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. 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.
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
32 * @(#)bt_search.c 8.8 (Berkeley) 7/31/94
33 * $DragonFly: src/lib/libc/db/btree/bt_search.c,v 1.6 2005/11/12 23:01:54 swildner Exp $
36 #include <sys/types.h>
43 static int __bt_snext (BTREE *, PAGE *, const DBT *, int *);
44 static int __bt_sprev (BTREE *, PAGE *, const DBT *, int *);
48 * Search a btree for a key.
53 * exactp: pointer to exact match flag
56 * The EPG for matching record, if any, or the EPG for the location
57 * of the key, if it were inserted into the tree, is entered into
58 * the bt_cur field of the tree. A pointer to the field is returned.
61 __bt_search(BTREE *t, const DBT *key, int *exactp)
64 indx_t base, index, lim;
70 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
73 /* Do a binary search on the current page. */
75 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) {
76 t->bt_cur.index = index = base + (lim >> 1);
77 if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) {
78 if (h->flags & P_BLEAF) {
91 * If it's a leaf page, we're almost done. If no duplicates
92 * are allowed, or we have an exact match, we're done. Else,
93 * it's possible that there were matching keys on this page,
94 * which later deleted, and we're on a page with no matches
95 * while there are matches on other pages. If at the start or
96 * end of a page, check the adjacent page.
98 if (h->flags & P_BLEAF) {
99 if (!F_ISSET(t, B_NODUPS)) {
101 h->prevpg != P_INVALID &&
102 __bt_sprev(t, h, key, exactp))
104 if (base == NEXTINDEX(h) &&
105 h->nextpg != P_INVALID &&
106 __bt_snext(t, h, key, exactp))
110 t->bt_cur.index = base;
115 * No match found. Base is the smallest index greater than
116 * key and may be zero or a last + 1 index. If it's non-zero,
117 * decrement by one, and record the internal page which should
118 * be a parent page for the key. If a split later occurs, the
119 * inserted page will be to the right of the saved page.
121 index = base ? base - 1 : base;
123 next: BT_PUSH(t, h->pgno, index);
124 pg = GETBINTERNAL(h, index)->pgno;
125 mpool_put(t->bt_mp, h, 0);
131 * Check for an exact match after the key.
137 * exactp: pointer to exact match flag
140 * If an exact match found.
143 __bt_snext(BTREE *t, PAGE *h, const DBT *key, int *exactp)
148 * Get the next page. The key is either an exact
149 * match, or not as good as the one we already have.
151 if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL)
154 if (__bt_cmp(t, key, &e) == 0) {
155 mpool_put(t->bt_mp, h, 0);
160 mpool_put(t->bt_mp, e.page, 0);
166 * Check for an exact match before the key.
172 * exactp: pointer to exact match flag
175 * If an exact match found.
178 __bt_sprev(BTREE *t, PAGE *h, const DBT *key, int *exactp)
183 * Get the previous page. The key is either an exact
184 * match, or not as good as the one we already have.
186 if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL)
188 e.index = NEXTINDEX(e.page) - 1;
189 if (__bt_cmp(t, key, &e) == 0) {
190 mpool_put(t->bt_mp, h, 0);
195 mpool_put(t->bt_mp, e.page, 0);