lib/libc/db/btree/bt_split.c

   1 /*      $NetBSD: bt_split.c,v 1.19 2009/04/22 18:44:06 christos 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 #if HAVE_NBTOOL_CONFIG_H
  36 #include "nbtool_config.h"
  37 #endif
  38
  39 #include <sys/cdefs.h>
  40 __RCSID("$NetBSD: bt_split.c,v 1.19 2009/04/22 18:44:06 christos Exp $");
  41
  42 #include "namespace.h"
  43 #include <sys/types.h>
  44
  45 #include <assert.h>
  46 #include <limits.h>
  47 #include <stdio.h>
  48 #include <stdlib.h>
  49 #include <string.h>
  50
  51 #include <db.h>
  52 #include "btree.h"
  53
  54 static int       bt_broot(BTREE *, PAGE *, PAGE *, PAGE *);
  55 static PAGE     *bt_page(BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t);
  56 static int       bt_preserve(BTREE *, pgno_t);
  57 static PAGE     *bt_psplit(BTREE *, PAGE *, PAGE *, PAGE *, indx_t *, size_t);
  58 static PAGE     *bt_root(BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t);
  59 static int       bt_rroot(BTREE *, PAGE *, PAGE *, PAGE *);
  60 static recno_t   rec_total(PAGE *);
  61
  62 #ifdef STATISTICS
  63 unsigned long   bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved;
  64 #endif
  65
  66 /*
  67  * __BT_SPLIT -- Split the tree.
  68  *
  69  * Parameters:
  70  *      t:      tree
  71  *      sp:     page to split
  72  *      key:    key to insert
  73  *      data:   data to insert
  74  *      flags:  BIGKEY/BIGDATA flags
  75  *      ilen:   insert length
  76  *      skip:   index to leave open
  77  *
  78  * Returns:
  79  *      RET_ERROR, RET_SUCCESS
  80  */
  81 int
  82 __bt_split(BTREE *t, PAGE *sp, const DBT *key, const DBT *data, int flags,
  83     size_t ilen, uint32_t argskip)
  84 {
  85         BINTERNAL *bi = NULL;   /* pacify gcc */
  86         BLEAF *bl = NULL, *tbl; /* pacify gcc */
  87         DBT a, b;
  88         EPGNO *parent;
  89         PAGE *h, *l, *r, *lchild, *rchild;
  90         indx_t nxtindex;
  91         uint16_t skip;
  92         uint32_t n, nbytes, nksize = 0; /* pacify gcc */
  93         int parentsplit;
  94         char *dest;
  95
  96         /*
  97          * Split the page into two pages, l and r.  The split routines return
  98          * a pointer to the page into which the key should be inserted and with
  99          * skip set to the offset which should be used.  Additionally, l and r
 100          * are pinned.
 101          */
 102         skip = argskip;
 103         h = sp->pgno == P_ROOT ?
 104             bt_root(t, sp, &l, &r, &skip, ilen) :
 105             bt_page(t, sp, &l, &r, &skip, ilen);
 106         if (h == NULL)
 107                 return (RET_ERROR);
 108
 109         /*
 110          * Insert the new key/data pair into the leaf page.  (Key inserts
 111          * always cause a leaf page to split first.)
 112          */
 113         _DBFIT(ilen, indx_t);
 114         h->upper -= (indx_t)ilen;
 115         h->linp[skip] = h->upper;
 116         dest = (char *)(void *)h + h->upper;
 117         if (F_ISSET(t, R_RECNO))
 118                 WR_RLEAF(dest, data, flags);
 119         else
 120                 WR_BLEAF(dest, key, data, flags);
 121
 122         /* If the root page was split, make it look right. */
 123         if (sp->pgno == P_ROOT &&
 124             (F_ISSET(t, R_RECNO) ?
