| 1 | /*- |
| 2 | * Copyright (c) 1990, 1993, 1994 |
| 3 | * The Regents of the University of California. All rights reserved. |
| 4 | * |
| 5 | * This code is derived from software contributed to Berkeley by |
| 6 | * Mike Olson. |
| 7 | * |
| 8 | * Redistribution and use in source and binary forms, with or without |
| 9 | * modification, are permitted provided that the following conditions |
| 10 | * are met: |
| 11 | * 1. Redistributions of source code must retain the above copyright |
| 12 | * notice, this list of conditions and the following disclaimer. |
| 13 | * 2. Redistributions in binary form must reproduce the above copyright |
| 14 | * notice, this list of conditions and the following disclaimer in the |
| 15 | * documentation and/or other materials provided with the distribution. |
| 16 | * 3. Neither the name of the University nor the names of its contributors |
| 17 | * may be used to endorse or promote products derived from this software |
| 18 | * without specific prior written permission. |
| 19 | * |
| 20 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
| 21 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 22 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 23 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
| 24 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 25 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 26 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 27 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| 28 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| 29 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 30 | * SUCH DAMAGE. |
| 31 | * |
| 32 | * @(#)bt_split.c 8.9 (Berkeley) 7/26/94 |
| 33 | * $DragonFly: src/lib/libc/db/btree/bt_split.c,v 1.8 2005/11/19 20:46:32 swildner Exp $ |
| 34 | */ |
| 35 | |
| 36 | #include <sys/types.h> |
| 37 | |
| 38 | #include <limits.h> |
| 39 | #include <stdio.h> |
| 40 | #include <stdlib.h> |
| 41 | #include <string.h> |
| 42 | |
| 43 | #include <db.h> |
| 44 | #include "btree.h" |
| 45 | |
| 46 | static int bt_broot(BTREE *, PAGE *, PAGE *, PAGE *); |
| 47 | static PAGE *bt_page(BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t); |
| 48 | static int bt_preserve(BTREE *, pgno_t); |
| 49 | static PAGE *bt_psplit(BTREE *, PAGE *, PAGE *, PAGE *, indx_t *, size_t); |
| 50 | static PAGE *bt_root(BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t); |
| 51 | static int bt_rroot(BTREE *, PAGE *, PAGE *, PAGE *); |
| 52 | static recno_t rec_total(PAGE *); |
| 53 | |
| 54 | #ifdef STATISTICS |
| 55 | u_long bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved; |
| 56 | #endif |
| 57 | |
| 58 | /* |
| 59 | * __BT_SPLIT -- Split the tree. |
| 60 | * |
| 61 | * Parameters: |
| 62 | * t: tree |
| 63 | * sp: page to split |
| 64 | * key: key to insert |
| 65 | * data: data to insert |
| 66 | * flags: BIGKEY/BIGDATA flags |
| 67 | * ilen: insert length |
| 68 | * skip: index to leave open |
| 69 | * |
| 70 | * Returns: |
| 71 | * RET_ERROR, RET_SUCCESS |
| 72 | */ |
| 73 | int |
| 74 | __bt_split(BTREE *t, PAGE *sp, const DBT *key, const DBT *data, int flags, |
| 75 | size_t ilen, u_int32_t argskip) |
| 76 | { |
| 77 | BINTERNAL *bi; |
| 78 | BLEAF *bl, *tbl; |
| 79 | DBT a, b; |
| 80 | EPGNO *parent; |
| 81 | PAGE *h, *l, *r, *lchild, *rchild; |
| 82 | indx_t nxtindex; |
| 83 | u_int16_t skip; |
| 84 | u_int32_t n, nbytes, nksize; |
| 85 | int parentsplit; |
| 86 | char *dest; |
| 87 | |
