1 #pragma ident "%Z%%M% %I% %E% SMI"
2
3 /*-
4 * Copyright (c) 1990, 1993, 1994
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Mike Olson.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 * must display the following acknowledgement:
20 * This product includes software developed by the University of
21 * California, Berkeley and its contributors.
22 * 4. Neither the name of the University nor the names of its contributors
23 * may be used to endorse or promote products derived from this software
24 * without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 */
38
39 #if defined(LIBC_SCCS) && !defined(lint)
40 static char sccsid[] = "@(#)bt_search.c 8.9 (Berkeley) 10/26/95";
41 #endif /* LIBC_SCCS and not lint */
42
43 #include <sys/types.h>
44
45 #include <stdio.h>
46
47 #include "db-int.h"
48 #include "btree.h"
49
50 static int __bt_snext __P((BTREE *, PAGE *, const DBT *, int *));
51 static int __bt_sprev __P((BTREE *, PAGE *, const DBT *, int *));
52
53 /*
54 * __bt_search --
55 * Search a btree for a key.
56 *
57 * Parameters:
58 * t: tree to search
59 * key: key to find
60 * exactp: pointer to exact match flag
61 *
62 * Returns:
63 * The EPG for matching record, if any, or the EPG for the location
64 * of the key, if it were inserted into the tree, is entered into
65 * the bt_cur field of the tree. A pointer to the field is returned.
66 */
67 EPG *
__bt_search(t,key,exactp)68 __bt_search(t, key, exactp)
69 BTREE *t;
70 const DBT *key;
71 int *exactp;
72 {
73 PAGE *h;
74 indx_t base, idx, lim;
75 db_pgno_t pg;
76 int cmp;
77
78 BT_CLR(t);
79 for (pg = P_ROOT;;) {
80 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
81 return (NULL);
82
83 /* Do a binary search on the current page. */
84 t->bt_cur.page = h;
85 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) {
86 t->bt_cur.index = idx = base + (lim >> 1);
87 if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) {
88 if (h->flags & P_BLEAF) {
89 *exactp = 1;
90 return (&t->bt_cur);
91 }
92 goto next;
93 }
94 if (cmp > 0) {
95 base = idx + 1;
96 --lim;
97 }
98 }
99
100 /*
101 * If it's a leaf page, we're almost done. If no duplicates
102 * are allowed, or we have an exact match, we're done. Else,
103 * it's possible that there were matching keys on this page,
104 * which later deleted, and we're on a page with no matches
105 * while there are matches on other pages. If at the start or
106 * end of a page, check the adjacent page.
107 */
108 if (h->flags & P_BLEAF) {
109 if (!F_ISSET(t, B_NODUPS)) {
110 if (base == 0 &&
111 h->prevpg != P_INVALID &&
112 __bt_sprev(t, h, key, exactp))
113 return (&t->bt_cur);
114 if (base == NEXTINDEX(h) &&
115 h->nextpg != P_INVALID &&
116 __bt_snext(t, h, key, exactp))
117 return (&t->bt_cur);
118 }
119 *exactp = 0;
120 t->bt_cur.index = base;
121 return (&t->bt_cur);
122 }
123
124 /*
125 * No match found. Base is the smallest index greater than
126 * key and may be zero or a last + 1 index. If it's non-zero,
127 * decrement by one, and record the internal page which should
128 * be a parent page for the key. If a split later occurs, the
129 * inserted page will be to the right of the saved page.
130 */
131 idx = base ? base - 1 : base;
132
133 next: BT_PUSH(t, h->pgno, idx);
134 pg = GETBINTERNAL(h, idx)->pgno;
135 mpool_put(t->bt_mp, h, 0);
136 }
137 }
138
139 /*
140 * __bt_snext --
141 * Check for an exact match after the key.
142 *
143 * Parameters:
144 * t: tree
145 * h: current page
146 * key: key
147 * exactp: pointer to exact match flag
148 *
149 * Returns:
150 * If an exact match found.