 125             bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR)
 126                 goto err2;
 127
 128         /*
 129          * Now we walk the parent page stack -- a LIFO stack of the pages that
 130          * were traversed when we searched for the page that split.  Each stack
 131          * entry is a page number and a page index offset.  The offset is for
 132          * the page traversed on the search.  We've just split a page, so we
 133          * have to insert a new key into the parent page.
 134          *
 135          * If the insert into the parent page causes it to split, may have to
 136          * continue splitting all the way up the tree.  We stop if the root
 137          * splits or the page inserted into didn't have to split to hold the
 138          * new key.  Some algorithms replace the key for the old page as well
 139          * as the new page.  We don't, as there's no reason to believe that the
 140          * first key on the old page is any better than the key we have, and,
 141          * in the case of a key being placed at index 0 causing the split, the
 142          * key is unavailable.
 143          *
 144          * There are a maximum of 5 pages pinned at any time.  We keep the left
 145          * and right pages pinned while working on the parent.   The 5 are the
 146          * two children, left parent and right parent (when the parent splits)
 147          * and the root page or the overflow key page when calling bt_preserve.
 148          * This code must make sure that all pins are released other than the
 149          * root page or overflow page which is unlocked elsewhere.
 150          */
 151         while ((parent = BT_POP(t)) != NULL) {
 152                 lchild = l;
 153                 rchild = r;
 154
 155                 /* Get the parent page. */
 156                 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
 157                         goto err2;
 158
 159                 /*
 160                  * The new key goes ONE AFTER the index, because the split
 161                  * was to the right.
 162                  */
 163                 skip = parent->index + 1;
 164
 165                 /*
 166                  * Calculate the space needed on the parent page.
 167                  *
 168                  * Prefix trees: space hack when inserting into BINTERNAL
 169                  * pages.  Retain only what's needed to distinguish between
 170                  * the new entry and the LAST entry on the page to its left.
 171                  * If the keys compare equal, retain the entire key.  Note,
 172                  * we don't touch overflow keys, and the entire key must be
 173                  * retained for the next-to-left most key on the leftmost
 174                  * page of each level, or the search will fail.  Applicable
 175                  * ONLY to internal pages that have leaf pages as children.
 176                  * Further reduction of the key between pairs of internal
 177                  * pages loses too much information.
 178                  */
 179                 switch (rchild->flags & P_TYPE) {
 180                 case P_BINTERNAL:
 181                         bi = GETBINTERNAL(rchild, 0);
 182                         nbytes = NBINTERNAL(bi->ksize);
 183                         break;
 184                 case P_BLEAF:
 185                         bl = GETBLEAF(rchild, 0);
 186                         nbytes = NBINTERNAL(bl->ksize);
 187                         if (t->bt_pfx && !(bl->flags & P_BIGKEY) &&
 188                             (h->prevpg != P_INVALID || skip > 1)) {
 189                                 size_t temp;
 190                                 tbl = GETBLEAF(lchild, NEXTINDEX(lchild) - 1);
 191                                 a.size = tbl->ksize;
 192                                 a.data = tbl->bytes;
 193                                 b.size = bl->ksize;
 194                                 b.data = bl->bytes;
 195                                 temp = t->bt_pfx(&a, &b);
 196                                 _DBFIT(temp, uint32_t);
 197                                 nksize = (uint32_t)temp;
 198                                 n = NBINTERNAL(nksize);
 199                                 if (n < nbytes) {
 200 #ifdef STATISTICS
 201                                         bt_pfxsaved += nbytes - n;
 202 #endif
 203                                         nbytes = n;
 204                                 } else
 205                                         nksize = 0;
 206                         } else
 207                                 nksize = 0;
 208                         break;
 209                 case P_RINTERNAL:
 210                 case P_RLEAF:
 211                         nbytes = NRINTERNAL;
 212                         break;
 213                 default:
 214                         abort();
 215                 }
 216
 217                 /* Split the parent page if necessary or shift the indices. */
 218                 if ((uint32_t)h->upper - (uint32_t)h->lower < nbytes + sizeof(indx_t)) {
 219                         sp = h;
 220                         h = h->pgno == P_ROOT ?