| 88 | bi = NULL; |
| 89 | bl = NULL; |
| 90 | nksize = 0; |
| 91 | /* |
| 92 | * Split the page into two pages, l and r. The split routines return |
| 93 | * a pointer to the page into which the key should be inserted and with |
| 94 | * skip set to the offset which should be used. Additionally, l and r |
| 95 | * are pinned. |
| 96 | */ |
| 97 | skip = argskip; |
| 98 | h = sp->pgno == P_ROOT ? |
| 99 | bt_root(t, sp, &l, &r, &skip, ilen) : |
| 100 | bt_page(t, sp, &l, &r, &skip, ilen); |
| 101 | if (h == NULL) |
| 102 | return (RET_ERROR); |
| 103 | |
| 104 | /* |
| 105 | * Insert the new key/data pair into the leaf page. (Key inserts |
| 106 | * always cause a leaf page to split first.) |
| 107 | */ |
| 108 | h->linp[skip] = h->upper -= ilen; |
| 109 | dest = (char *)h + h->upper; |
| 110 | if (F_ISSET(t, R_RECNO)) |
| 111 | WR_RLEAF(dest, data, flags) |
| 112 | else |
| 113 | WR_BLEAF(dest, key, data, flags) |
| 114 | |
| 115 | /* If the root page was split, make it look right. */ |
| 116 | if (sp->pgno == P_ROOT && |
| 117 | (F_ISSET(t, R_RECNO) ? |
| 118 | bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) |
| 119 | goto err2; |
| 120 | |
| 121 | /* |
| 122 | * Now we walk the parent page stack -- a LIFO stack of the pages that |
| 123 | * were traversed when we searched for the page that split. Each stack |
| 124 | * entry is a page number and a page index offset. The offset is for |
| 125 | * the page traversed on the search. We've just split a page, so we |
| 126 | * have to insert a new key into the parent page. |
| 127 | * |
| 128 | * If the insert into the parent page causes it to split, may have to |
| 129 | * continue splitting all the way up the tree. We stop if the root |
| 130 | * splits or the page inserted into didn't have to split to hold the |
| 131 | * new key. Some algorithms replace the key for the old page as well |
| 132 | * as the new page. We don't, as there's no reason to believe that the |
| 133 | * first key on the old page is any better than the key we have, and, |
| 134 | * in the case of a key being placed at index 0 causing the split, the |
| 135 | * key is unavailable. |
| 136 | * |
| 137 | * There are a maximum of 5 pages pinned at any time. We keep the left |
| 138 | * and right pages pinned while working on the parent. The 5 are the |
| 139 | * two children, left parent and right parent (when the parent splits) |
| 140 | * and the root page or the overflow key page when calling bt_preserve. |
| 141 | * This code must make sure that all pins are released other than the |
| 142 | * root page or overflow page which is unlocked elsewhere. |
| 143 | */ |
| 144 | while ((parent = BT_POP(t)) != NULL) { |
| 145 | lchild = l; |
| 146 | rchild = r; |
| 147 | |
| 148 | /* Get the parent page. */ |
| 149 | if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) |
| 150 | goto err2; |
| 151 | |
| 152 | /* |
| 153 | * The new key goes ONE AFTER the index, because the split |
| 154 | * was to the right. |
| 155 | */ |
| 156 | skip = parent->index + 1; |
| 157 | |
| 158 | /* |
| 159 | * Calculate the space needed on the parent page. |
| 160 | * |
| 161 | * Prefix trees: space hack when inserting into BINTERNAL |
| 162 | * pages. Retain only what's needed to distinguish between |
| 163 | * the new entry and the LAST entry on the page to its left. |
| 164 | * If the keys compare equal, retain the entire key. Note, |
| 165 | * we don't touch overflow keys, and the entire key must be |
