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Diffstat (limited to 'db/btree/bt_split.c')
| -rw-r--r-- | db/btree/bt_split.c | 827 |
1 files changed, 827 insertions, 0 deletions
diff --git a/db/btree/bt_split.c b/db/btree/bt_split.c new file mode 100644 index 0000000000..1646d82159 --- /dev/null +++ b/db/btree/bt_split.c @@ -0,0 +1,827 @@ +/*- + * Copyright (c) 1990, 1993, 1994 + * 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 8.9 (Berkeley) 7/26/94"; +#endif /* LIBC_SCCS and not lint */ + +#include <sys/types.h> + +#include <limits.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> + +#include <db.h> +#include "btree.h" + +static int bt_broot __P((BTREE *, PAGE *, PAGE *, PAGE *)); +static PAGE *bt_page + __P((BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, size_t)); +static int bt_preserve __P((BTREE *, pgno_t)); +static PAGE *bt_psplit + __P((BTREE *, PAGE *, PAGE *, PAGE *, indx_t *, size_t)); +static PAGE *bt_root + __P((BTREE *, PAGE *, PAGE **, PAGE **, indx_t *, 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(t, sp, key, data, flags, ilen, argskip) + BTREE *t; + PAGE *sp; + const DBT *key, *data; + int flags; + size_t ilen; + u_int32_t argskip; +{ + BINTERNAL *bi; + BLEAF *bl, *tbl; + DBT a, b; + EPGNO *parent; + PAGE *h, *l, *r, *lchild, *rchild; + indx_t nxtindex; + u_int16_t skip; + u_int32_t n, nbytes, nksize; + 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. + */ + skip = argskip; + 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 (F_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 && + (F_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, *(pgno_t *)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 && + (F_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(t, h, lp, rp, skip, ilen) + BTREE *t; + PAGE *h, **lp, **rp; + indx_t *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 = (PAGE *)malloc(t->bt_psize)) == NULL) { + mpool_put(t->bt_mp, r, 0); + return (NULL); + } +#ifdef PURIFY + memset(l, 0xff, t->bt_psize); +#endif + 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, MPOOL_DIRTY); + } + + /* + * 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(t, h, lp, rp, skip, ilen) + BTREE *t; + PAGE *h, **lp, **rp; + indx_t *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(t, h, l, r) + BTREE *t; + PAGE *h, *l, *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(t, h, l, r) + BTREE *t; + PAGE *h, *l, *r; +{ + BINTERNAL *bi; + BLEAF *bl; + u_int32_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, *(pgno_t *)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(t, h, l, r, pskip, ilen) + BTREE *t; + PAGE *h, *l, *r; + indx_t *pskip; + size_t ilen; +{ + BINTERNAL *bi; + BLEAF *bl; + CURSOR *c; + RLEAF *rl; + PAGE *rval; + void *src; + indx_t full, half, nxt, off, skip, top, used; + u_int32_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. + */ + c = &t->bt_cursor; + if (F_ISSET(c, CURS_INIT) && c->pg.pgno == h->pgno) { + if (c->pg.index >= skip) + ++c->pg.index; + if (c->pg.index < nxt) /* Left page. */ + c->pg.pgno = l->pgno; + else { /* Right page. */ + c->pg.pgno = r->pgno; + c->pg.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(t, pg) + 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(h) + 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); +} |