 221                             bt_root(t, h, &l, &r, &skip, nbytes) :
 222                             bt_page(t, h, &l, &r, &skip, nbytes);
 223                         if (h == NULL)
 224                                 goto err1;
 225                         parentsplit = 1;
 226                 } else {
 227                         if (skip < (nxtindex = NEXTINDEX(h)))
 228                                 memmove(h->linp + skip + 1, h->linp + skip,
 229                                     (nxtindex - skip) * sizeof(indx_t));
 230                         h->lower += sizeof(indx_t);
 231                         parentsplit = 0;
 232                 }
 233
 234                 /* Insert the key into the parent page. */
 235                 switch (rchild->flags & P_TYPE) {
 236                 case P_BINTERNAL:
 237                         h->linp[skip] = h->upper -= nbytes;
 238                         dest = (char *)(void *)h + h->linp[skip];
 239                         memmove(dest, bi, nbytes);
 240                         ((BINTERNAL *)(void *)dest)->pgno = rchild->pgno;
 241                         break;
 242                 case P_BLEAF:
 243                         h->linp[skip] = h->upper -= nbytes;
 244                         dest = (char *)(void *)h + h->linp[skip];
 245                         WR_BINTERNAL(dest, nksize ? nksize : bl->ksize,
 246                             rchild->pgno, bl->flags & P_BIGKEY);
 247                         memmove(dest, bl->bytes, nksize ? nksize : bl->ksize);
 248                         if (bl->flags & P_BIGKEY &&
 249                             bt_preserve(t, *(pgno_t *)(void *)bl->bytes) ==
 250                             RET_ERROR)
 251                                 goto err1;
 252                         break;
 253                 case P_RINTERNAL:
 254                         /*
 255                          * Update the left page count.  If split
 256                          * added at index 0, fix the correct page.
 257                          */
 258                         if (skip > 0)
 259                                 dest = (char *)(void *)h + h->linp[skip - 1];
 260                         else
 261                                 dest = (char *)(void *)l + l->linp[NEXTINDEX(l) - 1];
 262                         ((RINTERNAL *)(void *)dest)->nrecs = rec_total(lchild);
 263                         ((RINTERNAL *)(void *)dest)->pgno = lchild->pgno;
 264
 265                         /* Update the right page count. */
 266                         h->linp[skip] = h->upper -= nbytes;
 267                         dest = (char *)(void *)h + h->linp[skip];
 268                         ((RINTERNAL *)(void *)dest)->nrecs = rec_total(rchild);
 269                         ((RINTERNAL *)(void *)dest)->pgno = rchild->pgno;
 270                         break;
 271                 case P_RLEAF:
 272                         /*
 273                          * Update the left page count.  If split
 274                          * added at index 0, fix the correct page.
 275                          */
 276                         if (skip > 0)
 277                                 dest = (char *)(void *)h + h->linp[skip - 1];
 278                         else
 279                                 dest = (char *)(void *)l + l->linp[NEXTINDEX(l) - 1];
 280                         ((RINTERNAL *)(void *)dest)->nrecs = NEXTINDEX(lchild);
 281                         ((RINTERNAL *)(void *)dest)->pgno = lchild->pgno;
 282
 283                         /* Update the right page count. */
 284                         h->linp[skip] = h->upper -= nbytes;
 285                         dest = (char *)(void *)h + h->linp[skip];
 286                         ((RINTERNAL *)(void *)dest)->nrecs = NEXTINDEX(rchild);
 287                         ((RINTERNAL *)(void *)dest)->pgno = rchild->pgno;
 288                         break;
 289                 default:
 290                         abort();
 291                 }
 292
 293                 /* Unpin the held pages. */
 294                 if (!parentsplit) {
 295                         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 296                         break;
 297                 }
 298
 299                 /* If the root page was split, make it look right. */
 300                 if (sp->pgno == P_ROOT &&
 301                     (F_ISSET(t, R_RECNO) ?