| 166 | * retained for the next-to-left most key on the leftmost |
| 167 | * page of each level, or the search will fail. Applicable |
| 168 | * ONLY to internal pages that have leaf pages as children. |
| 169 | * Further reduction of the key between pairs of internal |
| 170 | * pages loses too much information. |
| 171 | */ |
| 172 | switch (rchild->flags & P_TYPE) { |
| 173 | case P_BINTERNAL: |
| 174 | bi = GETBINTERNAL(rchild, 0); |
| 175 | nbytes = NBINTERNAL(bi->ksize); |
| 176 | break; |
| 177 | case P_BLEAF: |
| 178 | bl = GETBLEAF(rchild, 0); |
| 179 | nbytes = NBINTERNAL(bl->ksize); |
| 180 | if (t->bt_pfx && !(bl->flags & P_BIGKEY) && |
| 181 | (h->prevpg != P_INVALID || skip > 1)) { |
| 182 | tbl = GETBLEAF(lchild, NEXTINDEX(lchild) - 1); |
| 183 | a.size = tbl->ksize; |
| 184 | a.data = tbl->bytes; |
| 185 | b.size = bl->ksize; |
| 186 | b.data = bl->bytes; |
| 187 | nksize = t->bt_pfx(&a, &b); |
| 188 | n = NBINTERNAL(nksize); |
| 189 | if (n < nbytes) { |
| 190 | #ifdef STATISTICS |
| 191 | bt_pfxsaved += nbytes - n; |
| 192 | #endif |
| 193 | nbytes = n; |
| 194 | } else |
| 195 | nksize = 0; |
| 196 | } else |
| 197 | nksize = 0; |
| 198 | break; |
| 199 | case P_RINTERNAL: |
| 200 | case P_RLEAF: |
| 201 | nbytes = NRINTERNAL; |
| 202 | break; |
| 203 | default: |
| 204 | abort(); |
| 205 | } |
| 206 | |
| 207 | /* Split the parent page if necessary or shift the indices. */ |
| 208 | if (h->upper - h->lower < nbytes + sizeof(indx_t)) { |
| 209 | sp = h; |
| 210 | h = h->pgno == P_ROOT ? |
| 211 | bt_root(t, h, &l, &r, &skip, nbytes) : |
| 212 | bt_page(t, h, &l, &r, &skip, nbytes); |
| 213 | if (h == NULL) |
| 214 | goto err1; |
| 215 | parentsplit = 1; |
| 216 | } else { |
| 217 | if (skip < (nxtindex = NEXTINDEX(h))) |
| 218 | memmove(h->linp + skip + 1, h->linp + skip, |
| 219 | (nxtindex - skip) * sizeof(indx_t)); |
| 220 | h->lower += sizeof(indx_t); |
| 221 | parentsplit = 0; |
| 222 | } |
| 223 | |
| 224 | /* Insert the key into the parent page. */ |
| 225 | switch (rchild->flags & P_TYPE) { |
| 226 | case P_BINTERNAL: |
| 227 | h->linp[skip] = h->upper -= nbytes; |
| 228 | dest = (char *)h + h->linp[skip]; |
| 229 | memmove(dest, bi, nbytes); |
| 230 | ((BINTERNAL *)dest)->pgno = rchild->pgno; |
| 231 | break; |
| 232 | case P_BLEAF: |
| 233 | h->linp[skip] = h->upper -= nbytes; |
| 234 | dest = (char *)h + h->linp[skip]; |
| 235 | WR_BINTERNAL(dest, nksize ? nksize : bl->ksize, |
| 236 | rchild->pgno, bl->flags & P_BIGKEY); |
| 237 | memmove(dest, bl->bytes, nksize ? nksize : bl->ksize); |
| 238 | if (bl->flags & P_BIGKEY && |
| 239 | bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) |
| 240 | goto err1; |
| 241 | break; |
| 242 | case P_RINTERNAL: |
| 243 | /* |
| 244 | * Update the left page count. If split |
| 245 | * added at index 0, fix the correct page. |
| 246 | */ |
| 247 | if (skip > 0) |
| 248 | dest = (char *)h + h->linp[skip - 1]; |
| 249 | else |
| 250 | dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; |
| 251 | ((RINTERNAL *)dest)->nrecs = rec_total(lchild); |
| 252 | ((RINTERNAL *)dest)->pgno = lchild->pgno; |
| 253 | |
| 254 | /* Update the right page count. */ |
| 255 | h->linp[skip] = h->upper -= nbytes; |
| 256 | dest = (char *)h + h->linp[skip]; |
| 257 | ((RINTERNAL *)dest)->nrecs = rec_total(rchild); |
| 258 | ((RINTERNAL *)dest)->pgno = rchild->pgno; |
| 259 | break; |
| 260 | case P_RLEAF: |
