skip = 0;
skip = MAX_PAGE_OFFSET;
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 STATISTICSu_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);	}	memset(l, 0xff, t->bt_psize);	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 intbt_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 intbt_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 + 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);}