2 * Copyright (c) 1990, 1993, 1994
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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.
16 * 3. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed by the University of
19 * California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * @(#)bt_search.c 8.8 (Berkeley) 7/31/94
39 #include <sys/types.h>
46 static int __bt_snext __P((BTREE *, PAGE *, const DBT *, int *));
47 static int __bt_sprev __P((BTREE *, PAGE *, const DBT *, int *));
51 * Search a btree for a key.
56 * exactp: pointer to exact match flag
59 * The EPG for matching record, if any, or the EPG for the location
60 * of the key, if it were inserted into the tree, is entered into
61 * the bt_cur field of the tree. A pointer to the field is returned.
64 __bt_search(t, key, exactp)
70 indx_t base, index, lim;
76 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
79 /* Do a binary search on the current page. */
81 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) {
82 t->bt_cur.index = index = base + (lim >> 1);
83 if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) {
84 if (h->flags & P_BLEAF) {
97 * If it's a leaf page, we're almost done. If no duplicates
98 * are allowed, or we have an exact match, we're done. Else,
99 * it's possible that there were matching keys on this page,
100 * which later deleted, and we're on a page with no matches
101 * while there are matches on other pages. If at the start or
102 * end of a page, check the adjacent page.
104 if (h->flags & P_BLEAF) {
105 if (!F_ISSET(t, B_NODUPS)) {
107 h->prevpg != P_INVALID &&
108 __bt_sprev(t, h, key, exactp))
110 if (base == NEXTINDEX(h) &&
111 h->nextpg != P_INVALID &&
112 __bt_snext(t, h, key, exactp))
116 t->bt_cur.index = base;
121 * No match found. Base is the smallest index greater than
122 * key and may be zero or a last + 1 index. If it's non-zero,
123 * decrement by one, and record the internal page which should
124 * be a parent page for the key. If a split later occurs, the
125 * inserted page will be to the right of the saved page.
127 index = base ? base - 1 : base;
129 next: BT_PUSH(t, h->pgno, index);
130 pg = GETBINTERNAL(h, index)->pgno;
131 mpool_put(t->bt_mp, h, 0);
137 * Check for an exact match after the key.
143 * exactp: pointer to exact match flag
146 * If an exact match found.
149 __bt_snext(t, h, key, exactp)
158 * Get the next page. The key is either an exact
159 * match, or not as good as the one we already have.
161 if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL)
164 if (__bt_cmp(t, key, &e) == 0) {
165 mpool_put(t->bt_mp, h, 0);
170 mpool_put(t->bt_mp, e.page, 0);
176 * Check for an exact match before the key.
182 * exactp: pointer to exact match flag
185 * If an exact match found.
188 __bt_sprev(t, h, key, exactp)
197 * Get the previous page. The key is either an exact
198 * match, or not as good as the one we already have.
200 if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL)
202 e.index = NEXTINDEX(e.page) - 1;
203 if (__bt_cmp(t, key, &e) == 0) {
204 mpool_put(t->bt_mp, h, 0);
209 mpool_put(t->bt_mp, e.page, 0);