| 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 = NEXTINDEX(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 = NEXTINDEX(rchild); |
| 276 | ((RINTERNAL *)dest)->pgno = rchild->pgno; |
| 277 | break; |
| 278 | default: |
| 279 | abort(); |
| 280 | } |
| 281 | |
| 282 | /* Unpin the held pages. */ |
| 283 | if (!parentsplit) { |
| 284 | mpool_put(t->bt_mp, h, MPOOL_DIRTY); |
| 285 | break; |
| 286 | } |
| 287 | |
| 288 | /* If the root page was split, make it look right. */ |
| 289 | if (sp->pgno == P_ROOT && |
| 290 | (F_ISSET(t, R_RECNO) ? |
| 291 | bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) |
| 292 | goto err1; |
| 293 | |
| 294 | mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); |
| 295 | mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); |
| 296 | } |
| 297 | |
| 298 | /* Unpin the held pages. */ |
| 299 | mpool_put(t->bt_mp, l, MPOOL_DIRTY); |
| 300 | mpool_put(t->bt_mp, r, MPOOL_DIRTY); |
| 301 | |
| 302 | /* Clear any pages left on the stack. */ |
| 303 | return (RET_SUCCESS); |
| 304 | |
| 305 | /* |
| 306 | * If something fails in the above loop we were already walking back |
| 307 | * up the tree and the tree is now inconsistent. Nothing much we can |
| 308 | * do about it but release any memory we're holding. |
| 309 | */ |
| 310 | err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); |
| 311 | mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); |
| 312 | |
| 313 | err2: mpool_put(t->bt_mp, l, 0); |
| 314 | mpool_put(t->bt_mp, r, 0); |
| 315 | __dbpanic(t->bt_dbp); |
| 316 | return (RET_ERROR); |
| 317 | } |
| 318 | |
| 319 | /* |
| 320 | * BT_PAGE -- Split a non-root page of a btree. |
| 321 | * |
| 322 | * Parameters: |
| 323 | * t: tree |
| 324 | * h: root page |
| 325 | * lp: pointer to left page pointer |
| 326 | * rp: pointer to right page pointer |
| 327 | * skip: pointer to index to leave open |
| 328 | * ilen: insert length |
| 329 | * |
| 330 | * Returns: |
| 331 | * Pointer to page in which to insert or NULL on error. |
| 332 | */ |
| 333 | static PAGE * |
| 334 | bt_page(BTREE *t, PAGE *h, PAGE **lp, PAGE **rp, indx_t *skip, size_t ilen) |
| 335 | { |
| 336 | PAGE *l, *r, *tp; |
| 337 | pgno_t npg; |
| 338 | |
| 339 | #ifdef STATISTICS |
| 340 | ++bt_split; |
| 341 | #endif |
| 342 | /* Put the new right page for the split into place. */ |
| 343 | if ((r = __bt_new(t, &npg)) == NULL) |
| 344 | return (NULL); |
| 345 | r->pgno = npg; |
| 346 | r->lower = BTDATAOFF; |
| 347 | r->upper = t->bt_psize; |
| 348 | r->nextpg = h->nextpg; |
| 349 | r->prevpg = h->pgno; |
| 350 | r->flags = h->flags & P_TYPE; |
| 351 | |
| 352 | /* |
| 353 | * If we're splitting the last page on a level because we're appending |
| 354 | * a key to it (skip is NEXTINDEX()), it's likely that the data is |
| 355 | * sorted. Adding an empty page on the side of the level is less work |
| 356 | * and can push the fill factor much higher than normal. If we're |
| 357 | * wrong it's no big deal, we'll just do the split the right way next |
| 358 | * time. It may look like it's equally easy to do a similar hack for |
| 359 | * reverse sorted data, that is, split the tree left, but it's not. |
| 360 | * Don't even try. |
| 361 | */ |
| 362 | if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) { |
| 363 | #ifdef STATISTICS |
| 364 | ++bt_sortsplit; |
| 365 | #endif |
| 366 | h->nextpg = r->pgno; |
| 367 | r->lower = BTDATAOFF + sizeof(indx_t); |
| 368 | *skip = 0; |
| 369 | *lp = h; |
| 370 | *rp = r; |
| 371 | return (r); |