 302                     bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR)
 303                         goto err1;
 304
 305                 mpool_put(t->bt_mp, lchild, MPOOL_DIRTY);
 306                 mpool_put(t->bt_mp, rchild, MPOOL_DIRTY);
 307         }
 308
 309         /* Unpin the held pages. */
 310         mpool_put(t->bt_mp, l, MPOOL_DIRTY);
 311         mpool_put(t->bt_mp, r, MPOOL_DIRTY);
 312
 313         /* Clear any pages left on the stack. */
 314         return (RET_SUCCESS);
 315
 316         /*
 317          * If something fails in the above loop we were already walking back
 318          * up the tree and the tree is now inconsistent.  Nothing much we can
 319          * do about it but release any memory we're holding.
 320          */
 321 err1:   mpool_put(t->bt_mp, lchild, MPOOL_DIRTY);
 322         mpool_put(t->bt_mp, rchild, MPOOL_DIRTY);
 323
 324 err2:   mpool_put(t->bt_mp, l, 0);
 325         mpool_put(t->bt_mp, r, 0);
 326         __dbpanic(t->bt_dbp);
 327         return (RET_ERROR);
 328 }
 329
 330 /*
 331  * BT_PAGE -- Split a non-root page of a btree.
 332  *
 333  * Parameters:
 334  *      t:      tree
 335  *      h:      root page
 336  *      lp:     pointer to left page pointer
 337  *      rp:     pointer to right page pointer
 338  *      skip:   pointer to index to leave open
 339  *      ilen:   insert length
 340  *
 341  * Returns:
 342  *      Pointer to page in which to insert or NULL on error.
 343  */
 344 static PAGE *
 345 bt_page(BTREE *t, PAGE *h, PAGE **lp, PAGE **rp, indx_t *skip, size_t ilen)
 346 {
 347         PAGE *l, *r, *tp;
 348         pgno_t npg;
 349
 350 #ifdef STATISTICS
 351         ++bt_split;
 352 #endif
 353         /* Put the new right page for the split into place. */
 354         if ((r = __bt_new(t, &npg)) == NULL)
 355                 return (NULL);
 356         r->pgno = npg;
 357         r->lower = BTDATAOFF;
 358         r->upper = t->bt_psize;
 359         r->nextpg = h->nextpg;
 360         r->prevpg = h->pgno;
 361         r->flags = h->flags & P_TYPE;
 362
 363         /*
 364          * If we're splitting the last page on a level because we're appending
 365          * a key to it (skip is NEXTINDEX()), it's likely that the data is
 366          * sorted.  Adding an empty page on the side of the level is less work
 367          * and can push the fill factor much higher than normal.  If we're
 368          * wrong it's no big deal, we'll just do the split the right way next
 369          * time.  It may look like it's equally easy to do a similar hack for
 370          * reverse sorted data, that is, split the tree left, but it's not.
 371          * Don't even try.
 372          */
 373         if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) {
 374 #ifdef STATISTICS
 375                 ++bt_sortsplit;
 376 #endif
 377                 h->nextpg = r->pgno;
 378                 r->lower = BTDATAOFF + sizeof(indx_t);
 379                 *skip = 0;
 380                 *lp = h;
 381                 *rp = r;
 382                 return (r);
 383         }
 384
 385         /* Put the new left page for the split into place. */
 386         if ((l = calloc(1, t->bt_psize)) == NULL) {
 387                 mpool_put(t->bt_mp, r, 0);
 388                 return (NULL);
 389         }
 390 #ifdef PURIFY
 391         memset(l, 0xff, t->bt_psize);
 392 #endif
 393         l->pgno = h->pgno;
 394         l->nextpg = r->pgno;
 395         l->prevpg = h->prevpg;
 396         l->lower = BTDATAOFF;
 397         l->upper = t->bt_psize;
 398         l->flags = h->flags & P_TYPE;
 399
 400         /* Fix up the previous pointer of the page after the split page. */
 401         if (h->nextpg != P_INVALID) {
 402                 if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) {
 403                         free(l);
 404                         /* XXX mpool_free(t->bt_mp, r->pgno); */
 405                         return (NULL);
 406                 }
 407                 tp->prevpg = r->pgno;
 408                 mpool_put(t->bt_mp, tp, MPOOL_DIRTY);
 409         }
 410
 411         /*
 412          * Split right.  The key/data pairs aren't sorted in the btree page so
 413          * it's simpler to copy the data from the split page onto two new pages
 414          * instead of copying half the data to the right page and compacting
 415          * the left page in place.  Since the left page can't change, we have
 416          * to swap the original and the allocated left page after the split.
