[apple/libc.git] / db / btree / FreeBSD / bt_put.c

/*-
 * 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.
 * 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_put.c	8.8 (Berkeley) 7/26/94";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/lib/libc/db/btree/bt_put.c,v 1.9 2009/03/28 05:45:29 delphij Exp $");

#include <sys/types.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <db.h>
#include "btree.h"

static EPG *bt_fast(BTREE *, const DBT *, const DBT *, int *);

/*
 * __BT_PUT -- Add a btree item to the tree.
 *
 * Parameters:
 *	dbp:	pointer to access method
 *	key:	key
 *	data:	data
 *	flag:	R_NOOVERWRITE
 *
 * Returns:
 *	RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key is already in the
 *	tree and R_NOOVERWRITE specified.
 */
int
__bt_put(const DB *dbp, DBT *key, const DBT *data, u_int flags)
{
	BTREE *t;
	DBT tkey, tdata;
	EPG *e;
	PAGE *h;
	indx_t idx, nxtindex;
	pgno_t pg;
	u_int32_t nbytes, tmp;
	int dflags, exact, status;
	char *dest, db[NOVFLSIZE], kb[NOVFLSIZE];

	t = dbp->internal;

	/* Toss any page pinned across calls. */
	if (t->bt_pinned != NULL) {
		mpool_put(t->bt_mp, t->bt_pinned, 0);
		t->bt_pinned = NULL;
	}

	/* Check for change to a read-only tree. */
	if (F_ISSET(t, B_RDONLY)) {
		errno = EPERM;
		return (RET_ERROR);
	}

	switch (flags) {
	case 0:
	case R_NOOVERWRITE:
		break;
	case R_CURSOR:
		/*
		 * If flags is R_CURSOR, put the cursor.  Must already
		 * have started a scan and not have already deleted it.
		 */
		if (F_ISSET(&t->bt_cursor, CURS_INIT) &&
		    !F_ISSET(&t->bt_cursor,
			CURS_ACQUIRE | CURS_AFTER | CURS_BEFORE))
			break;
		/* FALLTHROUGH */
	default:
		errno = EINVAL;
		return (RET_ERROR);
	}

	/*
	 * If the key/data pair won't fit on a page, store it on overflow
	 * pages.  Only put the key on the overflow page if the pair are
	 * still too big after moving the data to an overflow page.
	 *
	 * XXX
	 * If the insert fails later on, the overflow pages aren't recovered.
	 */
	dflags = 0;
	if (key->size + data->size > t->bt_ovflsize) {
		if (key->size > t->bt_ovflsize) {
storekey:		if (__ovfl_put(t, key, &pg) == RET_ERROR)
				return (RET_ERROR);
			tkey.data = kb;
			tkey.size = NOVFLSIZE;
			memmove(kb, &pg, sizeof(pgno_t));
			tmp = key->size;
			memmove(kb + sizeof(pgno_t),
			    &tmp, sizeof(u_int32_t));
			dflags |= P_BIGKEY;
			key = &tkey;
		}
		if (key->size + data->size > t->bt_ovflsize) {
			if (__ovfl_put(t, data, &pg) == RET_ERROR)
				return (RET_ERROR);
			tdata.data = db;
			tdata.size = NOVFLSIZE;
			memmove(db, &pg, sizeof(pgno_t));
			tmp = data->size;
			memmove(db + sizeof(pgno_t),
			    &tmp, sizeof(u_int32_t));
			dflags |= P_BIGDATA;
			data = &tdata;
		}
		if (key->size + data->size > t->bt_ovflsize)
			goto storekey;
	}

	/* Replace the cursor. */
	if (flags == R_CURSOR) {
		if ((h = mpool_get(t->bt_mp, t->bt_cursor.pg.pgno, 0)) == NULL)
			return (RET_ERROR);
		idx = t->bt_cursor.pg.index;
		goto delete;
	}

	/*
	 * Find the key to delete, or, the location at which to insert.
	 * Bt_fast and __bt_search both pin the returned page.
	 */
	if (t->bt_order == NOT || (e = bt_fast(t, key, data, &exact)) == NULL)
		if ((e = __bt_search(t, key, &exact)) == NULL)
			return (RET_ERROR);
	h = e->page;
	idx = e->index;