| 372 | } |
| 373 | |
| 374 | /* Put the new left page for the split into place. */ |
| 375 | if ((l = (PAGE *)calloc(1, t->bt_psize)) == NULL) { |
| 376 | mpool_put(t->bt_mp, r, 0); |
| 377 | return (NULL); |
| 378 | } |
| 379 | #ifdef PURIFY |
| 380 | memset(l, 0xff, t->bt_psize); |
| 381 | #endif |
| 382 | l->pgno = h->pgno; |
| 383 | l->nextpg = r->pgno; |
| 384 | l->prevpg = h->prevpg; |
| 385 | l->lower = BTDATAOFF; |
| 386 | l->upper = t->bt_psize; |
| 387 | l->flags = h->flags & P_TYPE; |
| 388 | |
| 389 | /* Fix up the previous pointer of the page after the split page. */ |
| 390 | if (h->nextpg != P_INVALID) { |
| 391 | if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) { |
| 392 | free(l); |
| 393 | /* XXX mpool_free(t->bt_mp, r->pgno); */ |
| 394 | return (NULL); |
| 395 | } |
| 396 | tp->prevpg = r->pgno; |
| 397 | mpool_put(t->bt_mp, tp, MPOOL_DIRTY); |
| 398 | } |
| 399 | |
| 400 | /* |
| 401 | * Split right. The key/data pairs aren't sorted in the btree page so |
| 402 | * it's simpler to copy the data from the split page onto two new pages |
| 403 | * instead of copying half the data to the right page and compacting |
| 404 | * the left page in place. Since the left page can't change, we have |
| 405 | * to swap the original and the allocated left page after the split. |
| 406 | */ |
| 407 | tp = bt_psplit(t, h, l, r, skip, ilen); |
| 408 | |
| 409 | /* Move the new left page onto the old left page. */ |
| 410 | memmove(h, l, t->bt_psize); |
| 411 | if (tp == l) |
| 412 | tp = h; |
| 413 | free(l); |
| 414 | |
| 415 | *lp = h; |
| 416 | *rp = r; |
| 417 | return (tp); |
| 418 | } |
| 419 | |
| 420 | /* |
| 421 | * BT_ROOT -- Split the root page of a btree. |
| 422 | * |
| 423 | * Parameters: |
| 424 | * t: tree |
| 425 | * h: root page |
| 426 | * lp: pointer to left page pointer |
| 427 | * rp: pointer to right page pointer |
| 428 | * skip: pointer to index to leave open |
| 429 | * ilen: insert length |
| 430 | * |
| 431 | * Returns: |
| 432 | * Pointer to page in which to insert or NULL on error. |
| 433 | */ |
| 434 | static PAGE * |
| 435 | bt_root(BTREE *t, PAGE *h, PAGE **lp, PAGE **rp, indx_t *skip, size_t ilen) |
| 436 | { |
| 437 | PAGE *l, *r, *tp; |
| 438 | pgno_t lnpg, rnpg; |
| 439 | |
| 440 | #ifdef STATISTICS |
| 441 | ++bt_split; |
| 442 | ++bt_rootsplit; |
| 443 | #endif |
| 444 | /* Put the new left and right pages for the split into place. */ |
| 445 | if ((l = __bt_new(t, &lnpg)) == NULL || |
| 446 | (r = __bt_new(t, &rnpg)) == NULL) |
| 447 | return (NULL); |
| 448 | l->pgno = lnpg; |
| 449 | r->pgno = rnpg; |
| 450 | l->nextpg = r->pgno; |
| 451 | r->prevpg = l->pgno; |
| 452 | l->prevpg = r->nextpg = P_INVALID; |
| 453 | l->lower = r->lower = BTDATAOFF; |
| 454 | l->upper = r->upper = t->bt_psize; |
| 455 | l->flags = r->flags = h->flags & P_TYPE; |
| 456 | |
| 457 | /* Split the root page. */ |
| 458 | tp = bt_psplit(t, h, l, r, skip, ilen); |
| 459 | |
| 460 | *lp = l; |
| 461 | *rp = r; |
| 462 | return (tp); |
| 463 | } |
| 464 | |
| 465 | /* |
| 466 | * BT_RROOT -- Fix up the recno root page after it has been split. |
| 467 | * |
| 468 | * Parameters: |
| 469 | * t: tree |
| 470 | * h: root page |
| 471 | * l: left page |
| 472 | * r: right page |
| 473 | * |
| 474 | * Returns: |
| 475 | * RET_ERROR, RET_SUCCESS |
| 476 | */ |
| 477 | static int |
| 478 | bt_rroot(BTREE *t, PAGE *h, PAGE *l, PAGE *r) |
| 479 | { |
| 480 | char *dest; |
| 481 | |