 417          */
 418         tp = bt_psplit(t, h, l, r, skip, ilen);
 419
 420         /* Move the new left page onto the old left page. */
 421         memmove(h, l, t->bt_psize);
 422         if (tp == l)
 423                 tp = h;
 424         free(l);
 425
 426         *lp = h;
 427         *rp = r;
 428         return (tp);
 429 }
 430
 431 /*
 432  * BT_ROOT -- Split the root page of a btree.
 433  *
 434  * Parameters:
 435  *      t:      tree
 436  *      h:      root page
 437  *      lp:     pointer to left page pointer
 438  *      rp:     pointer to right page pointer
 439  *      skip:   pointer to index to leave open
 440  *      ilen:   insert length
 441  *
 442  * Returns:
 443  *      Pointer to page in which to insert or NULL on error.
 444  */
 445 static PAGE *
 446 bt_root(BTREE *t, PAGE *h, PAGE **lp, PAGE **rp, indx_t *skip, size_t ilen)
 447 {
 448         PAGE *l, *r, *tp;
 449         pgno_t lnpg, rnpg;
 450
 451 #ifdef STATISTICS
 452         ++bt_split;
 453         ++bt_rootsplit;
 454 #endif
 455         /* Put the new left and right pages for the split into place. */
 456         if ((l = __bt_new(t, &lnpg)) == NULL ||
 457             (r = __bt_new(t, &rnpg)) == NULL)
 458                 return (NULL);
 459         l->pgno = lnpg;
 460         r->pgno = rnpg;
 461         l->nextpg = r->pgno;
 462         r->prevpg = l->pgno;
 463         l->prevpg = r->nextpg = P_INVALID;
 464         l->lower = r->lower = BTDATAOFF;
 465         l->upper = r->upper = t->bt_psize;
 466         l->flags = r->flags = h->flags & P_TYPE;
 467
 468         /* Split the root page. */
 469         tp = bt_psplit(t, h, l, r, skip, ilen);
 470
 471         *lp = l;
 472         *rp = r;
 473         return (tp);
 474 }
 475
 476 /*
 477  * BT_RROOT -- Fix up the recno root page after it has been split.
 478  *
 479  * Parameters:
 480  *      t:      tree
 481  *      h:      root page
 482  *      l:      left page
 483  *      r:      right page
 484  *
 485  * Returns:
 486  *      RET_ERROR, RET_SUCCESS
 487  */
 488 static int
 489 bt_rroot(BTREE *t, PAGE *h, PAGE *l, PAGE *r)
 490 {
 491         char *dest;
 492         uint32_t sz;
 493         size_t temp;
 494
 495         temp = t->bt_psize - NRINTERNAL;
 496         _DBFIT(temp, uint32_t);
 497         sz = (uint32_t)temp;
 498
 499         /* Insert the left and right keys, set the header information. */
 500         _DBFIT(sz, indx_t);
 501         h->linp[0] = h->upper = (indx_t)sz;
 502         dest = (char *)(void *)h + h->upper;
 503         WR_RINTERNAL(dest,
 504             l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno);
 505
 506         h->linp[1] = h->upper -= NRINTERNAL;
 507         dest = (char *)(void *)h + h->upper;
 508         WR_RINTERNAL(dest,
 509             r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno);
 510
 511         h->lower = BTDATAOFF + 2 * sizeof(indx_t);
 512
 513         /* Unpin the root page, set to recno internal page. */
 514         h->flags &= ~P_TYPE;
 515         h->flags |= P_RINTERNAL;
 516         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 517
 518         return (RET_SUCCESS);
 519 }
 520
 521 /*
 522  * BT_BROOT -- Fix up the btree root page after it has been split.
