flags &= ~P_TYPE; 598 h->flags |= P_BINTERNAL; 599 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 600 601 return (RET_SUCCESS); 602 } 603 604 /* 605 * BT_PSPLIT -- Do the real work of splitting the page. 606 * 607 * Parameters: 608 * t: tree 609 * h: page to be split 610 * l: page to put lower half of data 611 * r: page to put upper half of data 612 * pskip: pointer to index to leave open 613 * ilen: insert length 614 * 615 * Returns: 616 * Pointer to page in which to insert. 617 */ 618 static PAGE * 619 bt_psplit(t, h, l, r, pskip, ilen) 620 BTREE *t; 621 PAGE *h, *l, *r; 622 indx_t *pskip; 623 size_t ilen; 624 { 625 BINTERNAL *bi; 626 BLEAF *bl; 627 CURSOR *c; 628 RLEAF *rl; 629 PAGE *rval; 630 void *src; 631 indx_t full, half, nxt, off, skip, top, used; 632 u_int32_t nbytes; 633 int bigkeycnt, isbigkey; 634 635 /* 636 * Split the data to the left and right pages. Leave the skip index 637 * open. Additionally, make some effort not to split on an overflow 638 * key. This makes internal page processing faster and can save 639 * space as overflow keys used by internal pages are never deleted. 640 */ 641 bigkeycnt = 0; 642 skip = *pskip; 643 full = t->bt_psize - BTDATAOFF; 644 half = full / 2; 645 used = 0; 646 for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) { 647 if (skip == off) { 648 nbytes = ilen; 649 isbigkey = 0; /* XXX: not really known. */ 650 } else 651 switch (h->flags & P_TYPE) { 652 case P_BINTERNAL: 653 src = bi = GETBINTERNAL(h, nxt); 654 nbytes = NBINTERNAL(bi->ksize); 655 isbigkey = bi->flags & P_BIGKEY; 656 break; 657 case P_BLEAF: 658 src = bl = GETBLEAF(h, nxt); 659 nbytes = NBLEAF(bl); 660 isbigkey = bl->flags & P_BIGKEY; 661 break; 662 case P_RINTERNAL: 663 src = GETRINTERNAL(h, nxt); 664 nbytes = NRINTERNAL; 665 isbigkey = 0; 666 break; 667 case P_RLEAF: 668 src = rl = GETRLEAF(h, nxt); 669 nbytes = NRLEAF(rl); 670 isbigkey = 0; 671 break; 672 default: 673 abort(); 674 } 675 676 /* 677 * If the key/data pairs are substantial fractions of the max 678 * possible size for the page, it's possible to get situations 679 * where we decide to try and copy too much onto the left page. 680 * Make sure that doesn't happen. 681 */ 682 if (skip <= off && used + nbytes >= full) { 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 *)l + l->upper, src, nbytes); 693 } 694 695 used += nbytes; 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 = 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
Indexes created Thu Sep 25 16:09:42 GMT 2025