| 482 | /* Insert the left and right keys, set the header information. */ |
| 483 | h->linp[0] = h->upper = t->bt_psize - NRINTERNAL; |
| 484 | dest = (char *)h + h->upper; |
| 485 | WR_RINTERNAL(dest, |
| 486 | l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno); |
| 487 | |
| 488 | h->linp[1] = h->upper -= NRINTERNAL; |
| 489 | dest = (char *)h + h->upper; |
| 490 | WR_RINTERNAL(dest, |
| 491 | r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno); |
| 492 | |
| 493 | h->lower = BTDATAOFF + 2 * sizeof(indx_t); |
| 494 | |
| 495 | /* Unpin the root page, set to recno internal page. */ |
| 496 | h->flags &= ~P_TYPE; |
| 497 | h->flags |= P_RINTERNAL; |
| 498 | mpool_put(t->bt_mp, h, MPOOL_DIRTY); |
| 499 | |
| 500 | return (RET_SUCCESS); |
| 501 | } |
| 502 | |
| 503 | /* |
| 504 | * BT_BROOT -- Fix up the btree root page after it has been split. |
| 505 | * |
| 506 | * Parameters: |
| 507 | * t: tree |
| 508 | * h: root page |
| 509 | * l: left page |
| 510 | * r: right page |
| 511 | * |
| 512 | * Returns: |
| 513 | * RET_ERROR, RET_SUCCESS |
| 514 | */ |
| 515 | static int |
| 516 | bt_broot(BTREE *t, PAGE *h, PAGE *l, PAGE *r) |
| 517 | { |
| 518 | BINTERNAL *bi; |
| 519 | BLEAF *bl; |
| 520 | u_int32_t nbytes; |
| 521 | char *dest; |
| 522 | |
| 523 | /* |
| 524 | * If the root page was a leaf page, change it into an internal page. |
| 525 | * We copy the key we split on (but not the key's data, in the case of |
| 526 | * a leaf page) to the new root page. |
| 527 | * |
| 528 | * The btree comparison code guarantees that the left-most key on any |
| 529 | * level of the tree is never used, so it doesn't need to be filled in. |
| 530 | */ |
| 531 | nbytes = NBINTERNAL(0); |
| 532 | h->linp[0] = h->upper = t->bt_psize - nbytes; |
| 533 | dest = (char *)h + h->upper; |
| 534 | WR_BINTERNAL(dest, 0, l->pgno, 0); |
| 535 | |
| 536 | switch (h->flags & P_TYPE) { |
| 537 | case P_BLEAF: |
| 538 | bl = GETBLEAF(r, 0); |
| 539 | nbytes = NBINTERNAL(bl->ksize); |
| 540 | h->linp[1] = h->upper -= nbytes; |
| 541 | dest = (char *)h + h->upper; |
| 542 | WR_BINTERNAL(dest, bl->ksize, r->pgno, 0); |
| 543 | memmove(dest, bl->bytes, bl->ksize); |
| 544 | |
| 545 | /* |
| 546 | * If the key is on an overflow page, mark the overflow chain |
| 547 | * so it isn't deleted when the leaf copy of the key is deleted. |
| 548 | */ |
| 549 | if (bl->flags & P_BIGKEY && |
| 550 | bt_preserve(t, *(pgno_t *)bl->bytes) == RET_ERROR) |
| 551 | return (RET_ERROR); |
| 552 | break; |
| 553 | case P_BINTERNAL: |
| 554 | bi = GETBINTERNAL(r, 0); |
| 555 | nbytes = NBINTERNAL(bi->ksize); |
| 556 | h->linp[1] = h->upper -= nbytes; |
| 557 | dest = (char *)h + h->upper; |
| 558 | memmove(dest, bi, nbytes); |
| 559 | ((BINTERNAL *)dest)->pgno = r->pgno; |
| 560 | break; |
| 561 | default: |
| 562 | abort(); |
| 563 | } |
| 564 | |
| 565 | /* There are two keys on the page. */ |
| 566 | h->lower = BTDATAOFF + 2 * sizeof(indx_t); |
| 567 | |
| 568 | /* Unpin the root page, set to btree internal page. */ |
| 569 | h->flags &= ~P_TYPE; |
| 570 | h->flags |= P_BINTERNAL; |
| 571 | mpool_put(t->bt_mp, h, MPOOL_DIRTY); |
| 572 | |
| 573 | return (RET_SUCCESS); |
| 574 | } |
| 575 | |
| 576 | /* |
| 577 | * BT_PSPLIT -- Do the real work of splitting the page. |
| 578 | * |
| 579 | * Parameters: |
| 580 | * t: tree |
| 581 | * h: page to be split |
| 582 | * l: page to put lower half of data |
| 583 | * r: page to put upper half of data |