 523  *
 524  * Parameters:
 525  *      t:      tree
 526  *      h:      root page
 527  *      l:      left page
 528  *      r:      right page
 529  *
 530  * Returns:
 531  *      RET_ERROR, RET_SUCCESS
 532  */
 533 static int
 534 bt_broot(BTREE *t, PAGE *h, PAGE *l, PAGE *r)
 535 {
 536         BINTERNAL *bi = NULL;   /* pacify gcc */
 537         BLEAF *bl;
 538         uint32_t nbytes;
 539         char *dest;
 540
 541         /*
 542          * If the root page was a leaf page, change it into an internal page.
 543          * We copy the key we split on (but not the key's data, in the case of
 544          * a leaf page) to the new root page.
 545          *
 546          * The btree comparison code guarantees that the left-most key on any
 547          * level of the tree is never used, so it doesn't need to be filled in.
 548          */
 549         nbytes = NBINTERNAL(0);
 550         h->linp[0] = h->upper = t->bt_psize - nbytes;
 551         dest = (char *)(void *)h + h->upper;
 552         WR_BINTERNAL(dest, 0, l->pgno, 0);
 553
 554         switch (h->flags & P_TYPE) {
 555         case P_BLEAF:
 556                 bl = GETBLEAF(r, 0);
 557                 nbytes = NBINTERNAL(bl->ksize);
 558                 h->linp[1] = h->upper -= nbytes;
 559                 dest = (char *)(void *)h + h->upper;
 560                 WR_BINTERNAL(dest, bl->ksize, r->pgno, 0);
 561                 memmove(dest, bl->bytes, bl->ksize);
 562
 563                 /*
 564                  * If the key is on an overflow page, mark the overflow chain
 565                  * so it isn't deleted when the leaf copy of the key is deleted.
 566                  */
 567                 if (bl->flags & P_BIGKEY &&
 568                     bt_preserve(t, *(pgno_t *)(void *)bl->bytes) == RET_ERROR)
 569                         return (RET_ERROR);
 570                 break;
 571         case P_BINTERNAL:
 572                 bi = GETBINTERNAL(r, 0);
 573                 nbytes = NBINTERNAL(bi->ksize);
 574                 h->linp[1] = h->upper -= nbytes;
 575                 dest = (char *)(void *)h + h->upper;
 576                 memmove(dest, bi, nbytes);
 577                 ((BINTERNAL *)(void *)dest)->pgno = r->pgno;
 578                 break;
 579         default:
 580                 abort();
 581         }
 582
 583         /* There are two keys on the page. */
 584         h->lower = BTDATAOFF + 2 * sizeof(indx_t);
 585
 586         /* Unpin the root page, set to btree internal page. */
 587         h->flags &= ~P_TYPE;
 588         h->flags |= P_BINTERNAL;
 589         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 590
 591         return (RET_SUCCESS);
 592 }
 593
 594 /*
 595  * BT_PSPLIT -- Do the real work of splitting the page.
 596  *
 597  * Parameters:
 598  *      t:      tree
 599  *      h:      page to be split
 600  *      l:      page to put lower half of data
 601  *      r:      page to put upper half of data
 602  *      pskip:  pointer to index to leave open
 603  *      ilen:   insert length
 604  *
 605  * Returns:
 606  *      Pointer to page in which to insert.
