/* * CDE - Common Desktop Environment * * Copyright (c) 1993-2012, The Open Group. All rights reserved. * * These libraries and programs are free software; you can * redistribute them and/or modify them under the terms of the GNU * Lesser General Public License as published by the Free Software * Foundation; either version 2 of the License, or (at your option) * any later version. * * These libraries and programs are distributed in the hope that * they will be useful, but WITHOUT ANY WARRANTY; without even the * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR * PURPOSE. See the GNU Lesser General Public License for more * details. * * You should have received a copy of the GNU Lesser General Public * License along with these libraries and programs; if not, write * to the Free Software Foundation, Inc., 51 Franklin Street, Fifth * Floor, Boston, MA 02110-1301 USA */ /* $XConsortium: bt_split.c /main/3 1996/06/11 17:13:10 cde-hal $ */ /*- * Copyright (c) 1990, 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software contributed to Berkeley by * Mike Olson. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #if defined(LIBC_SCCS) && !defined(lint) static char sccsid[] = "@(#)bt_split.c 8.1 (Berkeley) 6/4/93"; #endif /* LIBC_SCCS and not lint */ #include #define __DBINTERFACE_PRIVATE #include #include #include #include #include #include "btree.h" static int bt_broot __P((BTREE *, PAGE *, PAGE *, PAGE *)); static PAGE *bt_page __P((BTREE *, PAGE *, PAGE **, PAGE **, u_int *, size_t)); static int bt_preserve __P((BTREE *, pgno_t)); static PAGE *bt_psplit __P((BTREE *, PAGE *, PAGE *, PAGE *, u_int *, size_t)); static PAGE *bt_root __P((BTREE *, PAGE *, PAGE **, PAGE **, u_int *, size_t)); static int bt_rroot __P((BTREE *, PAGE *, PAGE *, PAGE *)); static recno_t rec_total __P((PAGE *)); #ifdef STATISTICS u_long bt_rootsplit, bt_split, bt_sortsplit, bt_pfxsaved; #endif /* * __BT_SPLIT -- Split the tree. * * Parameters: * t: tree * sp: page to split * key: key to insert * data: data to insert * flags: BIGKEY/BIGDATA flags * ilen: insert length * skip: index to leave open * * Returns: * RET_ERROR, RET_SUCCESS */ int __bt_split(BTREE *t, PAGE *sp, const DBT *key, const DBT *data, u_long flags, size_t ilen, u_int skip) { BINTERNAL *bi = NULL; BLEAF *bl = NULL; BLEAF *tbl; DBT a, b; EPGNO *parent; PAGE *h, *l, *r, *lchild, *rchild; indx_t nxtindex; size_t n, nbytes; size_t nksize = 0; int parentsplit; char *dest; /* * Split the page into two pages, l and r. The split routines return * a pointer to the page into which the key should be inserted and with * skip set to the offset which should be used. Additionally, l and r * are pinned. */ h = sp->pgno == P_ROOT ? bt_root(t, sp, &l, &r, &skip, ilen) : bt_page(t, sp, &l, &r, &skip, ilen); if (h == NULL) return (RET_ERROR); /* * Insert the new key/data pair into the leaf page. (Key inserts * always cause a leaf page to split first.) */ h->linp[skip] = h->upper -= ilen; dest = (char *)h + h->upper; if (ISSET(t, R_RECNO)) WR_RLEAF(dest, data, flags) else WR_BLEAF(dest, key, data, flags) /* If the root page was split, make it look right. */ if (sp->pgno == P_ROOT && (ISSET(t, R_RECNO) ? bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) goto err2; /* * Now we walk the parent page stack -- a LIFO stack of the pages that * were traversed when we searched for the page that split. Each stack * entry is a page number and a page index offset. The offset is for * the page traversed on the search. We've just split a page, so we * have to insert a new key into the parent page. * * If the insert into the parent page causes it to split, may have to * continue splitting all the way up the tree. We stop if the root * splits or the page inserted into didn't have to split to hold the * new key. Some algorithms replace the key for the old page as well * as the new page. We don't, as there's no reason to believe that the * first key on the old page is any better than