| 584 | * pskip: pointer to index to leave open |
| 585 | * ilen: insert length |
| 586 | * |
| 587 | * Returns: |
| 588 | * Pointer to page in which to insert. |
| 589 | */ |
| 590 | static PAGE * |
| 591 | bt_psplit(BTREE *t, PAGE *h, PAGE *l, PAGE *r, indx_t *pskip, size_t ilen) |
| 592 | { |
| 593 | BINTERNAL *bi; |
| 594 | BLEAF *bl; |
| 595 | CURSOR *c; |
| 596 | RLEAF *rl; |
| 597 | PAGE *rval; |
| 598 | void *src; |
| 599 | indx_t full, half, nxt, off, skip, top, used; |
| 600 | u_int32_t nbytes; |
| 601 | int bigkeycnt, isbigkey; |
| 602 | |
| 603 | src = NULL; |
| 604 | /* |
| 605 | * Split the data to the left and right pages. Leave the skip index |
| 606 | * open. Additionally, make some effort not to split on an overflow |
| 607 | * key. This makes internal page processing faster and can save |
| 608 | * space as overflow keys used by internal pages are never deleted. |
| 609 | */ |
| 610 | bigkeycnt = 0; |
| 611 | skip = *pskip; |
| 612 | full = t->bt_psize - BTDATAOFF; |
| 613 | half = full / 2; |
| 614 | used = 0; |
| 615 | for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) { |
| 616 | if (skip == off) { |
| 617 | nbytes = ilen; |
| 618 | isbigkey = 0; /* XXX: not really known. */ |
| 619 | } else |
| 620 | switch (h->flags & P_TYPE) { |
| 621 | case P_BINTERNAL: |
| 622 | src = bi = GETBINTERNAL(h, nxt); |
| 623 | nbytes = NBINTERNAL(bi->ksize); |
| 624 | isbigkey = bi->flags & P_BIGKEY; |
| 625 | break; |
| 626 | case P_BLEAF: |
| 627 | src = bl = GETBLEAF(h, nxt); |
| 628 | nbytes = NBLEAF(bl); |
| 629 | isbigkey = bl->flags & P_BIGKEY; |
| 630 | break; |
| 631 | case P_RINTERNAL: |
| 632 | src = GETRINTERNAL(h, nxt); |
| 633 | nbytes = NRINTERNAL; |
| 634 | isbigkey = 0; |
| 635 | break; |
| 636 | case P_RLEAF: |
| 637 | src = rl = GETRLEAF(h, nxt); |
| 638 | nbytes = NRLEAF(rl); |
| 639 | isbigkey = 0; |
| 640 | break; |
| 641 | default: |
| 642 | abort(); |
| 643 | } |
| 644 | |
| 645 | /* |
| 646 | * If the key/data pairs are substantial fractions of the max |
| 647 | * possible size for the page, it's possible to get situations |
| 648 | * where we decide to try and copy too much onto the left page. |
| 649 | * Make sure that doesn't happen. |
| 650 | */ |
| 651 | if ((skip <= off && |
| 652 | used + nbytes + sizeof(indx_t) >= full) || nxt == top - 1) { |
| 653 | --off; |
| 654 | break; |
| 655 | } |
| 656 | |
| 657 | /* Copy the key/data pair, if not the skipped index. */ |
| 658 | if (skip != off) { |
| 659 | ++nxt; |
| 660 | |
| 661 | l->linp[off] = l->upper -= nbytes; |
| 662 | memmove((char *)l + l->upper, src, nbytes); |
| 663 | } |
| 664 | |
| 665 | used += nbytes + sizeof(indx_t); |
| 666 | if (used >= half) { |
| 667 | if (!isbigkey || bigkeycnt == 3) |
| 668 | break; |
| 669 | else |
| 670 | ++bigkeycnt; |
| 671 | } |
| 672 | } |
| 673 | |
| 674 | /* |
| 675 | * Off is the last offset that's valid for the left page. |
| 676 | * Nxt is the first offset to be placed on the right page. |
| 677 | */ |
| 678 | l->lower += (off + 1) * sizeof(indx_t); |
| 679 | |
| 680 | /* |
| 681 | * If splitting the page that the cursor was on, the cursor has to be |
| 682 | * adjusted to point to the same record as before the split. If the |
| 683 | * cursor is at or past the skipped slot, the cursor is incremented by |
| 684 | * one. If the cursor is on the right page, it is decremented by the |
| 685 | * number of records split to the left page. |
| 686 | */ |
| 687 | c = &t->bt_cursor; |