 607  */
 608 static PAGE *
 609 bt_psplit(BTREE *t, PAGE *h, PAGE *l, PAGE *r, indx_t *pskip, size_t ilen)
 610 {
 611         BINTERNAL *bi;
 612         BLEAF *bl;
 613         CURSOR *c;
 614         RLEAF *rl;
 615         PAGE *rval;
 616         void *src = NULL;       /* pacify gcc */
 617         indx_t full, half, nxt, off, skip, top, used;
 618         uint32_t nbytes;
 619         size_t temp;
 620         int bigkeycnt, isbigkey;
 621
 622         /*
 623          * Split the data to the left and right pages.  Leave the skip index
 624          * open.  Additionally, make some effort not to split on an overflow
 625          * key.  This makes internal page processing faster and can save
 626          * space as overflow keys used by internal pages are never deleted.
 627          */
 628         bigkeycnt = 0;
 629         skip = *pskip;
 630         temp = t->bt_psize - BTDATAOFF;
 631         _DBFIT(temp, indx_t);
 632         full = (indx_t)temp;
 633         half = full / 2;
 634         used = 0;
 635         for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) {
 636                 if (skip == off) {
 637                         _DBFIT(ilen, uint32_t);
 638                         nbytes = (uint32_t)ilen;
 639                         isbigkey = 0;           /* XXX: not really known. */
 640                 } else
 641                         switch (h->flags & P_TYPE) {
 642                         case P_BINTERNAL:
 643                                 src = bi = GETBINTERNAL(h, nxt);
 644                                 nbytes = NBINTERNAL(bi->ksize);
 645                                 isbigkey = bi->flags & P_BIGKEY;
 646                                 break;
 647                         case P_BLEAF:
 648                                 src = bl = GETBLEAF(h, nxt);
 649                                 nbytes = NBLEAF(bl);
 650                                 isbigkey = bl->flags & P_BIGKEY;
 651                                 break;
 652                         case P_RINTERNAL:
 653                                 src = GETRINTERNAL(h, nxt);
 654                                 nbytes = NRINTERNAL;
 655                                 isbigkey = 0;
 656                                 break;
 657                         case P_RLEAF:
 658                                 src = rl = GETRLEAF(h, nxt);
 659                                 nbytes = NRLEAF(rl);
 660                                 isbigkey = 0;
 661                                 break;
 662                         default:
 663                                 abort();
 664                         }
 665
 666                 /*
 667                  * If the key/data pairs are substantial fractions of the max
 668                  * possible size for the page, it's possible to get situations
 669                  * where we decide to try and copy too much onto the left page.
 670                  * Make sure that doesn't happen.
 671                  */
 672                 if ((skip <= off && used + nbytes + sizeof(indx_t) >= full) ||
 673                     nxt == top - 1) {
 674                         --off;
 675                         break;
 676                 }
 677
 678                 /* Copy the key/data pair, if not the skipped index. */
 679                 if (skip != off) {
 680                         ++nxt;
 681
 682                         l->linp[off] = l->upper -= nbytes;
 683                         memmove((char *)(void *)l + l->upper, src, nbytes);
 684                 }
 685
 686                 temp = nbytes + sizeof(indx_t);
 687                 _DBFIT(temp, indx_t);
 688                 used += (indx_t)temp;
 689                 if (used >= half) {
 690                         if (!isbigkey || bigkeycnt == 3)
 691                                 break;
 692                         else
 693                                 ++bigkeycnt;
 694                 }
 695         }
 696
 697         /*
 698          * Off is the last offset that's valid for the left page.
 699          * Nxt is the first offset to be placed on the right page.
 700          */
 701         temp = (off + 1) * sizeof(indx_t);
 702         _DBFIT(temp, indx_t);
 703         l->lower += (indx_t)temp;
 704
 705         /*
 706          * If splitting the page that the cursor was on, the cursor has to be
 707          * adjusted to point to the same record as before the split.  If the
 708          * cursor is at or past the skipped slot, the cursor is incremented by
 709          * one.  If the cursor is on the right page, it is decremented by the
 710          * number of records split to the left page.