151 */
152 static int
__bt_snext(t,h,key,exactp)153 __bt_snext(t, h, key, exactp)
154 BTREE *t;
155 PAGE *h;
156 const DBT *key;
157 int *exactp;
158 {
159 BINTERNAL *bi;
160 EPG e;
161 EPGNO *parent;
162 indx_t idx;
163 db_pgno_t pgno;
164 int level;
165
166 /*
167 * Get the next page. The key is either an exact
168 * match, or not as good as the one we already have.
169 */
170 if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL)
171 return (0);
172 e.index = 0;
173 if (__bt_cmp(t, key, &e) != 0) {
174 mpool_put(t->bt_mp, e.page, 0);
175 return (0);
176 }
177 mpool_put(t->bt_mp, h, 0);
178 t->bt_cur = e;
179 *exactp = 1;
180
181 /*
182 * Adjust the stack for the movement.
183 *
184 * Move up the stack.
185 */
186 for (level = 0; (parent = BT_POP(t)) != NULL; ++level) {
187 /* Get the parent page. */
188 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
189 return (0);
190
191 /* Move to the next index. */
192 if (parent->index != NEXTINDEX(h) - 1) {
193 idx = parent->index + 1;
194 BT_PUSH(t, h->pgno, idx);
195 break;
196 }
197 mpool_put(t->bt_mp, h, 0);
198 }
199
200 /* Restore the stack. */
201 while (level--) {
202 /* Push the next level down onto the stack. */
203 bi = GETBINTERNAL(h, idx);
204 pgno = bi->pgno;
205 BT_PUSH(t, pgno, 0);
206
207 /* Lose the currently pinned page. */
208 mpool_put(t->bt_mp, h, 0);
209
210 /* Get the next level down. */
211 if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL)
212 return (0);
213 idx = 0;
214 }
215 mpool_put(t->bt_mp, h, 0);
216 return (1);
217 }
218
219 /*
220 * __bt_sprev --
221 * Check for an exact match before the key.
222 *
223 * Parameters:
224 * t: tree
225 * h: current page
226 * key: key
227 * exactp: pointer to exact match flag
228 *
229 * Returns:
230 * If an exact match found.
231 */
232 static int
__bt_sprev(t,h,key,exactp)233 __bt_sprev(t, h, key, exactp)
234 BTREE *t;
235 PAGE *h;
236 const DBT *key;
237 int *exactp;
238 {
239 BINTERNAL *bi;
240 EPG e;
241 EPGNO *parent;
242 indx_t idx;
243 db_pgno_t pgno;
244 int level;
245
246 /*
247 * Get the previous page. The key is either an exact
248 * match, or not as good as the one we already have.
249 */
250 if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL)
251 return (0);
252 e.index = NEXTINDEX(e.page) - 1;
253 if (__bt_cmp(t, key, &e) != 0) {
254 mpool_put(t->bt_mp, e.page, 0);
255 return (0);
256 }
257
258 mpool_put(t->bt_mp, h, 0);
259 t->bt_cur = e;
260 *exactp = 1;
261
262 /*
263 * Adjust the stack for the movement.
264 *
265 * Move up the stack.
266 */
267 for (level = 0; (parent = BT_POP(t)) != NULL; ++level) {
268 /* Get the parent page. */
269 if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
270 return (1);
271
272 /* Move to the next index. */
273 if (parent->index != 0) {
274 idx = parent->index - 1;
275 BT_PUSH(t, h->pgno, idx);
276 break;
277 }
278 mpool_put(t->bt_mp, h, 0);
279 }
280
281 /* Restore the stack. */
282 while (level--) {
283 /* Push the next level down onto the stack. */
284 bi = GETBINTERNAL(h, idx);
285 pgno = bi->pgno;
286
287 /* Lose the currently pinned page. */
288 mpool_put(t->bt_mp, h, 0);
289
290 /* Get the next level down. */
291 if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL)
292 return (1);
293
294 idx = NEXTINDEX(h) - 1;
295 BT_PUSH(t, pgno, idx);
296 }
297 mpool_put(t->bt_mp, h, 0);
298 return (1);
299 }
300