| 688 | if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) { |
| 689 | if (c->pg.index >= skip) |
| 690 | ++c->pg.index; |
| 691 | if (c->pg.index < nxt) /* Left page. */ |
| 692 | c->pg.pgno = l->pgno; |
| 693 | else { /* Right page. */ |
| 694 | c->pg.pgno = r->pgno; |
| 695 | c->pg.index -= nxt; |
| 696 | } |
| 697 | } |
| 698 | |
| 699 | /* |
| 700 | * If the skipped index was on the left page, just return that page. |
| 701 | * Otherwise, adjust the skip index to reflect the new position on |
| 702 | * the right page. |
| 703 | */ |
| 704 | if (skip <= off) { |
| 705 | skip = MAX_PAGE_OFFSET; |
| 706 | rval = l; |
| 707 | } else { |
| 708 | rval = r; |
| 709 | *pskip -= nxt; |
| 710 | } |
| 711 | |
| 712 | for (off = 0; nxt < top; ++off) { |
| 713 | if (skip == nxt) { |
| 714 | ++off; |
| 715 | skip = MAX_PAGE_OFFSET; |
| 716 | } |
| 717 | switch (h->flags & P_TYPE) { |
| 718 | case P_BINTERNAL: |
| 719 | src = bi = GETBINTERNAL(h, nxt); |
| 720 | nbytes = NBINTERNAL(bi->ksize); |
| 721 | break; |
| 722 | case P_BLEAF: |
| 723 | src = bl = GETBLEAF(h, nxt); |
| 724 | nbytes = NBLEAF(bl); |
| 725 | break; |
| 726 | case P_RINTERNAL: |
| 727 | src = GETRINTERNAL(h, nxt); |
| 728 | nbytes = NRINTERNAL; |
| 729 | break; |
| 730 | case P_RLEAF: |
| 731 | src = rl = GETRLEAF(h, nxt); |
| 732 | nbytes = NRLEAF(rl); |
| 733 | break; |
| 734 | default: |
| 735 | abort(); |
| 736 | } |
| 737 | ++nxt; |
| 738 | r->linp[off] = r->upper -= nbytes; |
| 739 | memmove((char *)r + r->upper, src, nbytes); |
| 740 | } |
| 741 | r->lower += off * sizeof(indx_t); |
| 742 | |
| 743 | /* If the key is being appended to the page, adjust the index. */ |
| 744 | if (skip == top) |
| 745 | r->lower += sizeof(indx_t); |
| 746 | |
| 747 | return (rval); |
| 748 | } |
| 749 | |
| 750 | /* |
| 751 | * BT_PRESERVE -- Mark a chain of pages as used by an internal node. |
| 752 | * |
| 753 | * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the |
| 754 | * record that references them gets deleted. Chains pointed to by internal |
| 755 | * pages never get deleted. This routine marks a chain as pointed to by an |
| 756 | * internal page. |
| 757 | * |
| 758 | * Parameters: |
| 759 | * t: tree |
| 760 | * pg: page number of first page in the chain. |
| 761 | * |
| 762 | * Returns: |
| 763 | * RET_SUCCESS, RET_ERROR. |
| 764 | */ |
| 765 | static int |
| 766 | bt_preserve(BTREE *t, pgno_t pg) |
| 767 | { |
| 768 | PAGE *h; |
| 769 | |
| 770 | if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) |
| 771 | return (RET_ERROR); |
| 772 | h->flags |= P_PRESERVE; |
| 773 | mpool_put(t->bt_mp, h, MPOOL_DIRTY); |
| 774 | return (RET_SUCCESS); |
| 775 | } |
| 776 | |
| 777 | /* |
| 778 | * REC_TOTAL -- Return the number of recno entries below a page. |
| 779 | * |
| 780 | * Parameters: |
| 781 | * h: page |
| 782 | * |
| 783 | * Returns: |
| 784 | * The number of recno entries below a page. |
| 785 | * |
| 786 | * XXX |
| 787 | * These values could be set by the bt_psplit routine. The problem is that the |
| 788 | * entry has to be popped off of the stack etc. or the values have to be passed |
| 789 | * all the way back to bt_split/bt_rroot and it's not very clean. |
| 790 | */ |
| 791 | static recno_t |
| 792 | rec_total(PAGE *h) |
| 793 | { |
| 794 | recno_t recs; |
| 795 | indx_t nxt, top; |
| 796 | |
| 797 | for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt) |
| 798 | recs += GETRINTERNAL(h, nxt)->nrecs; |
| 799 | return (recs); |
| 800 | } |