 711          */
 712         c = &t->bt_cursor;
 713         if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) {
 714                 if (c->pg.index >= skip)
 715                         ++c->pg.index;
 716                 if (c->pg.index < nxt)                  /* Left page. */
 717                         c->pg.pgno = l->pgno;
 718                 else {                                  /* Right page. */
 719                         c->pg.pgno = r->pgno;
 720                         c->pg.index -= nxt;
 721                 }
 722         }
 723
 724         /*
 725          * If the skipped index was on the left page, just return that page.
 726          * Otherwise, adjust the skip index to reflect the new position on
 727          * the right page.
 728          */
 729         if (skip <= off) {
 730                 skip = MAX_PAGE_OFFSET;
 731                 rval = l;
 732         } else {
 733                 rval = r;
 734                 *pskip -= nxt;
 735         }
 736
 737         for (off = 0; nxt < top; ++off) {
 738                 if (skip == nxt) {
 739                         ++off;
 740                         skip = MAX_PAGE_OFFSET;
 741                 }
 742                 switch (h->flags & P_TYPE) {
 743                 case P_BINTERNAL:
 744                         src = bi = GETBINTERNAL(h, nxt);
 745                         nbytes = NBINTERNAL(bi->ksize);
 746                         break;
 747                 case P_BLEAF:
 748                         src = bl = GETBLEAF(h, nxt);
 749                         nbytes = NBLEAF(bl);
 750                         break;
 751                 case P_RINTERNAL:
 752                         src = GETRINTERNAL(h, nxt);
 753                         nbytes = NRINTERNAL;
 754                         break;
 755                 case P_RLEAF:
 756                         src = rl = GETRLEAF(h, nxt);
 757                         nbytes = NRLEAF(rl);
 758                         break;
 759                 default:
 760                         abort();
 761                 }
 762                 ++nxt;
 763                 r->linp[off] = r->upper -= nbytes;
 764                 memmove((char *)(void *)r + r->upper, src, nbytes);
 765         }
 766         temp = off * sizeof(indx_t);
 767         _DBFIT(temp, indx_t);
 768         r->lower += (indx_t)temp;
 769
 770         /* If the key is being appended to the page, adjust the index. */
 771         if (skip == top)
 772                 r->lower += sizeof(indx_t);
 773
 774         return (rval);
 775 }
 776
 777 /*
 778  * BT_PRESERVE -- Mark a chain of pages as used by an internal node.
 779  *
 780  * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the
 781  * record that references them gets deleted.  Chains pointed to by internal
 782  * pages never get deleted.  This routine marks a chain as pointed to by an
 783  * internal page.
 784  *
 785  * Parameters:
 786  *      t:      tree
 787  *      pg:     page number of first page in the chain.
 788  *
 789  * Returns:
 790  *      RET_SUCCESS, RET_ERROR.
 791  */
 792 static int
 793 bt_preserve(BTREE *t, pgno_t pg)
 794 {
 795         PAGE *h;
 796
 797         if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 798                 return (RET_ERROR);
 799         h->flags |= P_PRESERVE;
 800         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 801         return (RET_SUCCESS);
 802 }
 803
 804 /*
 805  * REC_TOTAL -- Return the number of recno entries below a page.
 806  *
 807  * Parameters:
 808  *      h:      page
 809  *
 810  * Returns:
 811  *      The number of recno entries below a page.
 812  *
 813  * XXX
 814  * These values could be set by the bt_psplit routine.  The problem is that the
 815  * entry has to be popped off of the stack etc. or the values have to be passed
 816  * all the way back to bt_split/bt_rroot and it's not very clean.
 817  */
 818 static recno_t
 819 rec_total(PAGE *h)
 820 {
 821         recno_t recs;
 822         indx_t nxt, top;
 823
 824         for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt)
 825                 recs += GETRINTERNAL(h, nxt)->nrecs;
 826         return (recs);
 827 }