the key we have, and, * in the case of a key being placed at index 0 causing the split, the * key is unavailable. * * There are a maximum of 5 pages pinned at any time. We keep the left * and right pages pinned while working on the parent. The 5 are the * two children, left parent and right parent (when the parent splits) * and the root page or the overflow key page when calling bt_preserve. * This code must make sure that all pins are released other than the * root page or overflow page which is unlocked elsewhere. */ while ((parent = BT_POP(t)) != NULL) { lchild = l; rchild = r; /* Get the parent page. */ if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) goto err2; /* * The new key goes ONE AFTER the index, because the split * was to the right. */ skip = parent->index + 1; /* * Calculate the space needed on the parent page. * * Prefix trees: space hack when inserting into BINTERNAL * pages. Retain only what's needed to distinguish between * the new entry and the LAST entry on the page to its left. * If the keys compare equal, retain the entire key. Note, * we don't touch overflow keys, and the entire key must be * retained for the next-to-left most key on the leftmost * page of each level, or the search will fail. Applicable * ONLY to internal pages that have leaf pages as children. * Further reduction of the key between pairs of internal * pages loses too much information. */ switch (rchild->flags & P_TYPE) { case P_BINTERNAL: bi = GETBINTERNAL(rchild, 0); nbytes = NBINTERNAL(bi->ksize); break; case P_BLEAF: bl = GETBLEAF(rchild, 0); nbytes = NBINTERNAL(bl->ksize); if (t->bt_pfx && !(bl->flags & P_BIGKEY) && (h->prevpg != P_INVALID || skip > 1)) { tbl = GETBLEAF(lchild, NEXTINDEX(lchild) - 1); a.size = tbl->ksize; a.data = tbl->bytes; b.size = bl->ksize; b.data = bl->bytes; nksize = t->bt_pfx(&a, &b); n = NBINTERNAL(nksize); if (n < nbytes) { #ifdef STATISTICS bt_pfxsaved += nbytes - n; #endif nbytes = n; } else nksize = 0; } else nksize = 0; break; case P_RINTERNAL: case P_RLEAF: nbytes = NRINTERNAL; break; default: abort(); } /* Split the parent page if necessary or shift the indices. */ if (h->upper - h->lower < nbytes + sizeof(indx_t)) { sp = h; h = h->pgno == P_ROOT ? bt_root(t, h, &l, &r, &skip, nbytes) : bt_page(t, h, &l, &r, &skip, nbytes); if (h == NULL) goto err1; parentsplit = 1; } else { if (skip < (nxtindex = NEXTINDEX(h))) memmove(h->linp + skip + 1, h->linp + skip, (nxtindex - skip) * sizeof(indx_t)); h->lower += sizeof(indx_t); parentsplit = 0; } /* Insert the key into the parent page. */ switch(rchild->flags & P_TYPE) { case P_BINTERNAL: h->linp[skip] = h->upper -= nbytes; dest = (char *)h + h->linp[skip]; memmove(dest, bi, nbytes); ((BINTERNAL *)dest)->pgno = rchild->pgno; break; case P_BLEAF: h->linp[skip] = h->upper -= nbytes; dest = (char *)h + h->linp[skip]; WR_BINTERNAL(dest, nksize ? nksize : bl->ksize, rchild->pgno, bl->flags & P_BIGKEY); memmove(dest, bl->bytes, nksize ? nksize : bl->ksize); if (bl->flags & P_BIGKEY && bt_preserve(t, *(char *)bl->bytes) == RET_ERROR) goto err1; break; case P_RINTERNAL: /* * Update the left page count. If split * added at index 0, fix the correct page. */ if (skip > 0) dest = (char *)h + h->linp[skip - 1]; else dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; ((RINTERNAL *)dest)->nrecs = rec_total(lchild); ((RINTERNAL *)dest)->pgno = lchild->pgno; /* Update the right page count. */ h->linp[skip] = h->upper -= nbytes; dest = (char *)h + h->linp[skip]; ((RINTERNAL *)dest)->nrecs = rec_total(rchild); ((RINTERNAL *)dest)->pgno = rchild->pgno; break; case P_RLEAF: /* * Update the left page count. If split * added at index 0, fix the correct page. */ if (skip > 0) dest = (char *)h + h->linp[skip - 1]; else dest = (char *)l + l->linp[NEXTINDEX(l) - 1]; ((RINTERNAL *)dest)->nrecs = NEXTINDEX(lchild); ((RINTERNAL *)dest)->pgno = lchild->pgno; /* Update the right page count. */ h->linp[skip] = h->upper -= nbytes; dest = (char *)h + h->linp[skip]; ((RINTERNAL *)dest)->nrecs = NEXTINDEX(rchild); ((RINTERNAL *)dest)->pgno = rchild->pgno; break; default: abort(); } /* Unpin the held pages. */ if (!parentsplit) { mpool_put(t->bt_mp, h, MPOOL_DIRTY); break; } /* If the root page was split, make it look right. */ if (sp->pgno == P_ROOT && (ISSET(t, R_RECNO) ? bt_rroot(t, sp, l, r) : bt_broot(t, sp, l, r)) == RET_ERROR) goto err1; mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); } /* Unpin the held pages. */ mpool_put(t->bt_mp, l, MPOOL_DIRTY); mpool_put(t->bt_mp, r, MPOOL_DIRTY); /* Clear any pages left on the stack. */ return (RET_SUCCESS); /* * If something fails in the above loop we were already walking back * up the tree and the tree is now inconsistent. Nothing much we can * do about it but release any memory we're holding. */ err1: mpool_put(t->bt_mp, lchild, MPOOL_DIRTY); mpool_put(t->bt_mp, rchild, MPOOL_DIRTY); err2: mpool_put(t->bt_mp, l, 0); mpool_put(t->bt_mp, r, 0); __dbpanic(t->bt_dbp); return (RET_ERROR); } /* * BT_PAGE -- Split a non-root page of a btree. * * Parameters: * t: tree * h: root page * lp: pointer to left page pointer * rp: pointer to right page pointer * skip: pointer to index to leave open * ilen: insert length * * Returns: * Pointer to page in which to insert or NULL on error. */ static PAGE * bt_page(BTREE *t, PAGE *h, PAGE **lp, PAGE **rp, u_int *skip, size_t ilen) { PAGE *l, *r, *tp; pgno_t npg; #ifdef STATISTICS ++bt_split; #endif /* Put the new right page for the split into place. */ if ((r = __bt_new(t, &npg)) == NULL) return (NULL); r->pgno = npg; r->lower = BTDATAOFF; r->upper = t->bt_psize; r->nextpg = h->nextpg; r->prevpg = h->pgno; r->flags = h->flags & P_TYPE; /* * If we're splitting the last page on a level because we're appending * a key to it (skip is NEXTINDEX()), it's likely that the data is * sorted. Adding an empty page on the side of the level is less work * and can push the fill factor much higher than normal. If we're * wrong it's no big deal, we'll just do the split the right way next * time. It may look like it's equally easy to do a similar hack for * reverse sorted data, that is, split the tree left, but it's not. * Don't even try. */ if (h->nextpg == P_INVALID && *skip == NEXTINDEX(h)) { #ifdef STATISTICS ++bt_sortsplit; #endif h->nextpg = r->pgno; r->lower = BTDATAOFF + sizeof(indx_t); *skip = 0; *lp = h; *rp = r; return (r); } /* Put the new left page for the split into place. */ if ((l = malloc(t->bt_psize)) == NULL) { mpool_put(t->bt_mp, r, 0); return (NULL); } l->pgno = h->pgno; l->nextpg = r->pgno; l->prevpg = h->prevpg; l->lower = BTDATAOFF; l->upper = t->bt_psize; l->flags = h->flags & P_TYPE; /* Fix up the previous pointer of the page after the split page. */ if (h->nextpg != P_INVALID) { if ((tp = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) { free(l); /* XXX mpool_free(t->bt_mp, r->pgno); */ return (NULL); } tp->prevpg = r->pgno; mpool_put(t->bt_mp, tp, 0); } /* * Split right. The key/data pairs aren't sorted in the btree page so * it's simpler to copy the data from the split page onto two new pages * instead of copying half the data to the right page and compacting * the left page in place. Since the left page can't change, we have * to swap the original and the allocated left page after the split. */ tp = bt_psplit(t, h, l, r, skip, ilen); /* Move the new left page onto the old left page. */ memmove(h, l, t->bt_psize); if (tp == l) tp = h; free(l); *lp = h; *rp = r; return (tp); } /* * BT_ROOT -- Split the root page of a btree. * * Parameters: * t: tree * h: root page * lp: pointer to left page pointer * rp: pointer to right page pointer * skip: pointer to index to leave open * ilen: insert length * * Returns: * Pointer to page in which to insert or NULL on error. */ static PAGE * bt_root(BTREE *t, PAGE *h, PAGE **lp, PAGE **rp, u_int *skip, size_t ilen) { PAGE *l, *r, *tp; pgno_t lnpg, rnpg; #ifdef STATISTICS ++bt_split; ++bt_rootsplit; #endif /* Put the new left and right pages for the split into place. */ if ((l = __bt_new(t, &lnpg)) == NULL || (r = __bt_new(t, &rnpg)) == NULL) return (NULL); l->pgno = lnpg; r->pgno = rnpg; l->nextpg = r->pgno; r->prevpg = l->pgno; l->prevpg = r->nextpg = P_INVALID; l->lower = r->lower = BTDATAOFF; l->upper = r->upper = t->bt_psize; l->flags = r->flags = h->flags & P_TYPE; /* Split the root page. */ tp = bt_psplit(t, h, l, r, skip, ilen); *lp = l; *rp = r; return (tp); } /* * BT_RROOT -- Fix up the recno root page after it has been split. * * Parameters: * t: tree * h: root page * l: left page * r: right page * * Returns: * RET_ERROR, RET_SUCCESS */ static int bt_rroot(BTREE *t, PAGE *h, PAGE *l, PAGE *r) { char *dest; /* Insert the left and right keys, set the header information. */ h->linp[0] = h->upper = t->bt_psize - NRINTERNAL; dest = (char *)h + h->upper; WR_RINTERNAL(dest, l->flags & P_RLEAF ? NEXTINDEX(l) : rec_total(l), l->pgno); h->linp[1] = h->upper -= NRINTERNAL; dest = (char *)h + h->upper; WR_RINTERNAL(dest, r->flags & P_RLEAF ? NEXTINDEX(r) : rec_total(r), r->pgno); h->lower = BTDATAOFF + 2 * sizeof(indx_t); /* Unpin the root page, set to recno internal page. */ h->flags &= ~P_TYPE; h->flags |= P_RINTERNAL; mpool_put(t->bt_mp, h, MPOOL_DIRTY); return (RET_SUCCESS); } /* * BT_BROOT -- Fix up the btree root page after it has been split. * * Parameters: * t: tree * h: root page * l: left page * r: right page * * Returns: * RET_ERROR, RET_SUCCESS */ static int bt_broot(BTREE *t, PAGE *h, PAGE *l, PAGE *r) { BINTERNAL *bi; BLEAF *bl; size_t nbytes; char *dest; /* * If the root page was a leaf page, change it into an internal page. * We copy the key we split on (but not the key's data, in the case of * a leaf page) to the new root page. * * The btree comparison code guarantees that the left-most key on any * level of the tree is never used, so it doesn't need to be filled in. */ nbytes = NBINTERNAL(0); h->linp[0] = h->upper = t->bt_psize - nbytes; dest = (char *)h + h->upper; WR_BINTERNAL(dest, 0, l->pgno, 0); switch(h->flags & P_TYPE) { case P_BLEAF: bl = GETBLEAF(r, 0); nbytes = NBINTERNAL(bl->ksize); h->linp[1] = h->upper -= nbytes; dest = (char *)h + h->upper; WR_BINTERNAL(dest, bl->ksize, r->pgno, 0); memmove(dest, bl->bytes, bl->ksize); /* * If the key is on an overflow page, mark the overflow chain * so it isn't deleted when the leaf copy of the key is deleted. */ if (bl->flags & P_BIGKEY && bt_preserve(t, *(char *)bl->bytes) == RET_ERROR) return (RET_ERROR); break; case P_BINTERNAL: bi = GETBINTERNAL(r, 0); nbytes = NBINTERNAL(bi->ksize); h->linp[1] = h->upper -= nbytes; dest = (char *)h + h->upper; memmove(dest, bi, nbytes); ((BINTERNAL *)dest)->pgno = r->pgno; break; default: abort(); } /* There are two keys on the page. */ h->lower = BTDATAOFF + 2 * sizeof(indx_t); /* Unpin the root page, set to btree internal page. */ h->flags &= ~P_TYPE; h->flags |= P_BINTERNAL; mpool_put(t->bt_mp, h, MPOOL_DIRTY); return (RET_SUCCESS); } /* * BT_PSPLIT -- Do the real work of splitting the page. * * Parameters: * t: tree * h: page to be split * l: page to put lower half of data * r: page to put upper half of data * pskip: pointer to index to leave open * ilen: insert length * * Returns: * Pointer to page in which to insert. */ static PAGE * bt_psplit(BTREE *t, PAGE *h, PAGE *l, PAGE *r, u_int *pskip, size_t ilen) { BINTERNAL *bi; BLEAF *bl; RLEAF *rl; EPGNO *c; PAGE *rval; void *src = NULL; indx_t full, half, nxt, off, skip, top, used; size_t nbytes; int bigkeycnt, isbigkey; /* * Split the data to the left and right pages. Leave the skip index * open. Additionally, make some effort not to split on an overflow * key. This makes internal page processing faster and can save * space as overflow keys used by internal pages are never deleted. */ bigkeycnt = 0; skip = *pskip; full = t->bt_psize - BTDATAOFF; half = full / 2; used = 0; for (nxt = off = 0, top = NEXTINDEX(h); nxt < top; ++off) { if (skip == off) { nbytes = ilen; isbigkey = 0; /* XXX: not really known. */ } else switch (h->flags & P_TYPE) { case P_BINTERNAL: src = bi = GETBINTERNAL(h, nxt); nbytes = NBINTERNAL(bi->ksize); isbigkey = bi->flags & P_BIGKEY; break; case P_BLEAF: src = bl = GETBLEAF(h, nxt); nbytes = NBLEAF(bl); isbigkey = bl->flags & P_BIGKEY; break; case P_RINTERNAL: src = GETRINTERNAL(h, nxt); nbytes = NRINTERNAL; isbigkey = 0; break; case P_RLEAF: src = rl = GETRLEAF(h, nxt); nbytes = NRLEAF(rl); isbigkey = 0; break; default: abort(); } /* * If the key/data pairs are substantial fractions of the max * possible size for the page, it's possible to get situations * where we decide to try and copy too much onto the left page. * Make sure that doesn't happen. */ if (skip <= off && used + nbytes >= full) { --off; break; } /* Copy the key/data pair, if not the skipped index. */ if (skip != off) { ++nxt; l->linp[off] = l->upper -= nbytes; memmove((char *)l + l->upper, src, nbytes); } used += nbytes; if (used >= half) { if (!isbigkey || bigkeycnt == 3) break; else ++bigkeycnt; } } /* * Off is the last offset that's valid for the left page. * Nxt is the first offset to be placed on the right page. */ l->lower += (off + 1) * sizeof(indx_t); /* * If splitting the page that the cursor was on, the cursor has to be * adjusted to point to the same record as before the split. If the * cursor is at or past the skipped slot, the cursor is incremented by * one. If the cursor is on the right page, it is decremented by the * number of records split to the left page. * * Don't bother checking for the B_SEQINIT flag, the page number will * be P_INVALID. */ c = &t->bt_bcursor; if (c->pgno == h->pgno) { if (c->index >= skip) ++c->index; if (c->index < nxt) /* Left page. */ c->pgno = l->pgno; else { /* Right page. */ c->pgno = r->pgno; c->index -= nxt; } } /* * If the skipped index was on the left page, just return that page. * Otherwise, adjust the skip index to reflect the new position on * the right page. */ if (skip <= off) { skip = 0; rval = l; } else { rval = r; *pskip -= nxt; } for (off = 0; nxt < top; ++off) { if (skip == nxt) { ++off; skip = 0; } switch (h->flags & P_TYPE) { case P_BINTERNAL: src = bi = GETBINTERNAL(h, nxt); nbytes = NBINTERNAL(bi->ksize); break; case P_BLEAF: src = bl = GETBLEAF(h, nxt); nbytes = NBLEAF(bl); break; case P_RINTERNAL: src = GETRINTERNAL(h, nxt); nbytes = NRINTERNAL; break; case P_RLEAF: src = rl = GETRLEAF(h, nxt); nbytes = NRLEAF(rl); break; default: abort(); } ++nxt; r->linp[off] = r->upper -= nbytes; memmove((char *)r + r->upper, src, nbytes); } r->lower += off * sizeof(indx_t); /* If the key is being appended to the page, adjust the index. */ if (skip == top) r->lower += sizeof(indx_t); return (rval); } /* * BT_PRESERVE -- Mark a chain of pages as used by an internal node. * * Chains of indirect blocks pointed to by leaf nodes get reclaimed when the * record that references them gets deleted. Chains pointed to by internal * pages never get deleted. This routine marks a chain as pointed to by an * internal page. * * Parameters: * t: tree * pg: page number of first page in the chain. * * Returns: * RET_SUCCESS, RET_ERROR. */ static int bt_preserve(BTREE *t, pgno_t pg) { PAGE *h; if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) return (RET_ERROR); h->flags |= P_PRESERVE; mpool_put(t->bt_mp, h, MPOOL_DIRTY); return (RET_SUCCESS); } /* * REC_TOTAL -- Return the number of recno entries below a page. * * Parameters: * h: page * * Returns: * The number of recno entries below a page. * * XXX * These values could be set by the bt_psplit routine. The problem is that the * entry has to be popped off of the stack etc. or the values have to be passed * all the way back to bt_split/bt_rroot and it's not very clean. */ static recno_t rec_total(PAGE *h) { recno_t recs; indx_t nxt, top; for (recs = 0, nxt = 0, top = NEXTINDEX(h); nxt < top; ++nxt) recs += GETRINTERNAL(h, nxt)->nrecs; return (recs); }