	/*
	 * Add the key/data pair to the tree.  If an identical key is already
	 * in the tree, and R_NOOVERWRITE is set, an error is returned.  If
	 * R_NOOVERWRITE is not set, the key is either added (if duplicates are
	 * permitted) or an error is returned.
	 */
	switch (flags) {
	case R_NOOVERWRITE:
		if (!exact)
			break;
		mpool_put(t->bt_mp, h, 0);
		return (RET_SPECIAL);
	default:
		if (!exact || !F_ISSET(t, B_NODUPS))
			break;
		/*
		 * !!!
		 * Note, the delete may empty the page, so we need to put a
		 * new entry into the page immediately.
		 */
delete:		if (__bt_dleaf(t, key, h, idx) == RET_ERROR) {
			mpool_put(t->bt_mp, h, 0);
			return (RET_ERROR);
		}
		break;
	}

	/*
	 * If not enough room, or the user has put a ceiling on the number of
	 * keys permitted in the page, split the page.  The split code will
	 * insert the key and data and unpin the current page.  If inserting
	 * into the offset array, shift the pointers up.
	 */
	nbytes = NBLEAFDBT(key->size, data->size);
	if ((u_int32_t)(h->upper - h->lower) < nbytes + sizeof(indx_t)) {
		if ((status = __bt_split(t, h, key,
		    data, dflags, nbytes, idx)) != RET_SUCCESS)
			return (status);
		goto success;
	}

	if (idx < (nxtindex = NEXTINDEX(h)))
		memmove(h->linp + idx + 1, h->linp + idx,
		    (nxtindex - idx) * sizeof(indx_t));
	h->lower += sizeof(indx_t);

	h->linp[idx] = h->upper -= nbytes;
	dest = (char *)h + h->upper;
	WR_BLEAF(dest, key, data, dflags);

	/* If the cursor is on this page, adjust it as necessary. */
	if (F_ISSET(&t->bt_cursor, CURS_INIT) &&
	    !F_ISSET(&t->bt_cursor, CURS_ACQUIRE) &&
	    t->bt_cursor.pg.pgno == h->pgno && t->bt_cursor.pg.index >= idx)
		++t->bt_cursor.pg.index;

	if (t->bt_order == NOT) {
		if (h->nextpg == P_INVALID) {
			if (idx == NEXTINDEX(h) - 1) {
				t->bt_order = FORWARD;
				t->bt_last.index = idx;
				t->bt_last.pgno = h->pgno;
			}
		} else if (h->prevpg == P_INVALID) {
			if (idx == 0) {
				t->bt_order = BACK;
				t->bt_last.index = 0;
				t->bt_last.pgno = h->pgno;
			}
		}
	}

	mpool_put(t->bt_mp, h, MPOOL_DIRTY);

success:
	if (flags == R_SETCURSOR)
		__bt_setcur(t, e->page->pgno, e->index);

	F_SET(t, B_MODIFIED);
	return (RET_SUCCESS);
}

#ifdef STATISTICS
u_long bt_cache_hit, bt_cache_miss;
#endif

/*
 * BT_FAST -- Do a quick check for sorted data.
 *
 * Parameters:
 *	t:	tree
 *	key:	key to insert
 *
 * Returns:
 *	EPG for new record or NULL if not found.
 */
static EPG *
bt_fast(BTREE *t, const DBT *key, const DBT *data, int *exactp)
{
	PAGE *h;
	u_int32_t nbytes;
	int cmp;

	if ((h = mpool_get(t->bt_mp, t->bt_last.pgno, 0)) == NULL) {
		t->bt_order = NOT;
		return (NULL);
	}
	t->bt_cur.page = h;
	t->bt_cur.index = t->bt_last.index;

	/*
	 * If won't fit in this page or have too many keys in this page,
	 * have to search to get split stack.
	 */
	nbytes = NBLEAFDBT(key->size, data->size);
	if ((u_int32_t)(h->upper - h->lower) < nbytes + sizeof(indx_t))
		goto miss;

	if (t->bt_order == FORWARD) {
		if (t->bt_cur.page->nextpg != P_INVALID)
			goto miss;
		if (t->bt_cur.index != NEXTINDEX(h) - 1)
			goto miss;
		if ((cmp = __bt_cmp(t, key, &t->bt_cur)) < 0)
			goto miss;
		t->bt_last.index = cmp ? ++t->bt_cur.index : t->bt_cur.index;
	} else {
		if (t->bt_cur.page->prevpg != P_INVALID)
			goto miss;
		if (t->bt_cur.index != 0)
			goto miss;
		if ((cmp = __bt_cmp(t, key, &t->bt_cur)) > 0)
			goto miss;
		t->bt_last.index = 0;
	}
	*exactp = cmp == 0;
#ifdef STATISTICS
	++bt_cache_hit;
#endif
	return (&t->bt_cur);

