aboutsummaryrefslogtreecommitdiffstats
path: root/utils/db1-ast/btree/bt_split.c
diff options
context:
space:
mode:
Diffstat (limited to 'utils/db1-ast/btree/bt_split.c')
-rw-r--r--utils/db1-ast/btree/bt_split.c829
1 files changed, 829 insertions, 0 deletions
diff --git a/utils/db1-ast/btree/bt_split.c b/utils/db1-ast/btree/bt_split.c
new file mode 100644
index 000000000..8fede1e45
--- /dev/null
+++ b/utils/db1-ast/btree/bt_split.c
@@ -0,0 +1,829 @@
+/*-
+ * 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 "../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 = 0;
+ BLEAF *bl = 0, *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 = 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.
+ */
+ 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 ((u_int32_t) (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 = 0;
+ 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 + sizeof(indx_t) >= full)
+ || nxt == top - 1) {
+ --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 + sizeof(indx_t);
+ 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);
+}