miss:
#ifdef STATISTICS
	++bt_cache_miss;
#endif
	t->bt_order = NOT;
	mpool_put(t->bt_mp, h, 0);
	return (NULL);
}
Commit	Line	Data
9385eb3d A	1	/*-
9385eb3d A	2	* Copyright (c) 1990, 1993, 1994
e9ce8d39 A	3	* The Regents of the University of California. All rights reserved.
	4	*
	5	* This code is derived from software contributed to Berkeley by
	6	* Mike Olson.
	7	*
	8	* Redistribution and use in source and binary forms, with or without
	9	* modification, are permitted provided that the following conditions
	10	* are met:
	11	* 1. Redistributions of source code must retain the above copyright
	12	* notice, this list of conditions and the following disclaimer.
	13	* 2. Redistributions in binary form must reproduce the above copyright
	14	* notice, this list of conditions and the following disclaimer in the
	15	* documentation and/or other materials provided with the distribution.
e9ce8d39 A	16	* 4. Neither the name of the University nor the names of its contributors
	17	* may be used to endorse or promote products derived from this software
	18	* without specific prior written permission.
	19	*
	20	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	21	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	22	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	23	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	24	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	25	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	26	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	27	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	28	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	29	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	30	* SUCH DAMAGE.
	31	*/
	32
9385eb3d A	33	#if defined(LIBC_SCCS) && !defined(lint)
	34	static char sccsid[] = "@(#)bt_put.c 8.8 (Berkeley) 7/26/94";
	35	#endif /* LIBC_SCCS and not lint */
	36	#include <sys/cdefs.h>
1f2f436a	37	__FBSDID("$FreeBSD: src/lib/libc/db/btree/bt_put.c,v 1.9 2009/03/28 05:45:29 delphij Exp $");
e9ce8d39 A	38
	39	#include <sys/types.h>
	40
	41	#include <errno.h>
	42	#include <stdio.h>
	43	#include <stdlib.h>
	44	#include <string.h>
	45
	46	#include <db.h>
	47	#include "btree.h"
	48
9385eb3d	49	static EPG bt_fast(BTREE , const DBT , const DBT , int *);
e9ce8d39 A	50
	51	/*
	52	* __BT_PUT -- Add a btree item to the tree.
	53	*
	54	* Parameters:
	55	* dbp: pointer to access method
	56	* key: key
	57	* data: data
	58	* flag: R_NOOVERWRITE
	59	*
	60	* Returns:
	61	* RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key is already in the
	62	* tree and R_NOOVERWRITE specified.
	63	*/
	64	int
1f2f436a	65	__bt_put(const DB dbp, DBT key, const DBT *data, u_int flags)
e9ce8d39 A	66	{
	67	BTREE *t;
	68	DBT tkey, tdata;
	69	EPG *e;
	70	PAGE *h;
1f2f436a	71	indx_t idx, nxtindex;
e9ce8d39	72	pgno_t pg;
59e0d9fe	73	u_int32_t nbytes, tmp;
e9ce8d39 A	74	int dflags, exact, status;
	75	char *dest, db[NOVFLSIZE], kb[NOVFLSIZE];
	76
	77	t = dbp->internal;
	78
	79	/* Toss any page pinned across calls. */
	80	if (t->bt_pinned != NULL) {
	81	mpool_put(t->bt_mp, t->bt_pinned, 0);
	82	t->bt_pinned = NULL;
	83	}
	84
9385eb3d A	85	/* Check for change to a read-only tree. */
	86	if (F_ISSET(t, B_RDONLY)) {
	87	errno = EPERM;
	88	return (RET_ERROR);
	89	}
	90
e9ce8d39	91	switch (flags) {
e9ce8d39 A	92	case 0:
	93	case R_NOOVERWRITE:
	94	break;
9385eb3d A	95	case R_CURSOR:
	96	/*
	97	* If flags is R_CURSOR, put the cursor. Must already
	98	* have started a scan and not have already deleted it.
	99	*/
	100	if (F_ISSET(&t->bt_cursor, CURS_INIT) &&
	101	!F_ISSET(&t->bt_cursor,
1f2f436a	102	CURS_ACQUIRE \| CURS_AFTER \| CURS_BEFORE))
9385eb3d A	103	break;
9385eb3d A	104	/* FALLTHROUGH */
e9ce8d39	105	default:
9385eb3d	106	errno = EINVAL;
e9ce8d39 A	107	return (RET_ERROR);
	108	}
	109
	110	/*
9385eb3d A	111	* If the key/data pair won't fit on a page, store it on overflow
	112	* pages. Only put the key on the overflow page if the pair are
	113	* still too big after moving the data to an overflow page.
e9ce8d39 A	114	*
e9ce8d39 A	115	* XXX
9385eb3d	116	* If the insert fails later on, the overflow pages aren't recovered.
e9ce8d39 A	117	*/
	118	dflags = 0;
	119	if (key->size + data->size > t->bt_ovflsize) {
	120	if (key->size > t->bt_ovflsize) {
	121	storekey: if (__ovfl_put(t, key, &pg) == RET_ERROR)
	122	return (RET_ERROR);
	123	tkey.data = kb;
	124	tkey.size = NOVFLSIZE;
	125	memmove(kb, &pg, sizeof(pgno_t));
59e0d9fe	126	tmp = key->size;
e9ce8d39	127	memmove(kb + sizeof(pgno_t),
59e0d9fe	128	&tmp, sizeof(u_int32_t));
e9ce8d39 A	129	dflags \|= P_BIGKEY;
	130	key = &tkey;
	131	}
	132	if (key->size + data->size > t->bt_ovflsize) {
	133	if (__ovfl_put(t, data, &pg) == RET_ERROR)
	134	return (RET_ERROR);
	135	tdata.data = db;
	136	tdata.size = NOVFLSIZE;
	137	memmove(db, &pg, sizeof(pgno_t));
59e0d9fe	138	tmp = data->size;
e9ce8d39	139	memmove(db + sizeof(pgno_t),
59e0d9fe	140	&tmp, sizeof(u_int32_t));
e9ce8d39 A	141	dflags \|= P_BIGDATA;
	142	data = &tdata;
	143	}
	144	if (key->size + data->size > t->bt_ovflsize)
	145	goto storekey;
	146	}
	147
	148	/* Replace the cursor. */
	149	if (flags == R_CURSOR) {
9385eb3d	150	if ((h = mpool_get(t->bt_mp, t->bt_cursor.pg.pgno, 0)) == NULL)
e9ce8d39	151	return (RET_ERROR);
1f2f436a	152	idx = t->bt_cursor.pg.index;
e9ce8d39 A	153	goto delete;
	154	}
	155
	156	/*
9385eb3d A	157	* Find the key to delete, or, the location at which to insert.
9385eb3d A	158	* Bt_fast and __bt_search both pin the returned page.
e9ce8d39 A	159	*/
	160	if (t->bt_order == NOT \|\| (e = bt_fast(t, key, data, &exact)) == NULL)
	161	if ((e = __bt_search(t, key, &exact)) == NULL)
	162	return (RET_ERROR);
	163	h = e->page;
1f2f436a	164	idx = e->index;
e9ce8d39 A	165
e9ce8d39 A	166	/*
9385eb3d A	167	* Add the key/data pair to the tree. If an identical key is already
	168	* in the tree, and R_NOOVERWRITE is set, an error is returned. If
	169	* R_NOOVERWRITE is not set, the key is either added (if duplicates are
	170	* permitted) or an error is returned.
e9ce8d39 A	171	*/
	172	switch (flags) {
	173	case R_NOOVERWRITE:
	174	if (!exact)
	175	break;
e9ce8d39 A	176	mpool_put(t->bt_mp, h, 0);
	177	return (RET_SPECIAL);
	178	default:
9385eb3d	179	if (!exact \|\| !F_ISSET(t, B_NODUPS))
e9ce8d39	180	break;
9385eb3d A	181	/*
	182	* !!!
	183	* Note, the delete may empty the page, so we need to put a
	184	* new entry into the page immediately.
	185	*/
1f2f436a	186	delete: if (__bt_dleaf(t, key, h, idx) == RET_ERROR) {
e9ce8d39 A	187	mpool_put(t->bt_mp, h, 0);
	188	return (RET_ERROR);
	189	}
	190	break;
	191	}
	192
	193	/*
	194	* If not enough room, or the user has put a ceiling on the number of
	195	* keys permitted in the page, split the page. The split code will
	196	* insert the key and data and unpin the current page. If inserting
	197	* into the offset array, shift the pointers up.
	198	*/
	199	nbytes = NBLEAFDBT(key->size, data->size);
1f2f436a	200	if ((u_int32_t)(h->upper - h->lower) < nbytes + sizeof(indx_t)) {
e9ce8d39	201	if ((status = __bt_split(t, h, key,
1f2f436a	202	data, dflags, nbytes, idx)) != RET_SUCCESS)
e9ce8d39 A	203	return (status);
	204	goto success;
	205	}
	206
1f2f436a A	207	if (idx < (nxtindex = NEXTINDEX(h)))
	208	memmove(h->linp + idx + 1, h->linp + idx,
	209	(nxtindex - idx) * sizeof(indx_t));
e9ce8d39 A	210	h->lower += sizeof(indx_t);
e9ce8d39 A	211
1f2f436a	212	h->linp[idx] = h->upper -= nbytes;
e9ce8d39 A	213	dest = (char *)h + h->upper;
	214	WR_BLEAF(dest, key, data, dflags);
	215
9385eb3d A	216	/* If the cursor is on this page, adjust it as necessary. */
	217	if (F_ISSET(&t->bt_cursor, CURS_INIT) &&
	218	!F_ISSET(&t->bt_cursor, CURS_ACQUIRE) &&
1f2f436a	219	t->bt_cursor.pg.pgno == h->pgno && t->bt_cursor.pg.index >= idx)
9385eb3d A	220	++t->bt_cursor.pg.index;
	221
	222	if (t->bt_order == NOT) {
e9ce8d39	223	if (h->nextpg == P_INVALID) {
1f2f436a	224	if (idx == NEXTINDEX(h) - 1) {
e9ce8d39	225	t->bt_order = FORWARD;
1f2f436a	226	t->bt_last.index = idx;
e9ce8d39 A	227	t->bt_last.pgno = h->pgno;
	228	}
	229	} else if (h->prevpg == P_INVALID) {
1f2f436a	230	if (idx == 0) {
e9ce8d39 A	231	t->bt_order = BACK;
	232	t->bt_last.index = 0;
	233	t->bt_last.pgno = h->pgno;
	234	}
	235	}
9385eb3d	236	}
e9ce8d39 A	237
	238	mpool_put(t->bt_mp, h, MPOOL_DIRTY);
	239
	240	success:
9385eb3d A	241	if (flags == R_SETCURSOR)
	242	__bt_setcur(t, e->page->pgno, e->index);
	243
	244	F_SET(t, B_MODIFIED);
e9ce8d39 A	245	return (RET_SUCCESS);
	246	}
	247
	248	#ifdef STATISTICS
	249	u_long bt_cache_hit, bt_cache_miss;
	250	#endif
	251
	252	/*
	253	* BT_FAST -- Do a quick check for sorted data.
	254	*
	255	* Parameters:
	256	* t: tree
	257	* key: key to insert
	258	*
	259	* Returns:
1f2f436a	260	* EPG for new record or NULL if not found.
e9ce8d39 A	261	*/
e9ce8d39 A	262	static EPG *
1f2f436a	263	bt_fast(BTREE t, const DBT key, const DBT data, int exactp)
e9ce8d39 A	264	{
e9ce8d39 A	265	PAGE *h;
9385eb3d	266	u_int32_t nbytes;
e9ce8d39 A	267	int cmp;
	268
	269	if ((h = mpool_get(t->bt_mp, t->bt_last.pgno, 0)) == NULL) {
	270	t->bt_order = NOT;
	271	return (NULL);
	272	}
	273	t->bt_cur.page = h;
	274	t->bt_cur.index = t->bt_last.index;
	275
	276	/*
9385eb3d A	277	* If won't fit in this page or have too many keys in this page,
9385eb3d A	278	* have to search to get split stack.
e9ce8d39 A	279	*/
e9ce8d39 A	280	nbytes = NBLEAFDBT(key->size, data->size);
1f2f436a	281	if ((u_int32_t)(h->upper - h->lower) < nbytes + sizeof(indx_t))
e9ce8d39 A	282	goto miss;
	283
	284	if (t->bt_order == FORWARD) {
	285	if (t->bt_cur.page->nextpg != P_INVALID)
	286	goto miss;
	287	if (t->bt_cur.index != NEXTINDEX(h) - 1)
	288	goto miss;
	289	if ((cmp = __bt_cmp(t, key, &t->bt_cur)) < 0)
	290	goto miss;
	291	t->bt_last.index = cmp ? ++t->bt_cur.index : t->bt_cur.index;
	292	} else {
	293	if (t->bt_cur.page->prevpg != P_INVALID)
	294	goto miss;
	295	if (t->bt_cur.index != 0)
	296	goto miss;
	297	if ((cmp = __bt_cmp(t, key, &t->bt_cur)) > 0)
	298	goto miss;
	299	t->bt_last.index = 0;
	300	}
	301	*exactp = cmp == 0;
	302	#ifdef STATISTICS
	303	++bt_cache_hit;
	304	#endif
	305	return (&t->bt_cur);
	306
	307	miss:
	308	#ifdef STATISTICS
	309	++bt_cache_miss;
	310	#endif
	311	t->bt_order = NOT;
	312	mpool_put(t->bt_mp, h, 0);
	313	return (NULL);
	314	}